How diet can help—or harm—your cognitive fitness.
Before you cut into a big T-bone steak with French fries, here is some food for thought: Research suggests that what we eat might have an impact on our ability to remember and our likelihood of developing dementia as we age.
Take that steak you're about to slice into, for example. It's loaded with saturated fat, which is known to raise blood levels of unhealthy low-density lipoprotein (LDL) cholesterol. Other kinds of fats, such as trans fats, do the same thing to LDL.
LDL cholesterol builds up in, and damages, arteries. "We know that's bad for your heart. There is now a lot of evidence that it's also bad for your brain," says Dr. Francine Grodstein, associate professor of medicine at Harvard Medical School and associate epidemiologist at Brigham and Women's Hospital.
Beta-amyloid plaque in the brainDiets high in cholesterol and fat might speed up the formation of beta-amyloid plaques in the brain. These sticky protein clusters are blamed for much of the damage that occurs in the brains of people with Alzheimer's.
The diet and memory connection
As evidence of this effect are the results of a study conducted by researchers at Brigham and Women's Hospital, published online May 17 in the journal Annals of Neurology. Women in the study who ate the most saturated fats from foods such as red meat and butter performed worse on tests of thinking and memory than women who ate the lowest amounts of these fats.
The exact reason for the connection between diets high in saturated and trans fats and poorer memory isn't entirely clear, but the relationship may be mediated by a gene called apolipoprotein E, or APOE. This gene is associated with the amount of cholesterol in your blood, and people with a variation of this gene, called APOE e4 are at greater risk for Alzheimer's disease. "About 65% of individuals who wind up with dementia due to Alzheimer's disease in their 60s and 70s have that gene," says Dr. Gad Marshall, assistant professor of neurology at Harvard Medical School.
How does the APOE e4 gene contribute to dementia? Researchers aren't exactly sure, but they have discovered that people with this genetic variation have a greater number of sticky protein clumps, called beta-amyloid plaques, in the brain. These plaque deposits, which are associated with the destruction of brain cells, are a hallmark of Alzheimer's disease.
The connection is a little clearer when it comes to memory loss that's related to blood vessel damage. The buildup of cholesterol plaques in brain blood vessels can damage brain tissue, either through small blockages that cause silent strokes, or a larger, more catastrophic stroke. Either way, brain cells are deprived of the oxygen-rich blood they need to function normally, which can compromise thinking and memory.
Other ways to protect memory as you age
Foods for memory
If saturated and trans fats are the food villains, then mono- and polyunsaturated fats may be the heroes in the dietary battle to preserve memory. In particular, the Mediterranean diet, with its menu of foods that are high in healthy unsaturated fats (olive oil, fish, and nuts) has been linked to lower rates of both dementia due to Alzheimer's disease and mild cognitive impairment (MCI)—the stage of memory loss that often precedes dementia.
The Mediterranean diet includes several components that might promote brain health:
Fruits, vegetables, whole grains, fish, and olive oil help improve the health of blood vessels, reducing the risk for a memory-damaging stroke.
Fish are high in omega-3 fatty acids, which have been linked to lower levels of beta-amyloid proteins in the blood and better vascular health.
Moderate alcohol consumption raises levels of healthy high-density lipoprotein (HDL) cholesterol. Alcohol also lowers our cells' resistance to insulin, allowing it to lower blood sugar more effectively. Insulin resistance has been linked to dementia.
Sample Mediterranean diet