We’ve all become accustomed to warnings about the role of diet and exercise in maintaining health. News stories about the dangers of being overweight, the foods we should or shouldn’t be eating, and how our lifestyle impacts our cardiovascular health are everywhere. But for many of us, these messages have simply become background noise. In our rush to keep up with our jobs, homes, families, and the incessant demands of our technological world, we typically think of diet in terms of immediate comfort, energy, or appearance. We rely on fast food when we don’t have time to shop or cook and hope that supplements will compensate for the nutritional shortfalls. We know that the buildup of the wrong sort of cholesterol (low-density lipoproteins) can clog our arteries and contribute to our heart disease risk, and that sugar and carbohydrates can contribute to diabetes. But all of this generic information does little to help us think about diet and health if we ignore the role the brain plays in these relationships.
The brain, which weighs on average 2-3 pounds, uses 15-20 percent of the body’s blood supply. Its 86 billion neurons, along with an equal number of support cells, rely on blood flow to deliver oxygen, nutrients, and sugar to fuel their activities. When the arteries in our body become clogged with cholesterol, lipids, and debris, the heart may not get enough blood to keep pumping, resulting in a heart attack. But when the arteries to the brain get blocked through the same process, we have a stroke. Depending on where the blockage occurs and how much damage it causes in the brain, strokes can damage our ability to think, feel, sense, and move. Some research suggests that chronically reduced blood flow to the brain can lead to cell death and may contribute to dementia as well.
Glucose
Neurons are also reliant on fuel in the form of glucose. Because the brain is very active, it uses about 25 percent of our total energy on a daily basis. The brain is so important that when food is in short supply, the rest of the body forgoes glucose in favor of the brain. This occurs because the cells of the body need access to insulin to use glucose, while the cells in the brain do not. If our glucose levels are low, the body reduces insulin release. This blocks cellular use of the available fuel, making it available to the brain. Diseases such as diabetes are the result of dysregulation in this system. In type 1 diabetes, the pancreas doesn’t make insulin, so the cells in the body can’t use glucose, even if it is available. In type 2 diabetes, people still produce insulin, but their body doesn’t respond to it effectively. In both cases, organs throughout the body become damaged or die, and the cells of the brain can be damaged as well.
Nutrition
When people do not have access to food, the cells in both their body and their brain suffer. This is particularly problematic in children. If they do not receive enough of the key nutrients they need to grow, they may not reach their full physical or mental capacity. At a less dramatic level, the lack of adequate nutrition can impact the activity of neurotransmitters, disrupting brain function. Leafy green vegetables (e.g., kale, spinach, and broccoli) containing nutrients such as vitamin K, folate, and beta-carotene appear to slow cognitive decline at a cellular level. Omega-3 fatty acids found in fish, avocado, and nuts may be protective against Alzheimer’s disease by lowering levels of a protein called B-amyloid, thought to contribute to the brain damage. Berries contain natural pigments called flavonoids that improve memory. Caffeine may help us form or solidify new memories. Clearly, keeping our brains supplied with the right types of food is a crucial aspect of well-being. While appearance is a visible indication of the state of our body, our brain can only maintain our health if we meet its nutritional needs.
Exercise
Exercise is equally crucial for brain health. Cardio exercise makes our body stronger. But it also ensures that our brain receives adequate blood flow. This is crucial because neurons require oxygen to generate energy. Reduced brain oxygen is associated with neuronal damage and cognitive decline. Exercise also triggers mechanisms that reduce inflammation and improve vascular health. Aerobic exercise facilitates the growth of neurons and blood vessels. Such brain growth may be a factor in helping us compensate for age- or disease-related changes in the brain. These cognitive reserves function in much the same way a well-developed network of surface streets might. If you have only one way to get to work, and there is an accident, you are stuck. If you have multiple available routes, you might be able to take a longer or slower path but still arrive at your destination. In the brain case, this could mean recovering a memory, coming up with a word, or solving a problem.
Philosophically, it is interesting to think about the intricacies of the human brain actively trying to understand its own function. Whether we will ever be fully successful is a debate for another time. But the fact that we can even try is amazing in itself. In the meantime, we need to think of our brains much like we think about our cars. We may not fully understand how they run, but we know they need fuel, oil, and coolants to function properly. Keeping glucose, oxygen, and water topped up is equally important for brain well-being.