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Consequence of Plants as Incomplete Protein Source

Consequence of Plants as Incomplete Protein Source


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Some years ago, in a 1000~ level biology course we learned that the DNA essentially encodes formulas for creating proteins from amino acids. While the human body can synthesize many many amino acids, some we are unable to synthesize and we dub these as essential amino acids because we must obtain them from our diet. However, surely something must be capable of synthesizing the amino acids, otherwise they would not make it up the food chain to us, which opens the door to the possibility that animals may have varying capabilities in regards to amino acid synthesis. Presumably, this is why cats have to obtain a high protein diet, as they have high need for protein but a poor ability to synthesize them?

Moreover, in doing basic research into nutrition to plan a regular workout schedule there is some need to distinguish protein sources as not all protein sources are considered to be complete proteins because they do not provide all amino acids, or otherwise do not provide them in the right balance. Particularly, many fruits and vegetables tend to be poor sources of protein.

For plants which are incomplete protein sources, they would seem to lack the ability to synthesize some amino acids. They also would not be able to obtain these through diet, as they're plants. Consequently, does this mean that some plants may not encode for a specific amino acid throughout their entire DNA?


With a few exceptions among some bacteria, all species on the planet make protein from the same 21 amino acids, and the relative abundances of amino acids is very similar in proteins from plants, animals, fungi and even prokaryotes. See for example this article (available as PDF here). So protein from pretty much any food provides the same amino acids.

The idea that plant proteins are "incomplete" and lack some amino acids seems to be a myth: see for example this correspondence in the American Heart Association's journal Circulation. Plants generally contain less protein than meats per weight, but there is nothing wrong with the protein they contain. Most people in the world obtain the majority of their protein from plants. There are probably some specific parts of some plants that are not nutritionally optimal --- if you for example lived exclusively on peanuts for a year, you might experience some problems… But any commonsense, varied plant diet will provide all amino acids. A detailed report (and some mythbusting) is here.

Regarding essential amino acids, as mentioned in comments this is a species-specific concept. Humans and most animals can synthesize about half of the 21 amino acids, while the remaining are essential. There are some species differences --- arginine is essential for cats, for example, but not for adult humans. In contrast, plants can synthesize all amino acids. But their protein composition is similar in the end.


Complete Vs. Incomplete Protein Sources

Delving into the world of fitness and nutrition, it’s easy to be overwhelmed by talk of nutrients. The one you inevitably end up hearing about – a lot— is protein.

But what is it? You’ve probably heard or read about it as a big part of building muscle, but there are some other important and often-overlooked aspects of the different protein sources that you may not know.

Let’s start with the basics…


Incomplete Food List

Sources of incomplete protein include:

  • grains
  • legumes
  • nuts
  • seeds
  • vegetables
  • barley
  • cornmeal
  • oats
  • buckwheat
  • pasta
  • rye
  • wheat
  • beans
  • lentils
  • dried peas
  • peanuts
  • chickpeas
  • soy products
  • sesame seeds
  • sunflower seeds
  • walnuts


Complete And Incomplete Proteins

Some proteins are complete, meaning that your body can readily use them for protein synthesis, whereas others are incomplete and by themselves cannot be fully utilized in protein synthesis.

In basic terms, complete proteins sustain lean muscle by themselves and incomplete proteins do not.

So, what makes a complete protein “complete” and an incomplete protein “incomplete”?


Top 15 sources of plant-based protein

More and more people are interested in following vegetarian or vegan diets or reducing their use of animal products. A shift away from animal products is getting easier with more fortified and nutritious plant-based foods available.

A person may try a vegan diet for health, animal welfare, or religious reasons. In 2016 , the Academy of Nutrition and Dietetics stated that a vegetarian or vegan diet could provide all the nutritional requirements of adults, children, and those who were pregnant or breast-feeding.

Even so, getting enough protein and essential vitamins and minerals can be harder for people who do not eat meat or animal products. A person must plan ahead to ensure they get enough protein, calcium, iron, and vitamin B-12, which people on an omnivorous diet get from animal products.

Read on for a list of some of the best plant-based foods for protein. We also discuss the differences between animal and plant proteins, and whether plant-based protein powders can be good sources of protein.

The right plant-based foods can be excellent sources of protein and other nutrients, often with fewer calories than animal products.

Some plant products, such as soy beans and quinoa, are complete proteins, which means that they contain all nine essential amino acids that humans need. Others are missing some of these amino acids, so eating a varied diet is important.

The following healthful, plant-based foods have a high-protein content per serving:

1. Tofu, tempeh, and edamame

Share on Pinterest Soy products such as tofu, tempeh, and edamame are among the richest sources of protein in a vegan diet.

Soy products are among the richest sources of protein in a plant-based diet. The protein content varies with how the soy is prepared:

  • firm tofu (soybean curds) contains about 10 g of protein per ½ cup beans (immature soybeans) contain 8.5 g of protein per ½ cup
  • tempeh contains about 15 g of protein per ½ cup

Tofu takes on the flavor of the dish it is prepared in so that it can be a versatile addition to a meal.

People can try tofu, as a meat substitute, in a favorite sandwich or soup. Tofu is also a popular meat substitute in some dishes, such as kung pao chicken and sweet and sour chicken.

These soy products also contain good levels of calcium and iron, which makes them healthful substitutes for dairy products.

Red or green lentils contain plenty of protein, fiber, and key nutrients, including iron and potassium.

Cooked lentils contain 8.84 g of protein per ½ cup.

Lentils are a great source of protein to add to a lunch or dinner routine. They can be added to stews, curries, salads, or rice to give an extra portion of protein.

3. Chickpeas

Cooked chickpeas are high in protein, containing around 7.25 g per ½ cup.

Chickpeas can be eaten hot or cold, and are highly versatile with plenty of recipes available online. They can, for example, be added to stews and curries, or spiced with paprika and roasted in the oven.

A person can add hummus, which is made from chickpea paste, to a sandwich for a healthful, protein-rich alternative to butter.

Peanuts are protein-rich, full of healthful fats, and may improve heart health. They contain around 20.5 g of protein per ½ cup.

Peanut butter is also rich in protein, with 3.6 g per tablespoon, making peanut butter sandwiches a healthful complete protein snack.

Almonds offer 16.5 g of protein per ½ cup. They also provide a good amount of vitamin E, which is great for the skin and eyes.

6. Spirulina

Spirulina is blue or green algae that contain around 8 g of protein per 2 tablespoons. It is also rich in nutrients, such as iron, B vitamins — although not vitamin B-12 — and manganese.

Spirulina is available online, as a powder or a supplement. It can be added to water, smoothies, or fruit juice. A person can also sprinkle it over salad or snacks to increase their protein content.

Quinoa is a grain with a high-protein content, and is a complete protein. Cooked quinoa contains 8 g of protein per cup.

This grain is also rich in other nutrients, including magnesium, iron, fiber, and manganese. It is also highly versatile.

Quinoa can fill in for pasta in soups and stews. It can be sprinkled on a salad or eaten as the main course.

8. Mycoprotein

Mycoprotein is a fungus-based protein. Mycoprotein products contain around 13 g of protein per ½ cup serving.

Products with mycoprotein are often advertised as meat substitutes and are available in forms such as “chicken” nuggets or cutlets. However, many of these products contain egg white, so people must be sure to check the label.

A very small number of people are allergic to Fusarium venenatum, the fungus from which the mycoprotein brand known as Quorn is made. People with a history of mushroom allergies or with many food allergies may wish to consider another protein source.

9. Chia seeds

Share on Pinterest Chia and hemp seeds are complete sources of protein that can be used to make smoothies, yogurts, and puddings.

Seeds are low-calorie foods that are rich in fiber and heart-healthy Omega-3 fatty acids. Chia seeds are a complete source of protein that contain 2 g of protein per tablespoon.

Try adding chia seeds to a smoothie, sprinkling them on top of a plant-based yogurt, or soaking them in water or almond milk to make a pudding.

Chia seeds are available from some supermarkets, health food stores, or to buy online.

10. Hemp seeds

Similarly to chia seeds, hemp seeds are a complete protein. Hemp seeds offer 5 g of protein per tablespoon. They can be used in a similar way to chia seeds. Hemp seeds can also be bought online.

11. Beans with rice

Separately, rice and beans are incomplete protein sources. Eaten together, this classic meal can provide 7 g of protein per cup.

Try rice and beans as a side dish, or mix rice, beans, and hummus together then spread on Ezekiel bread, which is made from sprouted grains, for a savory, protein-packed meal.

12. Potatoes

A large baked potato offers 8 g of protein per serving. Potatoes are also high in other nutrients, such as potassium and vitamin C.

Add 2 tablespoons of hummus for a flavorful snack that is healthier than butter-covered potatoes and increases the protein content. Two tablespoons of hummus contain about 3 g of protein.

13. Protein-rich vegetables

Many dark-colored, leafy greens and vegetables contain protein. Eaten alone, these foods are not enough to meet daily protein requirements, but a few vegetable snacks can increase protein intake, particularly when combined with other protein-rich foods.

  • a single, medium stalk of broccoli contains about 4 g of protein offers 2 g of protein per cup
  • 5 medium mushrooms offer 3 g of protein

Try a salad made from baby greens with some quinoa sprinkled on top for a protein-rich meal.

Seitan is a complete protein made from mixing wheat gluten with various spices. The high-wheat content means that it should be avoided by people with celiac or gluten intolerance. For others, it can be a protein-rich healthful meat substitute.

When cooked in soy sauce, which is rich in the amino acid lysine, seitan becomes a complete protein source offering 21 g per 1/3 cup.

15. Ezekiel bread

Ezekiel bread is a nutrient-dense alternative to traditional bread. It is made from barley, wheat, lentils, millet, and spelt. Ezekiel bread is an excellent choice for bread lovers who want a more nutritious way to eat toast or sandwiches.

Ezekiel bread offers 4 g of protein per slice. Get even more protein by toasting Ezekiel bread and spreading it with peanut or almond butter.

Some protein powders are plant-based. Depending upon the plants used to make the powders, they may be complete or incomplete proteins.

The position of the American Dietetic Association is that while food supplements can help people meet their daily nutrition goals, eating a wide variety of nutrients rich in protein is usually a better strategy for meeting daily goals.

Some protein supplements may also be high in sugar or sodium to improve the taste, so it is important to read the nutrition labels.

The Academy of Nutrition and Dietetics recommends a minimum daily protein intake of 0.8 grams (g) of protein per kilogram of body weight, or about 60 g for a person who weighs 165 pounds. People aiming to build muscle, pregnant or nursing women, and older adults may need more protein.

Animal products such as meat, eggs, and milk are naturally high in protein, which is an essential nutrient made up of amino acids. This makes it easier for people who consume animal products to meet their daily protein needs.

The human body creates 11 amino acids but must get another nine from food. Animal products are complete proteins, meaning they contain all the amino acids. Some plant products, such as soya beans and quinoa, are also complete proteins while others are incomplete proteins.

A person following a vegan or vegetarian diet should eat a varied diet of plant-based foods to get the required range of amino acids. This includes high-protein foods, such as tofu, tempeh, lentils, nuts, seeds, and quinoa.

A diet free of animal products requires planning and research to ensure a person’s nutritional needs are met. For some, this is a benefit, as it encourages them to think about their diet and understand the nutritional content of the foods they eat. For others, it can prove challenging and lead to nutritional deficits.

The Academy of Nutrition and Dietetic notes that a vegetarian or vegan diet can lower the risk of some diseases, such as certain forms of heart disease and cancer, and may promote weight loss.

A study from 2014 looked at the nutritional intakes of 1,475 people and found that people with a vegan diet consumed less saturated fat and less dietary cholesterol than those on omnivorous diets. But they also had the lowest protein, calcium, and energy intake scores. Vitamin B-12 levels were normal, possibly because people used fortified foods.

The Academy of Nutrition and Dietetics stated in 2016 that people on vegetarian or vegan diets are at a lower risk of various illnesses, including:

A study from 2017 looking at over 70,000 women found that those with a diet higher in healthful plant-based foods had a lower risk of coronary heart disease.

A vegan diet tends to be low calorie, making it easier for vegans to manage their weight. Because many processed foods are not vegan, a vegan diet may preclude many unhealthful, high-sodium prepackaged foods.

Another 2017 study found that a vegan whole foods diet could significantly reduce inflammation in people with coronary artery disease. This suggests that a vegan diet may improve heart health.

Going vegan or vegetarian requires some planning. With the right protein-based plant food, however, people who avoid animal products can eat balanced diets that support a healthy body and reduce the risks of some diseases.

It is important to discuss dietary portions with a doctor or nutritionist, since vegan or vegetarian diets may lack some vital nutrients, necessitating the use of dietary supplements or learning how to include certain foods that are high in these nutrients.

Some of the plant-based proteins listed in this article are available for purchase online.


Protein energy malnutrition

Protein energy malnutrition (PEM) describes a range of disorders occurring mainly in developing countries. It mainly affects young children and is the result of both too little energy and too little protein in the diet. The two most common forms of PEM are Marasmus and Kwashiorkor.

Marasmus is a chronic condition that occurs in young children who have been weaned off breast milk on to a diet containing too little energy and protein and is characterised by muscle wasting and an absence of subcutaneous fat. Inadequate hygiene often leads to contamination of foods which causes infections, particularly gastro-intestinal infections, and a further increase in energy requirements. The parent may treat the infection by fasting the child, giving only water or other fluids of little nutritional value. As a result, the child becomes severely underweight and very weak and lethargic.

Kwashiorkor tends to occur in slightly older children who, after an extended period of breast feeding, have been weaned onto a diet mainly comprising starchy foods, which is low in energy and protein. Kwashiorkor often follows an acute infection. A child with kwashiorkor is severely underweight but this is often masked by oedema (water retention) which makes the face moon-shaped, and the arms and legs look plump. The hair is thin and discoloured, and the skin may show patches of scaliness and variable pigmentation. Medical treatment and an adequate diet, combined with good hygiene practices, are vital if children with PEM are to recover and grow properly.


Not Enough Protein

Proteins are compounds made up of components called “amino acids.” There are about 20 common amino acids. Nine of those are considered “essential” because the body is unable to synthesize them, and therefore, they must be furnished by the food you eat.

If your diet does not provide enough of the essential amino acids, there may be serious consequences to your health.

Foods that supply all of the essential amino acids are called “complete proteins,” and are usually animal foods. Plant foods do not, as a rule, have complete proteins, but by eating combinations of plant foods, called “complementary proteins, ” you can still get a complete protein. ਌lick here for more information on incomplete protein.

Major functions of protein

-Building material for body tissues such as skin, bones, tendons, muscles, hair, nails and organs

-Maintain proper fluid balance in and out of the cells

-Promote proper pH of the body by buffering fluids

-Major component of hormones, enzymes and antibodies

-Needed for blood clotting

-Acts as transporters carrying nutrients to all parts of the body

-Provide energy and glucose for the brain when carbohydrate is unavailable for that purpose.

Severe protein deficiency is most often associated with starvation and malnutritionਊnd is a grave cause for concern in under-developed countries, especially among infants and children. Around the world, thousands of children perish every day from the effects of severe protein deficiency.

However, protein deficiency can also occur in more developed countries, where it is usually associated with those living in poverty, the elderly, or those with eating disorders, such as anorexia nervosa. Those addicted to drugs or alcohol may have a diet with not enough protein, since they often use their resources on the addictions instead of food or may suffer from poor appetite due to the effects of the drugs.

Groups most likely to suffer adverse effects from not enough protein.

--Infants and children in underdeveloped countries 

-Those around the world who live in extreme poverty

-The elderly who live by themselves

-Those with eating disorders such as anorexia nervosa, or who simply don’t eat enough

-Those addicted to drugs or alcohol, especially when combined with low income

-Those pursuing a low-protein diet for whatever reason, including fads or weight loss

-Those with tuberculosis or AIDS

-Those whose main diet is low in protein due to poor food choices, eating too much junk food

Health Problems Associated with Not Enough Protein

Protein is a vital nutrient for a healthy body. Depending on the level of protein deficiency, a person who does not eat enough protein may suffer from any of the following symptoms:

-Heart attack - wasting of heart muscle

-Inability to maintain body temperature

-Lack of growth in children

-Loss, thinning or discoloration of hair

-Malnutrition - poor absorption of nutrients

-Slow development in children

-Susceptibility to infections and disease

One form of protein deficiency is called kwashiorkor, which is associated with sudden malnutrition, such as when a mother weans one child to begin feeding another. In less developed countries or poverty stricken areas of more developed countries, the weaned child may receive a less adequate diet than when it was feeding on the nutrient-dense breast milk, resulting in not enough protein.

Kwashiorkor is often the reason for the distended bellies in those heart-wrenching photos of children that are used to encourage donations to world hunger relief organizations. The disruption of the fluid balance and a susceptibility to bacterial growth and infections and infestations, due to not enough protein causes the swollen belly. The liver may also be affected since they lack the protein to provide transporters to carry the lipids out of the liver and to synthesize the enzymes needed for liver detoxification.

Protein deficiency over a longer period of time may result in a condition called Marasmus. It's most common in infants and means that the child is literally starving to death. The distinguishing features of a child with marasmus is that they have very little flesh covering their bones and have spindly arms and legs. Due to a lack of protein, the muscles literally waste away. This muscle wasing includes the heart muscle, causing weakness and eventually even death.

If the protein deficiency is not addressed, the child will be unable to develop properly, since it will lack the basic materials needed for growth, as well as the enzymes and hormones needed for so many body processes. Protein deficiency can be self-perpetuating since over time, the body will be unable to digest and absorb even the protein it does get.

The effects of protein deficiency can be reversed if intervention occurs before too much damage has been done. In severe cases, it requires very careful introduction of protein into the diet, in small amounts at first, until the system is recovered sufficiently to handle larger servings.


The Power of Plant-Based Proteins

Eating more plant foods is associated with longevity and reduced risk for most chronic diseases, including heart disease and type 2 diabetes. Plant foods (such as whole grains, beans, fruits, vegetables, nuts, and seeds) are rich in health-promoting nutrients and compounds like vitamins, minerals, fiber, and phytochemicals. But plants can also be a good source of protein.

What is Protein? Proteins are found in the cells and tissues of all living things. They are chains of amino acids, molecules that are involved in a variety of biological functions. There are 20 amino acids, nine of which cannot be synthesized in the human body and must be acquired through diet. These are known as essential amino acids. Animal sources of protein (and a select few plant proteins including soy and quinoa) are considered “complete” in that they contain adequate amounts of all the essential amino acids the human body needs. Most plant foods are considered “incomplete” proteins, because they typically have low levels of, or are missing, one or more of the essential amino acids. For example, grains are low in the amino acid lysine, but have adequate methionine. Legumes (beans, lentils, chickpeas, peas, and peanuts), on the other hand, contain adequate lysine, but are low in methionine. Thus, a dietary pattern that includes both whole grains and legumes will provide a sufficient amount of all essential amino acids. Although it was once thought that complementary foods like these needed to be consumed at the same time, it is now understood that eating a variety of plant foods throughout the day can provide all the amino acids the body needs.

Most Americans get plenty of protein in their diets. “For the most part, given the foods commonly available, protein intake is not a major concern in the U.S., even if someone follows a plant-based diet,” says Alice H. Lichtenstein, DSc, director of Tufts’ HNRCA Cardiovascular Nutrition Laboratory and executive editor of Tufts Health & Nutrition Letter.

A Plant-Based Diet: Typical plant-based diets are vegetarian (which includes dairy products and eggs along with plant foods) and vegan (which eliminates all animal products, including honey), but a “plant-based” diet can also be one that simply maximizes plant food intake and reduces animal proteins.

Not all plant-based dietary patterns are equally beneficial. Researchers from Tufts University recently published a study in The Journal of Nutrition which found that plant-based dietary patterns with high levels of minimally processed plant foods (like whole grains, beans, nuts/seeds, fruits, and vegetables) were associated with lower risk of all-cause mortality, but plant-based diets with low levels of these choices were not. “The key is to make sure you follow a ‘healthy’ plant-based diet rich in minimally processed foods, not one based on refined grains and highly processed junk food,” says Lichtenstein.

Research, including a 2018 study by Nielsen and colleagues in the journal Nutrients, has shown that meals based on plant protein sources like beans are just as filling and satisfying as meals containing animal proteins. For an entirely plant-based diet, eating a wide variety of plant foods assures that essential amino acid requirements are met.

According to a 2018 report by a global information company, consumer demand for plant-based protein is growing. Fourteen percent of U.S. consumers surveyed for the report indicated regularly consuming plant-based protein sources such as tofu and veggie burgers, even though the vast majority did not consider themselves vegan or vegetarian. Choosing plant-based proteins has a dietary impact beyond protein quality. “We don’t eat a food or group of foods just to get a single nutrient (like protein),” says Lichtenstein. “Replacing animal proteins with plant foods like beans, for example, increases intake of fiber, which is generally under-consumed in the American diet.”

Besides potential health benefits, going meatless just one day a week has the potential to reduce greenhouse gas emissions and contribute to the overall health of the planet.

© FotografiaBasica | Getty Images

Plant Protein Sources: Since proteins are essential to all living things, every plant contains some protein.

Legumes (a broad category that includes all varieties of beans, lentils, chickpeas, peas, and peanuts) contain lysine, which is in short supply in many other plant foods. For those who choose to avoid or significantly reduce intake of animal foods, eating legumes daily supplies the needed amount of this amino acid. Just one half-cup serving of legumes can provide up to 10 grams of protein (along with a nice amount of fiber).

Whole Grains should not be ignored when considering dietary protein sources. Wheat, rice, corn, and oats are common grains in the American diet, but whole-grain choices like barley, buckwheat, millet, and teff, and a variety of whole wheat grains (like wheatberries, farro, and spelt ) are increasingly available options. (Whole grains are recommended because they have more beneficial components, such as fiber, minerals, and vitamins, than refined grains.)

    • Nuts and seeds provide six to 12 grams of protein per quarter cup, and make great snacks or accompaniments to plant-based meals.
    • Faux meats are becoming increasingly more available as consumers choose to eat more plant-based meals. While whole foods should be the bulk of one’s diet because they are the best source of nutrients and beneficial components like phytochemicals and fiber, meat substitutes can provide familiar tastes and textures in plant-based meals. Some meat alternatives are high in protein and may make predominantly plant-based meals more satisfying, but some are very high in sodium and even added sugar, so be sure to check the Nutrition Facts label. “One would need to assess each product on a case by case basis,” says Lichtenstein, “checking for levels of things like sodium and added sugar.” Options like tofu and tempeh are low-sodium, generally sugar-free, versatile meat replacement options.

    Animal foods, including meats, poultry, seafood, eggs, and dairy products, currently provide the bulk of Americans’ protein—and most people consume much more than they need. On the other hand, very few children or adults reach recommendations for daily servings of fruits, vegetables, whole grains, or fiber. Minimally processed plant foods that contain protein are also packaged with vitamins, minerals, fiber, and phytochemicals that are associated with a healthy diet pattern. So exchange some animal protein for plant proteins for a tasty and easy health boost.

    Increase plant-food intake to support good health by choosing plant-based proteins instead of animal proteins.

    Eat legumes (beans, lentils, chickpeas, peas, and peanuts) regularly.
    Try quinoa. This versatile choice has all the essential amino acids.
    Add edamame. These immature green soybeans are tasty sources of complete protein.
    Check the protein content of plant milks. Except for soy and pea milks, plant milks are generally low in protein.
    Include nuts and seeds. A handful a day is associated with health benefits.
    Check out meat substitutes like tofu, tempeh, and seitan.

    The Daily Value (DV) for protein, based on a 2,000 calorie diet, is 50 grams. While eggs, dairy, seafood, unprocessed meats, and poultry all provide protein, the examples below demonstrate that the DV can be reached using plant proteins alone. Round out these plant-based suggestions with fruits, vegetables, and unsweetened beverages:

    With Breakfast
    Oatmeal made from ½ cup oats 1 cup soymilk
    or
    1 slice whole grain toast with 2 tablespoons nut butter

    With Lunch
    A grain salad that includes 1 cup wheatberries and ½ cup shelled edamame beans

    With Dinner
    ½ cup quinoa or brown rice topped with a dish that includes 1 cup of beans, such as Mexican-style black beans, kidney beans in chili, or chickpeas in Indian or Mediterranean cuisine

    With Snacks
    ¼ cup of almonds
    or
    ¼ cup pumpkin seeds


    Recent advances in nano-encapsulation technologies for controlled release of biostimulants and antimicrobial agents

    2.4.2.2 Plant-based proteins

    Plant proteins such as zein, soy, and pea proteins are the most commonly used as carrier materials for nanoencapsulation and delivery of active materials. Zein protein from corn is a proline-rich storage protein ( Shewry and Casey, 2012 ). Zein is a brick-like shaped molecule, which can self-assemble into colloidal structures and encapsulate lipophilic molecules in their interiors ( Elzoghby et al., 2012 ). Due to its highly hydrophobic properties, it is applied for encapsulation and delivery of lipophilic compounds, such as essential oils, curcumin ( Zou et al., 2016 ), etc. The core active material is entrapped by various methods including electro-spinning and electro-spraying ( Gomez-Estaca et al., 2012 ), spray-drying ( Chen and Zhong, 2014 ) and super-critical fluid techniques ( Hu et al., 2012 ). Zein nanocapsules allow slow-release of water-soluble active compounds ( Xiao et al., 2011 ). The stability of zein particles in aqueous solution is improved by avoiding their aggregation, which is mainly carried out by coating them with emulsifiers, such as sodium caseinate ( Davidov-Pardo et al., 2015 ) or β-Lg ( Chen et al., 2014 ), or through adsorption of ionic polysaccharides such as pectin ( Hu et al., 2015 ) or alginate ( Hu and McClements, 2015 ) to their surfaces. In addition to zein, other cereal proteins such as wheat and barley proteins are also used as carriers for nanoencapsulation and delivery system.

    Another commonly used plant protein-based nanocarrier is pea protein. It consists of different types of globular proteins where globulins (65%) forms the major fraction, containing legumin, vicilin, and convicilin, while the minor fractions include albumins and glutelins ( Owusu-Ansah et al., 1987 ). Pea proteins with surface-active and structure-forming properties, have been used for encapsulation. The surface of pea proteins is predominantly hydrophilic and hence they show water-solubility. Pea proteins is used to form and stabilize oil-in-water nanoemulsions to generate emulsion, which leads to the generation of bioactive-loaded protein-coated lipid nanoparticle. Pea protein can also form electrostatic complexes with polysaccharides under pH conditions where the proteins and polysaccharides have opposite charges ( Gharsallaoui et al., 2012 ). These complexes increase the repulsive interactions between the lipid droplets and thus improve the stability of emulsions to aggregation ( Nesterenko et al., 2013 ). For example, lipid droplets coated by pea protein-pectin have better stability to pH changes and spray-drying as compared to capsules coated by proteins alone.

    In addition to zein and pea proteins, soy protein from soybean is also used as a coating material in nanoencapsulation. For example, soy protein has been applied for entrapment of β-carotene ( Deng, et al., 2017 ). Soy protein-based nanocapsules are produced using liquid-liquid dispersion ( Teng et al., 2012 ), cold gelation ( Zhang et al., 2012 ) and controlled thermal denaturation ( Zhu et al., 2017 ) techniques.


    The great nutrient collapse

    The atmosphere is literally changing the food we eat, for the worse. And almost nobody is paying attention.

    Irakli Loladze is a mathematician by training, but he was in a biology lab when he encountered the puzzle that would change his life. It was in 1998, and Loladze was studying for his Ph.D. at Arizona State University. Against a backdrop of glass containers glowing with bright green algae, a biologist told Loladze and a half-dozen other graduate students that scientists had discovered something mysterious about zooplankton.

    Zooplankton are microscopic animals that float in the world’s oceans and lakes, and for food they rely on algae, which are essentially tiny plants. Scientists found that they could make algae grow faster by shining more light onto them—increasing the food supply for the zooplankton, which should have flourished. But it didn’t work out that way. When the researchers shined more light on the algae, the algae grew faster, and the tiny animals had lots and lots to eat—but at a certain point they started struggling to survive. This was a paradox. More food should lead to more growth. How could more algae be a problem?

    Loladze was technically in the math department, but he loved biology and couldn’t stop thinking about this. The biologists had an idea of what was going on: The increased light was making the algae grow faster, but they ended up containing fewer of the nutrients the zooplankton needed to thrive. By speeding up their growth, the researchers had essentially turned the algae into junk food. The zooplankton had plenty to eat, but their food was less nutritious, and so they were starving.

    Loladze used his math training to help measure and explain the algae-zooplankton dynamic. He and his colleagues devised a model that captured the relationship between a food source and a grazer that depends on the food. They published that first paper in 2000. But Loladze was also captivated by a much larger question raised by the experiment: Just how far this problem might extend.

    “What struck me is that its application is wider,” Loladze recalled in an interview. Could the same problem affect grass and cows? What about rice and people? “It was kind of a watershed moment for me when I started thinking about human nutrition,” he said.

    In the outside world, the problem isn’t that plants are suddenly getting more light: It’s that for years, they’ve been getting more carbon dioxide. Plants rely on both light and carbon dioxide to grow. If shining more light results in faster-growing, less nutritious algae—junk-food algae whose ratio of sugar to nutrients was out of whack—then it seemed logical to assume that ramping up carbon dioxide might do the same. And it could also be playing out in plants all over the planet. What might that mean for the plants that people eat?

    What Loladze found is that scientists simply didn’t know. It was already well documented that CO2levels were rising in the atmosphere, but he was astonished at how little research had been done on how it affected the quality of the plants we eat. For the next 17 years, as he pursued his math career, Loladze scoured the scientific literature for any studies and data he could find. The results, as he collected them, all seemed to point in the same direction: The junk-food effect he had learned about in that Arizona lab also appeared to be occurring in fields and forests around the world. “Every leaf and every grass blade on earth makes more and more sugars as CO2 levels keep rising,” Loladze said. “We are witnessing the greatest injection of carbohydrates into the biosphere in human history―[an] injection that dilutes other nutrients in our food supply.”

    He published those findings just a few years ago, adding to the concerns of a small but increasingly worried group of researchers who are raising unsettling questions about the future of our food supply. Could carbon dioxide have an effect on human health we haven’t accounted for yet? The answer appears to be yes—and along the way, it has steered Loladze and other scientists, directly into some of the thorniest questions in their profession, including just how hard it is to do research in a field that doesn’t quite exist yet.

    IN AGRICULTURAL RESEARCH, it’s been understood for some time that many of our most important foods have been getting less nutritious. Measurements of fruits and vegetables show that their minerals, vitamin and protein content has measurably dropped over the past 50 to 70 years. Researchers have generally assumed the reason is fairly straightforward: We’ve been breeding and choosing crops for higher yields, rather than nutrition, and higher-yielding crops—whether broccoli, tomatoes, or wheat—tend to be less nutrient-packed.

    In 2004, a landmark study of fruits and vegetables found that everything from protein to calcium, iron and vitamin C had declined significantly across most garden crops since 1950. The researchers concluded this could mostly be explained by the varieties we were choosing to grow.

    Loladze and a handful of other scientists have come to suspect that’s not the whole story and that the atmosphere itself may be changing the food we eat. Plants need carbon dioxide to live like humans need oxygen. And in the increasingly polarized debate about climate science, one thing that isn’t up for debate is that the level of CO2 in the atmosphere is rising. Before the industrial revolution, the earth’s atmosphere had about 280 parts per million of carbon dioxide. Last year, the planet crossed over the 400 parts per million threshold scientists predict we will likely reach 550 parts per million within the next half-century—essentially twice the amount that was in the air when Americans started farming with tractors.

    If you’re someone who thinks about plant growth, this seems like a good thing. It has also been useful ammunition for politicians looking for reasons to worry less about the implications of climate change. Rep. Lamar Smith, a Republican who chairs the House Committee on Science, recently argued that people shouldn’t be so worried about rising CO2 levels because it’s good for plants, and what’s good for plants is good for us.

    “A higher concentration of carbon dioxide in our atmosphere would aid photosynthesis, which in turn contributes to increased plant growth,” the Texas Republican wrote. “This correlates to a greater volume of food production and better quality food.”

    But as the zooplankton experiment showed, greater volume and better quality might not go hand-in-hand. In fact, they might be inversely linked. As best scientists can tell, this is what happens: Rising CO2 revs up photosynthesis, the process that helps plants transform sunlight to food. This makes plants grow, but it also leads them to pack in more carbohydrates like glucose at the expense of other nutrients that we depend on, like protein, iron and zinc.

    In 2002, while a postdoctoral fellow at Princeton University, Loladze published a seminal research paper in Trends in Ecology and Evolution, a leading journal, arguing that rising CO2 and human nutrition were inextricably linked through a global shift in the quality of plants. In the paper, Loladze complained about the dearth of data: Among thousands of publications he had reviewed on plants and rising CO2, he found only one that looked specifically at how it affected the balance of nutrients in rice, a crop that billions of people rely on. (The paper, published in 1997, found a drop in zinc and iron.)

    Increasing carbon dioxide in the atmosphere is reducing the protein in staple crops like rice, wheat, barley and potatoes, raising unknown risks to human health in the future. | Getty Images

    Loladze’s paper was first to tie the impact of CO2 on plant quality to human nutrition. But he also raised more questions than he answered, arguing that there were fundamental holes in the research. If these nutritional shifts were happening up and down the food chain, the phenomenon needed to be measured and understood.

    Part of the problem, Loladze was finding, lay in the research world itself. Answering the question required an understanding of plant physiology, agriculture and nutrition―as well as a healthy dollop of math. He could do the math, but he was a young academic trying to establish himself, and math departments weren't especially interested in solving problems in farming and human health. Loladze struggled to get funding to generate new data and continued to obsessively collect published data from researchers across the globe. He headed to the heartland to take an assistant professor position at the University of Nebraska-Lincoln. It was a major agricultural school, which seemed like a good sign, but Loladze was still a math professor. He was told he could pursue his research interests as long as he brought in funding, but he struggled. Biology grant makers said his proposals were too math-heavy math grant makers said his proposals contained too much biology.

    “It was year after year, rejection after rejection,” he said. “It was so frustrating. I don’t think people grasp the scale of this.”

    It’s not just in the fields of math and biology that this issue has fallen through the cracks. To say that it’s little known that key crops are getting less nutritious due to rising CO2 is an understatement. It is simply not discussed in the agriculture, public health or nutrition communities. At all.

    When POLITICO contacted top nutrition experts about the growing body of research on the topic, they were almost universally perplexed and asked to see the research. One leading nutrition scientist at Johns Hopkins University said it was interesting, but admitted he didn’t know anything about it. He referred me to another expert. She said they didn’t know about the subject, either. The Academy of Nutrition and Dietetics, an association representing an army of nutrition experts across the country, connected me with Robin Foroutan, an integrative medicine nutritionist who was also not familiar with the research.

    “It’s really interesting, and you’re right, it’s not on many people’s radar,” wrote Foroutan, in an email, after being sent some papers on the topic. Foroutan said she would like to see a whole lot more data, particularly on how a subtle shift toward more carbohydrates in plants could affect public health.

    "We don't know what a minor shift in the carbohydrate ratio in the diet is ultimately going to do,” she said, noting that the overall trend toward more starch and carbohydrate consumption has been associated with an increase in diet-related disease like obesity and diabetes. "To what degree would a shift in the food system contribute to that? We can't really say.”

    Asked to comment for this story, Marion Nestle, a nutrition policy professor at New York University who’s one of the best-known nutrition experts in the country, initially expressed skepticism about the whole concept but offered to dig into a file she keeps on climate issues.

    After reviewing the evidence, she changed her tune. “I’m convinced,” she said, in an email, while also urging caution: It wasn’t clear whether CO2-driven nutrient depletion would have a meaningful impact on public health. We need to know a whole lot more, she said.

    Kristie Ebi, a researcher at the University of Washington who’s studied the intersection of climate change and global health for two decades, is one of a handful of scientists in the U.S. who is keyed into the potentially sweeping consequences of the CO2-nutrition dynamic, and brings it up in every talk she gives.

    "It's a hidden issue,” Ebi said. “The fact that my bread doesn't have the micronutrients it did 20 years ago―how would you know?"

    As Ebi sees it, the CO2-nutrition link has been slow to break through, much as it took the academic community a long time to start seriously looking at the intersection of climate and human health in general. “This is before the change,” she said. “This is what it looks like before the change."

    Soybeans growing in a field outside Lincoln, Nebraska, one of many crops whose nutrient content is shifting as a result of rising carbon dioxide levels. | Geoff Johnson for POLITICO

    LOLADZE'S EARLY PAPER raised some big questions that are difficult, but not impossible, to answer. How does rising atmospheric CO2 change how plants grow? How much of the long-term nutrient drop is caused by the atmosphere, and how much by other factors, like breeding?

    It’s also difficult, but not impossible, to run farm-scale experiments on how CO2 affects plants. Researchers use a technique that essentially turns an entire field into a lab. The current gold standard for this type of research is called a FACE experiment (for “free-air carbon dioxide enrichment”), in which researchers create large open-air structures that blow CO2 onto the plants in a given area. Small sensors keep track of the CO2 levels. When too much CO2 escapes the perimeter, the contraption puffs more into the air to keep the levels stable. Scientists can then compare those plants directly to others growing in normal air nearby.

    These experiments and others like them have shown scientists that plants change in important ways when they’re grown at elevated CO2 levels. Within the category of plants known as “C3”―which includes approximately 95 percent of plant species on earth, including ones we eat like wheat, rice, barley and potatoes―elevated CO2 has been shown to drive down important minerals like calcium, potassium, zinc and iron. The data we have, which look at how plants would respond to the kind of CO2 concentrations we may see in our lifetimes, show these important minerals drop by 8 percent, on average. The same conditions have been shown to drive down the protein content of C3 crops, in some cases significantly, with wheat and rice dropping 6 percent and 8 percent, respectively.

    Earlier this summer, a group of researchers published the first studies attempting to estimate what these shifts could mean for the global population. Plants are a crucial source of protein for people in the developing world, and by 2050, they estimate, 150 million people could be put at risk of protein deficiency, particularly in countries like India and Bangladesh. Researchers found a loss of zinc, which is particularly essential for maternal and infant health, could put 138 million people at risk. They also estimated that more than 1 billion mothers and 354 million children live in countries where dietary iron is projected to drop significantly, which could exacerbate the already widespread public health problem of anemia.

    There aren’t any projections for the United States, where we for the most part enjoy a diverse diet with no shortage of protein, but some researchers look at the growing proportion of sugars in plants and hypothesize that a systemic shift in plants could further contribute to our already alarming rates of obesity and cardiovascular disease.

    Another new and important strain of research on CO2 and plant nutrition is now coming out of the U.S. Department of Agriculture. Lewis Ziska, a plant physiologist at the Agricultural Research Service headquarters in Beltsville, Maryland, is drilling down on some of the questions that Loladze first raised 15 years ago with a number of new studies that focus on nutrition.

    Lewis Ziska, a plant physiologist with the U.S. Department of Agriculture, examines rice growing in his laboratory in Beltsville, Md. Ziska and his colleagues are conducting experiments to find out how rising carbon dioxide levels affect the nutrient profile of plants. Plant physiologist Julie Wolf harvests peppers to study changes in vitamin C, lower right. | M. Scott Mahaskey/POLITICO

    Ziska devised an experiment that eliminated the complicating factor of plant breeding: He decided to look at bee food.

    Goldenrod, a wildflower many consider a weed, is extremely important to bees. It flowers late in the season, and its pollen provides an important source of protein for bees as they head into the harshness of winter. Since goldenrod is wild and humans haven’t bred it into new strains, it hasn’t changed over time as much as, say, corn or wheat. And the Smithsonian Institution also happens to have hundreds of samples of goldenrod, dating back to 1842, in its massive historical archive—which gave Ziska and his colleagues a chance to figure out how one plant has changed over time.

    They found that the protein content of goldenrod pollen has declined by a third since the industrial revolution—and the change closely tracks with the rise in CO2. Scientists have been trying to figure out why bee populations around the world have been in decline, which threatens many crops that rely on bees for pollination. Ziska’s paper suggested that a decline in protein prior to winter could be an additional factor making it hard for bees to survive other stressors.

    Ziska worries we’re not studying all the ways CO2 affects the plants we depend on with enough urgency, especially considering the fact that retooling crops takes a long time.

    “We’re falling behind in our ability to intercede and begin to use the traditional agricultural tools, like breeding, to compensate,” he said. “Right now it can take 15 to 20 years before we get from the laboratory to the field.”

    AS LOLADZE AND others have found, tackling globe-spanning new questions that cross the boundaries of scientific fields can be difficult. There are plenty of plant physiologists researching crops, but most are dedicated to studying factors like yield and pest resistance—qualities that have nothing to do with nutrition. Math departments, as Loladze discovered, don’t exactly prioritize food research. And studying living things can be costly and slow: It takes several years and huge sums of money to get a FACE experiment to generate enough data to draw any conclusions.

    Despite these challenges, researchers are increasingly studying these questions, which means we may have more answers in the coming years. Ziska and Loladze, who now teaches math at Bryan College of Health Sciences in Lincoln, Nebraska, are collaborating with a coalition of researchers in China, Japan, Australia and elsewhere in the U.S. on a large study looking at rising CO2 and the nutritional profile of rice, one of humankind’s most important crops. Their study also includes vitamins, an important nutritional component, that to date has almost not been studied at all.

    USDA researchers also recently dug up varieties of rice, wheat and soy that USDA had saved from the 1950s and 1960s and planted them in plots around the U.S. where previous researchers had grown the same cultivars decades ago, with the aim of better understanding how today’s higher levels of CO2 affect them.

    Mathematician Irakli Loladze tosses sugar over vegetables outside his home in Lincoln Nebraska, to illustrate how the sugar content of the plants we eat is increasing as a result of rising carbon dioxide levels. Loladze was the first scientist to publish research connecting rising CO2 and changes in plant quality to human nutrition. | Geoff Johnson for POLITICO

    In a USDA research field in Maryland, researchers are running experiments on bell peppers to measure how vitamin C changes under elevated CO2. They’re also looking at coffee to see whether caffeine declines. “There are lots of questions,” Ziska said as he showed me around his research campus in Beltsville. “We’re just putting our toe in the water.”

    Ziska is part of a small band of researchers now trying to measure these changes and figure out what it means for humans. Another key figure studying this nexus is Samuel Myers, a doctor turned climate researcher at Harvard University who leads the Planetary Health Alliance, a new global effort to connect the dots between climate science and human health.

    Myers is also concerned that the research community is not more focused on understanding the CO2-nutrition dynamic, since it’s a crucial piece of a much larger picture of how such changes might ripple through ecosystems. "This is the tip of the iceberg," said Myers. "It's been hard for us to get people to understand how many questions they should have."

    In 2014, Myers and a team of other scientists published a large, data-rich study in the journal Nature that looked at key crops grown at several sites in Japan, Australia and the United States that also found rising CO2 led to a drop in protein, iron and zinc. It was the first time the issue had attracted any real media attention.

    “The public health implications of global climate change are difficult to predict, and we expect many surprises,” the researchers wrote. “The finding that raising atmospheric CO2 lowers the nutritional value of C3 crops is one such surprise that we can now better predict and prepare for.”

    The same year―in fact, on the same day―Loladze, then teaching math at the The Catholic University of Daegu in South Korea, published his own paper, the result of more than 15 years of gathering data on the same subject. It was the largest study in the world on rising CO2 and its impact on plant nutrients. Loladze likes to describe plant science as “noisy”―research-speak for cluttered with complicating data, through which it can be difficult to detect the signal you’re looking for. His new data set was finally big enough to see the signal through the noise, to detect the “hidden shift,” as he put it.

    PHOTOS: How to measure a plant

    What he found is that his 2002 theory—or, rather, the strong suspicion he had articulated back then—appeared to be borne out. Across nearly 130 varieties of plants and more than 15,000 samples collected from experiments over the past three decades, the overall concentration of minerals like calcium, magnesium, potassium, zinc and iron had dropped by 8 percent on average. The ratio of carbohydrates to minerals was going up. The plants, like the algae, were becoming junk food.

    What that means for humans―whose main food intake is plants―is only just starting to be investigated. Researchers who dive into it will have to surmount obstacles like its low profile and slow pace, and a political environment where the word “climate” is enough to derail a funding conversation. It will also require entirely new bridges to be built in the world of science―a problem that Loladze himself wryly acknowledges in his own research. When his paper was finally published in 2014, Loladze listed his grant rejections in the acknowledgements.

    Helena Bottemiller Evich is a senior food and agriculture reporter for POLITICO Pro.


    Watch the video: Plant Evolution and Adaptations (December 2022).