You can relax. Context matters.
Consuming foods rich in ascorbate (vitamin C) with foods rich in phytate can cancel the negative effects of phytate on mineral absorption.[1, pdf] Just eat some fruits and vegetables with foods that supply phytate.
Some studies have shown substantial degradation of phytate in the human gut (70-86%), indicating that humans adapt to diets high in phytate by increasing small intestinal production of phytase. [2 full text link, 3]
I have never seen any evidence that dietary phytate causes mineral deficiencies except in the context of overall poor quality diet, such as people attempting to live on diets composed entirely of unleavened grains and legume flours without adequate intake of vegetables, fruits, and other mineral sources.
If you live in a modern industrialized nation, when was the last time you had someone tell you that a physician diagnosed her with multiple mineral deficiencies caused by excessive dietary phytate?
I have never seen it.
Anticancer Effects of Phytates
Everything has a front and a back.
According to researchers from Linus Pauling Institute of Science and Medicine, phytates appear to have anticancer effects by binding excess minerals in tissues, depriving tumors of essential minerals.[4 pdf]
Vucenik and Shamsuddin discuss the anticancer properties of phytate in detail; all information and quotes remaining in this post come from their report in the Journal of Nutrition.[5 full text]
Almost all mammalian cells contain phytate in the inositol hexaphosphate (IP6) form and others with smaller numbers of phosphate groups (IP1-5). When we ingest dietary phytate, intracellular levels of IP6 increase, and from this cells increase the levels of the other forms, which appear involved in "cellular signal transduction, regulation of cell function, growth, and differentiation."
Dietary phytate enters the blood stream and reaches tissues, including tumors, far from the gut.
Tumor cells take up phytate, probably by pinocytosis or receptor-mediated endocytosis.
Phytate inhibits malignant growth in human leukemic, colon cancer, breast cancer, cervical cancer, prostate cancer, and liver cancer cells.
"IP6 inhibited the growth of all tested cell lines in a dose- and time-dependent manner. The growth of cells of hematopoietic lineage was inhibited: human leukemic hematopoietic cell lines, such as K-562 (26,27) and human normal and leukemic hematopoietic cells (27). The antiproliferative activity of IP6 was further reported in human colon cancer HT-29 cells (28), estrogen receptor–positive and estrogen receptor–negative human breast cancer cells (32), cervical cancer (25), prostate cancer (15,33,34), and HepG2 hepatoma cell lines (31). IP6 also inhibited the growth of mesenchymal tumors, murine fibrosarcoma (39), and human rhabdomyosarcoma (38)."Phytate also causes malignant cells to mature and differentiate into normal cells:
"The potential of IP6 to induce differentiation and maturation of malignant cells, often resulting in reversion to the normal phenotype, was first demonstrated in K-562 hematopoietic cells (26). IP6 was further shown to increase differentiation of human colon carcinoma HT-29 cells (28,29), prostate cancer cells (33), breast cancer cells (32), and rhabdomyosarcoma cells (38)."Phytates provide an intracellular antioxidant function by binding with iron, which suppresses formation of the most hazardous hydroxyl radicals:
"The antioxidant role of IP6 is known and widely accepted; this function of IP6 occurs by chelation of Fe3+ and suppression of ·OH formation (11). Therefore, IP6 can reduce carcinogenesis mediated by active oxygen species and cell injury via its antioxidative function."Phytate also stimulates the immune response and protects against carcinogen-induced depression of natural killer cell activity.
"Besides affecting tumor cells, IP6 can act on a host by restoring its immune system. IP6 augments natural killer cell activity in vitro and normalizes the carcinogen-induced depression of natural killer cell activity in vivo (59). "Phytate only adversely affects malignant cells, not normal cells:
" The most important expectation of a good anticancer agent is for it to only affect malignant cells and not affect normal cells and tissues. That property was recently shown for IP6. When the fresh CD34+ cells from bone marrow was treated with different doses of IP6, a toxic effect (inhibition of the clonogenic growth or as cytotoxicity on liquid cultures) was observed that was specific to leukemic progenitors from chronic myelogenous leukemia patients but no cytotoxic or cytostatic effect was observed on normal bone marrow progenitor cells under the same conditions."This indicates that normal cells are adapted to phytate. Of course, since phytate is abundant in the plant world and also present in almost every mammalian cell.
Phytate inhibits all of the several pathways supporting malignancy:
" From the behavior and characteristics of malignant cells, several principal pathways of malignancy have been established, such as proliferation, cell cycle progression, metastases and invasion, angiogenesis, and apoptosis; interestingly, IP6 targets and acts on all of them."In one pilot clinical trial, six patients with advanced colorectal cancer (Dukes C and D) with multiple liver and lung metastasis received oral phytate plus chemotherapy. One of the patients refused additional chemotherapy after one session and she was treated only with IP6 plus inositol. What happened?
"...her control ultrasound and abdominal computed tomography scan 14 mo after surgery showed a significantly reduced growth rate. A reduced tumor growth rate was noticed overall and in some cases a regression of lesions was noted."Say again? A simple, natural dietary ingredient reversed the progress of cancer!
Which reminds me:
"Pioneering experiments showing this novel anticancer feature of IP6 were performed by Shamsuddin et al. (18–20), who were intrigued by the epidemiologic data indicating that only diets containing a high IP6 content (cereals and legumes) showed a negative correlation with colon cancer."Most hunter-gatherer groups would have consumed significant phytate from nuts and seeds of various sorts, including legumes.
Dietary Phytate Safety
Vucenik and Shamsuddin agree that chronic phytate ingestion does not cause mineral deficiencies whether gotten from food or isolated form unless the overall diet lacks essential minerals:
"Some concerns have been expressed regarding the mineral deficiency that results from an intake of foods high in IP6 that might reduce the bioavailability of dietary minerals. However, recent studies demonstrate that this antinutrient effect of IP6 can be manifested only when large quantities of IP6 are consumed in combination with a diet poor in oligoelements (60–63). A long-term intake of IP6 in food (60,61) or in a pure form (64) did not cause such a deficiency in humans. Studies in experimental animals showed no significant toxic effects on body weight, serum, or bone minerals (Table 5) or any pathological changes in either male F344 or female Sprague-Dawley rats for 40 wk (40,51,52). Grases et al. (65) confirmed our findings and also reported that abnormal calcification was prevented in rats given IP6."Phytate has many benefits:
"In humans, IP6 not only has almost no toxic effects, but it has many other beneficial health effects such as inhibition of kidney stone formation and reduction in risk of developing cardiovascular disease. IP6 was administered orally either as the pure sodium salt or in a diet to reduce hypercalciuria and to prevent formation of kidney stones, and no evidence of toxicity was reported (64,65,79,80). A potential hypocholesterolemic effect of IP6 may be very significant in the clinical management of hyperlipidemia and diabetes (75,76,81). IP6 inhibits agonist-induced platelet aggregation (82) and efficiently protects myocardium from ischemic damage and reperfusion injury (83), both of which are important for the management of cardiovascular diseases. "Perhaps avoiding and removing phytates from food doesn't serve your best interests?
Perhaps we evolved to consume significant amounts of phytates, and cancer is a disease facilitated by a dietary deficiency of phytates?