Here's what you need to know about type 3 diabetes—plus, 8 ways that may help prevent it.

Carolyn Williams, PhD, RD
November 21, 2018

For years, dementia and development of Alzheimer’s disease has seemed to be largely based on genetics, somewhat outside our realm of control. However, there’s a growing body of research that suggests our lifestyle habits today—particularly ones that affect the body’s management of glucose and insulin such as diet, body weight and activity—are major determinants of our cognitive function years down the road. In fact, the connection is so compelling that some medical professionals now refer to Alzheimer’s disease as Type 3 diabetes.

Insulin Resistance and Dementia: What’s the Connection?

Insulin resistance occurs when cells in the body gradually become less sensitive or resistant to insulin made and secreted by the pancreas. It’s associated with having excess body weight, eating a poor diet, and/or a living a sedentary lifestyle, and insulin resistance leads to the development of type 2 diabetes (T2DM).

The effects of insulin resistance in T2DM are that cells can’t efficiently get energy, blood glucose levels stay above normal, and blood vessels and tissues have the potential to become damaged due to a lack of circulation and/or nutrients. While we don’t usually consider the brain as a site affected by diabetes, those with T2DM have an increased risk for damaged blood vessels in the brain. This damage, along with neurons that have also become insulin resistant, increase the risk for cognitive decline (memory loss, dementia) in those with T2DM, as well as those with prediabetes.

In fact, a study earlier this year suggested that those with higher HgbA1c levels (a blood measure of sustained high glucose) showed greater increases in mental decline over a 10-year period, compared to those with normal levels.

The Potential Connection to Alzheimer’s Disease

The same issues at the root of T2DM—insulin-resistance and metabolic imbalances—are what research suggests is at the root of Alzheimer’s disease (AD) development and/or progression. AD is characterized by a buildup of amyloid plaques and tangles in the brain. As more plaques and tangles develop, brain cells can’t properly use fuel sources, communication between neurons and synapses is altered, and inflammation develops—all of which can lead to neuron death and further metabolic imbalances in the brain. The effects seen are memory loss, dementia, and even personality changes.

The idea that AD should be considered a third type of diabetes is still being explored, but here is what research suggests about the connection between insulin-resistance and AD:

  • The cognitive decline associated in AD cases appears to be due to abnormal metabolic changes in the brain and insulin-resistance.
  • Only 5% of AD cases are attributed to a direct genetic link. This majority of cases are thought to be caused by genetic interactions with environmental and lifestyle factors such as diet, weight and activity.
  • There is a strong connection between high blood glucose levels and AD development. When a 2016 study examined diagnosed AD cases, almost half could be associated with high glucose levels.
  • T2DM doesn’t cause AD, but those with T2DM have a significantly increased risk of developing AD.

Maintaining Brain Health and Prevention

Some cognitive decline is a natural part of the aging process, but what’s important to note is that this natural age-associated decline appears to be fueled and encouraged by underlying insulin-resistance and metabolic imbalances—even in individuals who aren’t yet showing signs of T2DM or insulin-resistance.

Also, insulin-resistance may occur in the brain with or without signs of prediabetes or T2DM. All of this suggests that adopting healthy lifestyle habits to maintain good blood glucose management in early adulthood is key. Here are eight key areas to focus on now.

1. Monitor Overall Carb Intake: Our food system today makes it easy to consume more carbohydrates, so keep tabs on that intake to ensure it’s balanced with high-quality fats and lean proteins. While this doesn’t necessarily mean eating a low-carb diet, some preliminary research does suggest that reducing carbohydrates could play a role in maintaining brain health and even possibly slowing AD progression.

2. Be Picky About Carbs: Choose high-quality, less processed carbs like beans, legumes, vegetables, whole grains, and fruits. These foods usually have more nutrients, including fiber which helps with blood glucose regulation.

3. Skip the Added Sugars and Snack Foods: Even though you may have no signs of insulin resistance, limit high intakes added sugars, refined and processed carb-rich foods, and any others that trigger sudden spikes and then drops in blood glucose. Fluctuations in the body’s glucose-insulin management system could make you more prone to insulin-resistance down the road.

4. Get Moving: Regular physical activity is associated with reduced risks for T2DM, dementia, and AD. Circulation of blood, oxygen and nutrients is increased throughout the body during activity, including the brain, which may potentially help regenerate neurons or rebuild neuron connections. Regular activity also improves insulin-sensitivity and reduces blood glucose levels.

5. Work Towards a Healthy Body Weight: Studies have suggested that middle-aged individuals with a BMI >30 have increased risks for both dementia and AD. Working towards a healthy body weight now is key to decreasing risk of insulin-resistance today and down the road.

6. De-Stress Daily: Elevated stress levels also alter hormones and creates metabolic imbalances, potentially increasing risk of insulin-resistance. Working in regular relaxation or stress management activities—even just 5 minutes at a time—can help to reduce overall lower stress to improve physical and mental health.

7. Don’t Skimp on Sleep: Sleep allows the body time to rest, recuperate, and repair itself, so the body is able to function properly. A lack of regular, adequate sleep increases risk for insulin-resistance, T2DM, and AD.

8. Don’t Wait for Signs: The development of dementia and AD has been described as a slow-burning fire—one that’s often not noticed until it’s progressed when there’s little that can be done to reverse course. Don’t wait for symptoms to appear to change health habits. Also don’t assume risk is low because there’s not a family history of dementia or AD.

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