Phytic acid and the rickets-producing action of cereals / by Douglas Creese Harrison and Edward Mellanby.

  • Harrison, D. C. (Douglas Creese)
Date:
[1939?]
Catalogue details

Licence: In copyright

Credit: Phytic acid and the rickets-producing action of cereals / by Douglas Creese Harrison and Edward Mellanby. Source: Wellcome Collection.

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    In the first place it was found that the rickets-producing effect of cereals, even of those with the greatest activity, could be completely antagonized by the addition of sufficient vitamin D to the diet. In diets containing only a little vitamin D, the addition of one of the more powerfully rachitogenic cereals supplied a factor which counteracted the calcifying action of the vitamin and produced rickets. On adding more vitamin D to such diets, the effect of the vitamin became predominant and normal calcification resulted. The Ca and P of the cereals and other dietary constituents, which were lost to the body in the presence of the cereal factor when vitamin D was deficient, were absorbed and became incorporated in bones and teeth when the vitamin was present in suffi¬ cient quantity. It was this property of antagonizing the action of vitamin D which suggested the name anticalcifying toxamin for the unknown substance in cereals, for it was clearly a toxic substance, in that it interfered with Ca and P metabolism and thereby made animals abnormal, and yet its harmful action could be counteracted by a particular vitamin. A second point of interest is that the cereal effect can be largely antagonized by increasing the Ca of the diet by adding calcium carbonate or phosphate. With a cereal diet, if vitamin D is absent or very deficient, perfect teeth and bones are not produced even in the presence of abundance of Ca, but with the deficiency of vitamin D the extra Ca greatly improves the calcification processes [Mellanby, 1925]. It was mentioned above that boiling cereals with acid destroys their rachito¬ genic activity. Another observation relating to the destruction of the anti¬ calcifying activity may be mentioned. It is that malted cereals have usually lost their rickets-producing effect. A closer examination of this revealed that germi¬ nation of grains such as oats does not in itself bring about the loss of activity, but if the germinated oats are crushed and allowed to stand for 2 days at room temperature, the rachitogenic action disappears [Mellanby, 1929]. Templin & Steenbock [1933] later found that with maize, similarly, germination did not destroy the rachitogenic action but that the activity was lost on subsequent autolysis. They showed that this disappearance of rachitogenic action was accompanied by a change of organic P in the maize to the inorganic form. Steenbock et al. [1930] had previously drawn attention to the possibility that inorganic phosphate added to the diet may not be equivalent in physiological properties to the organic phosphoric compounds in cereals. There was indeed already some evidence on this point. It has long been known that a large part of the organic P of cereals, and of seeds in general, occurs in the form of phytic acid (inositolhexaphosphoric acid). This acid appears to be present, at any rate in part, as the CaMg salt which is known as phytin. The work of Starkenstein [1910] and of Plimmer [1913] had provided evidence that this substance, phytin, when fed to animals, is not directly absorbed from the alimentary canal, and that such breakdown of the compound as occurs in the intestine (leading to the formation of inositol and phosphoric acid) is probably largely the result of bacterial action. Bruce & Callow [1934] followed up the deduction from the work of Steenbock et al. [1930] that cereals contain a form of P less available than inorganic phos¬ phate. A high proportion of some such compound containing non-available P in a given cereal would mean that this cereal would probably show little calcifying power when added to a basal diet low in P, and under these experimental condi¬ tions it would be classed as a relatively rachitogenic cereal. Bruce & Callow tested this question, having particular regard to the possibility that the non-
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