The high phytate content of soy and plant-based diets might help to prevent the development of cancer. That speculation could be drawn from the publication of a case report in Melanoma Research describing cancer remission in response to phytate supplementation.1
First, some background.
Phytate (inositol hexaphosphate, IP6) is found in all whole grains and legumes including soybeans. Myo-inositol (inositol) is a parent compound of IP6; foods containing the highest concentrations of inositol include fruits, beans, grains, and nuts.2
Despite being found in abundance in healthy foods, IP6 is generally viewed as an anti-nutrient because it inhibits the absorption of divalent cations, which include minerals such as calcium, iron and zinc. The effect of phytate on mineral absorption is one reason the iron RDA is 80% higher for vegetarians than for nonvegetarians. So potentially impactful is phytate on mineral absorption, the European Food Safety Authority set dietary zinc requirements for adults based on four levels of dietary phytate.3
However, there appears to be adaption to the inhibitory effects of phytate.4 In 2015, researchers found that the inhibitory effect of phytate on iron absorption was mitigated by the chronic consumption of a high-phytate diet. If this result holds true for the other divalent cations, it means the effect of phytate on mineral status in individuals consuming plant-based diets is a lot less than commonly thought.
Despite its classification as an anti-nutrient, phytate was one of the five proposed chemopreventive agents in soybeans identified at a workshop held in 1990 that was sponsored by the U.S. National Cancer Institute.5 This workshop fueled much of the research interest in the role of soy in preventing cancer that followed. Dr. Ernst Graf, one of the workshop participants, offered the antioxidant effects of phytate as the explanation for the inverse relationship between the consumption of fiber-rich foods and colon cancer incidence, as fiber-rich foods tend to be very high in phytate.6 Much more recently, phytate was shown to inhibit the development of colon cancer in an animal model.7
Much of the work involving the role of phytate in reducing risk of cancer of all types has been conducted by Dr. AbulKalam M. Shamsuddin and colleagues from the University of Maryland School of Medicine.8 They postulate that the anticancer potential of phytate is due to a combination of antioxidant, anti-inflammatory, and immune-enhancing activities. Inositol and IP6 may work together additively or even synergistically. Nevertheless, despite a fair amount of promising research, it is fair to say the anti-cancer properties of phytate haven’t received a lot of attention over the years.
That is one reason this conclusion by Khurana and colleagues caught my attention: “Although this is a single clinical case showing IP6 + inositol’s potential role in controlling our patient’s stage IV disease and spontaneous regression of primary melanoma, and rarely metastatic melanoma has been reported in literature, we believe that there are ample preclinical and clinical data to suggest that this nontoxic, readily available supplement should be evaluated in clinical trials for its antitumor activity.”1 The patient in question had metastatic melanoma but declined traditional therapy and opted instead to try an over the counter supplement of IP6 + inositol. The patient achieved a complete remission and remains in remission 3 years later.
The patient took daily 4,000 mg of phytate and 1,100 mg of inositol. For comparison, a serving of a traditional soyfood, such as a serving of tempeh, tofu or soymilk, may provide 300 to 500 mg of phytate.9 That is a far cry from the amount consumed by the patient. A typical American may only consume from their diet only 1,000 mg of IP6 per day, although vegans may easily consume twice or even three times that amount.10
Although usual dietary intake is lower than the amount associated with cancer remission noted in the case report, it is reasonable to speculate that the high phytate content of plant-based diets might help to prevent the development of cancer. Hence, the phytate content of soyfoods may be one reason to incorporate these foods into the diet.
- Khurana S, Baldeo C, Joseph RW. Inositol hexaphosphate plus inositol induced complete remission in stage IV melanoma: a case report. Melanoma Res. 2019.
- Clements RS, Jr., Darnell B. Myo-inositol content of common foods: development of a high-myo-inositol diet. Am J Clin Nutr. 1980;33(9):1954-67.
- Gibson RS, Raboy V, King JC. Implications of phytate in plant-based foods for iron and zinc bioavailability, setting dietary requirements, and formulating programs and policies. Nutr Rev. 2018;76(11):793-804.
- Armah SM, Boy E, Chen D, et al. 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(8):1735-9.
- Messina M, Barnes S. The role of soy products in reducing risk of cancer. J Natl Cancer Inst. 1991;83(8):541-6.
- Graf E, Eaton JW. Antioxidant functions of phytic acid. Free Radic Biol Med. 1990;8(1):61-9.
- Liu C, Chen C, Yang F, et al. 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(2):121-30.
- Vucenik I, Shamsuddin AM. Protection against cancer by dietary IP6 and inositol. Nutr Cancer. 2006;55(2):109-25.
- Al-Wahsh IA, Horner HT, Palmer RG, et al. Oxalate and phytate of soy foods. J Agric Food Chem. 2005;53(14):5670-4.
- Schlemmer U, Frolich W, Prieto RM, et al. Phytate in foods and significance for humans: food sources, intake, processing, bioavailability, protective role and analysis. Mol Nutr Food Res. 2009;53 Suppl 2S330-75.