There is very little controversy, really, about whether salt is related to hypertension.
For decades scientists have seen blood pressures going up with additional sodium (salt) in a diet, and dropping when salt is restricted.
The reason scientists don't all just come right out and say that salt causes high blood pressure is basically this: The mechanism by which it happens is still one of those unsolved physiological mysteries. The scientific methodology for the absolute declarative that hypertension is caused by salt (in susceptible people) isn't quite strong enough -- and you know how doctors hate to say anything flat-out anyway.
However, it is agreed by almost all that salt causes the body to retain fluid and this increased fluid volume will increase blood pressure automatically, just as increased volume of water in a hose causes the water pressure to increase.
When fluid is lost, so are the salts, so there is that uncertainty about whether it was the fluid loss alone, or the combination that caused the blood pressure to drop. Weight loss will also lower blood pressure, but again, there is a loss of fluid and salts with the fat loss.
Of course, there are types of blood pressure problems caused by kidney ailments or hormonal imbalances which may not always be related to salt intake. But the most common problem is that known as essential hypertension.
It is here that the evidence pointing to salt as a key villain is mounting.
People crave salt, and indeed, must have some salt in a diet to remain healthy.
But once again, it is that 3-million-year-old hunter-gatherer in us all who is doing the craving. (Yes, the same cave dweller who wants to fight a tiger when the Blue Line breaks down. . .)
There isn't a whole lot of salt in the things hunter-gatherers eat: fruit, nuts, berries, roots (and an occasional brontosaurus).
But with our 20th-century "gathering" sophistication and our propensity for self-indulgence, when our hunger-gatherer craves salt, out comes the old shaker with the big holes.
Or the potato chips. Or the pretzels. Or even the can of tomato soup. . . And it isn't just salt, which is actually sodium-chloride. There's monosodium glutamate, for example, or sodium bicarbonate or other sodium compounds in other preservatives and taste-enhancers.
Up, up and away goes the old blood pressure and all that means -- stroke, heart disease, circulatory disorders, early death.
Laboratory studies have produced hypertensive rats by feeding them high-sodium diets. These are genetically susceptible rats, mind you, but genetically susceptible rats fed low sodium diets do not develop high blood pressure. This last information is from Dr. Henry Blackburn, director of the Ancel Keys Laboratory of Physiological Hygiene at the University of Minnesota. He was here recently to lend support to an effort by the Center for Science in the Public Interest to get the FDA to restrict sodium in processed foods.
Better than lab rats, nutritional studies of adolescents are beginning to produce evidence that sub-teen and teen snacking habits are potent predictors of future high blood pressure and heart disease.
For example, a recent government survey showed that black children and teens eat more salty snacks than whites, and -- according to CSPI figures -- the high blood pressure rate among blacks is twice that among whites, with a hypertension-related death rate in the under-50 population 6 times that of whites.
Salt is an acquired taste in the sense that taste buds become desensitized, so to satisfy the taste craving, more and more salt needs to be used.
By the same token, it only takes a couple of weeks of salt abstinence (or restriction) to re-educate the taste buds to be satisfied with less salt.
But because salt is so ubiquitous -- used in vast amounts in processed foods -- it is virtually impossible to restrict salt merely by putting oregano in the salt shaker (which isn't a bad idea).
"I have the feeling," says Dr. Blackburn, "that when you do have someone who wants to modify his or her weight or sodium intake, they're operating in an environment which is not supportive of that."
At the Minnesota lab (named for the eminent physician who pioneered the campaign against cholesterol and earlier invented the K-ration), Blackburn and his colleagues are involved in work encompassing all aspects of cardio-vascular diseases and in their control, examining all approaches from genetic coding to potato-chip manufacturers.
"Really," he says, "our idea is that if all disease is a reaction between host and environment, mass disease is interaction between a very powerful environment and cultural factors (like) genetic susceptibility -- and that's atherosclerosis and that's hypertension.:
These are, he says, the "mass diseases of mass culture," and even though the mechanisms are still uncertain, "there are so many obvious cultural influences on things, we ought to work on them . . . rather than just thinking of that DNA, or this amino acid configuration, or that enzyme making this happen that wouldn't be turned on if you weren't doing such and such. . . ."