They are a type of survival tactic used by plants to defend against fungi, bacteria, parasites, and insects - they taste bitter, and the seeds are indigestible leading to animals avoiding them. Edible anti-nutrients naturally occur in whole grains and legumes.
Studies show that anti-nutrients are not unsafe in actuality unless consumed in very high amounts, which is very unlikely as processing and cooking of food decreases anti-nutrients by a large proportion.
They also have various health benefits. Like how dietary fiber was once thought to be bad for our health at first but later turned out to be incredibly important, anti-nutrients are also turning heads. Now they are considered to be functional foods and health-promoting nutraceuticals. Some of the most frequently eaten anti-nutrients and their benefits are :-
Saponins - commonly present in legumes, they can boost our immune system, reduce the risks for kidney stones and cancer, lower our blood sugar, cavities and cholesterol and fight blood clots from heart attacks and strokes.
Tannins - commonly present in caffeinated products like tea and coffee, cheeses, and processed meats, they are antioxidants that prevent the growth of fungi, bacteria, viruses, and yeast and may also reduce cholesterol and blood pressure.
Lectins - commonly present in grains, legumes and cereals, they reduce the risks of diabetes, some cancers, obesity, and cardiovascular diseases.
Glucosinates - commonly present in brassica vegetables, they prevent tumor cell growth.
Phylates - commonly present in wheat, corn, rice, and barley, they may increase immune function and prevent cancer cell growth and spread by causing cancer cell death. They can also reduce inflammation because of their antioxidant properties.
Oxalates are found in common foods like legumes, beets, berries, etc., and mostly have a negative impact on the body - increase the risk of kidney stones, binding calcium in the digestive tract, and removing it from the body.
Since vegetarian and vegan diets rely heavily on fruits, whole grains, legumes, and vegetables, they may provide a higher risk of negative effects from anti-nutrients. But since these diets are also associated with various health benefits, in this case, the good outweighs the bad.
Taking steps like pairing high iron and zinc foods with foods high in Vitamin C, soaking legumes before cooking, avoiding the pairing of dairy victims with high oxalate foods, buy dairy products fortified with calcium, and take multivitamin supplements with 100% daily recommended dose of nutrients.