A friend’s daughter was wanting to swap a predominantly meat-based diet to completely plant-based diet. Since I had always followed a plant-based diet and learnt traditional culinary practices of soaking lentils and almonds, avoiding tea or coffee just before or after a meal to name a few, I set off to explore the science behind the culinary ‘Do’s’ and ‘Don’ts’.
I would like to share with you my learning around antinutrients.
What are antinutrients?
Antinutrients are natural or synthetic compounds that interfere with the absorption of nutrients or it can be overconsumption of nutrients themselves. Antinutrients bind to vitamins and minerals, preventing their uptake or inhibit enzymes (Wikipedia definition).
An antimetabolite is a chemical that inhibits the use of a metabolite, for example folic acid, so these compounds are used as chemotherapy for cancer.
Throughout history, humans have bred crops to reduce antinutrients, and cooking processes have developed to remove them from raw food materials and increase nutrient bioavailability, one such example being cassava.
Types of Antinutrients
These are substances naturally found in many plant foods. In plants they help to protect the plant from bacterial infection or being eaten by insects so the plant can live on and reproduce.
- Glucosinolates and Goitrogens in cruciferous vegetables (broccoli, Brussels sprouts, cabbage) can prevent the absorption of iodine, which may then interfere with thyroid function and cause goiter. Those already with an iodine deficiency or hypothyroidism are most susceptible.
- Lectins in legumes such as beans, peanuts, soybeans, red kidney beans, whole grains can interfere with the absorption of calcium, iron, phosphorus and zinc.
- Oxalates in green leafy vegetables and tea, can bind to calcium and prevent it from being absorbed contributing to renal stones.
- Phytates (phytic acid) in whole grains, seeds, legumes, some nuts can decrease the absorption of iron, zinc, magnesium, and calcium.
- Saponins in legumes and whole grains can interfere with normal nutrient absorption.
- Tannins in tea, coffee, legumes can decrease iron absorption.
As the name suggests, synthetic antinutrients occur in processed foods.
- high fructose corn syrup
How they affect our body
Some adverse symptoms we may experience are bloating, skin eruptions, brain fog and fatigue. However some antinutrients are beneficial such as polyphenols, carotenoids, organosulfur compounds and flavonoids. Of course an excess can be harmful.
Studies on vegetarians do not show deficiencies of iron or zinc, which suggests our body must be adapting by increasing the absorption.
What can be done to reduce the harmful effects
Many antinutrients can be avoided, deactivated, or removed.
A) Food Choices
- Eating a variety of nutritious foods through the day
- Avoid a large amount of one type of food at one meal
- Avoid food combinations –such as greens and dairy on a regular basis
- Gut microbiome has ability to degrade oxalates –so feed your gut microbiome by consuming prebiotic and probiotics
- Cooking, steaming, fermenting, autoclaving, sprouting
- Cooking lentils in the soaking water for 1 hour at 95 degrees and adding lemon juice / citric acid or tamarind water to lentils when cooking and eating
- Avoid freshly cultivated beans. Allow them to dry properly.
- Avoid raw legume flour.
- Microwave cooking does not eliminate antinutrients.
- Steaming broccoli and leafy greens for 5 mins is best
- Roasting peanuts, cashew and almonds does not reduce oxalates. Soaking overnight before eating helps.
- Pairing dairy with oxalates, reduces oxalates.
- Drink plenty of water to flush out oxalates, avoid eating a lot of greens at night to reduce risk of stones.
- Hyper absorption of oxalates occurs in IBD (inflammatory bowel disease) hence higher risk of renal stones.
- Tannins reduce absorption of iron hence avoid tea or coffee just before or after a meal.
- Ensure citrus foods in diet to enhance iron absorption.
Benefits of antinutrients
Phytates lower cholesterol and reduce sharp rise in blood sugar.
They can protect from cancer due to anti-inflammatory effect by reducing free radicals.
The health promoting effects of lectin containing foods, far outweigh any possible negative effects of lectins.
The impact of a varied diet is distinct to that of an individual compound. The complex interactions of vitamins, minerals and other phytochemicals in a whole food, and with the gut microbiome alters the bioavailability of metabolites.
Consuming these foods as part of a varied, colourful, plant-based diet should not pose significant risks in healthy individuals and conversely may be of great benefit.