Although I’m a cognitive psychologist and consequently think that memory and cognition is mostly about your mastery of effective strategies, when it comes to age-related cognitive decline, I’m a big believer in the importance of diet and exercise. But while we know these things can play an important role in why some people develop cognitive impairment and even dementia as they age, and others don’t, we don’t yet know with any great certainty exactly what exercise programs would be the best use of our time, and what diet would have the most benefit.
The role of diet in fighting age-related cognitive decline is quite complex. Many older people have inadequate diets, partly no doubt because of the shrinking in appetite and perhaps the dulling of taste and smell. It seems to me, for example (and this is purely a casual observation), that sweet foods tend to be appreciated more by the elderly, while other flavors are less able to be appreciated. The problem with the shrinking appetite is that it becomes even more vital, if the quantity of food is much reduced, that the nutritional quality is good. The less you eat, the less you can afford to eat “empty calories”. Everything must count.
Other factors concern the need to fight declining physical health. Cardiovascular problems, cholesterol problems, blood pressure problems, inflammation — all these have been implicated in contributing to cognitive decline. Therefore any diet that helps you fight these problems is also helping you fight cognitive decline.
A recent Swedish study tackled the inflammation problem. The study, involving 44 overweight people aged 50-75, found that after four weeks eating foods presumed to reduce low-grade inflammation, bad (LDL) cholesterol was reduced by 33%, blood triglycerides by 14%, blood pressure by 8% and a risk marker for blood clots by 26%. Memory and cognitive function was also improved (but no details on that were reported, and at present it appears only a press release is available — no academic paper).
The diet was high in antioxidants, low-GI foods (i.e. slow release carbohydrates), omega fatty acids, wholegrain products, probiotics and viscous dietary fibre. Examples of foods eaten were oily fish, barley, soy protein, blueberries, almonds, cinnamon, vinegar and a certain type of wholegrain bread. Some of the products are not yet available in the shops, but were developed specifically for the study.
Another study, involving 712 New Yorkers, found that those who most closely followed a Mediterranean-like diet over a six-year period, were 36% less likely to have brain infarcts compared to those who were least following the diet. Such a diet has also been associated with a lower risk of Alzheimer's disease.
The Mediterranean diet includes high intake of vegetables, legumes, fruits, cereals, fish and monounsaturated fatty acids such as olive oil; low intake of saturated fatty acids, dairy products, meat and poultry; and mild to moderate amounts of alcohol.
And an 11-year study of over 3800 seniors found that those who adhered more closely to an anti-hypertension diet (DASH) maintained their cognitive performance better over time, and that this appeared due to intake of four food groups: vegetables, whole grains, low-fat dairy, nut/legumes.
Other studies have pointed to the importance of maintaining blood sugar levels.(These studies, with the exception of the Swedish study, are all ones that have been previously reported on this site.)
We can be fairly sure that fighting inflammation, hypertension, and so on, help us fend off cognitive decline and impairment in our senior years. We can also be reasonably sure that fruit and vegetables are good for us. No one’s arguing much about fish either (although you do have to consider the toxicity of the fish, especially mercury load). There’s a messy ground however over the whole carbohydrate, sugar, fat, protein, dairy ground.
Recently I read a very interesting article reviewing a new book called Good Calories, Bad Calories. In this book, the author apparently “dispels nearly every belief doctors and the public health community hold to be true about nutrition and health”. According to the blogger, “It would be easy to dismiss his claims, except that he makes his case not with theories and conjectures, but through a meticulous review of the nutrition and medical literature going back a hundred years.” Moreover, the claims do help explain some of the more puzzling quandaries about the rise of obesity.
They also, I have to say, fit in with my own experience.
The basic tenet of the book is that it is carbohydrates, and most especially refined carbohydrates, that are to blame for our current epidemics of obesity, diabetes, coronary heart disease, and even cancer. We should avoid anything made with flour, cereals, potatoes, and anything with a lot of sugar (bananas, I’m afraid, are also a no-no). We don’t, on the other hand, need to worry about meat, dairy, or fat.
This is, in fact, exactly what I have found in my own struggles with weight (although of course my reason for discussing this here is not weight per se but more fundamental physical problems). When my weight climbed to what I regarded as appalling levels, I lost the desired 20kg through a rigorous low-carbohydrate diet (although my reasons actually had more to do with trying to work through my food sensitivities). And when I say low-carbohydrate, I was actually living mainly on fruit and vegetables. I did find, after a while, that the lack of carbohydrate created an energy problem, but a quarter-cup (uncooked) of brown rice every day fixed that. When, after a couple of years, I loosened up on my diet, having some bread (gluten-free; yeast-free!), the occasional bit of baking, the occasional small bit of potato … well, my weight immediately started climbing again. I complain that I only have to look at some baking to add weight!
I’m fully conscious that this wouldn’t be everyone’s experience — I live with three males, all of whom are the tall, lean type, who can eat vast quantities of baking without it apparently having any effect. But this is my point. I think the author of this book makes some good points about the difficulties of diet research, and he may well be right in his recommendations. But even when we get to the point when we can be certain of what is a “healthy diet”, it’s still not going to be true for everyone.
So my advice to individuals is that you don’t take the disputes among health and nutrition experts as an excuse for eating what you like, but instead as a basis for exploration. Look at the various diets for which there is some evidence, and work out which ones work for you. Which will depend not only on your genetic makeup, but most particularly on the damage you’ve already done to your body (not pointing a finger! We’ve all damaged our bodies just by living). As a reminder of which I was interested to read an interesting article in the New York Times on the high-fat diet recommended for epileptics.