In a large Mayo Clinic study, self-reported diet was found to be significantly associated with the risk of seniors developing mild cognitive impairment or dementia over a four-year period.

The study involved 1,230 older adults (70-89) who completed a 128-item food-frequency questionnaire about their diet during the previous year. Of these, around three-quarters (937) showed no signs of cognitive impairment at the beginning of the study period, and were asked to return for follow-up cognitive assessments. These assessments took place every 15 months. After about four years, 200 (21%) had developed mild cognitive impairment (MCI) or dementia.

The likelihood of cognitive deterioration was significantly affected by the type of diet. Those with the highest carbohydrate intake were nearly twice as likely to develop cognitive impairment compared to those with the lowest carbohydrate consumption, and when total fat and protein intake were taken into account, they were 3.6 times likelier to develop impairment.

Those with the highest sugar intake were 1.5 times more likely to develop cognitive impairment.

But — a finding that will no doubt surprise many — those with the highest fat consumption were 42% less likely to develop cognitive impairment, compared to those with the lowest level of fats.

Less surprisingly, those with highest intake of protein had a reduced risk of 21%.

In other words, the worst diet you can have, if you want to keep your brain healthy, is one that receives most of its calories from carbohydrates and sugar, and relatively little from fats and protein.

The findings about carbs, sugar, and protein are consistent with other research. The finding regarding fats is somewhat more surprising. The inconsistency may lie in the type of fat. Research implicating high-fat diets as a risk factor in Alzheimer’s have used saturated fats. Diets high in olive oil, on the other hand, have been found to be beneficial.

It seems likely that the danger of carbs and too much sugar lies in the effects on glucose and insulin metabolism. Saturated fats also interfere with glucose metabolism. Alzheimer’s has sometimes been called Type 3 diabetes, because of its association with insulin problems.

Roberts RO, Roberts LA, Geda YE, Cha RH, Pankratz VS, O'Connor HM, Knopman DS, Petersen RC. 2012. Relative intake of macronutrients impacts risk of mild cognitive impairment or dementia. Journal of Alzheimers Disease, 32(2), 329-39.

Older news items (pre-2010) brought over from the old website

Blood sugar linked to normal cognitive aging

Following research showing that decreasing brain function in the area of the hippocampus called the dentate gyrus is a main contributor of normal age-related cognitive decline, an imaging study has been investigating the cause of this decreasing function by looking at measures that typically change during aging, like rising blood sugar, body mass index, cholesterol and insulin levels. The study of 240 community-based nondemented elders (average age 80 years), of whom 60 had type 2 diabetes, found that decreasing activity in the dentate gyrus only correlated with levels of blood glucose. The same association was also found in aging rhesus monkeys and in mice. The finding suggests that maintaining blood sugar levels, even in the absence of diabetes, could help maintain aspects of cognitive health. It also suggests that one reason why physical exercise benefits memory may be its effect on lowering glucose levels.

[830] Mayeux, R., Vannucci S. J., Small S. A., Wu W., Brickman A. M., Luchsinger J., et al.
(2008).  The brain in the age of old: The hippocampal formation is targeted differentially by diseases of late life.
Annals of Neurology. 64(6), 698 - 706.

Right breakfast bread keeps blood sugar in check all day

A doctoral study has found that those given low glycemic index breakfasts could concentrate better and had a better working memory. Moreover, healthy individuals with low glucose tolerance (higher than average rises in blood sugar following a meal) generally performed less well. The study also found that eating the right whole-grains for breakfast didn’t simply regulate blood-sugar levels all morning, but all day — some ten hours. Experiments also showed that the blood sugar increase following breakfast can be moderated in a similar way by eating the right grain products the night before. Great variations in levels of blood sugar are being associated more and more with the risk of old-age diabetes, obesity, and cardiovascular diseases.

Nilsson, A. 2007. Effects of Indigestible Carbohydrates and GI of Cereal Products on Glucose Metabolism, Satiety and Cognitive Function in Healthy Subjects; Emphasising mechanisms for glycaemic regulation at the acute, second and third meal. Division of Applied Nutrition and Food Chemistry, Lund University, P.O Box 124, 221 00 Lund.

High sugar blood levels linked to poor memory

A new study takes an important step in explaining cognitive impairment in diabetics, and suggests a possible cause for some age-related memory impairment. The study assessed non-diabetic middle-aged and elderly people. Those with impaired glucose tolerance (a pre-diabetic condition) had a smaller hippocampus and scored worse on tests for recent memory. These results were independent of age or overall cognitive performance. The brain uses glucose almost exclusively as a fuel source. The ability to get glucose from the blood is reduced in diabetes. The study raises the possibility that exercise and weight loss, which help control blood sugar levels, may be able to reverse some of the memory loss that accompanies aging.

[543] Convit, A., Wolf O. T., Tarshish C., & de Leon M. J.
(2003).  Reduced glucose tolerance is associated with poor memory performance and hippocampal atrophy among normal elderly.
Proceedings of the National Academy of Sciences of the United States of America. 100(4), 2019 - 2022.

Energy consumption improves memory performance in the elderly

On four occasions, a small group of older people ( 61–79 years) were given, after the night's fast, either a drink containing protein (whey), carbohydrate (glucose), fat (safflower oil), or a nonenergy placebo. Cognitive tests were given 15 and 60 minutes later. Only the carbohydrate drink increased blood glucose levels, but all 3 of the energy drinks improved memory for paragraphs. Other memory improvements were specific to the type of drink. For example, fat was the only one that enhanced attention. In general, improvement was greater 60 minutes after drinking than 15 minutes after.

[1210] Kaplan, R. J., Greenwood C. E., Winocur G., & Wolever T MS.
(2001).  Dietary protein, carbohydrate, and fat enhance memory performance in the healthy elderly.
Am J Clin Nutr. 74(5), 687 - 693.

A good breakfast improves memory function in older adults

A study of 41 healthy seniors aged 60 to 84 found that memory function was improved after a breakfast of wholegrain unsweetened cereal, milk, and juice (compared to no breakfast). This improvement was greatest for those with memory problems and those with early signs of adult-onset diabetes. The study was carried out by researchers at the Baycrest Centre for Geriatric Care at the University of Toronto.

Findings were presented to the Society for Neurosciences 2000 annual meeting in New Orleans.