Classified as an anti-nutrient, phytic acid occurs naturally in plant seeds; the substance inhibits the body’s ability to absorb certain minerals from dietary sources.
Although it’s usually not a concern in developed countries where a variety of food is available, for those with certain circumstances, eating a substantial amount of food with high levels of phytic acid has the potential to cause mineral deficiencies. (1)
But even tagged as an anti-nutrient, phytic acid can be beneficial in the diet, so let’s take a close look at the big picture.
How Phytic Acid Affects the Absorption of Minerals
Also referred to as phytate and inositol hexaphosphate (IP6), phytic acid stores phosphorus in seeds. When environmental conditions such as warmth and water are right for the seed to sprout, the mineral is released to be fuel the seed’s natural growth cycle.
Found only in plant foods, phytate is present in legumes, nuts and seeds; roots and tubers may also contain phytates at lower levels.
The amount of phytates in a single food can vary greatly.
For example, almonds might contain anywhere from 0.4% to 9.4% by dry weight, which is a very large range. Levels in rice usually run at less than 1%, but rice bran can have more than 8% phytate content. (1)
Other foods like dry beans and various types of nuts and seeds like peas, sesame seeds and wheat are also on the list of foods containing phytate. If a food can be sprouted, it has phytate locked inside, waiting to be released by environmental circumstances.
Zinc and iron absorption in the human digestive system are negatively impacted by phytate; it also affects calcium absorption, but not to the same degree. (2)
These effects are time-sensitive, meaning that phytates present in a food only inhibit digestion during that meal. (3)
If you eat a handful of almonds for a mid-afternoon snack, phytic acid would reduce the amount of iron and other minerals absorbed in the digestive tract. But when dinner time rolls around, the food you eat won’t be affected by your snack a few hours before.
Deficiency problems can develop over time when phytates are present in a majority of foods being consumed.
That’s why it’s unlikely to have long-term repercussions with a balanced diet. However, people in developing countries can be at higher risk for deficiencies since cereal grains and legumes often serve as staples in the diet.
Reducing the Amount of Phytic Acids in Food
It’s not necessary to avoid foods rich in phytates; these are usually highly nutritious as well as being delicious additions to the diet.
These preparation methods can significantly reduce the amount of phytic acids in food:
- Soak legumes and cereal seeds overnight in water. (4)
- Sprout grains, legumes and seeds to degrade phytates. (5, 6)
- Ferment foods to release organic acids that contribute to the breakdown of phytates; an example of this is the process of making sourdough bread, which activates lactic acid , which in turn degrades phytates. (7, 8)
Combining these preparation methods is even more effective in dropping phytate levels.
When all three methods are used with quinoa seed, phytate content is reduced by 98%. (9)
The amounts of phytate remaining in maize and white sorghum following the application of these three preparation methods decreases to nearly zero. (10)
The same is true for soy products, which are made from soybeans. The phytic acid content decreases with each preparation method (soaking, boiling, steaming, and fermentation) until less than 10% of the phytate remains. (11)
The Pros and Cons of Phytic Acid
In some cases, foods can have both beneficial and detrimental effects on the body, which happens to be the case with foods containing phytates.
The antioxidant properties of phytate have been well-documented, and this may be a more healthful option for replacing harmful chemicals currently being used as preservatives in processed foods. (12)
If you’re healthy, eat a balanced diet, and don’t have any known mineral deficiencies, it’s not likely phytates will significantly impact the absorption of minerals in your system.
However, vegetarians may be at risk, and vegans who consume largely plant foods should be vigilant about degrading phytates in the diet, especially if they eat considerable amounts of nuts and seeds. (18, 19)
The absorption of iron in particular can be a concern for those who don’t eat meat. In order to understand how this works, it’s important to know how our bodies process dietary iron.
There are two different types of iron available through food sources:
- Heme iron comes from animal foods like meat and dairy products, seafood, pork, turkey and eggs
- Non-heme iron is found in plant foods like legumes, dried apricots, broccoli, wheat germ and pumpkin seeds
While heme iron is efficiently absorbed by the body, non-heme iron is not.
Non-heme iron is also much more susceptible to the inhibiting effects of phytate, making it difficult for vegans and vegetarians to get enough iron. (20)
A similar circumstance makes zinc absorption more difficult for those who don’t eat meat. But zinc is well-absorbed in the presence of meat, even when phytates are eaten at the same meal.
This is why mineral deficiencies aren’t nearly as common among meat-eaters as among vegans and vegetarians.
When legumes and whole grain cereals that aren’t properly prepared comprise a large part of the diet, whether by choice or because these are the main foods available, phytates can cause problems in the absorption of minerals over the long-term.
The Bottom Line
Foods containing high levels of phytates should not necessarily be avoided; they are also good sources of other valuable nutrients necessary for a healthy diet.
If you don’t eat meat, be sure to use preparation methods that decrease phytic acid content of the grains, legumes and other plant foods in your diet in order to maximize mineral absorption.
Summary: The naturally occurring phytates in nuts, seeds and grains are perfectly safe when properly prepared, and deliver a variety of nutrients that can be part of a healthy diet.