A recent online commentary in The New York Times makes the case that Alzheimer’s disease (AD) may in fact be a third type of diabetes.  Citing new and “increasingly persuasive” studies, columnist Mark Bittman explains:

We used to think there were two types of diabetes: the type you’re born with (Type 1) and the type you ‘get.’ That’s called Type 2, and was called “adult onset” until it started ravaging kids. Type 2 is brought about by a combination of factors, including overeating, American-style.

The idea that Alzheimer’s might be Type 3 diabetes has been around since 2005, but the connection between poor diet and Alzheimer’s is becoming more convincing…

Here’s the idea, in very basic terms: Insulin is a hormone that is critical for regulating our body’s ability to control blood sugar and to make sure it gets into the cells that need it for energy. Diabetes is caused by either an inability to make enough insulin (Type 1) or when cells lose ability to respond to insulin (Type 2). As brain cells also critically need blood sugar to survive and function, the new theory of a “Type 3” diabetes suggests that a similar insulin deficiency or resistance leading to negative cognitive effects could underlie some of the causes of AD.

Past studies have already found that people with diabetes are twice as likely to develop AD later in life.  But the new research, explains Bittman, suggests that “while diabetes doesn’t ‘cause’ Alzheimer’s, both may have the same root: an over consumption of those ‘foods’ that mess with insulin’s many roles.” Sugar and nitrates, for instance.  A healthier diet, he suggests, would make sense toward limiting one’s potential for getting diabetes, and according to the new research, for potentially Alzheimer’s as well.

Diabetes has also been suggested as a potential risk factor for Parkinson’s disease (PD), but the data are not yet as compelling, says Brian Fiske, PhD, vice president of research programs at The Michael J. Fox Foundation (MJFF).  Some findings have suggested a greater risk for PD in people with diabetes but this link has not been consistently seen in all studies.

Coincidently, some drugs used for diabetes have found their way into PD based on the fact that they may target cellular pathways that could be beneficial for brain cell survival. The Foundation has supported work testing a number of these so-called “repositioned” diabetes drugs (exendin-4, DPP-4 inhibitors and pioglitazone) to find out more about their potential as disease-modifying therapies for PD. Currently, a trial of pioglitazone is being supported by the National Institute of Neurological Disorders and Stroke (NINDS) in collaboration with MJFF.

Learn more about the pioglitazone study and check out the story of one person with Parkinson’s who has decided to participate.