Cancer

A New Take on Phytate

A New Take on Phytate
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New research suggests phytate, an “anti-nutrient” found in soybeans and other legumes, may reduce the risk of developing colon cancer.

Most plant foods contain multiple compounds historically classified as antinutrients and/or that are inherent toxicants.1 These compounds play myriad roles in the health and survival of plants.  Their impact on human physiology is, however, much more nuanced as they potentially have both negative and positive effects. For example, cruciferous vegetables contain glucosinolates, which can inhibit thyroid function when consumed in excess2 but are also widely studied for their chemopreventive properties.3

In comparison to other legumes, the soybean is especially high in several antinutrients. One of those is phytate, a phosphorus-containing compound found in whole grains and beans. Phytate is best known for its ability to inhibit the absorption of divalent cations including the minerals calcium, iron and zinc. But it also may function as an antioxidant, as was reviewed by Graf and Eaton nearly 30 years ago.4

Phytic acid may also inhibit the development of cancer as was recently shown by Liu and colleagues in an animal model.5 For this research, male rats were administered a colon carcinogen and except for the control animals, also given one of three doses of phytic acid daily throughout the four-week experimental period. At study end, tumor incidence was significantly decreased in the animals given phytic acid and serum levels of proinflammatory cytokine levels were significantly reduced.

Obviously, it is unwise to draw any conclusions about the chemopreventive effects of phytic acid based on work in rats. Nevertheless, this research serves to illustrate the potential benefits of plant compounds historically classified as antinutrients.

So how then does one put into perspective the potential adverse effects and benefits of phytic acid when considering the role of soyfoods in the diet? Actually, doing so may not be necessary.

Although phytate does moderately inhibit the absorption of calcium in soybeans,6 calcium absorption is still quite good and better than from other beans.7 More importantly, calcium absorption from calcium-set tofu8 and calcium-fortified soymilk9,10 is equal to the absorption of calcium from cow’s milk. Furthermore, in 2015, Armah et al.11 found that habitual consumption of a high-phytate diet can reduce the negative effect of phytate on nonheme-iron absorption. This finding contradicts older research on this topic that until recently wasn’t recognized as being deeply flawed.12 It is reasonable to speculate that the mitigating effect of chronically consuming a high-phytate diet on the effect of phytate on iron absorption applies to other minerals as well. Finally, in an analysis from the Nurses’ Health Study II, which included 96,245 women, over the eight-year follow up period, phytate intake was associated with a 63% reduced risk of stone formation.13

It’s pretty clear that classifying many compounds solely as antinutrients is misleading as some antinutrients may exert beneficial effects. Phytate appears to be one of them. Certainly, the high phytate content of soybeans is not a reason to avoid consuming soyfoods. Future research may show it is actually a reason to consume them.

References

  1. . Essers, A.J., Alink, G.M., Speijers, G.J., Alexander, J., Bouwmeister, P.J., van den Brandt, P.A., Ciere, S., Gry, J., Herrman, J., Kuiper, H.A., et al. Food plant toxicants and safety Risk assessment and regulation of inherent toxicants in plant foods. Environ Toxicol Pharmacol. 1998, 5, 155-72.
  2. Heaney, R.K. and Fenwick, G.R. Natural toxins and protective factors in brassica species, including rapeseed. Nat Toxins. 1995, 3, 233-7; discussion 242.
  3. Dinkova-Kostova, A.T. and Kostov, R.V. Glucosinolates and isothiocyanates in health and disease. Trends Mol Med. 2012, 18, 337-47.
  4. Graf, E. and Eaton, J.W. Antioxidant functions of phytic acid. Free Radic Biol Med. 1990, 8, 61-9.
  5. Liu, C., Chen, C., Yang, F., Li, X., Cheng, L., and Song, Y. Phytic acid improves intestinal mucosal barrier damage and reduces serum levels of proinflammatory cytokines in a 1,2-dimethylhydrazine-induced rat colorectal cancer model. Br J Nutr. 2018, 120, 121-130.
  6. Heaney, R.P., Weaver, C.M., and Fitzsimmons, M.L. Soybean phytate content: effect on calcium absorption. Am J Clin Nutr. 1991, 53, 745-7.
  7. Weaver, C.M., Heaney, R.P., Proulx, W.R., Hinders, S.M., and Packard , P.T. Absorbability of calcium from common beans. .J Food Sci. 1993, 58, 1401-3.
  8. Weaver, C.M., Heaney, R.P., Connor, L., Martin, B.R., Smith, D.L., and Nielsen, E. Bioavailability of calcium from tofu vs. milk in premenopausal women. J Food Sci. 2002, 68, 3144-3147.
  9. Zhao, Y., Martin, B.R., and Weaver, C.M. Calcium bioavailability of calcium carbonate fortified soymilk is equivalent to cow’s milk in young women. J Nutr. 2005, 135, 2379-82.
  10. Tang, A.L., Walker, K.Z., Wilcox, G., Strauss, B.J., Ashton, J.F., and Stojanovska, L. Calcium absorption in Australian osteopenic post-menopausal women: an acute comparative study of fortified soymilk to cows’ milk. Asia Pac J Clin Nutr. 2010, 19, 243-9.
  11. Armah, S.M., Boy, E., Chen, D., Candal, P., and Reddy, M.B. Regular consumption of a high-phytate diet reduces the inhibitory effect of phytate on nonheme-iron absorption in women with suboptimal iron stores. J Nutr. 2015, 145, 1735-9.
  12. Brune, M., Rossander, L., and Hallberg, L. Iron absorption: no intestinal adaptation to a high-phytate diet. Am J Clin Nutr. 1989, 49, 542-5.
  13. Curhan, G.C., Willett, W.C., Knight, E.L., and Stampfer, M.J. Dietary factors and the risk of incident kidney stones in younger women: Nurses’ Health Study II. Arch Intern Med. 2004, 164, 885-91.
Dr. Mark Messina

Author Dr. Mark Messina

PhD in Nutrition, Executive Director, Soy Nutrition Institute. Expert in soyfoods and isoflavones.

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