Carbs, protein, fat, minerals and vitamins are the major topics focussed on in the food world. But what about those nutrients that are present and are not reflected on food labels?
Anti-nutrients are plant-based compounds that inhibit the body’s ability to use nutrients that are essential for health. There are certain claims that lectin, a compound found in tomatoes and peppers, is the major cause for the auto immune disorders, heart diseases and diabetes (1). These claims need thought since vegetables are also proven to be cardio protective from several long-term robust studies. The research to prove the detrimental effects of anti-nutrients is very thin. Understanding the hysteria will help you take thoughtful and informed decisions in choosing a balanced diet, which could lessen the effects of anti-nutrients. They are of two types depending on their response to heat: 

• Heat stable – which can be maintained at high temperatures. This group includes phytic acid, poly-phenolic compounds like tannins, alkaloids, saponins, non-protein amino acids etc.
• Heat liable – those can be destroyed in high temperatures. This includes lectins, cyanogenic glycosides, protease inhibitors and toxic amino acids.

On the basis of the origin, the anti-nutritional factors are classified into 4 categories:

• Proteins: These include protease inhibitors 
• Glycosides: goitrogens 
• Phenolic compounds include tannins
• Other notable anti-nutrients are anti minerals like phytates or phytic acid

Effects of anti-nutrients on the body

• Phytates – Commonly found in beans, nuts, grains and seeds. They reduce the calcium and iron absorption.
• Oxalates – typically found in leafy greens, cocoa, fruits, nuts and seeds. They reduce calcium absorption and increases the risk of kidney stone formation when taken in excess as they bind with calcium.
• Cyanide – found in minute amounts in bitter almonds, seeds of apple, apricots and peaches. They act as respiratory inhibitors.
• Lectins (hemagglutinins) – found in beans, peanuts, lentils, tomatoes, potatoes, brinjal, fruits and wheat. They prevent the absorption of digestive end products in the small intestine.
• Protease inhibitors – are universally seen in tubers especially from Solanaceae family. They reduce protein digestion.
• Phenol compounds – they are found in plants, vegetables, chocolate, legumes and in beverages like tea, coffee, wine etc. they reduce the bioavailability of minerals like zinc. Tannins are usually heat stable.
• Saponins – they are foam producing compounds present in legumes like chickpeas, lentils, kidney beans etc. Saponins bind to various nutrients inhibiting our ability to use them. Digestive enzymes have been shown to be inhibited by saponins causing a decrease in protein digestibility and absorption. They only pose as a problem when consumed in very large quantities over a period of time.
• Oestrogens – seen in the form of isoflavons in soyabeans, and phtosterols in wheat, rice, chickpeas, groundnuts. They can cause growth inhibition, elevated levels of zinc in liver and bones and also causes increased deposition of calcium, phosphorus and magnesium in bones which can be alarming in rare cases.
• Glycosides or goitrogens – found in cruciferous vegetables and soy beans can cause the inhibition of thyroid absorption leading to abnormal growth of thyroid gland.

How to combat with anti-nutritional factors present in food: 

• Washing and straining the water used for soaking can reduce the cyanogen and saponins from the legumes.
• Boiling food can reduce the amounts of protease inhibitors. 
• Dry or moist heat cooking can inactivate the oestrogen and goitrogens activity in food.
• For the anti-nutrients like tannins which are heat stable, its best to avoid consumption of them with any other food group to avoid nutrient mal absorption. It is advised to give a gap of 60 mins before or after consumption of meals to take beverages present in tannins.
• Pressure cooking is effective in reducing the anti-nutritional factors from legumes.
• Blanching and cooking reduce the amounts of oxalic acid, phytic acid and polyphenol contents in leafy greens.
• Blanching and sprouting reduce the anti-nutrients in grains.
• Germination or fermentation of foods can improve the bioavailability of vitamins and minerals.
• Most of the toxic effects of the foods can be removed by day to day cooking methods like soaking, boiling, pressure cooking, blanching, fermenting.

Overall, including a balanced diet can keep you safe from anti-nutrients. Also, including a variety of foods helps ensures you get different kinds of nutrients in your diet and keeps you away from nutrient deficiencies while improving your overall health. 

References:
https://www.cookinglight.com/news/what-is-plant-paradox-lectin-free-diet
https://www.outsideonline.com/2327191/are-antinutrients-hurting-your-diet#close
https://www.outsideonline.com/2327191/are-antinutrients-hurting-your-diet
https://www.sciencedirect.com/topics/food-science/antinutrients
https://www.mdlinx.com/internal-medicine/article/4138
https://blog.daveasprey.com/4-top-antinutrients-to-avoid-and-why/
https://www.everydayhealth.com/columns/johannah-sakimura-nutrition-sleuth/antinutrients-are-nothing-to-fear/
https://www.healthline.com/nutrition/how-to-reduce-antinutrients
https://www.researchgate.net/publication/325651452_ANTINUTRITIONAL_FACTORS_IN_FOODS/link/5b1a8f56a6fdcca67b670631/download