Dietary influences of 1,25(OH)2 vitamin D in relation to prostate cancer: a hypothesis.

Diets high in dairy products and meats are related to higher risk of prostate cancer incidence or mortality in most ecologic, case-control, and prospective studies. Recent laboratory and epidemiologic evidence indicates that a high circulating level of 1,25(OH)2 vitamin D [1,25(OH)2D], the biologically active form of vitamin D, inhibits prostate carcinogenesis. This paper will examine the hypothesis that these observations may be linked, specifically that high dairy and meat consumption increase risk of prostate cancer by lowering 1,25(OH)2D. High intakes of calcium and phosphorus, largely from dairy products, lower circulating 1,25(OH)2D level, and sulfur-containing amino acids from animal protein lower blood pH, which also suppresses 1,25(OH)2D production. Additionally, high fructose consumption produces a transitory hypophosphatemia, and may adversely affect calcium and phosphate balance, all of which may stimulate 1,25(OH)2D production. The evidence that 1,25(OH)2D inhibits prostate carcinogenesis, and that diets that are high in calcium, phosphorus, and sulfur-containing amino acids from animal protein, as well as low in fructose, tend to decrease circulating 1,25(OH)2D will be presented. The studies examining these dietary factors in relation to prostate cancer risk will be reviewed.