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Is phytate blocking your iron absorption?

Adding more grains, beans, nuts, and seeds to one’s diet is shown to benefit health, but a few culinary tricks can unlock their potential and prevent phytate from blocking essential micronutrients.

For the past decade, I have followed a strictly plant-based diet which means my nutrients come solely from fruits, vegetables, beans, grains, nuts, and seeds. All these foods are part of a healthy dietary pattern, according to the key recommendations of the Dietary Guidelines for Americans. What many people may not know, however, is that plants contain a substance called phytate, which can block the absorption of some micronutrients. Because of this, phytate is often called an anti-nutrient, but that shouldn’t stop you from eating nutritious powerhouses like beans and whole grains. There is much more to these foods than just phytate, and a few simple kitchen tricks can unlock their full potential.

Phytate is predominately found in plant kernels such as whole grains, legumes (beans and peas), nuts, and seeds.1 These are parts of the plant that we eat, but their main purpose is to create new plants. Phytate is a strong chelator, which means it holds on tightly to micronutrients within the kernel. In other words, phytate is like a storage closet for phosphorus and other minerals that are essential for healthy plant growth.2 During germination, seed enzymes break up the phytate to release the minerals bound to it. Many of these plant kernels are rich sources of calcium, magnesium, iron, and zinc, but unfortunately, humans and other animals can’t break up phytate to access these minerals.

phytates
Photo by: Kelly Cara

When we consume phytate-rich plant foods, the chelating function of phytate prevents us from absorbing or accessing vital micronutrients within the plant kernels. It also binds up certain minerals from other foods we consume (like calcium- and iron-rich leafy greens). This is especially problematic in parts of the world where people consume diets heavy in phytate-rich staples like wheat, rice, and maize. It is also a problem for people who adhere to strictly plant-based diets.3,4 In both populations, anemia caused by lack of iron is a serious health concern, so reducing or removing phytate from foods could help alleviate this problem.

Ironically, the anti-nutrient mechanism of phytate also makes it a potent antioxidant – reigning in volatile substances like iron that can cause oxidative damage to cells.3 Research has suggested this antioxidant effect may help prevent diseases like Parkinson’s, which is associated with excess iron accumulation in the brain. Phytate has also been linked to possible protective effects against diseases such as Alzheimer’s, cirrhosis, arthritis, cancer, and osteoporosis.3,5,6,7

This presents a real dilemma: to improve our health, we are encouraged to eat micronutrient-rich plant foods, but the phytate in some of those foods may prevent us from accessing the micronutrients we need for improved and sustained health. If phytate is such a problem, how have people managed to survive on plant-heavy diets for so long? The answer lies in how we prepare foods. Despite our busy schedules, time may be the key ingredient to unlock the power of plant nutrition.

Practices like soaking, sprouting, and fermenting have been used for centuries to make grains and other kernels more palatable and easier to digest. These methods have all proven to reduce phytate content by initiating the germination phase of seed development.8 To some, these techniques may seem foreign or complex, but they need not be. Rehydrating dry beans or grains by soaking them overnight in water before cooking is a common culinary practice that decreases cooking time. Another common practice is soaking nuts or seeds in water for a few hours to soften before blending them into plant-based “milks,” sauces, or dressings. Soaking nuts and seeds to reduce phytate is especially important when making sauces or dressings for iron- and magnesium-rich foods like kale, collards, spinach, or broccoli.

phytates 3
Photo by: Kelly Cara

Sprouting goes one step further by allowing the soaked and drained kernels to germinate or grow small “tails” or sprouts. Sprouts can be grown in a simple mason jar with wire or mesh over the opening to allow for airflow, or they can be grown in sprouting trays specifically designed for growing sprouts. Leaving smaller seeds, like sesames, out on a damp paper towel can be enough to do the trick. Depending on the size and density of the grain, legume, nut, or seed you are using, sprouts can begin to show in just a few hours.

Fermented foods require more time and a bit more expertise, but luckily, a wide variety of fermented foods are available in most grocery stores. Products like kimchi, sauerkraut, kombucha, or pickled vegetables can be found in the refrigerated section, but even common items like sourdough breads, some vinegars, and yogurts made with live cultures are fermented. These days, several stores also dedicate entire sections to “raw and living” foods which can include items like sprouted nuts or seeds, sprouted grain breads, and soaked then dehydrated nut- or seed-based snack bars.

phytates 4
Photo by: Kelly Cara

We can gain a ton of essential micronutrients, fiber, and flavor by adding more plants to our diets. The most nutrients tend to come from richly colored plants such as dark leafy greens, cruciferous vegetables (like broccoli and Brussels sprouts), starchy tubers and root vegetables (like sweet potatoes, beets, and carrots), and a whole variety of squash and fruits. Keep in mind that phytate-rich foods like whole grains, beans, nuts, and seeds need a little culinary help to maximize their nutrition potential. Take the time to soak or sprout these kernels at room temperature before cooking, or reach for the whole grain sourdough bread the next time you’re at the store. If you like to experiment in the kitchen, pick up a yogurt-starter kit or a book on fermenting foods, and try some new recipes. Phytate doesn’t have to be a barrier to better health. You may just have to learn how to work around it to ensure the plants you consume are giving you their best.

References:

  1. Schlemmer U, Frolich W, Prieto RM, Grases F. Phytate in foods and significance for humans: Food sources, intake, processing, bioavailability, protective role and analysis. Mol Nutr Food Res. 2009;53(Suppl 2):S330-S375.
  2. Urbano G, Lopez-Jurado M, Aranda P, Vidal-Valverde C, Tenorio E, Porres J. The role of phytic acid in legumes: antinutrient or beneficial function? J Physiol Biochem. 2000;56(3):283-294.
  3. Bohn L, Meyer AS, Rasmussen SK. Phytate: impact on environment and human nutrition. A challenge for molecular breeding. J Zhejiang Univ Sci B. 2008;9(3):165-91.
  4. Konietzny U, Greiner R. Phytic acid: Nutritional impact. In Caballero B, Trugo L, Finglas P, Eds. Encyclopedia of Food Science and Nutrition. London, UK:Elsevier; 2003:4555-4563.
  5. Xu Q, Kanthasamy AG, Reddy MB. Neuroprotective effect of the natural iron chelator, phytic acid in a cell culture model of Parkinson’s disease. Toxicology. 2008;245(1-2):101-108.
  6. Greger M. Phytates for the prevention of osteoporosis. NutritionFacts.org. https://nutritionfacts.org/video/phytates-for-the-prevention-of-osteoporosis/. Published December 6, 2013(16). Accessed September 28, 2018.
  7. López-González AA, Grases F, Monroy N, Marí B, Vicente-Herrero MT, Tur F, Perelló J. Protective effect of myo-inositol hexaphosphate (phytate) on bone mass loss in postmenopausal women. Eur J Nutr. 2013;52(2):717-726.
  8. Masud T, Mahmood T, Latif A, Sammi S, Hameed T. Influence of processing and cooking methodologies for reduction of phytic acid content in wheat (Triticum aestivum) varieties. J Food Process Preserv. 2007;31(5):583–594.

Kelly Cara is a first-year graduate student in the Friedman School Nutrition Data Science program. Her research is focused on health outcomes related to various levels of food processing found in specific dietary patterns. She comes to Tufts after working for eight years in the field of experimental psychology and higher education research and four years in the culinary field as a health supportive chef and instructor.

The Friedman Sprout is a monthly student run newspaper that aims to serve the student population at the Friedman School of Nutrition Science and Policy, prospective students, and alumni. Our mission is to report on newsworthy information that affects the Friedman community including nutrition research, food policy, internship and volunteer opportunities, as well as school events. Our editorial slant is that of sustainability in food and nutrition.

5 comments on “Is phytate blocking your iron absorption?

  1. Jennifer Stickland

    Fantastic and comprehensive article on the complex role of phytates in food and our bodies. Thanks for presenting this in a way that people can understand and apply to their daily lives and eating habits. Well done.

  2. fullstridehealth

    Hi Kelly,
    Soaking hulled hemp seeds would turn them to mush. Is there another way to remove phytic acid from hemp seeds?
    I would be happy to include your response (with credits) in my article on hemp seeds: https://www.fullstridehealth.com/hemp-seed-oil-skin/
    I’m looking forward to your ideas.

    • Kelly Cara

      Great question. At present, the research seems to be lacking on techniques for reducing phytate in hemp. In a general search online, I found a few websites claiming that hemp seeds contain no phytic acid, but those pages included no citations to support their claims. My search on PubMed returned only one article with information on phytic acid content in hemp seed (an Italian study which found variable amounts of phytate in hemp seed based on genotype; content ranged from 43 to 75 g kg−1 DM; Citation – Galasso I, Russo R, Mapelli S, Ponzoni E, Brambilla IM, Battelli G and Reggiani R (2016) Variability in Seed Traits in a Collection of Cannabis sativa L. Genotypes. Front. Plant Sci. 7:688. doi: 10.3389/fpls.2016.00688). That study did not mention ways to reduce phytate in hemp seed, do I don’t have a good answer for you.

      Since commercial varieties of hemp seed are typically hulled and cannot be germinated, I am not sure that soaking methods would work very well for hemp anyway. I have read in articles about wheat that standard milling practices help to reduce phytic acid in wheat flours, so it is possible that the minimal processing that hemp goes through might reduce some of its phytic acid content. We’ll have to wait and see what scientific studies begin to surface as hemp becomes more popular and familiar in the market. I have great recipes for hemp seed milk and hemp tofu, so I know I will keep using these nutritious seeds which I especially love for their unique texture and earthy flavor in addition to their health properties.

      • fullstridehealth

        Hi Kelly,
        Thanks for your response.
        Since phytase will breakdown the phytic acid, it seems reasonable to mix high phytic acid content foods with high phytase containg foods. Such as: rye, wheat and buckwheat.
        I have started to mix my hemp seeds and oatmeal with buckwheat to take advantage of the high phytase content of buckwheat.

      • That’s an interesting idea. Thanks for sharing. For those who aren’t familiar, “phosphatase” or “phytase” (a class of phosphate enzymes) is what plants use to break down phytic acid. Humans and other animals don’t produce phytase, however, which is the main reason phytate can be problematic for us. The 2008 publication by Bohn, Meyer, and Rasmussen (reference #3 in my article) does a great job summarizing research on the use of phytase supplements to break down phytic acid in foods and animal feed. Scientists have explored adding bacterial-, fungal- and plant-derived phytase supplements to foods, and this has produced some positive results.

        As to the use of whole food sources of phytase (such as wheat, buckwheat, and rye) to break down phytate, I haven’t yet come across any research exploring these effects. The high levels of phytase in some plants certainly help reduce their phytate content during the germination process, but I am not certain if adding them to other high phytate grains can help in our digestive process. Specifically, I cannot speak to whether phytase-rich whole grains can reduce the anti-nutrient effects of phytate (whether they can improve the absorption of iron, for instance). This looks like a great opportunity for future research, though, so I’m glad you brought it up.

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