Dementia, Alzheimer’s and Cognitive Decline

This is an extract from Prof T. Colin Campbell’s book, The China Study, in the section entitled, Mind-Altering Diets, where he shows a clear link between diet and cognitive decline in older age. I would urge you to read the book.

“By the time this book hits the shelves, I will be seventy years old. I recently went to my high school’s fiftieth reunion, where I learned that many of my classmates had died. I receive the AARP magazine, get discounts on various products for being advanced in age and receive social security checks every month. Some euphemists might call me a “mature adult.” I just say old. What does it mean to be old? I still run every morning, sometimes six or more miles a day. I still have an active work life, perhaps more active than ever. I still enjoy all the same leisure activities, whether visiting grandchildren, dining with friends, gardening, traveling, golfing, lecturing or making outdoor improvements like building fences or tinkering with this or that as I used to do on the farm. Some things have changed, though. Clearly there is a difference between the seventy-year-old me and the twenty-year-old me. I am slower, not as strong, work fewer hours every day and am prone to taking naps more frequently than I used to.

We all know that getting old brings with it diminished capacities compared with our younger days. But there is good science to show that thinking clearly well into our later years is not something we need to give up. Memory loss, disorientation and confusion are not inevitable parts of aging, but problems linked to that all-important lifestyle factor: diet.

There is now good dietary information for the two chief conditions referring to mental decline. On the modest side, there is a condition called “cognitive impairment” or “cognitive dysfunction.” This condition describes the declining ability to remember and think as well as one once did. It represents a continuum of disease ranging from cases that only hint at declining abilities to those that are much more obvious and easily diagnosed.

Then there are mental dysfunctions that become serious, even life threatening. These are called dementia, of which there are two main types: vascular dementia and Alzheimer’s disease. Vascular dementia is primarily caused by multiple little strokes resulting from broken blood vessels in the brain. It is common for elderly people to have “silent” strokes in their later years. A stroke is considered silent if it goes undetected and undiagnosed. Each little stroke incapacitates part of the brain. The other type of dementia, Alzheimer’s, occurs when a protein substance called beta-amyloid accumulates in critical areas of the brain as a plaque, rather like the cholesterol-laden plaque that builds up in cardiovascular diseases.

Alzheimer’s is surprisingly common. It is said that 1% of people at age sixty-five have evidence of Alzheimer’s, a figure that doubles every five years thereafter. I suppose this is why we blandly accept “senility” as part of the aging process.

It has been estimated that 10-12% of individuals with mild cognitive impairment progress to the more serious types of dementia, whereas only 1-2% of individuals without cognitive impairment acquire these diseases. This means that people with cognitive impairment have about a tenfold risk of Alzheimer’s.

Not only does cognitive impairment often lead to more serious dementia, it is also associated with cardiovascular disease, stroke and adult-onset Type 2 diabetes. All of these diseases cluster in the same populations, oftentimes in the same people. This clustering means that they share some of the same risk factors. Hypertension (high blood pressure) is one factor; another is high blood cholesterol. Both of these, of course, can be controlled by diet.

A third risk factor is the amount of those nasty free radicals, which wreak havoc on brain function in our later years. Because free radical damage is so important to the process of cognitive dysfunction and dementia, researchers believe that consuming dietary antioxidants can shield our brains from this damage, as in other diseases. Animal-based foods lack antioxidant shields and tend to activate free radical production and cell damage, while plant-based foods, with their abundant antioxidants, tend to prevent such damage. It’s the same dietary cause and effect that we saw with macular degeneration.

Of course, genetics plays a role, and specific genes have been identified that may increase the risk of cognitive decline. But environmental factors also play a key role, most probably the dominant one.

In a recent study, it was found that Japanese American men living in Hawaii had a higher rate of Alzheimer’s disease than Japanese living in Japan. Another study found that native Africans had significantly lower rates of dementia and Alzheimer’s than African Americans in Indiana. Both of these findings clearly support the idea that environment plays an important role in cognitive disorders.

Worldwide, the prevalence patterns of cognitive disorders appear to be similar to other Western diseases. Rates of Alzheimer’s are low in less developed areas. A recent study compared Alzheimer’s rates to dietary variables across eleven different countries and found that populations with a high fat intake and low cereal and grain intake had higher rates of the disease.

We seem to be on to something. Clearly, diet has an important voice in determining how well we think in our later years. But what exactly is good for us?

With regard to the more mild cognitive impairment condition, recent research has shown that high vitamin E levels in the blood are related to less memory loss. Less memory loss also is associated with higher levels of vitamin C and selenium, both of which reduce free radical activity. Vitamins E and C are antioxidants found almost exclusively in plant foods, while selenium is found in both animal- and plant-based foods.

In a study of 260 elderly people aged sixty-five to ninety years, it was reported that: “A diet with less fat, saturated fat and cholesterol, and more carbohydrate, fiber, vitamins (especially folate, vitamins C and E and beta-carotenes) and minerals (iron and zinc) may be advisable not only to improve the general health of the elderly but also to improve cognitive function.” This conclusion advocates plant-based foods and condemns animal-based foods for optimal brain function. Yet another study on several hundred older people found that scores on mental tests were higher among those people who consumed the most vitamin C and beta-carotene. Other studies have also found that a low level of vitamin C in the blood is linked to poorer cognitive performance in old age, and some have found that B vitamins, including beta-carotene, 70 are linked to better cognitive function.


What about the more serious dementia caused by strokes (vascular dementia) and Alzheimer’s? How does diet affect these diseases? The dementia that is caused by the same vascular problems that lead to stroke is clearly affected by diet. In a publication from the famous Framingham Study, researchers conclude that for every three additional servings of fruits and vegetables a day, the risk of stroke will be reduced by 22%. Three servings of fruits and vegetables is less than you might think. The following examples count as one serving in this study: 1/2 cup peaches, 1/4 cup tomato sauce, 1/2 cup broccoli or one potato.73 Half a cup is not much food. In fact, the men in this study who consumed the most fruits and vegetables consumed as many as nineteen servings a day. If every three servings lower the risk by 22%, the benefits can add up fast (risk reduction approaches but cannot exceed 100%).

This study provides evidence that the health of the arteries and vessels that transport blood to and from your brain is dependent on how well you eat. By extension, it is logical to assume that eating fruits and vegetables will protect against dementia caused by poor vascular health. Research again seems to prove the point. Scientists conducted mental health exams and assessed food intake for over 5,000 older people and monitored their health for over two years. They found that the people who consumed the most total fat and saturated fat had the highest risk of dementia due to vascular problems.

Alzheimer’s disease is also related to diet and is often found in conjunction with heart disease, which suggests that they share the same causes. We know what causes heart disease, and we know what offers the best hope of reversing heart disease: diet. Experimental animal studies have convincingly shown that a high-cholesterol diet will promote the production of the beta-amyloid common to Alzheimer’s. In confirming these experimental animal results, a study of more than 5,000 people found that greater dietary fat and cholesterol intake tended to increase the risk of Alzheimer’s disease specifically, and all dementia in general.

In another study on Alzheimer’s, the risk of getting the disease was 3.3 times greater among people whose blood folic acid levels were in the lowest one-third range and 4.5 times greater when blood homocysteine levels were in the highest one-third. What are folic acid and homocysteine? Folic acid is a compound derived exclusively from plant-based foods such as green and leafy vegetables. Homocysteine is an amino acid that is derived primarily from animal protein. This study found that it was desirable to maintain low blood homocysteine and high blood folic acid. In other words, the combination of a diet high in animal-based foods and low in plant-based foods raises the risk of Alzheimer’s disease.

Mild cognitive impairment, the stuff jokes are made of, still permits the afflicted person to maintain an independent, functional life, but dementia and Alzheimer’s are tragic, imposing almost impossibly heavy burdens on victims and their loved ones. Across this spectrum, from minor difficulties in keeping your thoughts in order to serious degeneration, the food you eat can drastically affect the likelihood of mental decline.

The diseases I’ve covered in this chapter take a heavy toll on most of us in our later years, even though they may not be fatal. Because they are not usually fatal, many people afflicted with these illnesses still live a long life. Their quality of life, however, deteriorates steadily, until the illness renders them largely dependent on others and unable to function in most capacities.

I’ve talked to so many people who say, “I may not live as long as you health nuts, but I sure am going to enjoy the time I have by eating steaks whenever I want, smoking if I so choose and doing anything else that I want.” I grew up with these people, went to school with these people and made great friends with these people. Not long ago, one of my best friends suffered a difficult surgery for cancer and spent his last years paralysed in a nursing home. During the many visits I made to the nursing home, I never failed to come away with a deep appreciation for the health I still possess in my old age. It was not uncommon for me to go to the nursing home to visit my friend and hear that one of the new patients in the home was someone whom my friend and I knew from our earlier days. Too often, they had Alzheimer’s and were housed in a special section of the facility.

The enjoyment of life, especially the second half of life, is greatly compromised if we can’t see, if we can’t think, if our kidneys don’t work or if our bones are broken or fragile. I, for one, hope that I am able to fully enjoy not only the time in the present, but also the time in the future, with good health and independence.”

Campbell, T. Colin; Thomas M. Campbell II (2006-06-01). The China Study: The Most Comprehensive Study of Nutrition Ever Conducted And the Startling Implications for Diet, (p. 217 – 222)

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