Too Much of a Good Thing

Aware that she is "eating for two," a pregnant woman is likely to make sure she gets sufficient bread, cereals and milk--all of which, because of the long campaign to wipe out rickets, are usually fortified with vitamin D. Her obstetrician may well prescribe a daily capsule of supplemental calcium and vitamin D. And while the mother-to-be is taking it easy, she may do a little sunbathing, which stimulates her system to make still more vitamin D. It all adds up not only to a hefty dose of the vital vitamin but to some risk that her baby will have heart defects and be mentally retarded as well.

Thick & Narrow. Dr. Robert E. Cooke, pediatrician in chief at Johns Hopkins' exciting new Children's Medical and Surgical Center (TIME, May 22) based his warning on findings that originated in Britain, after the National Health Service offered free vitamins galore and several cases of vitamin D poisoning were recorded. Similar results were observed in Germany. And now, says Dr. Cooke, he is convinced that excessive vitamin D was responsible for the mental retardation and other abnormalities of 13 babies seen in 18 months in his hospital. This indicates that there are several hundred cases a year in the U.S. alone.

Dr. Cooke was careful to point out that for the vast majority of women and their babies, the prevailing intake of vitamin D does no harm. But in unpredictable cases, any excess over normal requirements causes unnatural calcium deposition in the fetus: its bones, especially the base of the skull, grow unusually dense, and chalky deposits narrow the aorta. Sometimes the aorta is narrowed around the origin of the renal arteries so that the kidneys are starved of blood and the affected baby suffers from extremely high blood pressure.

Incurable & Preventable. The trouble with vitamin D, said Dr. Cooke, is that the body has no effective mechanism for getting rid of an excess. It accumulates until it triggers the deposition of calcium. And it is easy for the susceptible unborn child to get too much of it: one pregnant woman in Baltimore, who was eating well, drinking a great deal of milk, and taking her prescribed multivitamin capsules, was getting 2,000 to 3,000 units of vitamin D daily along with her sunshine supplement, as against a recommended daily intake of only 400 units, even for a fast-growing child. Dr. Cooke suggested that women check with their doctors on their total vitamin D intake. The striking thing about this form of mental retardation, he noted, is that while it is severe and incurable, it is so easily preventable.

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