In my previous post, I referenced USDA guidelines which recommend consuming dairy but only in a low-fat form. How did the mainstream nutritional community decide the American public should shift from full fat dairy to low or no fat dairy? Prior to the 1950s there was little concern in nutritional research about fat in the American diet. Beginning in the 1950s, it became apparent that heart disease, coronary artery disease (the cause of heart attacks) in particular, had become the major cause of mortality in western countries.
The American epidemiologist, Ancel Keys, became convinced in the mid 1950s that dietary fat and cholesterol were related to heart disease. In 1970 published his “Seven Countries Study” which found a correlation between per capita fat consumption and the prevalence of heart disease in seven cherry-picked countries. These kinds of studies can be useful for developing theories about which factors might cause disease, however, they cannot prove that a dietary factor causes the disease.
Messerli recently published a tongue-in-cheek analysis of the relationship between per capita chocolate consumption in a particular country and the number of Nobel Laureates produced by that same country that illuminates the weakness of this type of study.
This is the main figure from that study: Chocolate Consumption and Nobel Laureates
There is a very nice relationship demonstrated which suggests that the more chocolate consumed in a particular country, the more Nobel Laureates produced. However, no one would seriously believe that chocolate consumption causes the kind of brilliance needed to do achieve a Nobel prize. Clearly, there are confounding variables or factors. Sometimes, confounding factors are clear and can be accounted for, but often they are not clear and cannot be accounted for.
Early studies of this type demonstrated that there was a relatively strong association between the per capital supply of milk or some component of milk and heart disease mortality. In other studies, changes in gross milk production over time and changes in heart disease deaths were shown to correlate.
Despite the weakness of such studies in proving causation, as Gary Taubes pointed out ,
“the National institute of Health (NIH) had begun (by 1988) advising every American old enough to walk to restrict fat intake, and the president of the American Heart Association (AHA) had told Time magazine that if everyone went along, “we will have (atherosclerosis) conquered” by the year 2000. The Surgeon General’s Office itself had just published its 700-page landmark “Report on Nutrition and Health,” declaring fat the single most unwholesome component of the American diet.”
Such recommendations have resulted in a whole industry devoted to developing low-fat food-like substances which the public has perceived as healthier than the natural high fat original foods. Arguably, adoption of highly processed low-fat foods, which usually increase palatability by adding refined carbohydrates , sugar, or high-fructose corn syrup have contributed to America’s obesity epidemic. This, in turn through increasing obesity-associated diabetes, hypertension, and abnormal lipid profiles could have the unintended consequence of increasing heart disease.
The major focus of low-fat dietary recommendations has been to lower red meat consumption due to the high levels of saturated fat found in pork and beef. However, despite having a significantly different saturated fat composition, dairy products have been tarred with the same brush, so to speak. This has progressed to the point where, if one enters a frozen yogurt establishment (these businesses have proliferated at an alarming rate in the last few years) it is virtually impossible to find a full fat formulation of yogurt. Prominently featured are the words “no-fat” or “low-fat” with the implication that this is healthy for you. Instead of the natural fat of dairy , you have now been convinced to eat a form of dairy that has been highly processed, depleted of most nutrients and full of sugar and unrefined carbohydrates. To make up for the fat calories which might have left you more satiated without sharp peaks in blood glucose, you can substitute a whole panoply of sugary materials, chocolate, candies, or fruit.
It turns out that when the best epidemiological studies are examined in this area, the evidence suggests a protective effect of dairy on heart disease risk. Dr. Peter Elwood, a highly respected epidemiologist at the University of Wales, has consistently pointed this out based on his and other researchers’ studies.
To quote Elwood, the best epidemiological studies are “prospective cohort studies, based on data for individual subjects within a single community, with detailed attention given to confounding” variables. Such studies “give a much better basis for the examination of independent associations between food items and disease incidence than studies based on either ecological data or relationships with risk factors.”
In 2004, Elwood published a review of such studies which was published in the European Journal of Clinical nutrition. He found 10 studies worthy of inclusion. All but one study suggested that milk protects against heart disease. Those subjects consuming the most milk were less likely to have a heart attack or stroke than those consuming no milk. The relative risk for high volume milk drinkers versus those drinking no milk for “ischaemic heart disease” (this refers to coronary artery disease , the major cause of heart attacks) was 0.87. In other words, if you drank a lot of milk you were 13% less likely to have heart disease than if you drank none.
Elwood’s original research on this was called the Caerphilly Prospective Study. Between 1979 and 1983, 2500 men completed a food frequency questionnaire. During the following 21 years, the relative risk in men who drank more than a pint of milk per day, compared with the risk in men who drank no milk was 0.66 for ischemic heart disease and 0.84 for ischaemic stroke. In other words, high milk drinkers were 34% less likely to develop coronary heart disease, the major cause heart attacks.
All the studies reviewed were set up at times when reduced-fat milk was unavailable or scarce therefore the conclusion from the best available evidence in 2004 should have been that full fat dairy lowers your risk of heart attack and stroke.
For both the general public and for my cardiac patients I, therefore, differ strongly in my advice regarding dairy consumption from most published dietary guidelines. Keeping in mind that “all things in moderation” applies just as much in this area as any other, I advise full fat dairy consumption. This means that they can consume butter, milk, full-fat cheese and yogurt. I strongly advise utilizing dairy that comes from grass-fed , pasture-raised cows for reasons I will examine in subsequent posts. Each of these dairy products has a different fatty acid profile and therefore, likely a different effect on cholesterol profiles. Butter, in particular, may warrant separating out from the other dairy products because it is a very highly concentrated fat. However, since reviewing the published data on butter consumption and cardiovascular disease, I have personally gone back to fairly liberally applying butter (again, hopefully from grass-fed, pasture-raised cows) to a lot of my foods because there are few data suggesting that butter raises my risk of cardiovascular disease and the stuff tastes awesome.