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Calcium Content of some New Zealand Foods.
[Read before the Otago Institute, 14th September, 1926; received by Editor, 31st December, 1926; issued separately, 8th November, 1927.]
It is possible that the notoriously bad condition of the teeth in the Dominion may be due in part to a lack of necessary teeth-building materials, of which calcium, phosphorus, and vitamin D are the most conspicuous. A condition of goitre is prevalent, and it is now known that a lack of iodine in the food is a primary factor in its cause. and that prophylactic treatment with iodine salts is efficacious. A disease known as “bush sickness” in the North Island, although affecting apparently only one kind of animal, is due to iron starvation and can be cured and prevented by administration of an iron citrate. It is a possibility that there may be a general and widespread shortage of calcium, phosphorus, or of vitamin D, in the foods ordinarily con-sumed, or we may not eat sufficient of the food supplying these sub-stances. If the supply of calcium or phosphorus or both is low in the food-supply, but vitamin D is adequate, it seems to effect a better utilization and economy of the calcium and phosphorus which are available, so that all three factors are important.
We have made some calcium determinations on foods, and have chosen those foods which, according to the analyses available from other countries are considered to be the most valuable and available sources of calcium, i.e., milk, cauliflower, carrot, and yellow turnip.
The calcium was determined by McCrudden's method (1) designed to quantitatively separate calcium and magnesium in the presence of phosphates and small amounts of iron, especially for analysis of foods, urine, and faeces. Each determination was done in duplicate or triplicate.
The following is a summary of results obtained compared with other data available:
| Milk | %CaO | No. of Determinations. | Extremes. |
|---|---|---|---|
| Storms | .1761 | 11 | .1642–.1872 |
| Sherman | .168 | Data gathered from many sources. | |
| Under hill | .179 | ||
| .199 | |||
| Rose | .161 | ||
| .165 | |||
| U.S. Dept. of Agriculture | .168 | ||
| Frank & Wang | .157 | 14 | .1472–.167 |
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| Carrot | |||
| Storms | .0576 | 7 | .0453–.0772 |
| Sherman | .0784 | ||
| Rose | .062 | ||
| Frank ā Wang | .0683 | 13 | .052–.0774 |
| Cauliflower | |||
| Storms | .0447 | 4 | .0402–.0466 |
| Sherman | .172 | ||
| Yellow turnip | |||
| Storms | .0607 | 1 | |
| Sherman | .1036 |
Milk is an animal food, and we believe the mammal tends to keep a constant composition of the milk secretion even at a sacrifice of the parent tissues. Our determinations of milk agree with the average of those obtained elsewhere. Milk is the most practicable source of calcium not only for growing children but also adults.
Carrot, cauliflower, and yellow turnip all have a lower percentage of calcium so far as our determinations have gone.
Sherman's figures are those ordinarily used for dietary calcula-tions. From studies made in our nutrition laboratory on dietaries actually consumed it appears that calcium is more apt to be below the standards which have been set than is any other one mineral substance. We are not yet able to calculate iodine content of foods. These standards have been set from human balance experiments, a considerable number of them done in different countries, and col-lected and summarized by Sherman. If in addition to an originally low calcium content in our foods we are figuring the calcium content of our dietaries using percentages higher than the actual content of calcium, then our calcium supply is even lower than we have calcu-lated. If that is the case, it is no wonder the teeth suffer, and espe-cially in cases of pregnancy.
It is therefore important to know the actual content of calcium in our foods and also to know exactly what is being eaten by the average family in the Dominion before we can state the condition of our diet with respect to calcium. Both of these lines of work are being carried on.
References.
1. Macrudden, F. H. 1911. Journal of Biological Chemistry, vol. 10, page 187.
2. Sherman, H. C. Chemistry of Food and Nutrition. 1918.
3. Underhill, F. P., Honeij and Bogart. Journal of Experimental Medi-cine, vol. 32, page 41.
4. Rose, M. S. and Macleod, G. 1923. Journal of Biological Chemistry, vol. 57, page 307.
5. U. S. Dept. of Agriculture, Bureau of Chemistry, Bulletin 107.
6. Frank, M. and Wang, C. C. 1925. Journal of Home Economics, vol. 17, page 494.