Vitamin D and intestinal phytase.

When it was revealed that the equalization of the phosphorus content of cereal grain rations did not equalize their antirachitogenic properties, it appeared probable that cereal phosphorus did not always have the same nutritive value as inorganic P (1). This was proved to be the case with high Ca, low P diets by Bruce and Callow (2). Krieger et al. (3) confirmed these findings with semisynthetic cereal-free diets to which phytic acid had been added. Later, with the same technique, the importance of the Ca:P ratio was stressed. An excessively high Ca intake depressed calcification, as was well known from the work of McCollum (4), but this effect was slight with inorganic P as contrasted with phytic acid P (5). Vitamin D improved calcification more with the latter than with inorganic P. Later Krieger et al. (6), using high calcium diets, demonstrated that phytic acid P was also inferior in value to the P of yeast nucleic acid and soy bean phosphatides. Vitamin D effected the most improvement with phytic acid, but the level of calcification never equaled that attained with P from other sources. Lately Boutwell et al. (7) found that bran P at a Ca:P ratio of 2: 1 was poorly utilized, but that its utilization was improved by vit,amin D to a level approaching that of inorganic P. Still more recently Spitzer et al. (8) obtained similar results with Ca phytate. The nature of the mechanism whereby this improvement in the value of phytic acid phosphorus may be effected has been a challenge to investigators for some time. Mellanby (9) and Green and Mellanby (10) found that the anticalcifying action of cereals for dogs was reduced by boiling t,he cereals with 1 per cent HCl. Bruce and Callow (2) and Lowe and Steenbock (11) obtained similar results with rats on high Ca cereal diets. They reported that maize had its rachitogenic properties reduced in proportion to the extent that its phytic acid was hydrolyzed. Mellanby (12) found that germination and autolysis reduced the anticalcifying properties of oats. Templin and Steenbock (13) found that maize was improved antirachitically by germination, followed by autolysis. Lowe and Steenbock