In the modern world, food has become a source of anxiety, identity, distrust and confusion. In our endless crusade for longevity, optimum health, better sleep, reduced levels of anxiety, improved cognitive performance, weight loss, self-fashioning, and eschatological ethics, we have become susceptible to a plurality of diets and curious eating habits.

In general, diets tend to address health problems, and offer the promise of weight loss, better health, or illness prevention. In some cases, particular diets, e.g., the spectrum diet (a low-fat, vegan diet championed by Dean Ornish), will claim that eating healthy inadvertently also implies eating ethically — a true blend of animal rights activism and orthorexia.

The quest for the perfect diet began in the 1950s. More precisely, it began in 1955 when then U.S. President Dwight Eisenhower experienced a major myocardial infarction (heart attack) on April 24th. The event quickly became a national fascination. Experts came together from far and wide to speculate about the condition, its root cause, and to speculate as to who may be susceptible to developing it.

In the wake of these events, it quickly became apparent that middle-aged men, precisely the demographic group who tended to hold office, were the most likely to be affected by the condition. These findings created a sense of urgency among elected officials, which eventually culminated in new government funding opportunities for those who were interested in researching the aetiology (cause) of cardiovascular disease (CVD).

Many different hypotheses emerged during this government lead effort. However, the most persuasive theory became known as the diet-heart hypothesis, which was spearheaded by Ancel Keys, an American physiologist, and John Yudkin, a British physiologist. The diet-heart hypothesis posited (argued) that CVD can be prevented through dietary intervention. Conversely, the hypothesis implied that myocardial infarctions were caused by poor eating habits.

Keys argued that saturated fat was the main dietary culprit for CVD, whereas Yudkin presented evidence against the consumption of sugar. Both Keys and Yudkin relied extensively on animal data to support their theories. For example, Keys pointed out that rabbits will develop atherosclerosis (thinning of the arteries: a key factor in the development of CVD) when they are fed saturated fat. Yudkin, on the other hand, showed that animals, including dogs, developed CVD when they consumed sugar, and criticized Keys for exporting the etiological characteristics of atherosclerosis in herbivores to humans (i.e., what applies to herbivores may not necessarily apply to humans). In spite of their diametrically opposed models, both hypotheses were given equal weight during the period. But, in the end, it was Keys who ended up prevailing.

By the mid seventies, both researchers had made substantial advances. At this point, Keys had gathered hard data in support for his hypothesis through his Seven Country Study (the largest epidemiological study of the period). Yudkin, on the other hand, had written a decisive case against sugar in his book Pure, White and Deadly: The Problem of Sugar — (now considered a rare collector’s item).

Keys’ epidemiological study (epidemiological studies investigate the geographic distribution of diseases) looked at the relationship between dietary habits in seven post World War II countries (U.S.A., Netherlands, Italy, the former Yugoslavia, Greece, Finland and Japan), in contrast to their CVD rates. His findings were unambiguous: lower dietary saturated fat consumption correlated with lower CVD mortality rates — a finding which ended up shaping official dietary recommendations for decades to come.

To the minds of many in the USDA (United State Department of Agriculture), it was now clear that saturated fat should be considered public enemy #1. Invoking Keys’ epistemic authority, who by that time was viewed as the most important figure in dietary research, the USDA began its crusade against saturated fat. Keys’ diet-heart model gradually became incorporated into national dietary recommendations; and was cemented in the public’s imagination with the initial publication of the first USDA food pyramid in 1992. At this point, Yudkin’s warning against the consumption of sugar was almost entirely forgotten.

To this day, the food pyramid represents the U.S.’s official dietary guidelines. The chart recommends the following servings:

1. Grains (42% of daily calories)

2. Vegetables (19% of daily calories)

3. Fruits (15% of daily calories)

4. Dairy products (10% of daily calories)

5. Meat, fowl, fish, eggs and nuts (12% of daily calories)

6. Fats, oils and sweets (less than 2% of daily calories)

Broken down into macronutrients, the food pyramid advocates for a diet that’s close to 76% in carbohydrates, less than 10% in fat, and about 12% in protein. This is what’s known as a high carb-low-fat diet (HCLF).

Another key feature of this diet is its quasi-vegetarian nature. Carbohydrates, which break down into simple sugars when digested, are predominantly found in grains, fruits and vegetables. Animal products, with the exception of dairy, tend to contain only trace amounts of carbohydrates and sugars. They are mostly composed of protein and fat (a mixture between monounsaturated, saturated and polyunsaturated fat).  So, if you want to avoid saturated fat, the easiest way to do it is by restricting the consumption of animal products (as a side note: nuts and seeds are predominantly made up of saturated fat. This is why they were placed under the same category as meat, fowl, fish and eggs).

Now, as interesting as all of this may be, not everyone agreed with these dietary recommendations. In fact, many experts during the period vehemently protested against their adoption. They based their concerns primarily on anthropological data, which unequivocally points towards a pre-agrarian carnivorous past. Evolutionary biologists also joined in on the discussion, and argued that saturated fat is an old nutrient, and because of this, it would make little sense to blame it for the new CVD epidemic.

By 2014, the story had taken a drastic turn. The cover of Time magazine read — “Eat Butter: Scientists labeled fat the enemy. Why they were wrong”?

To be continued…

Banner Photo by @5056468 // @ pixabay