Phytic acid is a unique natural substance found in plant seeds.
It has received considerable attention due to its effects on mineral absorption.
Phytic acid impairs the absorption of iron, zinc and calcium, and may promote mineral deficiencies ().
Therefore, it is often referred to as an anti-nutrient.
However, the story is a bit more complicated than that, because phytic acid also has a number of health benefits.
This article takes a detailed look at phytic acid and its overall effects on health.
Phytic acid, or phytate, is found in plant seeds. It serves as the main storage form of phosphorus in the seeds.
When seeds sprout, phytate is degraded and the phosphorus released for use by the young plant.
Phytic acid is also known as inositol hexaphosphate, or IP6.
It is often used commercially as a preservative due to its antioxidant properties.
Bottom Line: Phytic acid is found in plant seeds, where it serves as the main storage form of phosphorus.
Phytic acid is only found in plant-derived foods.
All edible seeds, grains, legumes, and nuts contain it in varying quantities, and small amounts are also found in roots and tubers.
The following table shows the amount contained in a few high-phytate foods, as a percentage of dry weight ():
As you can see, the phytic acid content is highly variable. For example, the amount contained in almonds can vary up to 20-fold.
Bottom Line: Phytic acid is found in all plant seeds, nuts, legumes and grains. The amount contained in these foods is highly variable.
Phytic acid impairs absorption of iron and zinc, and to a lesser extent calcium (, ).
This applies to a single meal, not overall nutrient absorption throughout the day.
In other words, phytic acid reduces mineral absorption during the meal, but doesn't have any effect on subsequent meals.
For example, snacking on nuts between meals could reduce the amount of iron, zinc and calcium you absorb from the nuts, but not from the meal you eat a few hours later.
However, when you eat high-phytate foods with most of your meals, mineral deficiencies may develop over time.
In well balanced diets, this is rarely a concern, but may be a significant problem during periods of malnutrition, and in developing countries where the main food source is grains or legumes.
Bottom Line: Phytic acid impairs the absorption of iron, zinc and calcium. It may contribute to mineral deficiencies over time, but this is rarely a problem with well-balanced diets.
Avoiding all foods that contain phytic acid is a bad idea, because many of them (like almonds) are nutritious, healthy and tasty.
Also, in many developing countries, food is scarce and people need to rely on grains and legumes as their main dietary staples.
Fortunately, several preparation methods can significantly reduce the phytic acid content of foods.
Here are the most commonly used methods:
- Soaking: Cereals and legumes are often soaked in water overnight to reduce their phytate content (, ).
- Sprouting: The sprouting of seeds, grains and legumes, also known as germination, causes phytate degradation (, ).
- Fermentation: Organic acids, formed during fermentation, promote phytate breakdown. Lactic acid fermentation is the preferred method, a good example of which is the making of sourdough (, ).
Combination of these methods can reduce phytate content substantially.
For example, soaking, sprouting and lactic acid fermentation can reduce the phytic acid content of quinoa seeds by 98% ().
In addition, sprouting and lactic acid fermentation of white sorghum and maize may almost completely degrade the phytic acid ().
Bottom Line: Several methods can be used to reduce the phytic acid content of foods. This includes soaking, sprouting, and fermentation.
Phytic acid is a good example of a nutrient that is both a "friend and foe", depending on the circumstances.
In addition to its antioxidant properties (), phytic acid may be protective against kidney stones (, ) and cancer (, , , , ).
It has even been suggested that phytic acid might be part of the reason whole grains may cut the risk of colon cancer ().
Bottom Line: Phytic acid may have several positive health effects, acting against both kidney stones and cancer.
The short answer is, probably not.
However, those at risk of mineral deficiency should diversify their diets and not include high-phytate foods in all meals.This is particularly important among those who suffer from iron deficiency ().
Vegetarians, especially vegans, are also at risk (, ).
The thing is, there are two kinds of iron in foods; heme iron and non-heme iron.
Heme-iron is found in foods of animal origin, such as meat, whereas non-heme iron comes from plants.
Non-heme iron from plant-derived foods is poorly absorbed, while the absorption of heme-iron is efficient. Non-heme iron is also highly affected by phytic acid, whereas heme-iron is not ().
In addition, zinc is well absorbed from meat, even in the presence of phytic acid ().
Therefore, mineral deficiencies caused by phytic acid are rarely a concern among meat-eaters.
However, phytic acid can be a significant problem when diets are largely composed of high-phytate foods while at the same time low in meat or other animal-derived foods.
This is of particular concern in many developing nations where whole grain cereals and legumes are a large part of the diet.
Bottom Line: Phytic acid is usually not a concern in industrialized nations, where food diversity and availability is adequate. However, vegetarians/vegans and those who eat a lot of high-phytate foods may be at risk.
High-phytate foods, such as grains, nuts, and legumes, can raise the risk of iron and zinc deficiency.
As a countermeasure, strategies such as soaking, sprouting and fermentation are often employed.
For those who eat meat regularly, deficiencies caused by phytic acid are not a concern.
In fact, consumption of certain high-phytate foods as part of a balanced, real food based diet has numerous benefits.
In many cases, these benefits outweigh any negative effects on mineral absorption.