Should I worry about anti-nutrients?
Ask Dr Libby
Q: I recently heard someone talking about anti-nutrients. What are they and where are they found? Thanks, Susan.
A: Foods don’t just contain nutrients; some foods also contain what are often referred to as antinutrients when eaten in excessive amounts. Anything consumed in excess can be harmful. Some common anti-nutrients are phytic acid, oxalates and lectins. Alcohol and caffeine also have antinutrient properties. Let’s look at phytic acid, lectins and oxalates.
Phytic acid or phytates perform many important functions for plants. Phytic acid is found in wholegrains, nuts, seeds and beans and are considered to be anti-nutrients because they represent a potential absorptive roadblock. Phytic acid is the principal storage form of the mineral phosphorus in many plant tissues, especially the bran portion of grains and other seeds.
For humans, the phosphorus in this molecule is not readily Email your questions for Dr Libby to email@example.com. Please note, only a selection of questions can be answered.
available. Components of the phytic acid molecule also bind with other minerals – such as calcium, magnesium, iron and zinc – so we are unable to absorb them. Soaking wholegrains, beans, nuts and seeds overnight is one of the most effective ways to reduce their phytic acid content.
Lectins are proteins found in animals and plants, particularly grains, legumes, nuts and seeds. They have many protective functions, from recognising pathogens to helping regulate protein levels in the blood.
However, lectins can confuse the immune system in some people, and drive it to create antibodies. Lectins can also mimic other proteins typically present in blood. Almost everyone has antibodies to some dietary lectins, so our responses to lectincontaining food can vary. Eating a variety of foods reduces the impact and some people benefit from fermented foods, such as sauerkraut and kombucha. Cooking, sprouting or soaking your grains, legumes, nuts and seeds helps decrease lectins.
Leafy green vegetables, nuts, seeds, most berries, certain other fruits, soy, meat and dairy all contain small amounts.
The main area of concern for oxalic acid is in relation to kidney stones. Approximately 80 per cent of kidney stones are composed of calcium oxalate. Oxalic acid binds with other minerals such as calcium, which under certain conditions form a salt known as an oxalate. Oxalic acid interferes with the absorption of calcium and iron, making it unusable by the body. Some individuals are more prone to problems with oxalates than others.
While some plant foods contain these anti-nutrients, the benefits of the vitamins, minerals, antioxidants, and beneficial phytochemicals that they also contain far outweigh any potential negatives. It’s the dose that is important – if we consumed huge quantities of one particular food, anti-nutrients may be of concern, but so would nutrient deficiencies.
When we eat a wide range of nutritious foods, there’s no need to worry about anti-nutrients.
❚ Dr Libby is a nutritional biochemist, best-selling author and speaker. The advice contained in this column is not intended to be a substitute for direct, personalised advice from a health professional. See drlibby.com.
Soaking beans overnight is an effective way to reduce their phytic acid.