BRITISH MEDICAL JOURNAL, 13 SEPTEMBER 1975, PP. 647-648
Ischaemic Heart Disease, Vitamins D and A, and Magnesium
Sir,—Professor V. Linden (14 September 1974 p. 647) has suggested that vitamin A, by protecting against the hypercholesterolaemic effect of vitamin D, may influence the incidence of myocardial infarction. His epidemiological study (in Norway) related to relatively high vitamin D intakes. Vitamin A also protects against the osteolysis and renal and arterial calcinosis of experimental hypervitaminosis D.1 The risk of hypervitaminosis D in the United States, where the greatest source is fortified milk, may be even greater than in northern Norway, where most of the vitamin D derives from fish liver, which is rich in vitamin A.
Normal full-term infants require about 100 IU of vitamin D daily to prevent rickets and premature infants about 200 IU. The adult requirements may be so low as to be met by the amount in unfortified foods and exposure to sunlight.2 A survey of American children (newborn to 17 years) showed that half ingest 400-800 IU daily; almost 10% consistently consume over 1000 IU daily.3
In contrast, in the past half-century magnesium intakes have fallen, whereas dietary contents of protein, fat, sugar, and calcium have risen.4 High intakes of these nutrients, and of vitamin D, increase magnesium requirements and increase susceptibility to magnesium deficit.5 6 Metabolic balance studies indicate that Occidental magnesium intakes are suboptimal.7 The cardiovascular and renal lesions of experimental magnesium deficiency and experimental hypervitaminosis D are similar, as are those of infantile hypercalcaemia, an outbreak of which in England was related to excessive vitamin D—2000-4000 IU daily.6 8 Increased magnesium intakes protect against cardiomyopathy produced by many agents, including excessive vitamin D.5 9
It may be the combination of excesses of most nutrients, with the exception of magnesium, that contributes to the high incidence of ischaemic heart disease in the industrialized countries. Perhaps the amount of magnesium provided by hard water10 may be sufficient to correct a marginal deficit, thereby contributing to the lower death rates from ischaemic heart disease in hard-water than in soft-water areas.—I am, etc.,
MILDRED S. SEELIG
Medical Service,
Goldwater Memorial Hospital,
New York University Medical Center,
New York
1 Clark, I., and Bassett, C. A., Journal of Experimental Medicine, 1962, l15, 147.
2 Recommended Dietary Allowances. Publication 1694, Food and Nutrition Board. National Academy of Sciences, Washington, D.C., 7th edn., 1968, p. 24.
3 Dale, A. E., and Lowenberg, M. E., Journal of Pediatrics, 1967, 70, 952.
4 Friend, B., American Journal of Clinical Nutrition, 1967, 20, 907.
5 Seelig, M. S., Myocardiology. Recent Advances in Studies on Cardiac Structure and Metabolism, 1972, 1, 626.
6 Seelig, M. S., and Bunce, G. E., Magnesium in the Environment, Proceedings of Symposium. Division of Agriculture, University of Georgia, Fort Valley, Georgia, 1972.
7 Seelig, M. S., American Journal of Clinical Nutrition, 1964, 14, 342.
8 Seelig., M. S., Annals of the New York Academy of Sciences, 1969, 147, 537.
9 Seelig, M. S., and Heggtveit, H. A., American Journal of Clinical Nutrition, 1974, 27, 59.
10 Hankin, J. H., Margen, S., and Goldsmith, N. F., Journal of the American Dietetic Association, 1970. 56, 212.
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