A plant-based diet is vital to reduce the risk of various chronic diseases due to the presence of phytochemicals that possess strong antioxidant activity and help reduce inflammation. Despite the increased consumption of fruits and vegetables, there have been some concerns related to 'anti-nutrients' in them. So, what are they?
What Are Anti-Nutrients?
Anti-nutrients are naturally-occurring compounds found in plants that interfere with the absorption of nutrients in the digestive system. Some of the anti-nutrients that have been questioned in spite of their health benefits include lectin, phytates, phytic acid, tannins, goitrogens, oxalates and cyanogenic glycosides.
For example, phytic acid is found in varieties of cereals, grains, nuts, seeds and legumes; cyanogenic glycosides in cassava; oxalates and oxalic acid in the spinach family, and glucosinolates in broccoli, cabbage and cauliflower.
Phytic acid has a strong binding affinity for iron, copper, calcium, zinc and magnesium; oxalic acid for calcium, and glucosinolates for iodine and flavonoids.
The aforementioned anti-nutrients, though having essential functions in the body, bind the vital minerals from plant-based sources and reduce their absorption, which results in the deprivation of the vital nutrients in the body. [1]
Therefore, foods rich in anti-nutrients such as lectins, phytic acid, oxalate and many others should be consumed in a limited amount and in certain ways, so as to get their vital nutrients without any harmful impact on the body.
Examples Of Anti-Nutrients, Food Sources And How To Reduce Their Effect
1. Lectins
Plant-based foods contain around 500 different types of lectins which may primarily help in boosting immunity and creating defence mechanism against pathogens such as moulds, insects, fungi and diseases. [2]
Food sources: Seeds, legumes, fruits, nuts, cereal grains and vegetables
Binds to: Carbohydrates
Can cause conditions: inflammation and problems in intestinal functions
Food preparation that reduces: Soaking, fermentation, boiling and germination
Food preparation that increases: Roasting and baking
2. Phytic acid or Phytates
Salts of phytic acids are called phytates. Phytic acid is ideal for skin-related problems such as acne, pores, blackheads, inflammation and dry skin. It is also known for its antioxidative effects. [3]
Food sources: Wheat, barley, maize, gram, rice, soybean, sesame, cottonseed and groundnut
Binds to: Calcium, iron, zinc, magnesium and copper
Can cause conditions: May inhibit the absorption of the aforementioned nutrients, cause oxidative stress and increase the risk of tumours.
Food preparation that reduces: Soaking, germination, boiling and fermentation
Food preparation that increases: Not available
3. Oxalates
Oxalates or oxalic acid are insoluble salts packed with minerals such as potassium, sodium, magnesium, iron and calcium. People with kidney stones should limit the intake of oxalate-rich foods, however, healthy people should not avoid an oxalate diet as those foods are also rich in other vital nutrients.
Food sources: Spinach, beetroot, sweet potatoes, swiss chard, turnips, raw legumes (lentils, peas and beans), raw whole grains, nuts (peanuts and almonds) and many leafy vegetables.
Binds to: Calcium
Can cause conditions: Calcium kidney stones
Food preparation that reduces: Soaking, steaming, boiling and combining oxalate-rich foods with high calcium foods
Food preparation that increases: Grilling, roasting, baking and low calcium-rich foods.
4. Saponins
Saponins are bitter-taste anti-nutrients but are also vital for several body functions. They help boost the immune system, reduce the risk of cancer, lower cholesterol levels and manage diabetes.
Food sources: Quinoa, kidney beans, lentils, onion, garlic, tea, yam and spinach.
Binds to: Iron
Can cause conditions: Leaky gut syndrome and dysfunction of epithelial cells that perform a variety of functions such as protection, absorption, secretion and excretion.
Food preparation that reduces: Washing until no or little foam is left and abrasive dehulling (a process of removing hulls from seeds.
Food preparation that increases: Not washing before cooking or not removing the hulls.
5. Goitrogens or Glucosinolates
They are not necessarily harmful to individuals who have healthy thyroid functions. These people can consume foods containing goitrogens as they are also rich in other vital nutrients with health-promoting benefits. [4]
Food sources: Vegetables of Brassica genus such as kale, brussels sprout, broccoli, cabbage, cassava and millets.
Binds to: Iodine
Can cause conditions: Deficiency of iodine leading to goitre and hypothyroidism.
Food preparation that reduces: Steaming and boiling
Food preparation that increases: Not available
6. Tannins
They are responsible for the astringent taste of many food items. Tannins are known to be strong antioxidants along with other properties such as immunomodulatory, cardioprotective and anticarcinogenic.
Food sources: Wines, tea, black grapes, nuts, cocoa beans, dark chocolates, apples, cherries, peaches, walnuts, pecans, red kidney beans and apples.
Binds to: Iron
Can cause conditions: Anaemia and irregular heartbeat due to deficiency of iron.
Food preparation that reduces: Peeling of the fruits and nuts and cooking.
Food preparation that increases: Eating without peeling the skin.
Other Anti-Nutrients
- Protease inhibitors that prevent the absorption of pepsin, trypsin and protease. [5]
- Amylase inhibits that prevent the absorption of starch and complex carbohydrates by impairing the action of enzymes that break them into their simpler forms.
- Lipase inhibitors that disturb the functioning of enzymes that helps with catalysing cholesterol and fats.
- Cyanogenic glycosides that help resist pests and diseases in plants but can release hydrogen cyanide upon chewing.
To Conclude
Anti-nutrients are part of almost all fruits, vegetables, nuts, seeds, whole grains, legumes and other foods. They may interfere with the absorption of certain nutrients but it does not mean to avoid those foods completely, as they are also packed with other vital phytoestrogens, phytochemicals and antioxidants.
Traditional methods such as soaking, cooking, washing, germinating and fermentation can reduce the number of anti-nutrients from toxic levels to non-toxic levels. Also, people who eat high plant-based foods generally do not show a deficiency of any vital nutrients such as iron and zinc as their body adapts to the presence of anti-nutrients and don't interfere much with the absorption of nutrients.
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