ESSENTIALS: SCIENCE

Dr. Malcolm Kendrick, MD, discusses two populations that exhibit high levels of Type 2 diabetes (T2D) and explains how they can help to further illuminate the underlying cause of T2D in the general population.

An extensive 2018 review summarizes the biological underpinnings of brain aging and proposes how metabolic dysfunction may contribute to their progression.

A 2017 review links hyperinsulinemia and other components of the metabolic syndrome to the development and progression of Alzheimer’s disease.

In the first article in his new series on diabetes, Dr. Malcolm Kendrick, MD, discusses the long history of diabetes research and introduces several models for understanding the causes of the disease, as well as its progression. While the mechanism underlying Type 1 diabetes is generally agreed upon, debate continues over whether Type 2 is related to fat consumption or raised insulin levels resulting from carbohydrate intake. Kendrick explains and evaluates the arguments for each model.

Several studies support the hypothesis that diet, particularly carbohydrate consumption, affects vision. One study compares the eyesight of hunter-gatherer and industrialized groups and finds myopia skyrockets when indigenous populations adopt a Western diet involving more refined carbohydrates. Another study explores the mechanism behind dietary contribution to myopia and finds increases in insulin promote eyeball elongation in animal models. A third study explores dietary sugar’s links to glaucoma, cataracts, diabetic retinopathy, and macular degeneration. Its authors ultimately recommend avoiding high glycemic index foods.

A 2015 review explores behavioral and mechanistic links between diabetes and depression.

Georgia Ede argues the dramatic fluctuations in glucose and insulin levels caused by eating high-glycemic-index foods lead to a variety of negative psychological effects.

Georgia Ede summarizes the potential contributions of insulin resistance in the brain to Alzheimer’s disease and Parkinson’s disease.

A 2016 review finds preliminary evidence suggesting intermittent fasting and similar eating patterns can reduce markers of cancer risk and progression. More intensive fasts, such as complete fasting on alternating days, show more consistent benefits; more moderate fasts show equivocal clinical impact.

“Since 1990, Uffe Ravnskov MD PhD has published over 100 scientific papers critical of the cholesterol campaign, proposing new hypotheses and also contending that ‘the successful dissemination of the diet-heart idea is due to authors systematically ignoring or misquoting (contradictory) studies.’”

This brief 2017 review surveys evidence that suggests increased consumption of added sugars increases heart disease risk, both indirectly by increasing the risk of diabetes and directly through other mechanisms.

Prof. Timothy Noakes provides evidence in support of Nina Teicholz’s argument that “the story of nutritional science is not, as we would expect, one of sober-minded researchers moving with measured judicious steps.” Teicholz claims it instead falls under “the ‘great man’ theory of history, whereby strong personalities steer events using their personal charisma, intelligence, wisdom, or wits.” According to Noakes, these qualities are precisely what allowed Ancel Keys to convince his colleagues to support his diet-heart and lipid hypotheses — even when the science did not.

This 2018 paper on the Diabetes Remission Clinical Trial (DiRECT) reports the small share of diabetic subjects who fail to achieve glycemic control with weight loss differ only from successful responders in the ability of their pancreatic beta-cells to return to normal function. The DiRECT study thus further establishes that diabetes can be reversed through diet alone. Significantly, it also reinforces the importance of early intervention, as a diet started soon after diagnosis (before stressors have begun to degrade pancreatic beta-cell function) is more likely to successfully reverse diabetes.

Three case reports demonstrate durable (in two cases permanent) remission of Type 1 diabetes through the introduction of a low-carbohydrate diet soon after diagnosis.

Prof. Tim Noakes separates fact from fiction in his examination of the data from the Framingham Heart Study (FHS). Despite the efforts of some of the study's lead scientists to wrench the data into supporting the association of dietary fat and blood cholesterol concentration with coronary heart disease (CHD), the study instead demonstrated insulin resistance is a significant risk factor for CHD mortality whereas blood cholesterol concentration has little or no practical predictive value, especially after age 50. Noakes also highlights the insights shared by Dr. George Mann, “who was initially one of the scientific leaders of the FHS but later resigned to express his displeasure at the fake science he detected."

Two 2012 reviews argue the primary cause of diabetes is not insulin resistance but hyperinsulinemia — and thus, that treatment with exogenous insulin may drive disease progression.

This 2014 review summarizes cases of statin-induced rhabdomyolysis (rhabdo). Any detrimental effects statins may have on muscle weakness and/or muscle function are worth observing closely given the clinical significance of mobility in the elderly populations frequently prescribed statin drugs.

This 2019 study tested a variety of dietary interventions designed to elevate serum ketone levels on autosomal dominant polycystic kidney disease (ADPKD). The study found time-restricted feeding, fasting, a ketogenic diet, and beta-hydroxybutyrate supplementation each slowed the progression of, and in some cases even reversed, ADPKD in rats.

Dr. Malcolm Kendrick concludes his series on the response to injury hypothesis for cardiovascular disease (CVD) by observing that reducing risk relies on doing at least one of three things, and ideally all three: protecting the endothelium from damage, reducing blood coagulability, and improving the body’s healing processes. Kendrick highlights several specific ways to protect the endothelium, from quitting smoking to getting more sun to increasing potassium intake.

This 2018 review describes the causes and benefits of “flipping the metabolic switch” — that is, using fasting to transition the body from a state of fat storage to one of fatty acid release and oxidation.