Too Much Salt, Too Much Sugar

Last month we reported that Dr. Thomas R. Frieden, New York City’s Commissioner of Health and Mental Hygiene, was on a campaign against excessive salt in processed foods and restaurant meals. We also reported that his campaign was criticized on the grounds that many people needed salt, and that the answer to that criticism was that people who needed salt could add it, but people who were getting too much couldn’t take it out.

But that wasn’t the end of it. On February 6, the day after our newseletter went to bed, The New York Times carried an Op-Ed contribution by Dr. Michael H. Alderman, a professor of medicine and epidemiology at Albert Einstein College of Medicine, arguing that a low salt diet actually increased the risk of death from heart disease.

Setting aside observational studies, which can be distorted by unknown factors, Dr. Alderman claimed that in the only rigorous randomized clinical trial on salt intake reported so far there were more deaths from heart disease and stroke in the group that had the low sodium diet. Without a specific reference to the study it’s hard to evaluate that claim. For one thing, the low salt diet might have been too low in salt.

But one of his arguments stands out. He wrote: “Another bit of evidence to consider is that, over the past generation, while sodium intake in the United States appears to be increasing, deaths from heart attacks and strokes have declined by half.” We know that’s false reasoning. Many risk factors have increased, including salt consumption, and so has the incidence of heart disease. The death rate has declined in spite of this, probably due to better treatment.

Contrary evidence exists. An article in BMJ, April 2007, by N.R. Cook et al. followed up on the participants in the TOHP (trials of hypertension prevention). Subjects were randomly assigned to either a low salt diet or a control group. Over the next ten to fifteen years the low salt group had a 25 percent lower risk of a cardiovascular event.

According to sources on the World Wide Web, Dr. Alderman is an unpaid consultant to the Salt Institute. He never received any fees from them, but he once accepted a modest honorarium from them for a presentation.

Reducing salt intake would not necessarily benefit everyone. Some people are salt sensitive: salt intake gives them high blood pressure. Other people aren’t. A study led by Dr. Jing Chen of Tulane University, published last month in The Lancet, found that people with the cluster of risk factors called metabolic syndrome are more salt-sensitive than others.

To explore the conjecture that insulin resistance affects salt retention, residents of rural China (where salt intake is typically higher than here) were put on a low salt diet for one week and then a high salt diet for another week. Of the 1881 participants, the 283 who had metabolic syndrome (having at least three of these five risk factors: abdominal obesity, high blood pressure, high triglycerides, low HDL and high glucose) averaged wider swings in blood pressure during the trial and were almost twice as likely to have high salt sensitivity.

Dr. Frieden’s campaign against salt is matched by an attack on sugar by Jane Brody, a health writer for The New York Times, in two articles on February 10 and 17. Excess sugar consumption, she reports, can be blamed for the current epidemic of obesity, diabetes and heart disease.

The current recommendation is a maximum of 8 teaspoons of sugars a day. One 12-ounce can of regular soda hits that limit all by itself. Add cookies, fruit yogurt, commercial soup, etc., and the average intake is more than 20 teaspoons.

High-fructose corn syrup, widely used as a sweetener, has come in for extra blame, though some experts say it’s safe. Gram for gram, fructose, glucose (the sugar that circulates in the blood) and sucrose (ordinary table sugar) are equally fattening, though not equally sweet.

Natural corn syrup is essentially pure glucose. Fructose is made from the starch in corn. Some studies suggest that fructose raises cardiac risk factors. But ordinary table sugar - a chemical compound (not a simple mixture) of fructose and glucose - is immediately split into fructose and glucose during digestion, so it should have the same side effects as high fructose corn syrup. That is, it’s just as bad.

Artificial non-nutritive sweeteners are probably safe and probably effective. In one observational study, adjusted for demographic and other confounding variables, middle school children given noncaloric drinks lost weight compared with those who consumed ordinary sweetened drinks.