Advice About Food Is Sometimes Half-Baked
Back in the early 70s, just as I was developing an interest in the chemistry of food, I came across a witty quote by Mark Twain. “Part of the secret of success in life is to eat what you like and let the food fight it out inside.” Twain was likely reacting to the plethora of health fads that were rippling through the American landscape at the time. As evidenced by a passage in his classic work Tom Sawyer, he didn’t approve:
“Aunt Polly was a subscriber for all the “Health” periodicals and phrenological frauds; and the solemn ignorance they were inflated with was breath to her nostrils. All the “rot” they contained about what to eat, and what to drink, and how much exercise to take, and what frame of mind to keep one’s self in was all gospel to her, and she never observed that her health-journals of the current month customarily upset everything they had recommended the month before.”
Indeed, there was health advice galore in the nineteenth century. Sylvester Graham urged people to eschew white flour, cooked vegetables and meat. Drinking water during a meal was verboten. If a vegetarian and a meat eater were shot and killed, Graham maintained, the body of the vegetable eater would take two to three times as long to become intolerably offensive from the process of putrefication. There is no record of Graham ever putting this to a test. Dr. John Harvey Kellogg followed in Graham’s footsteps, curing the rich and famous of diseases they never had with a regimen of vegetables, fruits, over baked bread and yogurt.
Horace Fletcher, the “Apostle of Correct Nutrition,” suggested that the secret of life lay in chewing food until the last hint of flavour disappeared, and Lydia Pinkham promoted her Vegetable Compound as just the thing for “female complaints and weaknesses.” Dr. James Salisbury claimed that heart disease, tumours, mental illness and tuberculosis were the result of vegetables and starchy foods producing poisonous substances in the digestive system. His solution was the “Salisbury steak,” essentially fried ground beef with onion and seasonings. According to the good doctor the steak was to be eaten eaten three times a day with lots of water. This would cleanse the digestive system and as a bonus, the high meat-low carbohydrate diet would lead to weight loss. Early shades of Atkins.
Little wonder that Mark Twain poked fun at these half-baked, contradictory fragments of advice with his suggestion to let the food fight it out once inside. That of course was pure whimsy, but foods really do duke it out, though not inside our bodies. Rather, it is in the scientific literature that dietary components vie for infamy or honour. And the biggest battles take place when the stakes are high, such as in the struggle against heart disease.
I’ve now been overlooking that battlefield for more than four decades. My bookshelves sag with dozens of books about the relationship between diet and heart disease ranging from the “China Study” in which Dr. T. Colin Campbell urges us to reduce blood cholesterol by eliminating all animal products to Dr. Malcolm Kendrick’s The Great Cholesterol Con and Dr. Ernest Curtis’ Cholesterol Delusion which claim that a high fat diet does not put a person at risk for coronary artery disease and that lowering the cholesterol level with diet or drugs will not prevent heart attacks. My filing cabinets continue to swell with the studies referenced in these books plus with numerous others. One would think that a definitive conclusion about the relationship between diet and heart disease could be arrived at by digging through all this material. Alas, it is possible to find reputable studies to either support or oppose the obsession with cholesterol. When it comes to dueling studies, there rarely is a clear cut winner.
When I began my search for light at the end of the misty tunnel of nutrition oh so many years ago, one name kept cropping up. Ancel Keys was a physiologist who had noted that well-fed American businessmen suffered a higher rate of heart disease than post-war undernourished Europeans. Keys knew that atherosclerosis, was characterized by deposits of cholesterol in the walls of the arteries, and that in the early 1900s Russian scientist Nikolai Anichkov had shown a link between feeding cholesterol to rabbits and artery damage. He was also aware that in the 1940s John Gofman had identified lipoproteins as the molecules that transport cholesterol through the bloodstream and that he had demonstrated a relationship between blood levels of these lipoproteins and the risk of heart disease.
Since cholesterol was present in the human diet, mostly in fatty animal foods, Keys thought a relationship between diet and heart disease was likely. One way to explore this possibility was to compare disease patterns in countries with different amounts of fat in the diet. In his famous “Seven Countries Study,” Keys showed that both elevated mean blood cholesterol levels and deaths from heart disease correlated with the percent of calories attributed to fat in the diet, although there were a few exceptions. Inhabitants of the island of Crete had the lowest heart disease rate but ate lots of fat. However, their fat intake was mostly of the unsaturated variety as found in fish and olive oil. So Keys concluded that the real culprit was saturated fat and promoted a “Mediterranean diet,” emphasizing unsaturated over saturated fats.
Correlation, of course, is not the same as causation, and critics quickly pointed out that increased heart disease rates correlated even better with the number of radios produced or with the amount of gasoline sold. There were also questions about the reliability of death certificates to determine heart disease mortality, as well as about the calculation of fat consumption. Then there was the bothersome point of Keys choosing only seven countries when statistics about food consumption and mortality were available for at least 22 others. Did he leave these out because the data did not fit the straight line relationship that was evident when only seven countries were considered? And with that salvo of criticisms the war between the pro and anti fat forces was launched. The outcome? I’m afraid I have to leave you hanging till next week.