Type 2 Diabetes May Promote Alzheimer’s Disease

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People who are obese in middle age are known to be at increased risk of developing Alzheimer’s disease (AD) and vascular dementia - the two most common causes of senility. Obesity is largely due to excessive calorie intake coupled with inactivity. Excessive calorie intake often results from the consumption of a diet high in fatty meats and dairy products and also refined carbohydrates but low in vegetables, fruits, and whole grains. Such diets not only lead to weight gain but also in many people also promote insulin resistance, the metabolic syndrome and eventually type 2 diabetes mellitus (DM). A study of monkeys fed either a calorie restricted diet or allowed to eat freely published in the November 2006 issue of Journal of Alzheimer’s Disease showed that monkeys fed fewer calories were much less likely to accumulate significant amounts of beta-amyloid in their brains. Beta-amyloid accumulation is believed to play a major role in the loss of brain function that leads to AD.

A study published in the August 2010 issue of Neurology examined the brains of 135 people who lived and died in Hisayama, Japan. The sub- jects of this study had all had vari- ous metabolic factors tracked for 10 to 15 years before they died. Of the 135 subjects 21 had been diagnosed with AD before they died. However, the autopsies of their brains revealed that 88 of 135 contained an abnormal accumulation of tau protein, which have been associated with the development of AD. Those who had type 2 DM or the metabolic syndrome were more likely to have the accumulation of tau peptides in their brains. They also found that those who had higher blood sugar levels and more insulin resistance were more likely to have their brains gummed up with beta-amyloid plaques, another protein that accumulates in the brains and is believed to contribute to neurological damage leading to AD. Another study by Japanese researchers gave 1017 people 60 and older a glucose tolerance test and monitored them for the next 11 years. During that time 232 developed dementia. Of the initial 150 subjects with type 2 DM over twice as many developed dementia as those without diabetes. Those whose glucose tolerance put them in the pre-diabetic range were also more likely to develop dementia than those who blood sugar regulation was normal.

Bottom Line: Given the ineffectiveness of current treatment options for AD it is clear more emphasis needs to be placed on preventing its development. Data continues to accumulate, linking AD and dementia with the typical modern diet and an inactive lifestyle that leads to excessive calorie intake, increased body fat, and a host of metabolic problems associated with the development of type 2 DM and cardiovascular disease. Perhaps the time has come to alert people to the possibility that adopting a healthier diet and exercise program may prevent dementia as well as cardiovascular diseases.

By James J. Kenney, PhD, FACN