British Food Journal Volume 45 Issue 9 1943

Abstract

I now pass on to an aspect of calcium metabolism which is more topical, but probably more controversial. I refer to the incidence of calcium deficiency. By what means can we determine if people are getting enough, too much, or too little calcium? It is the last condition which concerns us. There are four standard methods. Each have their advantages and their disadvantages. They are (i) a clinical examination; (ii) a dietary survey; (iii) a radiographic examination of the skeleton ; (iv) A study of the calcium balance. (i) The clinical examination is the simplest, but it is the least sensitive method for determining either the early or the mild stages of calcium deficiency. The clinical signs are a softening and bending of the bones (osteomalacia), brittle bones liable to fracture, and tetany. These, however, are signs of late or advanced calcium deficiency, and failure to detect them does not imply that the subject is having enough calcium. Nevertheless, in this country osteomalacia and tetany due to a poor calcium intake have been reported. (ii) A dietary survey is the second method. Before the war several surveys were made, in this country and in America. From their findings there was agreement among reliable authorities that calcium deficiency was present in large sections of the population. Orr has divided the population of this country into six groups according to income. The three lower groups with a total population of over 22,000,000, he found, were getting insufficient calcium. It was shown first, that the consumption of the low calcium foods such as bread and potatoes was practically uniform throughout the classes, and secondly, that the consumption of the calcium‐rich foods, milk, eggs, cheese, green vegetables was low in the poorer classes and rose with income. As income increased the following improvements occurred—disease decreased; children grew more quickly; adult stature was greater; general health and physique improved. It may be argued, that the improvement in health in the higher income groups was due not to better food, but to better housing. This is not so. For, if people in the lower income groups are only given better food, their health approaches that of the higher income groups. Then there are the observations of Dr. McGonigle at Stockton‐on‐Tees. A slum clearance resulted in the removal of poor people to better houses and improved living conditions. The sickness rate increased. Why? Because the higher rents of the new houses prevented these people spending as much money on food as they did when they lived in the slums. Dietary surveys before the war, therefore, support the belief that many people in this country were getting too little calcium. As most of our staple foods have a low calcium content, it follows that the absence of hunger does not necessarily mean the absence of calcium deficiency. (iii) Radiographic examination of the skeleton is the third method. Unfortunately X‐rays of the bone density of the trabeculæ do not readily give an indication of its calcium content unless the decalcification is severe. If we may judge by thyrotoxicosis, where there is an increased loss of calcium from the body, X‐rays show the decalcification only in the most severe 25 per cent. of cases. Radiographic studies will detect however an excessive withdrawal of calcium from the skeleton, before such clinical signs as softening of bones, brittle bones, and tetany develop. In this country there is radiographic evidence of decalcification resulting from low calcium intakes. (iv) Finally there are the observations on the calcium balance. Earlier in this paper it was stated that a normal healthy person requires to ingest 0·55 gram of calcium daily to avoid persistently losing calcium from his skeleton. A daily dose of 0·55 gram calcium then produces calcium equilibrium, and intake equals output. It has also been stated that a daily intake of 0·8 gram is the minimum amount of calcium which will bring about the maximum storage. In other words no matter how much in excess of 0·8 gram calcium daily a healthy adult ingests, he will not store any more calcium than he would if he were taking 0·8 gram. These facts provide us with two means of determining whether calcium deficiency is present or not. Calcium deficiency is present if the figure for calcium equilibrium falls significantly below 0·55 gram daily. Calcium deficiency is present if more storage of calcium takes place with intakes above 0·8 gram daily, than at 0·8 gram daily. Is there any evidence from calcium balance studies in this country that calcium deficiency exists? There is evidence. I have just described the methods which are available for determining whether calcium deficiency is present or not. I believe, on the evidence obtained from all four methods, that, before the war, a large proportion of people in this country were taking too little calcium. I would like at this point to digress for a moment. There are certain people who would have us believe that clinical and radiographic evidence is essential to prove the presence of calcium deficiency. As I have explained, these methods only showed the advanced stages. I reply: “ Must we wait for secondary deposits in the liver, extreme emaciation, ascites, before diagnosing cancer ?”

Citation

(1943), "British Food Journal Volume 45 Issue 9 1943", British Food Journal, Vol. 45 No. 9, pp. 81-90. https://doi.org/10.1108/eb011381