“When I left France, I couldn’t imagine that there was a population in the world that didn’t drink wine with meals.” That remark by a young Serge Renaud, who had come to study veterinary science at Université de Montréal in 1951, was prompted by his observation of dietary habits in Quebec. He was also surprised by the low consumption of fruits and vegetables and the high intake of saturated fats. Renaud also noted statistics about the high rate of heart attacks in Quebec and was particularly taken by reports of young hockey players developing coronary disease. Was there a causal link between diet and heart disease? Exploration of that possibility would come to dominate Renaud’s career and lead to him being anointed as the father of the “French Paradox.”
After graduating first in his class from veterinary school, Renaud enrolled in a PhD program in experimental medicine. His research focused on thrombosis, the blockage of arteries or veins by blood clots, a problem he would pursue as head of the Laboratory of Experimental Pathology at the Montreal Heart Institute. Renaud concluded that the tendency of tiny cells called platelets to aggregate and form clots was the main cause of heart attacks, and he suspected that this was related to diet.
In 1973, he returned to France, and at the National Institute of Health and Medical Research, began to study the behaviour of platelets. He observed that aggregation was reduced in rats that had been fed alcohol. This was intriguing, especially because he had heard that the famous Framingham study in the United States had found that alcohol protects against heart disease. That information had not been publicized because The National Institutes of Health was concerned that if people learned that a little alcohol was protective, they would conclude that more is better.
To explore the diet connection further, Renaud organized a mobile laboratory to travel around France to take blood samples and determine platelet reactivity. The goal was to investigate a possible link with heart disease, given that a geographic variation had been observed in France, with a high incidence of cardiovascular conditions in the Moselle region and a low rate in Provence. Indeed, as it turned out, the disease incidence was connected to platelet aggregation. But why did platelet reactivity vary regionally? Dietary questionnaires people had filled out suggested that saturated fats and smoking were likely to cause blood clots, while calcium, polyphenols, wine and alpha-linolenic acid in the diet were protective.
That was interesting, especially since the famous Seven Countries Study by Ansel Keys had also investigated a possible connection between diet and heart disease and had found that the inhabitants of the island of Crete had the lowest rate despite having a relatively high level of blood cholesterol. Something was protecting the Cretans! Could it be the alpha-linolenic acid found in the snails, nuts and purslane that are prominently featured in the Cretan diet?
To investigate this possibility Renaud launched the Lyon Diet Heart Study in which men who had suffered a heart attack were divided into two groups. The control group followed the usually recommended low-fat diet, while the experimental group ate a diet modelled on that in Crete. No butter, cream or milk and very little meat. Lots of vegetables, fruit, bread and whole grains. And wine with meals. They also ate a specially formulated a margarine rich in alpha-linolenic acid since walnuts, snails and purslane were not easily incorporated into the diet. The trial was stopped early because a striking difference between the groups was noted just two months after diet modification began. Compared with the “prudent” diet, the ‘‘Cretan’’ diet reduced cardiac death by 76 per cent, non-fatal heart attacks by 73 per cent, and total death by 70 per cent.
By 1991, Renaud’s research had garnered publicity and came to the attention of the CBS program 60 Minutes. In a segment titled The French Paradox, he was asked how it was that the rate of heart disease in United States was more than three times greater than in France despite the French love of fatty cheeses, cholesterol-laden goose liver and buttery croissants? Renaud suggested that there were several differences. The French didn’t eat between meals, had the main meal at lunch, ate lots of cheese, and of course drank wine. He explained that his studies of rat poop had shown that calcium in cheese can tie up fats and cause them to be excreted, and he also described his lab studies of wine decreasing platelet aggregation. Renaud was careful to point out that while he believed a moderate amount of wine to be protective, certainly more was not better. The next day wine sales in the U.S. soared!
Since that classic 60 Minutes segment, a large number of studies have examined the link between wine consumption and health. You can pick and choose among these studies to show either that that there is no safe amount of alcohol or that moderate consumption protects against heart disease. The only point on which there is universal agreement is that more than “moderate consumption,” usually taken to mean more one to two servings of alcohol a day, is detrimental to health. Then there is the niggling issue of alcohol being carcinogenic. Indeed, the International Agency for Research on Cancer (IARC) has placed alcohol in Group 1, reserved for substances known to cause cancer in humans. In spite of all the studies, whether the phrase “to your health” while clicking wine glasses is or is not backed by science remains an open question.
Joe Schwarcz is director of McGill University’s Office for Science & Society (mcgill.ca/oss). He hosts The Dr. Joe Show on CJAD Radio 800 AM every Sunday from 3 to 4 p.m.