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 (1).
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 to be used by the young plant.
Phytic acid is also known as inositol hexaphosphate, or IP6.
It’s often used commercially as a preservative due to its antioxidant properties.
Summary Phytic acid is found in plant seeds, where it functions 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 (1):
As you can see, the phytic acid content is highly variable. For example, the amount contained in almonds can vary up to 20-fold.
Summary Phytic acid is found in all plant seeds, nuts, legumes and grains. The amount contained in these foods is highly variable.
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 these 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.
This is rarely a concern for those who follow well-balanced diets but may be a significant problem during periods of malnutrition and in developing countries where the main food source is grains or legumes.
Summary Phytic acid impairs the absorption of iron, zinc and calcium. It may contribute to mineral deficiencies over time, but this is rarely a problem for those following well-balanced diets.
Avoiding all foods that contain phytic acid is a bad idea because many of them are healthy and nutritious.
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 (1, 4).
- Sprouting: The sprouting of seeds, grains and legumes, also known as germination, causes phytate degradation (5, 6).
- 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 (7, 8).
Combining these methods can reduce phytate content substantially.
In addition, sprouting and lactic acid fermentation of white sorghum and maize may almost completely degrade the phytic acid (10).
Summary Several methods can be used to reduce the phytic acid content of foods, including soaking, sprouting and fermentation.
Phytic acid is a good example of a nutrient that is both good and bad, depending on the circumstances.
Summary Phytic acid may have several positive health effects, such as protection against kidney stones and cancer.
Phytic acid is not a health concern for those who follow a balanced diet.
However, those at risk of an iron or zinc deficiency should diversify their diets and not include high-phytate foods in all meals.
There are two types of iron in foods: heme iron and non-heme iron.
Heme-iron is found in animal foods, 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 (18).
In addition, zinc is well absorbed from meat, even in the presence of phytic acid (19).
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 products.
This is of particular concern in many developing nations where whole grain cereals and legumes are a large part of the diet.
Summary Phytic acid is usually not a concern in industrialized nations, where food diversity and availability is adequate. However, vegetarians, vegans and others 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.
On the contrary, consuming high-phytate foods as part of a balanced diet has numerous benefits.
In most cases, these benefits outweigh any negative effects on mineral absorption.