Diet for the MIND

CHAPTER 1

Cognitive Decline and Dementia

As we age, our brains age, too. Our ability to think slows down, and we may experience occasional difficulty in, for example, recalling where we left our keys or retrieving a word or name. By all accounts, this is considered a normal degree of cognitive decline. It is a very different and more painful story, however, when you can no longer remember the way to get home or the names of your grandchildren. That is the experience of those who suffer from dementia, including Alzheimer’s disease. No wonder dementia and cognitive decline are among the most feared consequences of aging. Being able to reason, remember, and make decisions the way we always have connects us to the identity, personality traits, and relationships we spend our lives building. To live out our golden years with a healthy degree of brainpower is what we all hope for our future. I am happy to say that there is a great deal we can do to make this the reality for much of our lifetime.

Dementia is a widespread and growing public health problem. In 2015, Alzheimer’s disease, the leading type of dementia, affected more than five million adults in the United States and was the sixth leading cause of death. And while Alzheimer’s disease accounts for some 60 to 80 percent of all cases of dementia, many adults experience other forms of dementia, with symptoms including memory loss, difficulties with communication and language, trouble with focus and attention, and errors in visual perception, reasoning, and judgment. Fully one in three seniors dies with Alzheimer’s or another form of dementia. At this time, there is no cure for Alzheimer’s disease, and the treatments are largely ineffective. But take heart: the picture for prevention is not as bleak as we once thought.

At one time, Alzheimer’s disease was thought to be genetic, and the signs of dementia, like memory loss and confusion, were thought to be inevitable consequences of aging. However, over the last thirty to forty years, researchers have identified many factors that can cause or prevent the disease, most of which can be managed with effective treatments and/or through healthy lifestyle choices. This means that it is possible to delay the symptoms of dementia in later life by taking control of your health in your young and middle-aged adult years. And because many of these factors are known to be important for heart health, by adopting healthy lifestyle choices, you will be increasing your chances of maintaining not only a healthy brain but a healthy heart, too.

Rest assured that debilitating cognitive decline does not have to be your destiny. In fact, in this book you will learn many ways to keep your brain functioning at its best and your overall health vibrant as you age—and a lot of this has to do with what is on your plate. I am often asked whether young or middle-aged adults need to be concerned with changing their diet to prevent Alzheimer’s disease or to keep their brain healthy in old age, and the answer is a resounding yes! Key studies that followed young adult populations into old age observed that high levels of blood pressure, blood cholesterol, and obesity in middle age were associated with increased risk of developing Alzheimer’s disease and other dementias in old age. Healthy behaviors over a lifetime do matter, in terms of both optimum functioning in the moment and your health in the future. It is never too early or too late, and you are never too old to benefit from a healthy diet and lifestyle that preserve your mind and overall health.

In this chapter, I’ll describe the difference between normal cognitive aging and dementia, as well as the primary risk factors for dementia and why diet is important. I’ll discuss the role that supportive organs, like the heart, play in mind preservation and how oxidative stress and inflammation fit into the picture. Throughout, I have taken a strong scientific approach that encompasses the highest-quality data out there. My diet suggestions are based on a thorough review of the scientific literature from a broad spectrum of animal and human investigations—not just my own research. Each nutrient and food that I propose for brain health has the foundational backing of demonstrated biological mechanisms in the brain, metabolic system, or cardiovascular system and consistent results among high-quality epidemiological studies to support its relationship with health in human populations. In other words, every food and nutrient proposed is based on scientific evidence.

As a researcher, scientific evidence is obviously important to me, but it should also be important to you when creating a nutrition plan that supports your mind and body. If you’re being asked to tweak your diet, you deserve a substantial set of reasons why. Change is hard, and you shouldn’t have to cut back on cheese and meat just because I think it’s a good idea! Scientific evidence, on the other hand, is obtained through the systematic study of behavior and biological systems. This means that it is not a general impression formed by, say, a medical doctor through the evaluation and treatment of patients. It is also not the extrapolation of biochemical properties of cells in the petri dish to the hugely complex disease state in the human body. There are many ways in which these two theoretical approaches to disease causation are faulty and likely to result in theories that are completely off the mark. Unfortunately, they are the foundation of all too many books on diet and disease. What you will find here is advice based on my comprehensive review of the most rigorous scientific studies of nutrition and the brain. As an epidemiologist, my expertise is on the strengths and weaknesses of research study designs. This has allowed me to filter out the biased and unreliable studies and to focus on the strongest scientific evidence to identify the foods and nutrients that are important to brain health.

WHAT’S DIET GOT TO DO WITH IT?

Following a diet that is based on scientifically driven dietary recommendations is one of the most assured ways to keep your brain functioning at its best. You may have read that exercising, learning new tasks, and keeping socially active are helpful—and they sure are—but none of these activities would be possible without the right foods to fuel the brain.

The food you eat does more for your body than simply fill your stomach and satisfy your taste buds. At its most basic, you would die without food, because every organ of the body requires nutrients and other dietary components to function. Some of these dietary components are used to form basic cell structures. For example, dietary fats are incorporated into the membranes of neurons, or nerve cells, and the type of fat determines how well neurons transmit signals to other nerve cells in the brain or to your muscles and other organs. The omega-3 fatty acid DHA (docosahexaenoic acid), which comes from foods like fish and walnuts, is an important part of a brain-healthy diet. In fact, when DHA is part of the neuron’s surrounding membrane, it makes that neuron flexible and dynamic. This improves neurotransmission, which in turn impacts your ability to think more clearly and quickly. Also required are nutrients like folate, which builds DNA and new cells, and the powerful antioxidant vitamin E, which protects cells against oxidative injury. Other dietary components like carbohydrates and fats provide the fuels that are necessary for organs to function, including your brain.

The growing ranks of middle-aged and older adults in the population, along with commonly held fears of losing one’s memories and the ability to think, have increased the demand for dietary guidelines. I can speak directly to this demand because the link between Alzheimer’s disease, cognitive decline, and diet has been my major focus of research for the past twenty years. I am the principal investigator of the diet studies in two large population-based studies conducted at Rush University of risk factors for the development of Alzheimer’s disease, cognitive decline, and other common problems in older people. One of these studies, the Chicago Health and Aging Project (CHAP), began in 1993 and includes more than ten thousand residents age sixty-five and older living on the south side of Chicago. Participants of the study were evaluated every three years for health and lifestyle behaviors. Neurological evaluations for the diagnosis of Alzheimer’s disease and other dementias were also performed on a smaller number of randomly selected participants. The second study, the Memory and Aging Project (MAP), includes more than eighteen hundred residents living in retirement communities and senior public housing throughout the Chicago metropolitan area. Participants of the MAP study are evaluated annually for neurological conditions, cognitive abilities, and diet, among many other factors, and all participants have agreed to donate their brains when they die. These studies, funded by multiple grants from the National Institutes of Health and the Alzheimer’s Association, have generated numerous findings of dietary associations with neurodegenerative diseases like Alzheimer’s and have helped shape my understanding of how diet can affect the way the brain ages and potentially declines. The results of these studies were also instrumental in my team’s development of the MIND (Mediterranean-DASH Intervention for Neurodegenerative Delay) diet to prevent cognitive decline and Alzheimer’s disease. We are currently conducting a large randomized trial of the MIND diet that will be the definitive test of whether the diet is truly protective against cognitive decline and neurodegenerative changes to the brain.

To briefly sum up the findings of my Rush diet studies, we found that study participants had a lower risk of Alzheimer’s disease and slower rate of cognitive decline with:

We’ll explore these dietary factors in later chapters, along with recipes that incorporate the foods that best support them.

COGNITIVE AGING 101

Cognitive function—or more simply, your ability to think—is central to navigating everyday life. Reasoning, planning, remembering, using language to communicate, and processing information efficiently are a few ways that you do this. In fact, simply getting dressed in the morning involves many of these cognitive skills all at once. You use reasoning to realize it’s cold outside and you should put on wool pants instead of shorts; planning, to first take off your pajamas and underwear before putting on clean clothes; and memory, to remember where you keep your clean clothes. We are not even aware of how much our cognitive skills get us through the day—until, that is, we observe the breakdown of these skills in a person with dementia.

Most of us will experience some decline in thinking abilities as we age as part of the normal aging process. Even so, there is a lot of variability from one person to the next in the rate at which thinking abilities decline, just as there is a lot of variability in peak intelligence. By peak intelligence, I mean our most fully developed intelligence, which occurs at some point in young adulthood. A host of factors determine a person’s peak intelligence, including genetics, education, nutrition, and physical activity, to name just a few. Environmental and social factors also play a role—just as good nutrition and lots of exercise contribute to a better functioning brain, a person who grew up in an environment with books, games, and a lot of positive interactions with loving adults will benefit intellectually. And while aspects of these factors will also impact the rate at which your cognitive abilities decline during old age, the degree to which these early life factors affect cognitive decline is not currently known. What we do know is that a well-developed and healthy brain going into old age has a far greater capacity to ward off infections, oxidation, and other injuries that are a part of normal life. Biologically speaking, an optimally developed brain is likely to have more neurons and neural connections to carry on brain function when neurons die or cell systems fail, both of which are an inevitable consequence of aging.

In the large Chicago Health and Aging Project population study I mentioned earlier, we measured cognitive abilities of the same individuals every three years. One of the things we did was track how each person’s mental function changed over six years, across participants age sixty-five and older—years in which cognitive decline is most likely and apparent. What’s interesting is that many people did not exhibit decline over the six-year period, or even improved their scores on the cognitive tests, and the rates of decline for others ranged from a little to quite a bit. Studies that investigate cognitive decline are designed to identify the factors that are associated with either an increase or decrease in individual rates of decline. The best scientific evidence comes from studies that use multiple cognitive tests to measure a range of cognitive abilities and that use multiple time points of cognitive assessment. This type of study design makes it possible to tease apart individuals’ peak cognitive performance from the decline in that peak ability. When you consider how complex the brain is, and all the different types of thinking skills that go into everyday activities, you can appreciate that measuring all of this with accuracy is quite difficult but also essential.

The best studies, then, are those that use a number of tests to measure each cognitive skill, such as memory, attention, reasoning, and thinking speed. The use of multiple cognitive tests ensures that researchers have an accurate picture of a person’s thinking ability at that point in time. Now, to investigate changes in thinking abilities, we need to conduct these tests multiple times over a number of years. In the Rush Memory and Aging Project, nineteen cognitive tests are administered to the study participants every year, and many of the participants have been in the study for ten years or more. This kind of study provides precise information about cognitive decline. As you can imagine, this is also expensive and time-consuming; for that reason, there are few studies out there with this kind of extensive information on cognitive decline. In fact, many of the studies in the field of aging have used just one test to measure cognitive function, and have administered the test at just one or two points in time. It is difficult to interpret the findings from these kinds of studies, particularly those with just one test at one time point. And in these cases, it is not possible to separate a person’s peak intelligence during his or her younger adult years from declines due to aging or disease. That’s why long-term assessments are not only the best way for us to understand a disease process but also the most precise way for us to translate what we’ve learned into advice that will help you live your very best life. The advice that I give in this book is backed up by findings from these high-quality research studies conducted at Rush.

WHEN COGNITIVE DECLINE ISN’T DEMENTIA

Dementia is a general term for decline in mental abilities that is severe enough to interfere with daily life. There are a number of different types of dementia, but the primary ones are Alzheimer’s disease, vascular dementia, and Lewy body dementia. They are largely distinguished by the type of pathology found in the brain. Lewy body dementia, for instance, occurs when protein deposits, called Lewy bodies, accumulate in the neurons, which causes them to die. Lewy bodies are also found in patients with Parkinson’s disease, which is a progressive disorder of the nervous system that affects movement. There are also dementias associated with nutrient deficiencies, such as pellagra, a disease caused by niacin deficiency, and hypocobalaminemia, a neurologic syndrome caused by vitamin B₁₂ deficiency. Alzheimer’s disease is the most common type of dementia.

Many older people—some 15 to 20 percent—will experience a significant decline in their usual cognitive abilities, such as memory or reasoning, but not to the extent that it interferes with their ability to perform daily-life activities. This condition is known as mild cognitive impairment (MCI). Individuals who have MCI are still able to take care of their usual responsibilities. Even though they are at increased risk of developing dementia, many people with MCI never present with the disease.

A significant amount of age-related cognitive decline can’t be attributed to the brain pathologies that have been identified and associated with dementia. In fact, a number of treatable conditions can cause dementia-like symptoms. Some of the more common ones are depression, drug use and interactions, thyroid problems, alcohol abuse, and certain vitamin deficiencies. If you notice problems with your memory or thinking abilities, please see a doctor, preferably a neurologist, who can evaluate you for these conditions.

Thyroid issues and vitamin B₁₂ deficiency, for instance, are two of the more common alternative causes for dementia-like symptoms. Hypothyroidism, or low thyroid levels, affects one in eight adults—with women being more than five times as likely to have this condition than men, and about 60 percent go undiagnosed! Confusion and memory loss are among these symptoms, along with weight gain, low energy, fatigue, depression, and stiffness or aches in muscles and joints. Daily use of the synthetic thyroid hormone levothyroxine restores thyroid levels and reverses the symptoms. And then there’s vitamin B₁₂ deficiency. A small percentage of vitamin B₁₂ deficiency cases are due to a condition called pernicious anemia, caused by an inability to absorb vitamin B₁₂. However, many more middle-aged and older adults have insufficient levels of vitamin B₁₂ due to less efficient absorption, common with aging; low intake of vitamin B ₁₂–containing foods; excessive alcohol consumption; or use of antacids and other medications that lower the acidity of the stomach, which makes it harder to absorb vitamin B₁₂ from the diet. Vitamin B₁₂ is essential to the formation and maintenance of myelin, a fatty sheath that covers the axons of neurons and enhances electrical impulses in neurotransmission. This vitamin is obtained almost exclusively from animal products, such as meats, fish, eggs, cheese, and milk—so vegans, vegetarians, or others who consume a limited amount of animal products are at greater risk of insufficient nutrient intake of vitamin B₁₂.

Middle-aged and older adults who experience low levels of energy, shortness of breath, tingling in their fingers, confusion, or depression would do well to have their physicians check whether their levels of vitamin B₁₂ are low or low-normal. Depending on the reason for vitamin B₁₂ insufficiency, vitamin supplements or monthly injections may be the most effective way to restore the vitamin levels. Without treatment, vitamin B₁₂ deficiency syndrome can cause irreversible neurologic damage, including cognitive impairment. Vitamin B₁ (thiamin) and vitamin B₃ (niacin) also have deficiency syndromes that involve cognitive impairment, but deficiencies in these nutrients are rare in the United States, and the scientific evidence to link low-normal dietary intake of these vitamins to cognitive decline or dementia is limited.

A DETAILED LOOK AT ALZHEIMER’S DISEASE

Dementia that entails a decline in memory-related abilities is central to Alzheimer’s disease. And while memory loss is the defining clinical characteristic of Alzheimer’s, to be diagnosed with the disease, a second type of cognitive impairment must also be evident. Such deterioration could include problems paying attention, orienting to time or place, understanding the lines of a story or conversation, communicating an idea to others, understanding visual images and spatial relationships, or making the right decision when presented with alternative options.

The memory loss that is associated with Alzheimer’s disease is much more serious than the mild, occasional mental lapses that come with normal aging—for instance, temporarily forgetting the name of an acquaintance. Alzheimer’s disease typically begins in the part of the brain that controls learning, so one of the early symptoms is difficulty remembering newly learned information. In this scenario, the person might have trouble remembering appointments or upcoming events or need to rely more heavily on memory aids like reminder notes. Another early sign is asking for the same information repeatedly. An initial Alzheimer’s diagnosis commonly comes when a family member notices that a loved one asks the same questions over and over and also has problems with dressing or preparing a meal, or is suddenly mismanaging money. Think of the sixty-five-year-old man who can’t figure out how he’s related to his son and doesn’t know how to operate a can opener, or the fifty-year-old woman who can no longer manage her checkbook to pay bills and gets lost driving to the local grocery store.