“I may be wrong,” the distinguishedphysiologist admitted to the American Heart Association meeting inManhattan. But if he was right, Dr. Henry A. Schroeder had not onlyprovided an explanation for millions of hitherto inexplicable cases ofhigh blood pressure; he had also suggested a possible method oftreatment. Dr. Schroeder had also pointed out a mechanism by whichdiabetes may develop in adult Americans, and he had outlined anapproach to prevention of the disease.
If an investigator of less repute had reported such heady stuff, theaudience of hypercritical physicians would surely have scoffed. Indeed,many of them smiled tolerantly when Dr. Schroeder first drew attentionto a puzzling association between the softness of the drinking water inan area and the frequency of hardened arteries among men who live there(TIME, May 2, 1960). However, the determined physiologist had alreadytaken to the hills and found both an explanation and supportingevidence for his observations.
Sunken Nails. From the start, Dr. Schroeder did not believe that thegrowing incidence of arterial disease reflected the presence of suchcommon and natural drinking-water constituents as calcium bicarbonate,with which man has lived throughout history. What concerned theimaginative researcher was pollution by metals that modern man, themetallurgist, now scatters around him in profusion.
What was needed was a laboratory free from metallic contamination. Dr.
Schroeder constructed one high on a 1,600-ft. Vermont hill near his homebase at Dartmouth Medical School.
The building was all wood, with the nails sunk and sealed in. Anythingthat might contain lead or cadmium was excluded; the principalexception to the no-metal rule was stainless steel for the cages thatcontained experimental rats and mice. Water pipes, where possible, weremade of plastic. The pure mountain air was electrostatically filtered.Visitors were barred because they might carry metalliferous dust; evenresearch-staff members had to take their shoes off before entering theanimal rooms. The animals were fed a diet with a meticulously definedmetallic content, and their pure drinking water was superpurified.Whether it was hard or soft depended on how the investigators treated it.
Kidney Analyses. Among the 20 elements that Dr. Schroeder investigatedas potential artificial pollutants, cadmium produced the most strikingresults. Rats given minute traces of cadmium salts in drinking waterall their lives developed high blood pressure of a type remarkablysimilar to the human disease. More females than males developed thedisease, but it was deadlier to the males; the animals developed fattyplaques in their aortas, and showed enlargement of the heart. When ratsreceiving cadmium were divided into two groups, 80% of those on softwater developed high blood pressure as against only 17% of those onhard (calcium-containing) water. When the animals were treated with adrug that substituted zinc for the cadmium already in their tissues,blood pressures returned to normal.
The next question was obvious: Do humans react like rats when theyingest cadmium and other metals? By way of answer, Dr. Schroederoffered chemical analyses of 400 human kidneys showing that Americansat birth have a negligible amount of cadmium stored there, that theamount of the metal increases gradually with age and reaches itshighest levels in patients with high blood pressure of unknown origin.He did not have to remind his medical audience that kidney function isimportant in regulating blood pressure, and that many cases of highblood pressure are clearly associated with kidney disorders.
Civilized man, said Dr. Schroeder, ingests an excess of cadmium from teaand coffee, refined flour and polished rice, some phosphate-fertilizedcrops— and water pipes. Soft water, he declared, takes up cadmium, acontaminant in copper and galvanized pipes, far more readily than doeshard water.
Chromium Decline. Another of the 20 elements studied was chromium. Allover the world, people are born with relatively generous amounts ofchromium in their vital organs, but in the U.S. the levels declineprecipitously around age ten. By juggling his rats’ intake of chromium,Dr. Schroeder found that a severe shortage, such as afflicts many adultAmericans, caused many of the rats to develop first diabetes and thenartery disease—a condition remarkably like progressive human diabetes.With animals kept at what Dr. Schroeder considers a normal chromiumlevel, there was virtually no diabetes or atherosclerosis. “Specialistsin diabetes and in atherosclerosis,” he said, “are beginning to seetheir disciplines overlap.”
Cautiously, Dr. Schroeder pointed out that he was not simplisticallylaying all the blame for high blood pressure and atherosclerosis oncadmium and chromium. Other exotic elements such as vanadium, zirconiumand niobium, all “abundant in the human body,” influence the level offats in the blood.
And these, said Dr. Schroeder, are metals to which newly exposed man haslittle or no ability to adapt.