Tuesday, October 12, 2010

Soy Dangers - Phytate/ Phytic Acid

It is time to look at another common rumor regarding soy foods; the dangers posed by phytates. Phytate is the name for the salt form of phytic acid, a phosphorus containing molecule in many plant tissues.

The Weston A. Price Foundation writes, “High levels of phytic acid in soy reduce assimilation of calcium, magnesium, copper, iron and zinc. Phytic acid in soy is not neutralized by ordinary preparation methods such as soaking, sprouting and long, slow cooking. High phytate diets have caused growth problems in children.”

The “natural health” website Mercola writes, “Soy contains phytates. Phytates (phytic acid) bind to metal ions, preventing the absorption of certain minerals, including calcium, magnesium, iron, and zinc -- all of which are co-factors for optimal biochemistry in your body. This is particularly problematic for vegetarians, because eating meat reduces the mineral-blocking effects of these phytates (so it is helpful—if you do eat soy—to also eat meat).”

Soy Online Service adds, “Soybeans contain very high levels of phytate and their[sic] are numerous reports of reduced bioavailablity[sic] of various metals from foods containing soy; this has particular significance for vegetarians and infants fed soy-formulas.”

We already learned from last year's post on The Dangers of Phytoestrogens that, “Comprehensive literature reviews and clinical studies of infants fed SBIFs[soy based infant formulas] have resolved questions or raise no clinical concerns with respect to nutritional adequacy, sexual development, neurobehavioral development, immune development, or thyroid disease. SBIFs provide complete nutrition that adequately supports normal infant growth and development.” Interestingly however, there is still quite a bit of truth to these concerns over phytate. Soy does contain phytate and phytate does reduce our absorption of several minerals.

There is one redeeming aspect to all of this however. Soy is not a particularly exceptional source of phytate. The 2001 book Food Phytates brought together a lot of information about phytates and published it in a very convenient fashion. Part of this book involved gathering data on quantity of phytate in various foods and arranging that into a convenient table. Here are a few bits of data from that table:

Source - %Phytate by mass
Dolique Beans – 5.92-9.15%
Brazil Nut – 1.97-6.34%
Almond – 1.35-3.22%
Tofu – 1.46-2.90%
Linseed – 2.15-2.78%
Pinto Beans – 0.61-2.38%
Soybeans – 1.00-2.22%
Peanuts – 1.05-1.76%
Kidney Beans – 0.89-1.57%
Tempe – 0.67-1.08%
Soy Milk – 0.05-0.11%

Do keep in mind that you probably consume much more soy milk by mass than you would soybeans or almonds. The book also mentions that, “Dry cereals account for 69.5% of the total global crop seeds/grains/fruit each year but synthesized 77.3% of the total PA [Phytic Acid]. Legumes account for 7.6% of the annual global production of crop seeds/grains/fruits and 13.0% of the total PA.” I encourage you to look through the entire table for yourself, which is available via Google Books.

The American Dietetic Association in their position paper regarding vegan and vegetarian diets brings up phytic acid or phytate several times, regarding calcium, zinc, and iron.

One recent study attempted to measure the absorption of calcium and zinc in Nigerian children with and without rickets. In the study the authors, “sought to examine 1) the effect of a typical Nigerian meal on the absorption of zinc and calcium 2), the effect of meal dephytinization on calcium and zinc absorption, and 3) whether the relationships between mineral absorption, meal consumption, and dephytinization were different in children with and without rickets.” Dephytinization is the word for removing phytate from a substance. The study authors went about this by giving the study participants a bowl of porridge along with a cup of orange juice fortified with both calcium and zinc to be consumed half way through. They repeated this process with both regular and phytate reduced porridges. While the study was largely about rickets, those findings had no detectable effect on the results. “Calcium absorption did not differ significantly between children with and without rickets for any permutation of meal.” Interestingly, they also note that the phytic acid had no significant impact on calcium absorption either. “Calcium absorption with fermented[phytate reduced] porridge (50.7 ± 19.1%) did not differ from unfermented porridge (50.1 ± 17.3%; P = 0.94).” The study also found rickets to have no detectable effect on zinc absorption. It did however find that dephytinization had a significant impact. “Enzymatic dephytinization increased zinc absorption during the second absorption study (55.5 ± 18.0% vs. 32.2 ± 14.8%; P < 0.001). Dephytinization resulted in a mean relative increase in zinc absorption of 101 ± 88%.” This study suggests that phytic acid has at most a modest impact on calcium absorption, but may affect the absorption of zinc fairly significantly.

The effect of phytic acid on iron absorption has been much more thoroughly studied. One study attempted to model iron absorption based off a number of factors and was able to achieve an r^2 value of .987 (usually interpreted as 98.7% of the variation in iron absorption rates could be accounted for by their model). The two main terms in their model were phytic acid content and ascorbic acid content (more commonly known as vitamin C). Their model found that the ratio of iron that was absorbed from an ordinary wheat roll increased linearly with the amount of ascorbic acid, decreased with the logarithm of phytic acid content. This means that as vitamin c increases the rate of iron absorption continues to increase at a similar rate, while as phytic acid increases it has a diminishing impact on the amount it inhibits absorption. Overall however, if you look at absorption from the vegetarian meals they studied the absorption of iron in those meals was still much lower than absorption from meat-containing meals. Perhaps this is why the American Dietetic Association suggests, “because of lower bioavailability of iron from a vegetarian diet, the recommended iron intakes for vegetarians are 1.8 times those of nonvegetarians.”

So while soy certainly isn't a guilty culprit, phytic acid absolutely has a negative impact on our absorption of minerals as vegetarians. What, however, is the net impact of all this on overall health? Perhaps a paper titled Health Effects of Vegan Diets in the American Journal of Clinical Nutrition can help answer this for us.

“[T]he risk of iron deficiency anemia are similar for vegans compared with omnivores and other vegetarians. Vegans often consume large amounts of vitamin C–rich foods that markedly improve the absorption of the nonheme iron.”

“Phytates, a common component of grains, seeds, and legumes, binds zinc and thereby decreases its bioavailability. However, a sensitive marker to measure zinc status in humans has not been well established, and the effects of marginal zinc intakes are poorly understood. Although vegans have lower zinc intake than omnivores, they do not differ from the nonvegetarians in functional immunocompetence as assessed by natural killer cell cytotoxic activity. It appears that there may be facilitators of zinc absorption and compensatory mechanisms to help vegetarians adapt to a lower intake of zinc.”

“More recent studies with postmenopausal Asian women showed spine or hip BMD was significantly lower in long-term vegans. Those Asian women, who were vegetarian for religious reasons, had low intakes of protein and calcium. […] The higher risk of bone fracture seen in vegans appears to be a consequence of a lower mean calcium intake. No difference was observed between the fracture rates of the vegans who consumed >525 mg calcium/d and the omnivore fracture rates.”

Overall it seems that our lower rates of absorption of zinc and iron are accounted for by higher intakes of those minerals. Getting enough calcium can be a concern for some vegans, but for those who do they seem to utilize it just fine. If there is one thing to take away from all this, I think the American Dietetic Association summarizes it best. “[A]ppropriately planned vegetarian diets, including total vegetarian or vegan diets, are healthful, nutritionally adequate, and may provide health benefits in the prevention and treatment of certain diseases. Well-planned vegetarian diets are appropriate for individuals during all stages of the life cycle, including pregnancy, lactation, infancy, childhood, and adolescence, and for athletes.”

Plan your diet well, eat a healthy variety of foods, and no, eating soy is not going to kill you.


  1. Well stated. Truth is always balanced, and this article has that mark on it.

    1. Phytic acid is easy to remove so there no need to be afraid of beans which are very ecofriendly and healthy.

    2. Skethup11, you might want to view the original post and look at the other concerns. It isn't just phytates. Use your knoggin for a bit of critical thinking and look at the other health concerns which he hasn't spoken about. There is absolutely nothing balanced in this post he's written because he only looks at the phytic acid aspect. This is only 1 minor element of it. There is more.

    3. https://www.researchgate.net/publication/229471466_Anti-cancer_function_of_phytic_acid

  2. Thank you for an objective article.

  3. I appreciate that not only do you write honestly (without alarm) regarding the subject matter, but you back it up with links to studies as well. Thank you for your well written articles.

  4. If anyone is still concerned with phytic acid you could take a phytase supplement. Phytase the enzyme which breaks down phytic acid.

  5. Check some studies Phytic Acid can only reduce absorption mineral only in foods with contain phytic acid and minerals binded for example if you eat grain with phytic acid and some veggs only minerals from grains will have reduce absorption BTW absorpiton is lower only by 20% Second phytic acid is linked to reduce risk of heart disease, diabetes, obesity, and other chronic diseases and even cancer one link for example http://www.ncbi.nlm.nih.gov/pubmed/17044765

  6. P.S My comment is not critique but new information for you should which you should post.

  7. what to say i praise of this blog, which contains a lot of amazing information as well as the thoughtful writes.
    Adisoy brings forward Soy products delightful mouth-watering soy cheese in both plain and spice options. Now you can take home health, happiness and taste for the whole family available at http://www.adisoy.in/Default.aspx

  8. Stupid meat eaters need to justify animal abuse. Phytic is easy to remove by 12 hour soaking, also sprouting and heat helps. Healthiest soy is fermented. Soy is much more ecofriendly and requiring less resources.

    1. Look at my post. I'm a vegan and the original author. craigsvegansolutions.com Just recently started a website and I have a lot of work to do on it yet but I am a vegan not "A stupid meat eater" as you would say.


  9. الفك والتركيب والتغليف والتحرك من خلال شركة نقل اثاث بجدة متميزة تحتاج الي ركن البيت للاستفادة من خدماتها التي لا تقدم غير خدمات نقل اثاث بجدة رائعة لتلبية طلبات العميل. فرؤية الشركة لدينا وضعت طريقة جيدة وضعت كخبراء في نقل الخدمات التي يحتاجها العملاء عند التعاون مع شركة نقل عفش بجدة فاختيار المواد الخاصة بك التي تستخدم في تغليف الاثاث فهذه المواد أو الأشياء ستكون موجودة على عتبة المنزل للتحرك بكل آمن و بقوة إلى المكان الذي ترغب فيه
    شركة نقل الاثاث بالدمام
    استخدام الأصول الأولى داخل الاستراتيجية التي تستخدمها شركة نقل عفش بالدمام لدينا تدفعنا إلى التفكير في إعطاء نوع من الخدمات المتميزة الي العملاء التي تترك نجاحا مباشرا يمكن أن تنقش على نفسية الزبائن التي تقدم لهم خدمة نقل العفش.فلدينا ميل إلى أن يشار جيدا إلى العاملون والفنين والمغلفون ان يقوموا بعملهم في شركة نقل اثاث بالدمام نتيجة للمعيار والتنمية والعقل
    شركة نقل الاثاث بمكة
    مجموعة معينة لدينا في شركة نقل عفش بمكة تساعدنا في خدمتك في أي وقت من اليوم، وأنهم على استعداد للبقاء على طول هذه الخطوط لاعطاءك خدمة متميزة عن باقي شركات نقل اثاث بمكة التي توجد بهذه المنطقة فلا أحد لدينا في خدمات النقل يترك شيئا حتي لا نقع في قليلا من السخط.
    شركة تخزين الاثاث بالرياض
    التعبئة والتغليف يبدأ بالعمل المتميز من اجل الحصول علي شركة تخزين عفش بالرياض متميزة تمتلك مستودعات تخزين اثاث بالرياض تحافظ علي الممتلكات الخاصة بكم من الخراب. كما ان التعبئة والتغليف على استعداد فريد للتعامل مع كل نوع من الأدوات والأشياء الزجاجية والمواد التي تميل إلى الإضرار أو تحمل بانتظام أسوأ جزء في عملية الحركة. فخدمات شركة تخزين اثاث بالرياض تقوم بإرسال أفضل مجموعة يتقن الوصول إليها في الوقت المناسب لتلبية طلب العميل وفقا لمتطلبات محددة خاصة بك في هذا المجال بسبب الطريقة التي كانت لدينا مجموعة من الخبراء في كيفية ادارة مستودعات تخزين اثاث منذ فترة طويلة في هذه الصناعة لفترة طويلة جدا.
    شركة تخزين اثاث
    شركة تخزين عفش

  10. Phytase catalyzes the hydrolysis of phytic acid to inositol and free orthophosphate. Wheat phytase can degrade inositol phosphate-6 and 5 at a pH of 4 and 5. phytase supplement

  11. As the original author of the soy post Weston A. Price foundation is passing off as their own. (They plagiarised me) Let me start by asking you this question. CRITICAL THINKING. Are you aware of what it is and are you aware of how to use it? True. Phytate levels are higher in peanuts but how foolish to base your argument on one single facet. What about the trypsin inhibitors linked with causing pancreatic disorders and stunted growth. What about the soy phytoestrogens disrupting the endocrine function, hypothyroidism and what about the toxic lysinoalanine or carcinogenic nitrosamines MSG and high aluminium levels. Please read the post again from the original author and look at the other concerns I had when I wrote this letter in June 2011 to my up line in Herbalife.

    Remember, the only safe soy is that which is fermented first such as soy sauce. Soy protein powders are in my opinion the worst.

    Craig ....................@gmail.com>
    Tue, Jun 28, 2011, 9:18 PM
    to Herbalife:

    OK. David. I've already asked you to take me off your mailing list. If your going to keep pestering me then I'll tell you what I know about soy.

    High levels of phytic acid in soy reduce assimilation of calcium, magnesium, copper, iron and zinc. Phytic acid is not neutralized by ordinary preparation methods such as soaking, sprouting, and long slow cooking. High phytate diets have caused growth problems in children. Trypsin inhibitors in soy interfere with protein digestion and may cause pancreatic disorders. In test animals, soy containing trypsin inhibitors caused stunted growth.
    Soy phytoestrogens disrupt endocrine function and have the potential to cause infertility and to promote breast cancer in adult women. Soy phytoestrogens are potent antithyroid agents that cause hypothyroidism and may cause thyroid cancer. In infants, consumption of soy formula has been linked to autoimune thyroid disease/ vitamin B12 analogs in soy are not absorbed and actually increase the bodys requirement for B12.
    Soy foods increase the body's requirement for vitamin D. Fragile proteins are denatured during high temperature processing to make soy protein isolate and textured vegetable protein. Processing of soy protein results in the formation of toxic lysinoalanine and highly carcinogenic nitrosamines. Free glutamic acid or MSG, a potent neurotoxin, is formed during soy food processing and additional amounts are added to many soy foods. Soy foods contain high levels of aluminum which is toxic to the nervous system and kidneys.

    Take a good long look at this post and please feel free to do further research and do yourself a favour. Connect the other dots which is not being connected. The truth is always balanced when you have ALL THE FACTS.Not just some.

  12. Phytase catalyzes the hydrolysis of phytic acid to inositol and free orthophosphate. Wheat phytase can degrade inositol phosphate-6 and 5 at a pH of 4 and 5. phytase