Antinutrients

What are antinutrients?

Antinutrients are defined as natural or synthetic compounds that inhibit the absorption of nutrients and thus prevent their utilization ^[1,4].

Antinutrients that may have practical importance occur mainly in plant foods, especially in the hulls of cereal grains (bran), legumes and tea.

Food processing, such as fermentation, germination, malting, soaking and cooking can greatly reduce the amount of antinutrients in foods ^[2,3,5].

Antinutrients Examples

• Inhibitors of digestive enzymes, which prevent the digestion and hence absorption of certain nutrients:
  • Phytates from whole grain cereals and legumes can reduce digestibility of proteins and carbohydrates ^[4,21].
  • Carb blockers:
    • Alpha-glucosidase inhibitors inhibit the digestion of carbohydrates; acarbose is used as a glucose-lowering drug in diabetes mellitus ^[20].
    • Amylase inhibitors, such as white bean extract, inhibit the digestion of carbohydrates, so they may reduce the absorption of glucose, but their role in weight loss or diabetes is uncertain.
    • Lectins in legumes (black, lima and kidney beans, soybeans and lentils) can inhibit carbohydrate digestion ^[21].
  • Protease inhibitors, for example trypsin inhibitors in soy, sweet potatoes or raw potatoes ^[18], inhibit the digestion of proteins.
  • Lipase inhibitors, for example, orlistat— the anti-obesity drug–inhibit the digestion of fats ^[6].
• Chelating agents, which bind to nutrients in the intestine and prevent their absorption:
  • Dietary fiber can speed up peristalsis and thus decrease the time available for absorption of certain nutrients. In one study, high fiber diet (50 g fiber, from which 25 g soluble) did not significantly affect the absorption of calcium in magnesium ^[10].
  • Oxalic acid (oxalate) from dark beer, black tea, rhubarb, spinach, Swiss chard, beet greens, taro (cocoyam), tiger nut ^[23], amaranth and dried beans can inhibit the absorption of calcium from these foods but less likely from other foods ^{[11,12,13,14,18,26]}. Oxalate is not destroyed by cooking.
  • Phytic acid (phytate) ^[2] from wheat bran, maize ^[37] and legumes (dried beans, peas and lentils) can inhibit the absorption of iron from plant foods ^[5,15,32,33], zinc, magnesium and manganese.
  • Polyphenols (flavonoids and tannins) from coffee ^[2], black tea ^[2,7], certain fruits, Yod kratin (a Thai vegetable) ^[8] and red wine can inhibit the absorption of iron ^[15,17].
  • Egg proteins, milk proteins (casein and whey) and soy protein isolates can inhibit the absorption of iron ^[15,17].
  • Calcium, iron, zinc and magnesium supplements, when taken together, can inhibit the absorption of each other.
• Compounds that interact with hormones:
  • Glucosinolates found in raw cruciferous vegetables (broccoli, Brussel’s sprouts, cabbage, cauliflower, kale, mustard greens), cassava ^[18], rapeseed oil ^[37], peanuts and sweat potatoes are converted (in your body) to thiocyanates, which inhibit the uptake of iodine by the thyroid gland, but may cause goiter only in a pre-existing iodine deficiency, when consumed raw and long-term in large amounts ^[19,21].
• Other possible antinutrients:
  • Saponins

Foods High in Antinutrients

Legumes

Beans, peas and lentils contain phytates, oxalates and tannins that can inhibit the absorption of calcium from these foods ^[9,13]. Calcium from soy is well absorbed, though ^[30].

Cereal Grains

• Bran of cereal grains (whole grain bread, whole oatmeal, brown rice, black, brown and red [finger] millet) contains phytates, oxalates and tannins ^[2,13,36].
• Brown rice and whole quinoa ^[22] contain phytates, saponins, lectins and protease inhibitors, while white rice and dehulled quinoa are low in antinutrients ^[22]. Brown rice, despite its higher nutritional content, has no greater nutritional value than white rice, possibly due to presence of antinutrients ^[35].

Raw Eggs

The protein avidin in raw eggs inhibits the absorption of biotin (vitamin B7). Avidin is destroyed by cooking.