Phytic acid and the rickets-producing action of cereals / by Douglas Creese Harrison and Edward Mellanby.
- Harrison, D. C. (Douglas Creese)
- Date:
- [1939?]
Licence: In copyright
Credit: Phytic acid and the rickets-producing action of cereals / by Douglas Creese Harrison and Edward Mellanby. Source: Wellcome Collection.
4/26 (page 1662)
![available cereal P might be phytic acid P. They used rats as experimental animals and fed them on a high Ca-low P diet which was deficient in vitamin D. Such a diet by itself produces rickets in rats, the intensity of rickets being diminished by the addition of inorganic phosphate in sufficient amounts to bring the Ca: P ratio within more normal limits. They found that on adding different P-containing compounds to the diet there was a reduction in the intensity of the disease in proportion to the availability of the P of the compound, and that phytin (CaMg inositolhexaphosphate) or sodium phytate caused only a small decrease in the rachitic potency of the diet, while addition of disodium hydrogen phosphate having the same content of P caused a large reduction in rachitic action. Their results established the fact that, under these dietetic conditions, the P of phytin was much less available to the animal than that of sodium phosphate and that the relative effect of these substances in combating rickets of a high Ca-low P type was dependent on this difference of availability. This comparative unavailability of phytic acid P holds also for man, as was shown shortly afterwards by McCance & Widdowson [1935], who determined the actual amount of phytic acid P in the faeces after adding phytin to the diet of human beings. They found that 20-60 % of the phytin was excreted unchanged in the faeces and suggested that much of the remaining phytin P may also have been unabsorbed and have been present in the faeces in other forms. The question of unavailability to animals of phytin P in the diet was also investigated by Lowe & Steenbock [1936, 1] who found that phytin P is partially available to the rat on a low Ca ration, but that the addition of CaC03 makes it almost completely unavailable. All these experimental results made it clear that the statement of Steenbock et al. [1930] that the physiological properties of the compounds in cereals containing P were probably different from those of inorganic phosphates was certainly true. Further, however, the fact that phytic acid was converted into inorganic phosphoric acid and inositol when boiled with dilute HC1 or by the action of phytase fitted in well with the earlier observations that the rachitogenic factor of cereals is destroyed by boiling with HC1 or by exposure to the action of the cereal enzymes after germination, and the results seemed to indicate at first sight that the rachitogenic factor of cereals was in fact phytin. On further consideration it became clear, however, that these various experi¬ ments on the relative availability of P in different compounds had little direct bearing on the positive, rickets-producing action of cereals described by Mellanby. Quite apart from the phytin P, there was abundant P in other forms to produce good bones in Mellanby’s experiments on dogs; moreover, unlike Bruce & Callow, and Steenbock, Mellanby found that, under his experimental conditions, the addition of inorganic phosphate produced no improvement in calcification. The high Ca-low P diets used by Bruce & Callow to produce rickets in rats are not the types of diet which usually produce rickets in children, and rickets in children cannot normally be improved, much less cured, by adding inorganic phosphate to the diet. From the point of view of its relation to human nutrition, the high Ca- low P diet used for studying rickets in rats is a very artificial one. The dietary conditions in Mellanby’s experiments with puppies approach much more closely the conditions leading to rickets in children. The point at issue is clearly not whether phytin P is available but whether phytin itself in cereals is responsible for their positive, rickets-producing effect under ordinary dietetic conditions. Bruce & Callow themselves pointed out that their interpretation of the phytin effect as being due to its unavailable P was](https://iiif.wellcomecollection.org/image/b3063149x_0004.jp2/full/800%2C/0/default.jpg)
