Eggs’ effect on Alzheimer’s

In addition to increasing your risk of heart disease, poor cholesterol scores have been linked to a greater risk of developing dementia and the formation of the plaques that characterize Alzheimer's Disease. For decades eggs, with their relatively high levels of cholesterol, were considered foods to avoid for those with poor cholesterol scores. More recently, however, we have learned that for the vast majority of people the cholesterol you consume has far less effect on your cholesterol scores than the amount of saturated fat in your diet.

This begs the question: if the cholesterol you consume is unlikely to affect your cholesterol scores, will that mean that the cholesterol you consume have little effect on your risk of dementia or Alzheimer's? As you know, medicine is not mathematics: if A = B and B = C, that doesn't necessarily mean that A = C.

A team in Finland decided to look at whether egg consumption was linked to a higher risk of dementia or Alzheimer's (Am J Clin Nutr 2017;105:476-84). They recruited nearly 2,500 men between the ages of 42 and 60 who had no symptoms of dementia or other mental problems. About half of those men were carriers of a gene known as apolipoprotein E4 (Apo-E4), which we know carries a higher risk of dementia.

At the start of the study the participants filled out a 4-day food record with the assistance of a trained nutritionist and provided blood samples for cholesterol tests. They also responded to a detailed demographic and health history and had their blood pressures taken. Four years later about 500 of the oldest men participated in cognitive performance tests that measured language facility, long- and short-term memory, and visual memory.

After an average of 22 years the authors gathered information from Finland's health records regarding how many and which participants had been diagnosed with dementia or Alzheimer's Disease. They could then analyze the diet, and when possible, the cognitive scores of those who developed dementia or Alzheimer's and compare them with those who did not.

They found that the neither the number of eggs nor the amount of dietary cholesterol the participants consumed were linked to an increased risk of Alzheimer's or dementia, even when the participant carried the Apo-E4 gene. Indeed, the surprising result was that those who consumed a moderate number of eggs (averaging less than 1 per day) performed better on the cognitive tests and may even reduce the overall risk of Alzheimer's.

What this means for you

This is another study whose results should be approached with caution: those who consumed more eggs might have other characteristics that influenced their risk of dementia or Alzheimer's. The take home message is still that for the vast majority of people, eggs are okay in moderation.

First posted: March 8, 2017