ANTI-NUTRIENTS: ARE THEY REAL AND HOW HARMFUL ARE THE EFFECTS?

Everyone consumes antinutrients on a daily basis and excessive amounts may detract from health.

The below discussion summarizes potential dangers of antinutrients, who is at the highest risk and how dietary antinutrients can be reduced or neutralized.

What Are Anti-Nutrients?

Anti-nutrients are any components of food which counter the actions of nutrients. Some of them prevent nutrient uptake or utilization; while other anti-nutrients promote inflammation and damage, depleting nutrient reserves in the process. Anti-nutrients may be classified alongside other nutrients or as toxins.

They are found in many foods, including a variety of both plant and animal products. In plants, anti-nutrients are produced as a form of protection that prevents the plant from being eaten or getting infected.^[1]

Consuming a food with a high concentration of an anti-nutrient usually is not harmful, unless the food is consumed all the time or specifically contraindicated for a health condition. The levels of anti-nutrients in any given food form a ratio with the food’s nutrient levels. Just like anti-nutrients detract from the actions of nutrients, so too do nutrients detract from the actions of anti-nutrients.

Are There Benefits to Consuming Anti-Nutrients?

Yes, depending on the anti-nutrient in question and the context. The harmful actions of an anti-nutrient may be a benefit to an organism requiring it. For example, inhibiting the uptake of a nutrient can be a good thing if one has excessive levels of the nutrient. Furthermore, some anti-nutrients have been reported to act as antioxidants under certain conditions, serving dual purposes.

While the above is true, long-term consumption of an anti-nutrient-rich diet is not recommended, as nutritional deficiencies are usually the outcome.

10 Types of Anti-Nutrients & Their Anti-Nutritional Properties

The deleterious effects of anti-nutrients are often unique to the compound in question, and depend on the ratio of nutrients in the food.

The following anti-nutrients are known to contribute towards various states of disease when overly consumed:

1. Lectins

Lectins (also known as phyto-hemagglutinins) are glycoproteins that bind to carbohydrates and are found in many plant foods. Plants adapted to produce lectins to make them resistant to digestion and decomposition. This typically prolongs the survivability of the plant species, allowing for seeds to be a lot hardier and sprout when the conditions are suitable. 

Depending on the individual and the concentration, lectins may prevent nutrient uptake and trigger gut inflammation when they are unable to be properly broken down. This is due to the ability of lectins to bind to membrane components of cells in the gut and interfere with bacterial growth.^[2] Lectins are known to enhance the severity of digestive disorders, allergies, sensitivities and intolerances, rheumatoid arthritis and autoimmune kidney disease.^[3]

Nonetheless, lectins are typically consumed in small, harmless quantities, alongside many other nutrients. Improper preparation of lectins can however lead to lectin poisoning. Preparation reduces lectin count, while dietary nutrients can help to counter the effect of dietary lectins.

The rinds and seeds of a plant contain the highest amount of lectin, with some plant species being more lectin-heavy than others. Seeds, cereal grains, peanuts and legumes are considered lectin-heavy foods. The lectin content decreases after removing the husks, sprouting, soaking, or cooking.

2. Gossypol

Gossypol is an aldehyde that is derived from the cotton plant. It is a toxic yellow pigment that the plant produces in order to deter predators.

Potential toxic effects of gossypol include inhibiting a variety of enzymes, disrupting calcium transport at the cellular level and interfering with cell-to-cell communication^[4]. Animal studies suggest that acute Gossypol poisoning encourages infertility, respiratory distress, severe muscle wasting, weakness, apathy and in the worst cases, fatality. Too much dietary gossypol can suppress immune function, resulting in increased susceptibility to infection.^[5]

As the effects of gossypol are known to be toxic in high concentrations, cotton is grown in such a way that discourages gossypol formation. While cotton is mostly used to make fabric, cottonseed oil is extracted and used in a variety of foods. Cottonseed oil contains a much higher concentration of gossypol than would cotton fabric. It is advisable to limit one’s intake of gossypol in light of the side effects.

3. Goitrogens

Goitrogens are any chemical compounds that detract from thyroid function and promote thyroid disease, often by blocking iodine uptake. Most goitrogens tend to promote the risk of hypothyroidism, however they may also promote hyperthyroidism risk.

Examples of goitrogens in foods include^[6]:

• Glucosinolates compete with iodine uptake into the thyroid. Found in mustard, cruciferous vegetables, turnips and rapeseed.
• Cyanogenic Glucosides form thiocyanates, which also compete with iodine uptake. Found in various foods, including lima beans, linseed, sorghum, sweet potato and cassava.
• Flavonoids in soy and millet impair thyroid peroxidase activity, which inhibits the utilization of thyroid hormones. This may increase the risk for hyperthyroidism.

Deficiencies in selenium, iron, iodine and vitamin A may make the effects of goitrogens worse by similarly affecting thyroid function.

In spite of having a bad rap as goitrogens, glucosinolates and glucosides are metabolized into a variety of compounds, some of which are beneficial for health. Furthermore, cooking and boiling can reduce the content of these groitrogens in food by more than 50%.

4. Phytates

Phytates are forms of phytic acid, which also goes by the name of myo-inositol hexaphosphate (IP6). It is produced by plants and found in seeds, serving as a source of phosphate for energy requirements. These compounds readily bind to positively charged minerals, such as Ca2+ (calcium), Cu2+ (copper), Fe3+ (iron) and Zn2+ (zinc), inhibiting their absorption during digestion.

In some instances, phytate may be beneficial for chelating excess iron, which is known to contribute towards chronic low-grade inflammation. In heme-rich foods, such as animal meat products, phytates can help to offset the negative effects of excessive iron consumption. Other studies suggest phytates may reduce the risk of type 2 diabetes by lowering the levels of Advanced Glycation End-Products (AGEs) in diabetics^[7].

Legumes, cereal grains and seeds contain the highest amounts of phytate, with levels varying depending on growing conditions and the cultivar used. Germination, fermentation, and soaking, all reduce the phytate content of these foods by using the natural enzymes they contain (phytases). Cooking and processing may also reduce the phytate content, however it is still advisable to sprout, soak or ferment phytate-heavy foods beforehand. Vitamin C-rich foods may offset mineral chelating properties of phytates, as can increasing one’s mineral intake.

5. Tannins

Tannins are a broad class of plant-based chemicals with a high molecular weight that are found in many foods. These include herbal teas, nuts, seeds, legumes, coffee, wine, chocolate, brightly-colored fruits, and cereal grains.

Hydrolysable tannins consist of gallotannins and ellagitannins, while condensed tannins comprise proanthocyanidins. These compounds give food items an assortment of astringent flavors and bright coloring, including red, orange, blue and purple.

Like phytates, tannins display both beneficial and anti-nutritional properties. On the one hand, they are potent antioxidants and on the other hand, they may lower mineral absorption by chelating a wide variety of minerals.

Many studies illustrate the beneficial effects of tannins in promoting health, with the negative effects being pronounced in those with deficiencies or who consume nutrient deficient diets. High levels of tannins should not be consumed by those with anemia caused by iron deficiency or those who are severely deficient in other minerals.

6. Oxalates

Oxalates are forms of oxalic acid which bind with minerals to form insoluble salts. Animals, plants and photosynthetic organisms, like algae, produce oxalates endogenously. It is suspected that plants produce oxalates in order to chelate heavy metals, protect themselves from predators and to regulate calcium.

Dietary oxalates are known to deplete mineral and nutrient absorption by binding to nutrients in food. If oxalates are absorbed in the gut, they may contribute towards oxalate kidney stone formation as well as joint pain and stiffness. Those prone tend to eat a diet high in oxalate and absorb more than 10% of the oxalates they consume.

Soluble oxalates are a lot more damaging than insoluble oxalates. Foods high in oxalates include: herbal teas, spinach, chard, sweet potatoes, taro, amaranth, rhubarb, beets, sorrel, soybeans and other legumes. Roasting, baking and grilling can increase the oxalate content; while soaking, autoclaving (canning and bottling), boiling and steaming reduced oxalate levels. Additionally, dietary calcium can bind to and decrease the soluble oxalate content. Potassium, magnesium and phytate may all participate in reducing the risk of kidney stone formation.

7. Enzyme Inhibitors

Many foods contain enzymes as well as enzyme inhibitors. Enzyme inhibitors typically block the actions of digestive enzymes, which promotes improper digestion and reduced nutrient absorption. Legumes, seeds and cereal grains generally carry enzyme inhibitors to prevent digestive enzymes from breaking them down in the digestive tracts of animals that consume them.

Well-studied dietary enzyme inhibitors include^[8]:

• Protease inhibitors block protein-degrading enzymes in cells. This interferes with a number of cellular functions for which proteases are required. Common symptoms of excessive protease inhibition include a swollen or enlarged pancreas, growth inhibition, improper digestion and nutritional deficiencies. As a high consumption of protease inhibitors is associated with an increase in pancreatic enzyme release, it may contribute towards insulin resistance in susceptible individuals.
• Alpha-amylase inhibitors block the actions of alpha-amylase, a main ingredient in saliva that helps to break food down, particularly carbohydrates. Alpha-amylase inhibitors lower insulin levels, restrict carbohydrate digestion and protect against dental cavities. This in excess may result in digestive complaints.
• Trypsin inhibitors block the action of trypsin, a pancreatic digestive enzyme that facilitates optimal protein digestion. Legumes are known to have higher quantities of trypsin inhibitors than other foods^[9], alongside nightshade family foods.
• Saponins are sugar metabolites of glucosides that may inhibit various digestive enzymes, as well as bind to and prevent absorption of trace minerals. This in turn interferes with glucose uptake, protein digestion and may promote gut inflammation and permeability. They are also known to lower cholesterol levels, which may not always be beneficial.

Hidden Anti-Nutrients

The below are some unexpected sources of dietary anti-nutrients:

8. Nutrients

Some nutrients may become anti-nutrients in the wrong forms and at the wrong concentrations. Whether a nutrient can be considered an anti-nutrient or not also depends on the person consuming the nutrient. Some nutrients may be useful in disease prevention while others may contribute towards pathology. ^[10] Moreover, an excessively consumed nutrient that competes with a deficient nutrient and inhibits its uptake may be considered an anti-nutrient.

9. Bacterial Metabolites

There is a very complex interplay between our gut microbes, the components in our food and the products they go on to make from that food. Bacteria may metabolize anti-nutrients and lessen their toxicity, however they may also increase absorption of the anti-nutrient. The by-products they make from a nutrient or anti-nutrient may be toxic as well.

Some toxins are only transiently produced before being transformed into another potentially beneficial product. The ability of the gut to tolerate anti-nutrients depends on digestive function, the diet and the ratio of bacteria in the gut. This is a prime reason why bacterial diversity is very important for optimal digestive function.

10. Refinement and Oxidized By-products

Heating and other food refining techniques, such as alkalization, can generate oxidized by-products in food which act as antinutrients. Alongside an increase in antinutrients, these techniques also tend to lower the nutrient content of the foods in question.

Examples include oxidized sulfur amino acids, D-amino acids and other harmful amino acid derivatives, such as lysinoalanine. In animal studies, Lysoalanine and D-amino acids proved to be poorly digestible and impaired the breakdown of other proteins in the gut by as much as 28%^[11].

Who is at the Most Risk for Anti-Nutrient Toxicity?

As many common antinutrients reduce protein digestion and absorption as well as increase gut inflammation; they may promote disease risk or severity.

Antinutrients may be more of a risk for individuals with the following health conditions:

• Hypothyroidism
• Hormonal Imbalances
• Autoimmunity
• Cancer
• Arthritis
• Kidney Disease
• Severe nutritional deficiency diseases, such as Beriberi

The elderly appear to be more susceptible to the side effects of overconsuming anti-nutrients than younger individuals.

4 Tips for Working with Dietary Anti-Nutrients

As dietary antinutrients are present in trace amounts in almost all foods, consuming them does not tend to be immediately harmful for most individuals. However, long-term consumption of a diet high in antinutrients can detract from general well-being.

The following tips can help to reduce the antinutrient content of one’s diet, promoting optimal health.

1. Consume a Nutritionally-Balanced Diet

A nutritionally balanced diet is able to counter many of the potential effects dietary antinutrients pose.^[12] 

In general, nightshade family foods, legumes, cereal grains and seeds have the highest quantities of antinutrients. One can balance the intake of these foods by consuming a higher amount of nutritious whole fruits and vegetables. Fruits and vegetables will also improve the digestibility of these foods, improving overall nutritional status. These foods are also associated with overall health.^[13]

Minerals are another important dietary component to consider when balancing a diet. Moderate intake of potassium, phosphorus, calcium, magnesium, and zinc can all help to counter dietary antinutrients and regulate digestive function.

2. Food Preparation

Depending on the way in which food is processed, anti-nutrients may be formed or reduced during food refinement. Cooking can serve to lower both the nutritional and anti-nutritional content of foods.

Boiling, steaming or soaking tends to reduce many types of anti-nutrients in food. Phytates and lectins may be reduced through germination or fermentation. Tannins are reduced in cooking, peeling, and deshelling. Roasting, grilling, and baking may increase the concentration of lectins and oxalates in food.

3. Probiotics and Fermentation

Increased gut permeability, as well as impaired fat and calcium metabolism can increase the absorption of dietary oxalates and many other anti-nutrients. The gut microbiome can help to regulate intestinal permeability^[14], increase nutrient uptake^[15] and enhance the inert excretion of antinutrients.

Gut microbes, particularly oxalobacter subspecies, are able to degrade oxalates and may help to regulate oxalate metabolism and excretion^{[16] [17]}. Vegetarians that consume many foods rich in oxalates have been shown to have a reduced risk of oxalate-associated disease states. Some studies suggest that vegetarians have a higher proportion of oxalobacter in their guts that help them to process oxalates.

While probiotics made using oxalobacter seem promising, human trials have shown them to be ineffective. Instead, optimizing gut health, increasing nutrient content and consuming a variety of prebiotic foods with oxalate in them (e.g. herbal tea, leafy greens) can help to increase gut oxalobacter counts.

Lactobacillus and Bifidobacterium bacteria are also able to degrade oxalates alongside a whole host of other anti-nutrients. Moreover, these particular strains tend to produce nutrients we need when a wide diversity of them are present^[18]. As many modern exposures, such as antibiotics and detergents, can detract from the gut microbiome, probiotic foods are essential for offsetting the anti-nutritional components of the diet.

Probiotic foods should be consumed alongside prebiotics and in moderation, particularly by someone with increased gut permeability.

4. Prebiotics and Dietary Enzymes

Prebiotic foods promote optimal probiotic bacterial growth^[19] and consist of foods high in water-soluble fiber^[20], probiotic-promoting nutrients, digestive enzymes and mucilaginous substances. Brightly colored fruits tend to be some of the most prebiotic foods, as well as high-fiber vegetables like celery, spinach and onion family foods.

Bitter tasting foods are also able to enhance the production of digestive enzymes in the gut^[21]. The trillions of bacteria in the gut rely on digestive enzymes in order to facilitate optimal nutrient uptake. Food breaks down in the upper portion of the tract making it digestible to colonic bacteria. Digestive enzymes help create the right pH for the right bacterial species to populate the colon. ^{[22] [23] [24]}

Mucilagenous foods are any foods that produce a prebiotic mucous, including chia seeds and flaxseeds that have been soaked. This mucilaginous layer feeds probiotic bacteria and provides an optimal substrate for growth in a similar way to water-soluble fiber. ^[25]

Conclusion

The long-term effects of consuming a diet deficient in nutrients or high in antinutrients may promote various states of disease. Nonetheless, while excess anti-nutrients can detract from one’s well-being, the human body is well-equipped at handling them at the small amounts present in a healthy, balanced diet.

Consuming nutrient-dense foods and moderating foods high in antinutrients is conducive to optimal health. Foods high in the most harmful antinutrients include processed food, raw legumes, cereal grains and nightshade family produce. Antinutrients in herbal teas, fruits and other types of vegetables are often negligible, with nutrients to counteract any negative effects.

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