Eggs' Effect on Alzheimer Disease

Sam is a 55-year-old man who is concerned about his risk of developing Alzheimer disease later in life. Recently, he read that because of their high cholesterol content, eggs could increase his risk of dementia. He asks if he should cut eggs out of his diet all together, to reduce this risk.

How would you advise your patient?
(Answer and discussion on next page)

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Answer: For the vast majority of people, eggs are okay in moderation.

In addition to increasing your patients' 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 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 they consume has far less effect on their cholesterol scores than the amount of saturated fat in their diet.
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This begs the question: if the cholesterol your patients consume is unlikely to affect their cholesterol scores, will that mean that the cholesterol they consume has little effect on their risk of dementia or Alzheimer disease? As you know, medicine is not mathematics: if A = B and B = C, that doesn't necessarily mean that A = C.

The Research

A team in Finland decided to look at whether egg consumption was linked to a higher risk of dementia or Alzheimer disease. They recruited nearly 2,500 men between the ages of 42 and 60 who had no symptoms of dementia or cognitive decline. About half of those men were carriers of apolipoprotein E4 (Apo-E4), a gene 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 disease. They could then analyze the participants' dietary records, and, when possible, correlate the cognitive scores of those who developed dementia or Alzheimer disease and compare them with those who did not.

The Results

They found that the neither the number of eggs specifically nor the amount of dietary cholesterol in general the participants consumed were linked to an increased risk of Alzheimer disease 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, suggesting that egg consumption may reduce the overall risk of Alzheimer disease.

What’s the “Take-Home”?

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 disease. For your patients, the take home message is still that for the vast majority of people, including carriers of the Apo-E4 gene, eggs are okay in moderation.

Reference:

Ylilauri MPT, Voutilainen S, Lonnroos E, et al. Association of dietary cholesterol and egg intakes with the risk of incident dementia or Alzheimer disease: the Kuopio Ischaemic Heart Disease Risk Factor Study. Am J Clin Nutr. 2017;105:476-84.