A Low Phosphorus Diet and the Response of Rats to Vitamin D: by H. Schneider

For the past decade or more the experimental production of rickets in rats has generally involved the use of cereal rachitogenie diets (Sherman and Pappenheimer (l), McCollum et al. (2), and Steenbock and Black (3)). Metabolic studies have revealed that the rickets thus produced is referable to a phosphorus defmiency in the growing animal, as indicated by a lowered inorganic P content of the blood and a lowered ash content of the bones. However, Bruce and Callow (4) and Lowe and Steenbock (5) have shown that the cereal, so called “low phosphorus” diets are so in effect only because of the low availability of their phytin phosphorus. Giri (6) reports that 50 to 70 per cent of the phosphorus of cereals is phytin phosphorus. Maize, the main constituent of the Steenbock-Black diet, is reported as having 69.1 per cent of its P present as phytin P. Giri (6) has also shown that the phytase activity of cereals is in inverse relation to the phytin content. Patwardhan (7) has demonstrated a low phytase activity in the intestine of the rat. Phytases evidently can introduce a factor of uncertainty in studies in phosphorus metabolism, for it is obviously essential that all sources of physiologically available phosphorus be known and controlled. Synthetic diets actually low in total phosphorus would offer obvious advantages over those composed of naturally occurring foods.