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Does high dietary P accelerate cancer and aging?

June 20, 2010

Some very recent findings with manipulations of dietary P contents in mice raise interesting questions about the possible role of elevated dietary P in both cancer and aging.  They also provide pretty strong new motivation for reducing P in your diet, which would have the added benefit of helping to close the human P cycle with benefits for present and future generations of humanity.

In the cancer studies, mice model systems of lung cancer and skin cancer received diets in which only the levels of dietary P were manipulated (in the case of lung cancer, P was increased from normal chow; for skin cancer, P was decreased from the normal level).  In both cases, there were substantial changes in the number, size, and progression rates of tumors associated with higher dietary P.  In the case of aging, the researchers studied mice with known genetic mutations that affect their ability to regulate blood P levels; these mutant mice age rapidly and show various signs of premature dis-repair.  When these mutant mice were fed diets with low P, however, they did NOT show such accelerated aging and led happy mouse lives similar to those in genetically normal controls.

Lungs from mice on normal diet (L) and high P diet (R). Note increase in number and size of tumors! (From Jin et al. 2009)

The cancer result is consistent with ideas generated by the Elser lab at ASU proposing that some tumors might be P-limited because rapidly growing cells (like those in tumors) need a lot of P to make P-rich ribosomes to sustain growth.

It seems like P is a “universal biological accelerant”, promoting rapid biological growth and proliferation in the body, as it does in lakes and as it does in agricultural fields.

These findings, while still a bit preliminary, present yet another compelling reason to increase the efficiency of P use in the human system – by reducing meat and dairy intake (lots of P in meat and milk; lots of P lost in making meat and milk) and by avoiding foods with P additives (e.g. many soft drinks).  Perhaps we also need to find a way to reduce the content of P in grains, fruits, and vegetables, at least for those in developed world markets where most people routinely get much more than the “daily adult requirement” for P.

How many more motivations do we need?

Here are the original papers:

Jin, H., C.-X. Xu, H.-T. Lim, H.-T. Lim, S. J. Park, J.-Y. Shin, Y.-S. Chang, S.-C. Park, S.-H. Chang, H.-J. Youn, K.-H. Lee, Y.-S. Lee, Y.-C. Ha, C. H. Chae, G. R. Beck, and M. H. Cho. 2009. High dietary inorganic phosphate increases lung tumorigenesis and alters Akt signaling.  American Journal of Respiratory and Critical Care Medicine 179:1-59.

Camalier, C. E., M. R. Young, G. Bobe, C. M. Perella, N. H. Colburn, and G. R. Beck, Jr. 2010. Elevated phosphate activates N-ras and promotes cell transformation and skin tumorigenesis. . Cancer Prev Res (Phila Pa) 3: 359-370. 3:359-370.

Ohnishi, M. and M. Shawkat. 2010. Dietary and genetic evidence for phosphate toxicity accelerating mammalian aging. The FASEB Journal 24:1-10.

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