I have studied nutrition for many years starting in my youth and then formally in my undergraduate degree and yet did not come across much about the potential deleterious effects of anti-nutrients such as phytic acid in grains, beans, nuts, seeds and some other plant foods. (An antinutrient is a component in food that limits or interferes with nutrient absorption.) It was not until I continued with naturopathic studies and pursued additional education in functional nutrition and medicine that the concept of antinutrients even came up as a potential problem in the modern diet. So it is of little surprise to me that many of my nutritionally savvy patients (including vegans and vegetarians who are at particular risk from high phytic acid diets) are unaware of the importance of traditional food preparation methods to get the most from their food. And thus I felt compelled to educate patients and my readers by writing this article.
There is a lot to cover broadly on optimizing nutrient absorption in one’s diet that is beyond the scope of what can be covered in a single article, so stay tuned for more on this in future. In this article, I will be focusing on how to reduce a compound found in grains, beans, nuts and seeds that can interfere with mineral absorption: phytic acid.
Phytic Acid in Foods Binds Minerals: Phytic acid is the storage form of phosphorus in plants and is present in the bran or hull of grains, nuts, legumes and seeds. There it is an important source of energy for a sprouting seed. Herbivores have enzymes to digest this compound, but humans do not. Once ingested, phytic acid (known as phytate when bound to a mineral) can bind minerals (calcium, magnesium, phosphorus, iron, zinc and others) in the digestive tract and block their absorption. In addition, phytic acid can inhibit enzymes needed to break down protein and carbohydrates in our diet. Additionally, commercially grown food (using modern high phosphate fertilizers) increases the amount of phytic acid in food (growing foods with natural compost does not increase phytic acid levels).
Phytic Acid and Digestion: So what impact does this really have on your nutrient intake? If steps are not taken to reduce phytic acid in grains, nuts, legumes and seeds, you will obtain only a fraction of the nutrients from this food, and potentially suffer from decreased absorption of the macronutrients (protein and carbohydrate) contained in the food as well ( I will provide more specific examples later in this article). Moreover, those with imbalanced gut flora (many of the patients whom I see suffer from this) have a harder time tolerating foods with phytic acid, as the microbes in a healthy gut flora have been shown to produce phytase (an enzyme that can break down some of the phytic acid in foods).
Phytic acid is a particular challenge for those following more plant-based diets such as vegetarians and especially vegans (who often rely on grains, beans, nuts and seeds for a considerable amount of their protein, carbohydrate and mineral needs). Phytic acid is the reason that the RDA (Recommended Dietary Allowance) for iron and zinc in vegetarians is higher than for omnivores.
The Effect of Phytic Acid on Mineral Absorption: To give an example, 1 ounce of almonds (approximately 23 almonds) contains 0.9 mg of zinc and 77 mg of magnesium. If soaking and dehydrating were sufficient to eliminate the phytic acid in the almonds, this is the amount of zinc and magnesium that you would obtain from the ounce of almonds. If no steps were taken to reduce phytic acid, absorption of zinc may be decreased by 20 percent (you would only get about 0.72 mg of zinc from the almonds) and absorption of magnesium by 60 percent (46 mg of magnesium). As many people today struggle to meet their nutrient needs from their diet alone, this can add up over a day (or if consuming a diet high in phytic acid over time). Further, magnesium is of critical importance in reducing anxiety, insomnia, muscle tension and constipation (which I see frequently in my patients) and zinc tends to be deficient in a number of psychiatric conditions.
Traditional Methods of Food Preparation to decrease Phytic Acid:
So how can we minimize the phytic acid content of these foods? This requires a return to traditional methods of food preparation carried out by our ancestors:
- Soaking in an acidic solution (with lemon juice or apple cider vinegar) and cooking for grains and legumes (dried beans). Sprouting is considered the most effective method for reducing phytic acid in legumes.
- Soaking in a salt water solution and dehydrating (and roasting?) for nuts and seeds (note that further research is needed to determine the degree of efficacy of this preparation approach)
- Sprouting (grains, beans)
- Leavening (sourdough for bread, as well as yeast)
- Consume foods grown without high phosphate fertilizers
Note that the mineral-binding effects of phytic acid in coconut is considered minimal. The mineral-binding effects of phytic acid in chia seed and flax seeds is debated and thus, to be prudent, soaking them is recommended until we learn more.
Soaking can reduce, or even neutralize phytic acid. Dehydrating nuts and seeds (after soaking) allows longer-term storage of nuts and seeds after soaking and improves their flavor. Dehydrating at low temperatures typically adheres to rules of a raw diet and maintains good quality fats and nutrients in the nuts and seeds. Roasting can reduce phytic acid as well, but may destroy some of the essential fats and nutrients in the process Cooking grains and legumes can further reduce phytic acid.
Digestion is a bit of a weak link for me and I have noticed considerable benefit from soaking and dehydrating nuts and seeds. I hope that you experience the benefits of stronger digestive and overall health as a result of incorporating these suggestions in your diet!
And finally, as with most things, moderation is a good goal. It is unrealistic to completely eliminate phytic acid from your diet (as it is also in roots, tubers and other vegetables (in low amounts), chocolate (raw, unfermented cacao, and some other plant-based foods), but it is important to not count on these foods exclusively to meet your nutrient needs. A handful of nuts or a serving or 2 of properly prepared grains, beans, nuts or seeds a day may be well-tolerated and have minimal impact on digestion and nutrient intake in a generally healthy individual with a good gut flora and nutrient intake. In someone with digestive compromise or marked nutrient deficiencies, increased restriction may be necessary until greater health is restored.
Here are a couple of recipes for getting started:
Uncooked version (Overnight oats):
Combine the following in a bowl or container with a lid:
- 1/2 cup of oats (rolled, gluten-free if needed (not instant))
- 2-3 TBSP dairy or non-dairy yogurt (coconut is nice)
- 1-2 TBSP chia seeds
- maple syrup or honey or molasses (optional, 1-2 tsp. or to taste)
- Milk to cover (about 3/4 cup) (non-dairy milks without sweeteners or carageenan and other gums/gels are preferred)
- Nutmeg and/or cinnamon (optional)
- Place in fridge overnight. Remove lid, add a little more ‘milk’ if desired and some soaked nuts and/or fresh or dried fruit.
Makes 1 serving
(I have had several patients who did not feel that they tolerated regular cooked oats well, report that this recipe caused them no digestive distress.)
Soaking Brown Rice
- Mix 2 cups short grain brown rice with 4 cups of filtered water and 4 TBSP of lemon juice or cider vinegar. Leave covered at room temperature for 8 hours or overnight.
- When ready to cook, bring to a boil, skim off foam and reduce heat. Cook on low, covered, for about 45 minutes
- Larger beans (kidney): Rinse 1 cup of dried beans, pick out any stones or debris and place in ceramic or glass bowl. Cover (by about an inch) with filtered water and a pinch of baking soda. Soak for 12 -24 hours. Soaking for 24 hours (with a refresh of fresh water and vinegar/lemon juice at 12 hours) is preferred.
- Smaller beans: Rinse 1 cup of dried beans, pick out any stones or debris and place in ceramic or glass bowl. Cover (by about an inch) with filtered water and 1 TBSP of cider vinegar or lemon juice. Soak for 12 -24 hours. Soaking for 24 hours (with a refresh of fresh water and vinegar/lemon juice at 12 hours) is preferred.
- Drain, rinse, add fresh water (see instructions for the particular bean you are cooking/recipe that you are including the beans in for the quantity) and bring to a boil. Reduce heat and simmer on low for 4-8 hours or until soft.
If you enjoy bread, sourdough or sprouted bread contains the lowest amount of phytic acid. And rye breads also have lower levels of phytic acid (as it contains high levels of phytase (the enzyme needed to break down phytic acid). Rye should only be consumed if you can tolerate gluten as rye is a gluten-containing grain.
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Nagel, R. (2010, March 26). Living with Phytic Acid. Retrieved from https://www.westonaprice.org/health-topics/vegetarianism-and-plant-foods/living-with-phytic-acid/
Matus, M. (2015, January 19). Raw Food Solution. Retrieved from https://rawfoodsolution.com/phytic-acid-and-the-raw-food-diet/
OSU Linus Pauling Institute. Micronutrient Information Center. (2015, June 11). Zinc. Retrieved from https://lpi.oregonstate.edu/mic/minerals/zinc
OSU Linus Pauling Institute. Micronutrient Information Center. (2014, May). Magnesium. Retrieved from https://lpi.oregonstate.edu/mic/minerals/magnesium
Pope, S. (2011, September 19). Proper Preparation of Grains and Legumes Video. Retrieved from https://www.westonaprice.org/proper-preparation-of-grains-and-legumes-video-by-sarah-pope/