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Dr. Thomas Johnson discusses Harvard Medical School's A Guide to Cognitive Fitness, especially their recommendation to follow a plant-based diet.

A Guide to Cognitive Fitness
From Dr. Thomas Johnson, NCSP, CPQ
March 2025

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A GUIDE TO COGNITIVE FITNESS
7 steps to optimizing brain function and improving brain health
Edited by Dr. Avaro Pascual-Leone
published by Harvard Medical School (2024)

This Harvard Guide refers to cognitive and fitness in the following way:

"The word 'cognitive' relates to thought processes, and 'fitness' means being able to do what you aspire to do, while feeling satisfied with it. But you may be surprised to learn just how many skills are included. Obviously, memory is a key component, but cognitive fitness also encompasses a variety of brain-based skills, such as reasoning, learning, problem solving, perceiving the world around you, processing what you see and hear, communicating, and making sound decisions. It includes the ability to focus attention, comprehend new information, use language effectively, interact with others, control impulses, weigh options and formulate and pursue plans" (p. 3).

This definition is basically in line with what psychologists mean when we are conducting cognitve psychological evaluations.

Over the last few decades, I have conducted and/or supervised over a thousand psychological evaluations of public and private school students.

My evaluations have generally included cognitive tests, personality tests as well as interviews with those referring the clients/patients .Those being evaluated have included elementary, middle and high school students. I have also evaluated hundreds of college and graduate school age students as well as individuals who have already completed their formal education. These individuals have been referred by family members, themselves, as well as by various types of helping professionals including lawyers, educators, nurse practitioners, and physicians.

Referral sources generally need diagnostic impressions and determination as to what might be interfering with the student/patient's learning and/or health. The results of the evaluation might help in determining the need for special education, eligibility for gifted and talented programs, eligibility for disability benefits, and/or specialized health care such as the need for substance abuse treatment. Regardless of the specific need for appropriate care, cognition will generally need to be included as part of the assessment.

“Researchers at Harvard Medical School have identified seven components for any effective brain health and cognitive fitness program. Though we refer to them as “steps,” they should all be done together rather than sequentially:

STEP 1: Eat a plant-based diet.
STEP 2: Exercise regularly.
STEP 3: Get enough sleep.
STEP 4: Challenge your brain.
STEP 5: Nurture social contacts.
STEP 6: Manage your stress.
STEP 7: Cultivate positivity and identify your purpose.

Together, these strategies can yield real results, leading to changes in both your brain's structure and function. But the key word is “together.” These factors are equal parts of a cohesive plan—they don't work in isolation. Simply eating more fiber or adding a morning walk to your routine isn't enough to forestall mental decline. Rather, diet exercise, sleep, mental stimulation, social interaction, stress management, and a sense of purpose work in concert to yield results.” (p.6).

My graduate studies began at Brown University as a Public Health Fellow in a Ph.D. program in social psychiatry and medical sociology.

My training in cognitive assessment began at Harvard University in an interdisciplinary master's degree program as part of my graduate education as a psychologist. That training continued in a doctor's degree program at the University of California at Berkeley. After completing my course work, I completed my post-doctoral internship at Duke University.

During my 5 years of graduate education, I don't recall any research being referenced regarding the importance of plant-based nutrition in enhancing cognitive functioning and health.

Partly because of having discovered the importance of eating a whole food plant-based or ethical vegetarianism diet in enhancing my own health, I started looking more intensely at the role of nutrition in enhancing cognitive functioning and health. I also discovered the dark sides of eating a diet reflected in the SAD or Standard American Diet which tends to emphasize animal flesh, eggs, dairy and limited plant foods . Most of the people I evaluated were unfamiliar with the role of food and beverages in their learning and health or were being misled into thinking that a “balanced” SAD diet was a healthy way of eating. Since I made these discoveries, I took advanced post-doctoral courses to become more knowledgeable as a practitioner and educator.

In addition to being a practitioner, I have been a part time professor and a health services therapist working with undergraduate students at Bates College. Courses that I have taught at Bates included general psychology, educational psychology and psychopathology.

My graduate school teaching has included working with master's and doctoral degree students at Rutgers, the University of Southern Maine and the University of New England. In one way or another cognitive fitness has been part of the curriculum. However, I have not had the comprehensive curriculum that is reflected in this Harvard publication. I have added a great deal of personal knowledge as I have studied the guide and hope that I am effective in my paper in informing readers of this review.

Partly, due to space limitations I will focus on chapter one of the publication which is STEP 1: Eat a Plant based diet. This subject is one that I have studied intensively and probably have the most to offer in my review.

When I received my copy of this guide, I was excited to read about the importance this Harvard group was placing on plant-based nutrition. What do they mean by plant-based nutrition?

The authors point out that food nourishes all your body including your brain. The range of foods chosen can have an enormous impact on heart health, cancer risks and mood level, mental sharpness, and risk of developing dementia. Selecting a brain healthy diet “makes a very appropriate first step in any program to boost brain health” (p.26).

The plant foods linked to better brain power include green, leafy vegetables such as kale, spinach and collards. These vegetables are rich in brain healthy nutrients like vitamin K, lutein, folate and beta carotene. They all have antioxidants that can help protect the brain. They can also slow down cognitive decline.

Berries are emphasized as they have both antioxidant and anti-inflammatory properties that prevent cell damage and improve memory. Blueberries and strawberries are singled out as being particularly healthy in improving brain as well as cardiovascular health.

Nuts and particularly walnuts are at the top of the list and are excellent sources of protein and healthy fats. Walnuts are high in omega-3 fatty acid called alpha-linolenic acid (ALA), and this helps improve brain and heart health. Walnuts have also been proven to improve memory and mental performance.

Tea and coffee in the right amount have been demonstrated to improve both short- term and long-term memory and may improve processing speed but not attention.

Beans are discussed and emphasized as great sources of protein, dietary fiber, B vitamins and various minerals. They contribute to heart and brain health. There are references to the “Blue Zones” which have historically included beans as mainstays in their diets and have been referred to as making significant contributions to health and longevity to those people using them as mainstays in their diets. The interested reader can read my previous article posted on the All-Creatures.org web site (There is only one "Blue Zone" left -July 2024- issue).

Whole grains provide numerous health benefits for the brain, heart and other parts of the body particularly digestive health because they are high in fiber and promote regular bowel movements.

According to the Guide foods that can harm the brain include red meat, butter, cream and whole milk. They are all high in saturated fat, which raise blood levels of unhealthy LDL cholesterol. When cholesterol builds up in the arteries it can set up a chain of events which can lead to a stroke and increase the risk of dementia including Alzheimer's.

Added sugars as found in soft drinks, cookies, cakes and pies should be eaten sparingly. Sugar has been linked to diabetes and obesity. Therefore, it is recommended that they be avoided or minimized when trying to maintain a healthy brain and heart healthy diet.

There are short sections of the Guide discussing the dark sides of alcohol and tobacco. For example, alcohol can blur your judgement, slur your reaction time. The ethyl alcohol in beer, wine, and liquor is a central nervous system depressant that interferes with thought, memory, and motor control over the long term, heavy drinking (more than two drinks a day for months) can lead to nutritional deficiencies which your brain needs to survive.” (p.19).

Smoking is another cause of trouble. It damages the heart and blood vessels, limiting essential blood flow to the brain and increasing your risk for stroke and vascular dementia. It also damages the lungs, thereby reducing the oxygen supply to the brain.” (p.19).

Fish are a more controversial type of food to consider when seeking a heart and brain healthy diet. The Guide is cautious in promoting fish as a brain fitness enhancing food due to the presence of mercury in a high percentage of fish. For people who do not have ethical reasons for avoiding fish they suggest varieties that are thought of as having lower amounts of brain damaging mercury such as cod and salmon. For those of us who have ethical reasons for not eating fish (i.e. some of the ethical reasons for refraining from eating fish and other creatures are discussed in detail in my article a Review of “Eating Our Way to Extinction” published the June 2023 edition of All-Creatures.org) they recommend flaxseeds, avocados and walnuts—all of which are high in omega-3.

Other authoritative scientific sources that they recommend against eating fish like the Physicians for Responsible Medicine (PCRM) refer to research that point to the unhealthy side of eating fish or fish oil in addition to the ethical reasons for not eating any kind of flesh.

If the reader goes to the pcrm.org web site, the reader will find a FACT SHEET entitled Health Concerns About Fish. PCRM scientists argue that healthy fish is a myth. After reviewing the recent research findings, they conclude their summary in this way on page 2 of the fact sheet:

“Given the clear evidence that fish are commonly contaminated with toxins that have well-known and irreversible damaging effects on children and adults, the consumption of fish should not be encouraged. The risks are significant, especially for infants and women of childbearing age. It's important to consider the amount of saturated fat and cholesterol found in fish, compounds which are linked to heart disease, diabetes,and other chronic conditions. By focusing on plant foods like vegetables, fruits, whole grains, beans, peas, nuts, and seeds,one can get the full range of essential nutrients without the toxins and other health risks associated with fish consumption. High levels of fat, and cholesterol along with a lack of fiber make fish a poor dietary choice.”(p.2).

When following up with patients/students with recommendations to them and their referral sources I provide a PCRM publication entitled Good Nutrition: The Power of a Plant-Based Diet. The publication discusses the health benefits of fruits, legumes, whole grains and vegetables. They elaborate on the following benefits:

• Reduced risk for heart disease and stroke
• Lower blood pressure and cholesterol levels
• Better blood pressure control
• Healthy weight maintenance
• Lower cancer risk

One question that frequently comes up is What about cow's milk and other forms of dairy?

The response in the publication states: “By eating a varied plant-based diet, you'll get all the calcium you need to build strong bones without the added risks of milk and other dairy products. Leafy green vegetables, beans, fortified juices, and plant milks are all great sources of calcium.”(p.5).

One of the testimonials quoted in the PCRM publication that I found particularly meaningful was by Dr. Kim Williams. He stated :“I became a vegan in 2003 because I was concerned that my LDL 'bad' cholesterol was too high. As a cardiologist and former president of the American College of Cardiology, I let my patients know that plant-based diets lead to better outcomes, reduce health risks, and have a much more favorable effect on obesity, compared with the standard American diet. They say knowledge is power. In this case being aware of risk factors helps motivate people to make a difference.”(p.6).

Another scientific group that has taken positions like PCRM is forksoverknives.com. There are many scientific articles referenced as well as the book The China Study by T. Colin Campbell, Ph.D. and the second author is his son Thomas Campbell, MD. Their study was reviewed by the New York Times and referred to as “the most comprehensive study of nutrition ever conducted.” Their positions are referred to as whole-foods plant-based nutrition. There is no place for fish, animal flesh, eggs or dairy in their recommendations. All their recommendations are evidenced based.

The senior author Dr. T. Colin Campbell is recognized internationally as an outstanding nutritional scientist and is now a Professor Emeritus at Cornell the second author is Dr. Thomas Campbell. He is a board-certified family physician and a certified diplomate of the American Board of Obesity Medicine. He is the founder and co-director of the University of Rochester School of Medicine/Highland Hospital Nutrition in Medicine Research Center, where he conducts trials to study the effects of comprehensive dietary change, with a focus on plant-based nutrition, and on outcomes related to various diseases. Dr. Campbell has extensive experience working with individuals and groups to prevent and treat chronic conditions using diet and lifestyle.

In conclusion and summary, A Guide to Cognitive Fitness edited by Dr. Avaro Pascual-Leone (Professor of Neurology) and published by the Harvard Medical School (2024) is a comprehensive review of 7 steps to optimizing brain function and in improving health. This analysis was looked at through the eyes of a practicing health psychologist with many years of experience conducting and/or supervising over a thousand cognitive psychological assessments with children and adults ages 5 through 80.

I have focused on the first step which is plant-based nutrition. The editor's example of plant-based nutrition was not limited to plant foods as he included some animal-based food in the guide. While the overall guide is impressive and a good introduction to the topic, I found it important to supplement the discussion with 2 scientific alternative models which exclude fish and other so called meat products. I highly recommend this guide to psychologists and other health care practitioners and educators as well as others who want to improve their cognitive health and fitness.

Biographical Notes

Thomas Johnson completed his graduate studies as a US Public Fellow at Brown University in social psychiatry and medical sociology. He earned his master's degree from Harvard University in counseling psychology and doctor's degree in counseling psychology from the University of California at Berkeley. He completed his internship at Duke University. In addition to his work as a practitioner he has had faculty positions at Rutgers University, the University of Southern Maine and Bates College. He is the founder and first president of the Maine Division of the American Association of Marriage and Family Therapy. Dr. Johnson is currently limiting his practice to research and consulting psychology.

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Posted on All-Creatures: March 6, 2025
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