Debates about the influence of nutrition on health are ongoing. For years, researchers have considered nutrients that contribute to chronic disease and ones that promote long, healthy lives. Although current headlines highlight the ill effects of high-sugar and low-fat diets, this wasn’t always the case.
In the 1950s, increased sugar consumption was identified as a contributor to chronic disease, including heart disease. But wait, haven’t we been told that fat is the main culprit? The sugar-fat debate and misconceptions about both nutrients have persisted for many years. More recent discoveries have revealed some interesting facts – not all fats are bad, low-fat diets have led to increased refined sugar consumption, and high sugar intake can cause health concerns. If it was known long ago that sugar is a factor in increasing rates of coronary heart disease and other illnesses, why wasn’t this widely shared to help prevent these harmful health conditions faced by generations?
Let’s rewind to the time of John Yudkin, a British nutritionist and the founding professor of the Department of Nutrition at Queen Elizabeth College in London. Dr. Yudkin examined the relationship between health and diet, in particular the impact of sugar on health. In 1957, he stated his hypothesis that the rise in sugar consumption correlated with the rise in heart disease. He wrote numerous publications stating his views, but he met adversity from other researchers and an expanding food industry.
Around the same time, Americans were determining the cause of increased heart disease cases. In 1948, 44% of U.S. deaths were connected to cardiovascular disease, an evident increase of 20% since 1940. When President Dwight Eisenhower suffered a heart attack in 1955, his own physician began to provide advice on preventing heart disease. Part of his guidance was to focus on the reduction of fats, especially saturated fats. This direction was influenced by the diet-heart hypothesis proposed by American physiologist Ancel Keys. In comparing the health and diet of men from Italy, Greece, Yugoslavia, Finland, the Netherlands, Japan, and the U.S., Dr. Keys concluded that saturated fat intake increased blood cholesterol and was a risk factor for coronary heart disease.
High sugar intake can affect blood sugar and insulin levels and set the stage for the development of obesity, metabolic syndrome, and inflammatory diseases.
Over the years, Keys’ methods and findings have been questioned. For example, it is said that he specifically chose countries that would correctly prove his hypothesis, and countries such as Switzerland and France, which had low rates of heart disease but consumed high amounts of animal fats, were not included. Despite these shortcomings and Yudkin’s sugar warnings, Keys and his conclusions on saturated fat gained acceptance. Organizations such as the American Heart Association (AHA) recommended that people reduce the intake of total fat, saturated fat, and cholesterol, and increase the intake of polyunsaturated fats, among other measures.
Steps to decrease fat intake while simultaneously increasing sugar intake have not been beneficial for cardiovascular health.
Advice on low-fat intake was further shaped by a food industry that was using refined sugar to support an expanding market of convenience foods. Saturated fats were replaced by foods with added sugars such as sucrose or high-fructose corn syrup, and refined grains. Ultimately, steps to decrease fat intake while simultaneously increasing sugar intake have not been beneficial for cardiovascular health.
You may be wondering what happened to John Yudkin. With greater support to remove saturated fats instead of refined sugars from diets, Yudkin faced criticism and hardship. Although he went on to write numerous publications, including his most notable book Pure, White, and Deadly (1972), his work was discredited and labelled as “science fiction.” Despite losing research funding and being uninvited to conferences, he continued to warn about the dangers of sugar.
Interestingly, by the 1980s, studies began to emerge in support of Yudkin’s theories. Research has revealed that high sugar intake, especially specific types of sugars such as fructose, can affect blood sugar and insulin levels and set the stage for the development of obesity, metabolic syndrome, and inflammatory diseases. It has also become clear that only certain types of fats negatively impact health, while other fats are beneficial.
Would knowing Yudkin’s claims that sugar is poisonous and harmful to our health change the rising rates of chronic disease we have witnessed? Professor and neuroendocrinologist Robert Lustig said it best: “Science took a disastrous detour in ignoring Yudkin. It was to the detriment of the health of millions.” We now know that both Keys and Yudkin had legitimate points, and research continues to unravel how certain fats and sugars can contribute to heart disease and other chronic health conditions. There can only be great value in exploring and discussing ideas from visionaries such as Yudkin so we do not make the same mistakes again.