In theory, unbound phytic acid can bind up more than just calcium. I haven't read much of the research, but don't you think that other mineral imbalances can occur? This can even happen when eating bound phytates from food like nuts and whole grains, though that's less likely to be an issue.
I've seen some conflicting opinions about whether IP6 in bound food form or unbound supplemented form is more beneficial.
Here a good read.
PHARAMACOLOGY AND ACTION
Inositol hexaphosphoric acid (phytic acid, INN Fytine acid Roempps Chemie Lexicon, 1983) serves as a phosphate depot in the body and is broken down by phytase to myo-inositol. The human body contains about 40 g of myo-inositol. It also plays the role of a growth factor and is identical in action to the formerly designated as "bios I" factor, necessary for optimal growth. Based on its mode of action, myo-inositol can be classified to the vitamin complex of ht B-group (Roempps Chemie Lexicon, 1983). In the body, myo-inositol can be synthesized from glucose-6-phosphate, but human requirements are chiefly covered through consumption of fruit and cereals, where it occurs in the form of inositol-hexaphosphate (phytic acid).
By competitive chelate formation phytic acid participates in the process of intestinal absorption of calcium, magnesium and iron ions. The formation of insoluble chelate complexes of phytic acid accounts for some of its extremely important properties, such as its anticancer and antiviral activity.
Myo-inositol increases the oxygen transporting capacity of hemoglobin in red blood cells, improves and regulates cellular metabolism, especially in conditions of phosphorus deficiency in the body, stimulates hemopoiesis and bone tissue formation, and improves the tone of the nervous system.
The overall complex effect of Phytin is expressed in a general tonic action which, combined with its involvement in the regulatory metabolic processes, improves the intensity and stability of attention, increases performance and work capacity, removes the feeling of fatigue, and stimulates the organism's defenses through yet not entirely clear mechanisms (Torre et al., 1991).
Phytin as a food supplement is very good for prophylaxis in conditions of physical and mental strain, and for increasing general endurance during active exercise and sports. Phytin can also be included in the complex therapy of such conditions of the nervous system that are associated with phosphorous deficiency. For bone diseases, in combination with calcium preparations, it can be used rickets, osteomalacia, and bone fractures. In combination with iron preparations, it can be used for anemia in adults and children. It is recommended for insomnia and loss of appetite, either alone or in combination with various prescription drugs.
The inhibitory effect of phytic acid on the proliferation of human immune deficiency viruses (HIV), implicated as causative agents of the acquired immune deficiency syndrome (AIDS), has been tested in vitro by Japanese scientists (Otaka et al., 1989). They found that phytic acid, at a concentration of 1.67 mg/ml, inhibits the cytotoxic effect of the immune deficiency virus and the specific antigenic reaction in the effected cells.
Several studies (Nicoletti F. et al. 1989) have demonstrated an increase of calcium ion influx in cerebellar neurons. They provide evidence for a direct activating effect of phytic acid and its salts on the functional activity of the central nervous system. These data are further confirmed by other authors, who established an important role of phytic acid in the regulation of cell metabolism.
Various studies (Shamsuddin A. M. et al., 1989; Ullah A. et al. 1990) in recent years investigated the anticancer effect of phytic acid and its salts. Interesting results were obtained on experimental intestinal tumors in mice and rats. The antineoplastic effect was tested in physiologic pH. The reported anticancer activity in test animals, expressed in significant tumor reduction, suggests a likely prophylactic use for phytic acid and its salts in humans who are predisposed to intestinal and pancreatic tumors.
Repeated dose administration of Phytin has revealed no changes in the body mass and electrolytic balance, and no signs of toxicity in the test animals, even at higher doses.
The inclusion of inositol-hexaphosphate (InsP6 or IP6) as an active ingredient of fiber-rich diets is being discussed in literature. The anti-carcinogenic activity of inositol-hexaphosphate has been confirmed on in vitro and in vivo models (Shamsuddin A. M. 1996). The investigation of Graf (1993) on the inhibitory effect of phytic acid containing dietetic foods also corroborated that activity.
According to most recent studies of phytic acid as a major component of cereal grains and beans is considered an important antioxidant and is increasingly used in various therapeutic diets for its protective effect on cancer of the colon and rectum (Owen R.W. et al. 1996). Rao P.S. et al (1991) studied the antioxidation properties of phytic acid at oral doses of up to 15 mg/100g body mass in rats for its protective effect on ischemic heart disease and found improved perfusion in the ischemic myocardial region.