Good Calories, Bad Calories (59 page)

The notion of a carbohydrate-restricted diet based exclusively on fatty meat was publicized after World War I by the Harvard anthropologist-turned-Arctic-explorer Vilhjalmur Stefansson, who was concerned with the overal healthfulness of the diet, rather than its potential for weight loss. Stefansson had spent a decade eating nothing but meat among the Inuit of northern Canada and Alaska. The Inuit, he insisted, as wel as the visiting explorers and traders who lived on this diet, were among the healthiest if not the most vigorous populations imaginable.

Among the tribes with whom Stefansson lived and traveled, the diet was primarily caribou meat, “with perhaps 30 percent fish, 10 percent seal meat, and 5 or 10 percent made up of polar bear, rabbits, birds and eggs.” The Inuit considered vegetables and fruit “not proper human food,” Stefansson wrote, but they occasional y ate the roots of the knotweed plant in times of dire necessity.

The Inuit paid little attention to the plants in their environment “because they added nothing to their food supply,” noted the Canadian anthropologist Diamond Jenness, who spent the years 1914–16 living in the Coronation Gulf region of Canada’s Arctic coast. Jenness described their typical diet during one three-month stretch as “no fruit, no vegetables; morning and night nothing but seal meat washed down with ice-cold water or hot broth.” (The ability to thrive on such a vegetable-and fruit-free diet was also noted by the lawyer and abolitionist Richard Henry Dana, Jr., in his 1840 memoirs of life on a sailing ship, Two Years Before the Mast. For sixteen months, Dana wrote, “we lived upon almost nothing but fresh beef; fried beefsteaks, three times a day…[in] perfect health, and without ailings and failings.”

None of Stefansson’s observations would have been controversial had not the conventional wisdom at the time been—as it is stil —that a varied diet is essential for good health. A healthy diet, it is said, must contain protein, fats, and carbohydrates, the latter because of the misconception that the brain and central nervous system require dietary glucose to function, and the debatable assumption that fresh vegetables and fruit, which contain carbohydrates, are essential to prevent deficiency diseases.

Because it is stil common to assume that a meat-rich, plant-poor diet wil result in nutritional deficiencies, it’s worth pausing to investigate this issue.

The assumption dates to the early decades of the twentieth century, the golden era of research on vitamins and vitamin-deficiency diseases, as one disease after another—scurvy, pel agra, beriberi, rickets, anemia—was found to be caused by a lack of essential vitamins and minerals. This was The Newer Knowledge of Nutrition, as it was cal ed by the Johns Hopkins nutritionist Elmer McCol um; it dictated that the only way to ensure al the essential elements for health was to eat as many types of foods as possible, and nutritionists stil hold by this logic today. “A safe rule of thumb,” as it was recently described, “is that the more components there are in a dietary, the greater the probability of balanced intake.”

This philosophy, however, was based almost exclusively on studies of deficiency diseases, al of which were induced by diets high in refined carbohydrates and low in meat, fish, eggs, and dairy products. When the Scottish naval surgeon James Lind demonstrated in 1753 that scurvy could be prevented and cured by the consumption of citrus juice, for example, he did so with British sailors who had been eating the typical naval fare “of water gruel sweetened with sugar in the morning, fresh mutton broth, light puddings, boiled biscuit with sugar, barley and raisins, rice and currants.” Pel agra was associated almost exclusively with corn-rich diets, and beriberi with the eating of white rice rather than brown. When beriberi broke out in the Japanese navy in the late 1870s, it was only after the naval fare had been switched from vegetables and fish to vegetables, fish, and white polished rice.

The outbreak was brought under control by replacing the white rice with barley and adding meat and evaporated milk. Pel agra, too, could be cured or ameliorated, as Carl Voegtlin demonstrated in 1914, by adding fresh meat, milk, and eggs to a pel agra-causing diet, which in Voegtlin’s experiments constituted primarily wheat bread, cabbage, cornmeal and corn syrup, turnips, potatoes, and sugar. Nutritionists working with lab animals also found that they could induce deficiency diseases by feeding diets rich in refined grains and sugar. Guinea pigs were given scurvy in a series of laboratory experiments in the 1940s when they were fed diets of mostly crushed barley and chickpeas.

This research informed the conventional wisdom of the era that fresh meat, milk, and eggs were what the Scottish nutritionist Robert McCarrison cal ed

“protective foods” (which is how they were known before Ancel Keys and his contemporaries established them as the fat-rich agents of coronary disease), but it also bolstered the logic that a “balanced” diet, with copious vegetables, fruits, and grains, was necessary for health. Because diets of mostly grains and starches, or diets of refined grains, fish, and vegetables, such as the Japanese sailors consumed, might be deficient in a vitamin or vitamins essential for health, nutritionists considered it a reasonable assumption that this might be true of any such “unbalanced” diets, including those that were made up exclusively of animal products.

What the nutritionists of the 1920s and 1930s didn’t then know is that animal foods contain al of the essential amino acids (the basic structural building blocks of proteins), and they do so in the ratios that maximize their utility to humans.*94 They also contain twelve of the thirteen essential vitamins in large quantities. Meat is a particularly concentrated source of vitamins A, E, and the entire complex of B vitamins. Vitamins D and B12 are found only in animal products (although we can usual y get sufficient vitamin D from the effect of sunlight on our skin).

The thirteenth vitamin, vitamin C, ascorbic acid, has long been the point of contention. It is contained in animal foods in such smal quantities that nutritionists have considered it insufficient and the question is whether this quantity is indeed sufficient for good health. Once James Lind demonstrated that scurvy could be prevented and cured by eating fresh fruits and vegetables, nutritionists assumed that these foods are an absolutely essential dietary source of vitamin C. What had been demonstrated, they wil say, is that scurvy is “a dietary deficiency resulting from lack of fresh fruit and vegetables.” To be technical y accurate, however, Lind and the nutritionists who fol owed him in the study of scurvy demonstrated only that the disease is a dietary deficiency that can be cured by the addition of fresh fruits and vegetables. As a matter of logic, though, this doesn’t necessarily imply that the lack of vitamin C is caused by the lack of fresh fruits and vegetables. Scurvy can be ameliorated by adding these to the diet, but the original lack of vitamin C

might be caused by other factors. In fact, given that the Inuit and those Westerners living on the Inuit’s vegetable-and fruit-free diet never suffered from scurvy, as Stefansson observed, then other factors must be involved. This suggested another way of defining a balanced diet. It’s possible that eating easily digestible carbohydrates and sugars increases our need for vitamins that we would otherwise derive from animal products in sufficient quantities.

This was the issue that Stefansson was raising in the early 1920s. If the Inuit thrived in the harshest of environments without eating carbohydrates and whatever nutrients exist in fruits and vegetables, they, by definition, were consuming a balanced, healthy diet. If they did so solely because they had become evolutionarily adapted to such a diet, which was a typical rejoinder to Stefansson’s argument, then how can one explain those traders and explorers, like Stefansson himself and the members of his expeditions, who also lived happily and healthful y for years at a time on this diet?

Nutritionists of the era assumed that al -meat diets were unhealthy because (1) excessive meat consumption was al eged to raise blood pressure and cause gout; (2) the monotony of eating only meat—or any other single food—was said to induce a physical sense of revulsion; (3) the absence of fresh fruit and vegetables in these diets would cause scurvy and other deficiency diseases, and (4) protein-rich diets were thought to induce chronic kidney damage, a belief based largely on early research by Louis Newburgh.

None of these claims were based on compel ing evidence. Newburgh, for instance, had based his conclusions largely on experiments in which he fed excessive quantities of soybean, egg whites, and beef protein to rabbits, which, as critics would later observe, happen to be herbivores. Their natural diet is buds and bark, not their fel ow animals, and so there was little scientific value in force-feeding them meat or animal protein. Nonetheless, the dangers of an al -meat diet were considered sufficiently likely that even Francis Benedict, as Stefansson told it, claimed that it was “easier to believe” that Stefansson and al the various members of his expeditions “were lying, than to concede that [they] had remained in good health for several years on an exclusive meat regimen.”

In the winter of 1928, Stefansson and Karsten Anderson, a thirty-eight-year-old Danish explorer, became the subjects in a yearlong experiment that was intended to settle the meat-diet controversy. The experiment was planned and supervised by a committee of a dozen respected nutritionists, anthropologists, and physicians.*95 Eugene Du Bois and ten of his col eagues from Cornel and the Russel Sage Institute of Pathology would oversee the day-to-day details of the experiment.

For three weeks, Stefansson and Anderson were fed a typical mixed diet of fruits, cereals, vegetables, and meat while being subjected to a battery of tests and examinations. Then they began living exclusively on meat, at which point they moved into Bel evue Hospital in New York and were put under twenty-four-hour observation. Stefansson remained at Bel evue for three weeks, Anderson for thirteen weeks. After they were released, they continued to eat only meat for the remainder of one year. If they cheated on the diet, according to Du Bois, the experimenters would know it from regular examinations of Stefansson’s and Anderson’s urine. “In every individual specimen of urine which was tested during the intervals when they were living at home,” Du Bois wrote, “acetone [ketone] bodies were present in amounts so constant that fluctuations in the carbohydrate intake were practical y ruled out.”

The experimental diet included many types of meat. To test the argument that the vitamins necessary in such a diet to avoid scurvy and remain healthy could be obtained only by eating raw meat, as was incorrectly assumed to be the practice of the Inuit, al of the meat was cooked. (In fact, the Inuit only occasional y ate raw meat.) Stefansson and Anderson each consumed an average of almost two pounds of meat per day, or twenty-six hundred calories: 79 percent from fat, 19 percent protein, and roughly 2 percent from carbohydrates (a maximum of fifty calories a day), which came from glycogen contained in the muscle meat. (Glycogen is the compound that stores glucose, a carbohydrate, in the liver and the muscle.)

“The only dramatic part of the study was the surprisingly undramatic nature of the findings,” wrote Du Bois, when he later summarized the results. “Both men were in good physical condition at the end of the observation,” he reported in 1930, in one of the nine articles he and his col eagues published on the study. “There was no subjective or objective evidence of any loss of physical or mental vigor.” Stefansson lost six pounds over the course of the year, and Anderson three, even though “the men led somewhat sedentary lives.” Anderson’s blood pressure dropped from 140/80 to 120/80; Stefansson’s remained low (105/70) throughout. The researchers detected no evidence of kidney damage or diminished function, and “vitamin deficiencies did not appear.” Nor did mineral deficiencies, although the diet contained only a quarter of the calcium usual y found in mixed diets, and the acidic nature of a meat-rich diet was supposed to increase calcium excretion and so deplete the body of calcium. Among the minor health issues reported by Du Bois and his col eagues was the observation that Stefansson began the experiment with mild gingivitis (inflammation of the gums), but this “cleared up entirely, after the meat diet was taken.”

When Stefansson published Not by Bread Alone, a popular treatise on fat-and-protein diets, in 1946, a New York Times reviewer wrote, “Mr.

Stefansson makes the mixed-diet technicians and the nuts-and-fruits addicts look terribly sil y.” Du Bois, who supervised the experiments, wrote an introduction to Stefansson’s book. After Stefansson and Anderson were living exclusively on meat, he said, “a great many dire predictions and bril iant theories faded into nothingness.” A diet that should have left Stefansson and Anderson deathly il from scurvy had left them as healthy as or healthier than the balanced diet they had been eating in the years immediately preceding the study. “Quite evidently we must revise some of our text book statements,”

Du Bois concluded.

The textbook statements on vitamins would go unrevised, however, despite laboratory research that has confirmed Stefansson’s speculations.

Nutritionists would establish by the late 1930s that B vitamins are depleted from the body by the consumption of carbohydrates. “There is an increased need for these vitamins when more carbohydrate in the diet is consumed,” as Theodore Van Ital ie of Columbia University testified to McGovern’s Select Committee in 1973. A similar argument can now be made for vitamin C. Type 2 diabetics have roughly 30 percent lower levels of vitamin C in their circulation than do nondiabetics. Metabolic syndrome is also associated with “significantly” reduced levels of circulating vitamin C, which suggests that vitamin-C deficiency might be another disorder of civilization. One explanation for these observations—described in 1997 by the nutritionists Julie Wil and Tim Byers, of the Centers for Disease Control and the University of Colorado respectively, as both “biological y plausible and empirical y evident”—is that high blood sugar and/ or high levels of insulin work to increase the body’s requirements for vitamin C.