Anti-amino acids and anti-enzymes
Raw foods often contain substances that hinder normal protein digestion. For instance, legumes, grains, and egg white contain anti-enzymes that block the action of trypsin, chymotrypsin, and amylase. To eliminate their negative effects, it is sufficient to subject the food to heat treatment.
Another issue arises from improper culinary processing. If foods rich in sugars are heated for a long time together with sources of lysine (an essential amino acid), fructosyllysine is formed—a compound the body cannot absorb. An excess of certain amino acids can also interfere with the absorption of others: for example, excessive consumption of millet, which is rich in leucine, reduces tryptophan absorption.
Vitamin destroyers
Many vitamins are sensitive to specific anti-nutritional factors that destroy them or convert them into an inactive form:
- Vitamin C (ascorbic acid): destroyed by enzymes (ascorbate oxidase, peroxidase) when slicing vegetables and fruits. In greens, it also suffers from contact with chlorophyll in a slightly acidic environment. The solution is blanching vegetables before slicing or consuming them whole.
- Vitamin B1 (thiamine): inactivated by the enzyme thiaminase (in raw river fish) and bioflavonoids when consuming excess tea and coffee. Prolonged heating of acidic fruits leads to the formation of oxythiamine.
- Vitamin B7 (biotin): bound by the protein avidin from raw egg white. Heat treatment denatures avidin, releasing the vitamin.
- Vitamin PP (niacin): less absorbed on a monotonous diet based on corn due to the presence of indoleacetic acid.
- Vitamin A (retinol): destroyed by hydrogenated and prolonged heated fats (e.g., during frying or excess margarine).
- Vitamin E: its absorption drops with excessive consumption of vegetable oils rich in polyunsaturated fatty acids.
Demineralizing agents
Certain food components bind macro- and microelements, preventing their absorption in the gastrointestinal tract:
- Calcium: its absorption is hindered by oxalic acid (spinach, sorrel, rhubarb) and an excess of phosphorus in the diet. To compensate, one should consume more dairy products.
- Iron: dietary fiber (dark bread, vegetables) and tannins (tea) reduce its absorption. It is recommended to increase the proportion of heme iron from meat and combine it with vitamin C.
- Magnesium, calcium, and sodium: their absorption drops with excessive coffee consumption due to the action of caffeine.
- Iodine: sulfur-containing compounds (goitrogens) present in cruciferous vegetables (cabbage, radish) may exacerbate iodine deficiency.
Biologically active substances (BAS)
Unlike anti-nutritional factors, BAS exert a pronounced positive physiological effect.
A special place is occupied by polyphenols, which are concentrated in the dark-colored skins of berries and fruits. These include flavonoids, anthocyanins, catechins, quercetin, and resveratrol. Foods also contain alkaloids, glycosides, and biogenic amines.
These compounds strengthen the cardiovascular system, slow down cellular aging, and inhibit oncological processes.
Briefly: answers to topical questions
Which substances reduce iron absorption in the gastrointestinal tract?
Iron absorption in the gastrointestinal tract is reduced by ballast substances and tannins.
- Ballast substances (dietary fiber)—their negative impact manifests with excessive consumption of dark bread, grains, vegetables, and fruits.
- Tannins—prevent mineral absorption when tea is consumed in excess.
To improve iron absorption and eliminate the harmful effects of these factors, it is recommended to increase the intake of heme iron (meat, fish) and ascorbic acid, as well as to consume tea in moderation.
What is the mechanism of the antithyroid action of cruciferous goitrogens?
The mechanism of action of goitrogens lies in reducing the body's absorption of iodine.
- Sulfur-containing compounds (goitrogens)—prevent iodine absorption when cruciferous vegetables (white cabbage, cauliflower, kohlrabi, radish, turnip, black radish) and peanuts are consumed in excess.
To eliminate the harmful effects of these anti-nutritional factors, it is recommended to limit the consumption of the listed foods in cases of background iodine deficiency in the diet.
What compounds are formed during the Maillard reaction between sugars and amino acids upon heating?
When sugars and lysine are heated together, fructosyllysine is formed—a compound poorly absorbed by the body. Anti-amino acids block the absorption of amino acids, predominantly lysine. To reduce the harmful effect, proper food combination and gentle heat treatment are recommended.
What substances prevent the absorption of calcium from food?
Calcium absorption from food is hindered by demineralizing agents, excess phosphorus, and caffeine.
- Oxalic acid—reduces absorption with excessive consumption of sorrel, spinach, rhubarb, figs, blueberries, and potatoes.
- Excess phosphorus—disrupts the calcium-phosphorus ratio as it is found in most foods.
- Caffeine—prevents mineral absorption when coffee is consumed in excess.
To correct the diet in case of excess oxalic acid, increasing the proportion of sources of readily available calcium (milk, cottage cheese, cheese) is recommended, and in case of excess caffeine, moderate coffee consumption.
Class and exam questions
Why is it impossible to eat exclusively raw food (raw veganism)?
Raw foods, especially legumes and grains, retain anti-enzymes that block digestion, while raw fish and eggs contain vitamin-destroying substances (thiaminase and avidin).
How to preserve vitamin C when cooking?
Vegetables and greens are best used whole or blanched before slicing to destroy oxidizing enzymes.
Why is cabbage consumption restricted in iodine deficiency?
Cruciferous vegetables contain sulfur-containing compounds (goitrogens) that prevent the normal absorption of iodine by the body.
What else to study on this topic
- Mechanisms of avidin denaturation during thermal processing
- Balance of the calcium-phosphorus ratio in the diet
- The role of heme iron and ascorbic acid in trace element absorption
- Biochemical properties of polyphenols and flavonoids
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