BOSTON—Should dairy product packages carry cigarette-style warning panels detailing the potential for cardiovascular risk?
Well, that’s a little extreme. But Steven Horowitz, MD, chief of medical cardiology, Beth Israel Medical Center, New York, believes America ought to re-consider its love affair with Elsie the Cow.
Speaking at a conference on complementary and integrative medicine, sponsored by Harvard Medical School, Dr. Horowitz said the simple epidemiologic fact is, coronary heart disease death rates world-wide correlate clearly with milk and dairy consumption. This is not a new finding, but it is one US cardiovascular experts and dietary pundits have somehow managed to not notice, he said.
The link between dairy and cardiovascular disease was shown most clearly in the “40 Country” study, published in 1993—the same study that led to discovery of the so-called French paradox and the notion that moderate red wine consumption is cardioprotective.
“If you’re gonna have a cheeseburger, by all means, wash it down with some red wine,” quipped Dr. Horowitz (see above). But that does not address what he sees as the most critical implication of the landmark study: on a population basis, milk and many dairy components including butterfat, milk protein, and calcium from milk, remain positively related to heart disease mortality after adjusting for cholesterol and saturated fat consumption (Artaud-Wild SM et al., Circulation 1993; 88(6): 2771–9).
Cardiovascular mortality is lowest in countries where dairy is not a routine part of the diet, and highest in countries where it is a staple. The exceptions were France, which has a lower than expected CHD death rate (hence the “French paradox”), and Finland which had higher than expected mortality. The authors suggested the latter may be due to lower plant food consumption in Finland.
Mike Lefevre, MD, director of the Dairy Institute on Diet, Genetics and Heart Disease, Pennington Biomedical Research Center, Baton Rouge, LA, acknowledged there are six individual studies published since the 1970’s—including the Artaud-Wild study—showing univariate correlations between milk fat and milk products, and CHD.
In aggregate, the data suggest roughly 50% of the difference in CHD between countries can be attributed to differences in per capita milk consumption.
In an article published on the National Dairy Council’s website, Dr. Lefevre reasoned that, “populations that consume large quantities of milk fat and milk products would also have a high saturated fat intake, which in turn would be expected to raise total and LDL cholesterol levels, thereby leading to a greater CHD mortality.”
Ronald Krauss, MD, chairman of the American Heart Association’s Dietary Guidelines Committee, said the correlation observed in the 40 Country study, “raises a hypothesis, but does not lead to a conclusion.” This hypothesis has not been clinically tested.
“It is a bit of a leap to take this one statistical manipulation and make a broad condemnation of all dairy products including the low or non-fat dairy,” he told Holistic Primary Care. “Observational studies assume you have the statistical power to control for all the different variables that could influence the observed relationship.” That assumption is highly questionable.
Dr. Krauss, head of molecular medicine, Lawrence Berkeley National Laboratory, said there is equally valid though equally inconclusive evidence that low-fat dairy may have cardiovascular benefits. He pointed to the DASH studies in which there was a statistically-significant blood pressure drop in hypertensive patients on a low-salt, low-fat diet that included low- or non-fat dairy.
“This is certainly not an ironclad case, and it doesn’t prove that dairy was responsible, but it is a study that at least supports the conclusion that one cardiovascular risk factor can be improved on a diet that includes low fat dairy,” said Dr. Krauss, who acknowledged receiving sponsorship for his genetics research from the National Dairy Council.
A more recent study, presented at the American Heart Association’s annual conference on epidemiology and prevention suggested a beneficial effect of increasing low fat dairy intake on the so-called “metabolic syndrome,” a cluster of CV risk factors including low HDL, high TGL, elevated pressure, and insulin resistance.
Though there are clearly questions to be answered, Dr. Krauss and the AHA’s committee believe there is insufficient grounds to exclude dairy from the AHA dietary recommendations. The 2000 AHA dietary guidelines closely resemble the modified DASH diet—low fat, low salt, high-vegetable content, but including low or non-fat dairy.
Dr. Horowitz, a committed vegetarian, is not impressed with the AHA’s guidelines. In his presentation at the Harvard conference, he called them, “a placebo diet.”
Cardiologists may be at odds on the virtues of dairy, but American consumers are not. They’ve consistently answered those “Got milk?” ads with a hearty, “Sure do!” In 1993, the average dairy consumption in the US was 572 lb per person per year, down just slightly from the 1987 peak of 599 lb.
Dr. Horowitz, professor of medicine at Albert Einstein College of Medicine, said he is not attributing the whole burden of heart disease to dairy intake or any other dietary habit. Dietary factors are only part of the picture.
He estimated between 5% and 10% of any population will be at high-risk due to unmodifiable genetic predispositions. This appeared to be the case with Arthur Ashe, the tennis star, who was presumably in top physical condition. Then, there is another 5%–10% of any population that is genetically resistant to CHD—the Winston Churchills, who don’t develop heart disease no matter what they eat, drink or smoke.
But there is a solid 80%–90% of the population for whom CVD is far from inevitable. “Most of us have environmentally influenced CVD, and it is dependent on how we choose to live our lives,” said Dr. Horowitz, who advocates a vegetarian diet and physical activity for all of his patients.
He charged the American medical and nutritional mainstream with turning a blind eye to certain types of data—especially if the data implicate favored foods like meat and dairy. These two remain “essential” food groups, even though there is evidence that CAD is inversely related to per capita consumption of both. “There is clearly a belief-system problem,” he said.
