Dissecting Anti-Nutrients: The Good and Bad of Phytic Acid
Along with saponins and lectins, phytic acid is considered an anti-nutrient, which means thoe who follow paleo nutrition have probably eliminated it from their diet. Phytic acid (aka phytate) is a substance found in many types of plant foods, such as grains, legumes (including peanuts and soybeans), nuts, and seeds. It’s the storage form of phosphorus, animportant mineral used in the production of energy as well as the formation of structural elements like cell membranes.
It turns out that phytic acid is found predominantly (about 80% of it) in the bran, or outermost shell, of whole grains. In legumes and seeds, phytic acid resides almost entirely in the endosperm.1 This is significant when you consider that most whole grain and high-fiber food products include all of the phytic acid, while processed or refined grains have it removed entirely.
The problem is these foods, considered healthy and nutritious by many, are getting a bad reputation based on their phytic acid content. This is due to phytic acid’s ability to bind to essential minerals such as iron, zinc, calcium, and magnesium in the digestive tract and inhibit their absorption by the body.1,2
What’s the Big Deal?
Where this is most detrimental is in developing countries that rely heavily on grains and legumes to provide the majority of people’s nutrient needs. In this context, when individuals are already hard-pressed to get all the nutrients they need, phytic acid can make already low nutrient bioavailability and mineral deficiency worse. This is especially true with iron and zinc (and to a lesser extent calcium and magnesium).
However, in developed countries without the same limitations in the food supply, the severity of phytic acid’s effect on overall health tends to be a bit exaggerated. That means for those of us living in the United States, the threat of significant nutrient deficiency, as related to phytic acid, is not as imminent as we might think. That being said, there are certainly arguments to be made for increasing mineral and nutrient intake in certain populations such as vegetarians, vegans, and children.
Despite being somewhat demonized for its ability to reduce mineral absorption, phytic acid actually has some potentially beneficial properties.
Phytic acid can act as an antioxidant, particularly in regards to iron.3-5 It is known that iron can behave as a free radical, contributing to oxidative stress in the body. In this context, phytic acid’s ability to sequester and trap iron is beneficial. In fact, it does such a good job of binding to iron that it can effectively neutralize any free radical.
Keep in mind that oxidation in the body is a normal day-to-day activity but it can get out of hand, especially when the body is under stress, which includes rigorous exercise. In this case it may be a good thing to have phytic acid around to protect cells that might otherwise be at risk for excessive oxidative damage.
In addition to acting as an antioxidant, phytic acid also has been shown to exhibit some anti-cancer properties.6-10 Though research in humans is a bit scarce, there have been several studies demonstrating the potential positive effects of phytic acid in fighting cancerous tumor cells. This may partially explain why high-fiber diets tend to be associated with reducing colon cancer risk.
Cholesterol and Blood Sugar
Finally, phytic acid has shown some capacity to reduce cholesterol and triglycerides, and positively impact the glycemic response of certain foods.11-13 In some cases, phytic acid seems to have an ability to slow down a potential blood sugar spike following the ingestion of certain high-carbohydrate foods. Again, this may explain why high-fiber foods have been associated with improved blood sugar control.
Finding a Solution
Now here’s the catch. The potential benefits of phytic acid occur in instances with high dietary phytic acid intake. However, a high intake has also been associated with reduced mineral absorption. So, in order for us to get the best of both worlds (if such a thing is possible) it’s important to discover some ways in which we can minimize the negative effects while maximizing the beneficial effects.
One way we can do this (specifically in regards to iron) is by incorporating more vitamin C (ascorbic acid) into our diet. These two work well together, with vitamin C placing iron in a chemical state that is more readily absorbed by the body.14
Preparation methods such as soaking, germinating, or fermenting can be very effective in reducing the amount phytic acid present in foods. Some methods are better for different foods. In the case of nuts and legumes, soaking and germinating are most successful, but for grains and cereals, all three are effective.
Another way to maximize benefit of phytic acid is to simply increase the consumption of foods rich in iron, zinc, magnesium, and calcium that are naturally low in phytic acid. For example, consider eating more animal-based proteins. Understandably, this can be challenging for vegetarians and vegans and may warrant the inclusion of a vitamin and mineral supplement.
One last strategy is to focus more on meal timing. In other words, eat foods that contain phytic acid separately from foods that are richer in minerals. From a practical standpoint, one could accomplish this by eating meals of protein and fat separate from meals of carbohydrate and fat.
The Bottom Line
Phytic acid can bind to minerals in the digestive tract and make them less available to the body. However, this is most problematic in areas of the world with already-established nutrient and mineral deficiency that rely primarily on foods containing high amounts of phytic acid.
On the plus side, phytic acid can act as antioxidant, exhibits anti-cancer properties, and may have a positive impact on cholesterol and blood sugar. Preparation methods can reduce the phytic acid content in food, as well as adjusting meal times and food choices.
One of the easiest mistakes to make in the world of nutrition is to assume that any nutrient or substance behaves in just one way, whether it’s good or bad. Truth is, the body is much more unique and complex than we can truly understand, and stuff we eat tends to have many different functions once it’s inside of us. Every person, though sharing similar nutrient needs, is going to respond differently and accommodate foods, such as those containing phytic acid, more or less easily than others. Keep an open mind, think critically, and don’t lose sight of the forest for the trees.
1. Schlemmer U, Frølich W, Prieto RM, Grases F. Phytate in foods and significance for humans: Food sources, intake, processing, bioavailability, protective role and analysis. Molecular Nutrition & Food Research. 2009;53(S2):S330–S375.
2. Gibson RS, Bailey KB, Gibbs M, Ferguson EL. A review of phytate, iron, zinc, and calcium concentrations in plant-based complementary foods used in low-income countries and implications for bioavailability. Food Nutr Bull. 2010;31(2 Suppl):S134–146.
3. Graf E, Empson KL, Eaton JW. Phytic acid. A natural antioxidant. Journal of Biological Chemistry. 1987;262(24):11647–11650.
4. Hawkins PT, Poyner DR, Jackson TR, et al. Inhibition of iron-catalysed hydroxyl radical formation by inositol polyphosphates: a possible physiological function for myo-inositol hexakisphosphate. Biochemical Journal. 1993;294(Pt 3):929.
5. Phillippy BQ, Graf E. Antioxidant functions of inositol 1,2,3-trisphosphate and inositol 1,2,3,6-tetrakisphosphate. Free Radic. Biol. Med. 1997;22(6):939–946.
6. Shamsuddin AM. Anti-cancer function of phytic acid. International Journal of Food Science & Technology. 2002;37(7):769–782.
7. Shamsuddin AM, Vucenik I, Cole KE. IP6: a novel anti-cancer agent. Life Sci. 1997;61(4):343–354.
8. Shamsuddin AM. Inositol phosphates have novel anticancer function. J. Nutr. 1995;125(3 Suppl):725S–732S.
9. Vucenik I, Shamsuddin AM. Cancer inhibition by inositol hexaphosphate (IP6) and inositol: from laboratory to clinic. J. Nutr. 2003;133(11 Suppl 1):3778S–3784S.
10. Vucenik I, Shamsuddin AM. Protection Against Cancer by Dietary IP6 and Inositol. Nutrition and Cancer. 2006;55(2):109–125.
11. Thompson LU, Button CL, Jenkins DJ. Phytic acid and calcium affect the in vitro rate of navy bean starch digestion and blood glucose response in humans. Am J Clin Nutr. 1987;46(3):467–473.
12. Lee SH, Park HJ, Chun HK, et al. Dietary phytic acid lowers the blood glucose level in diabetic KK mice. Nutrition research. 2006;26(9):474–479.
13. Lee SH, Park HJ, Chun HK, et al. Dietary phytic acid improves serum and hepatic lipid levels in aged ICR mice fed a high-cholesterol diet. Nutrition research. 2007;27(8):505–510.
14. Hummers Jr WS, Offeman RE. Iron absorption in man: ascorbic acid and dose-dependent inhibition by phytate. Journal of the American Chemical Society. 1958;80(6):1339–1339.
Photos courtesy of Shutterstock.