The Water of Life

3: The Water of Life, Brain Food


When I first became interested in neuro-nutrition, I realized that there was a lot of confusion over which foods and nutrients were good for the brain and which were harmful. Depending on the day and whom you listened to, you would hear that eggs are good for you one day and bad the next, that sodium is responsible for high blood pressure . . . until it’s not, while carbs and fats take turns playing hero and villain.

Personally, I find that much confusion is due to the fact that few health-care professionals know how the brain actually works, and fewer yet have the advantage of having studied brain chemistry.

What most people don’t realize is that the nutritional requirements of the brain are substantially different from those of the other organs of the body. As we have begun to see in the previous chapter, the human brain is a very peculiar organ, working in accordance with its own rules and preferences. We are now going to see how the brain is highly unique also in terms of its diet. As hungry as it might be, the brain is at the same time a very picky eater. In comparison with the rest of the body, which figured out a way to process most nutrients to its advantage, our brains are very strict and highly selective when it comes to food.

If we were to compare the human body to the world’s food trading system, we could say that the brain asserts austere international trade regulations in comparison to other organs. In the real world, if a country can provide enough food on its own, it can limit the importing of those foods from elsewhere. When you eat fresh blueberries with your oatmeal on a winter day, it’s because those blueberries were imported from South America. But if you are adding milk to that same oatmeal, it most likely comes from a U.S. farm.

The brain is just as conservative when it comes to importing food. Whatever the brain can make locally is made locally. Yes, you read correctly. The brain has the capacity to supply its own nutrition. Not all of it, mind you, but some of it. Everything else must be obtained from the food we eat.

“Everything else” means all the nutrients that the brain needs but cannot make itself (or make enough of to meet its needs)—which I’ll refer to as brain-essential nutrients. How do we know which nutrients are brain-essential and which aren’t? For starters, brain-essential nutrients have the distinct honor of being among the few substances that are able to cross the blood-brain barrier so that they can successfully arrive at our brains in the first place. This is when studying brain chemistry comes in particularly handy.

The human brain requires more than forty-five nutrients to be at its best, and the ways these nutrients are used are as different as the molecules, cells, and tissues they help to create. Nutrients are usually divided into five major groups, representing the basic components of our food: proteins, carbohydrates, fats, vitamins, and minerals.

Now for a very distinctive difference between our bodies and brains.

On average, our bodies are made of a fair amount of water (60 percent), followed in prevalence by proteins (20 percent), fats (15 percent), carbohydrates (2 percent), and some vitamins and minerals. These proportions shift in the brain, since water content is even more prevalent there than in the rest of the body. In fact, the brain is made of almost 80 percent water. That’s quite a lot of water for such an active organ. Fats (i.e., lipids) come in second (approximately 11 percent), followed by proteins (8 percent), vitamins and minerals (3 percent), and a pinch of carbs.

We’ll discover even more differences between body and brain as we start to look into each of these nutrients in more detail. In the meantime, let’s let the brain lead the way as we begin our exploration of neuro-nutrition, starting with the most prevalent brain nutrient of all.


If you don’t think of water as being nutritious, think again. Many scientists believe that life on Earth itself was made possible by the presence of water on the planet, and that the very first living creatures were born in the depths of the oceans of 4 billion years ago.

Water is undeniably vital to human life and, as it turns out, also to our intelligence. Besides constituting most of its weight, water is involved in every chemical reaction occurring in the brain. In fact, brain cells require a delicate balance of water and other elements such as minerals and salts to work efficiently at all. These electrolytes (minerals and salts that help you stay hydrated, such as chloride, fluoride, magnesium, potassium, and sodium) flow in and out of your brain with every sip of water you drink. Further, water is indispensable for energy production—that’s because it carries oxygen, which is needed for your working cells to breathe and burn sugar to produce energy. Water also plays a structural role, filling in the spaces between brain cells, and also helps to form proteins, absorb nutrients, and eliminate waste products.

As further proof of its importance, we can last weeks without food but only days without water. The body can’t store water, so we need a fresh supply every day to make up for the loss that occurs from the functioning of our lungs, skin, urine, and stools. When water supply is too low, we become dehydrated. Dehydration occurs when we use or lose more water than we take in, and the body doesn’t have enough fluids to carry out its normal functions. This could be surprisingly dangerous, especially to our delicate brains. Dehydration disrupts energy processes and causes loss of electrolytes, a loss to which the brain is particularly sensitive. It has been estimated that as little as a 3 to 4 percent decrease in water intake will almost immediately affect the brain’s fluid balance, causing a number of issues like fatigue, brain fog, reduced energy, headaches, and mood swings, for starters. If 3 to 4 percent sounds like a small degree of water loss, that’s because it is. You could easily reach that level of dehydration just by going about an average day that included moderate exercise and neglecting to drink water throughout.

What’s worse, most people don’t drink nearly enough water to start with. According to a recent study by the Centers for Disease Control and Prevention, 43 percent of adult Americans report drinking less than 4 cups of water a day, including 36 percent who drink 1 to 3 cups, and 7 percent who drink none.

This is particularly disconcerting, as dehydration was shown to accelerate the brain shrinkage that occurs with aging and dementia. MRI studies show that when we are dehydrated, several parts of the brain appear to get thinner and lose volume. Clearly this is a much more pressing issue than many might have thought. The good news is that the effects of dehydration can be fully reversed in a matter of days by simply drinking more water.

There is some debate over how much water we really need to drink. On average, the recommended amount is eight 8-ounce glasses a day. If you need more of an incentive, this number is backed by research showing that drinking 8 to 10 cups per day can boost your brain’s performance by almost 30 percent. Researchers in the U.K. ran an experiment to test the potential effects of water on cognitive performance and mood. They had several participants complete a series of mental tests after eating a cereal bar. Some participants consumed just the cereal bar alone. The rest were also given water to drink. Those who drank around 3 cups of water just before completing the tests showed significantly faster reaction times compared with those who did not drink any water.

Think about the advantages of thinking faster. Drinking a glass of water first thing in the morning can increase your ability to shower, have breakfast, get dressed, and be out the door right on time to catch the subway. Conversely, your ability to calculate how much time this all takes is compromised when your fluids are low, and you end up hitting the snooze button for another half hour (and missing the train).

Overall, the prescription is not difficult to follow: make a point of drinking eight 8-ounce glasses of water a day, or close to 2 liters (2 quarts). Then adjust the amount based on your own particular needs. Depending upon your age, environment, and activity level, you might need more. If you live in a warm climate, you’ll need to drink more water than someone who lives in Alaska. If you are a professional athlete, you’ll need to drink more water (and electrolytes) than someone sedentary. Plus, we all need more water as we get older. For reasons yet unclear, aging alters thirst and drinking responses, making older people more vulnerable to fluid imbalance in their brains, which might very well contribute to cognitive decline and neurological disorders like Alzheimer’s.

As a neuro-nutritionist and brain health advocate, I’m convinced of the value of drinking enough water. Of all the tricks I’ve learned for keeping my mind sharp, staying hydrated might be the one I follow most religiously, starting with a glass of water first thing in the morning (which is essential after a night without any fluid intake) and ending the day with a cup of herbal tea.


When doctors prescribe water as a key part of one’s health regime, what precisely do they mean? Are they talking about tap water or filtered water? Does seltzer count? And herbal tea—isn’t that practically water? Don’t we get some benefits from the water content in juices or caffeinated beverages, too? There are, after all, many people who drink very little water and manage to survive. Let’s look a little more closely at what’s what.

Sure enough, according to the U.S. Department of Agriculture (USDA), carbonated soft drinks are the most-consumed beverages in the United States, along with purified bottled water and beer. Milk, coffee, fruit juice, and sports beverages come in a close second, as well as iced tea. Wine and distilled spirits are also present on the list but in smaller amounts per capita. Is this enough “water”?

From a purely scientific perspective, anything that increases water content in the body counts as a fluid. That said, there is quite a marked difference between drinking a glass of spring water and having a cup of coffee. While the extent of this reaction varies with each person, many of us are sensitive to the caffeine contained in our coffee. When you are consuming water in coffee or black tea, the caffeine is actively dehydrating you as you drink it, rendering its water content decidedly less than effective. Soft drinks, on the other hand, contain water but not nearly as much as they contain refined sugar. Even milk could be tricky. In its purest form, milk contains water as well as several important nutrients. However, in many industrialized countries, milk is one of the most highly processed products on the market, and widely overchugged at that.

The bottom line is, replacing water with beverages that contain unwanted fat, hard-core sugars, artificial sweeteners, preservatives, and coloring, and that at the same time promote dehydration and weight gain, clearly defeats our purpose.

The longevity and well-being of both your brain and your body are critically dependent upon your consumption of what we call hard water. This refers to plain water that is high in minerals like calcium and magnesium.

Hard water isn’t hard to find. Being a fan of all things natural, my preference is to drink spring water. Whether from an unpolluted underground spring in France or from an artesian well in Fiji, spring water comes from rain and snow. After being collected in natural basins, it is slowly filtered through layers of rock, where it picks up all sorts of valuable minerals, salts, and sulfur compounds.

Sparkling water that comes from a natural spring also contains various healthful minerals. In this case, the carbonation isn’t added by the bottler but from the spring itself. That means that the bubbles in these bottles are completely natural. The only downside is that it can be quite expensive.

Seltzer and club soda, instead, are just plain waters that have been artificially carbonated. Seltzer contains no sodium salts (and therefore won’t help you stay hydrated), while club soda usually contains mineral-like ingredients that are added by the bottler to enhance the flavor of the water. As we’ll discuss in more depth in the next chapters, lab-produced nutrients aren’t nearly as effective as natural nutrients at improving health, metabolism, or resilience against disease. My personal recommendation is to stick to natural hard water as much as you can.

This reminds me of my first trip to the supermarket in New York City, soon after my arrival in the United States. Having found the tap water lacking, I went in search of bottled water. But that was easier said than done. First, to my surprise, I was directed to the refrigerated aisles. As I later learned, bottled water can be found on the shelves as well as refrigerated, but most Americans prefer to drink their water cold—even better, with a few ice cubes thrown in. It never occurred to me to look for bottled water in a fridge. Most Italians drink their water at room temperature as it’s easier on the stomach, so our bottled water is rarely sold cold. To this day, I abide by that principle. Finally, once I located the fridge, I was so overwhelmed by such a plethora of seltzers, sodas, and sports and energy drinks, along with all the juices, flavored milks, and smoothies, that the water options paled in comparison. The final blow was that once I located the water selection, most bottles sported a “purified” label that baffled me.

As it turns out, purified water is currently the most consumed water in the United States. Unfortunately, although the word purified usually implies a good thing, in this case it refers to water that has been stripped of its chemical content—thus wiping out all its precious minerals in the process. Although purified water might be safer to drink than tap water, it has been rendered nutritionally void. As a result, it is entirely incapable of hydrating you or your thirsty brain. If you drink purified water because you’re concerned about impurities, you should take mineral supplements along with it.

Even better, consider filtering the water yourself. Personally, since nutrient-rich bottled water can be expensive, I invested in a high-quality faucet filter to filter tap water at home. Tap water is needed for other things besides drinking and cooking, such as washing and cleaning, so it’s important to ensure that it is as clean as possible. The goal is for your filter to get rid of harmful chemicals like asbestos, chlorine, lead, benzene, and trichloroethylene—all of which can be found in tap water. Filters can take out what’s harmful in your water while leaving its good mineral content intact. There are many available filtration options, so if you are interested in learning more about them, speak to a specialist. I can attest to the fact that installing a water filter is easier and more affordable than you might think, and it is a great first step in making sure that you and your family have easy access to plenty of drinkable, nutritious water on a daily basis.

Contrary to what many people believe, hard water is also better than sports and energy drinks for rehydrating after a workout. The vast majority of these beverages are high in sugar and sodium, in addition to being chockful of manufactured minerals and salts, and therefore are not good for you. If you feel that water alone is not enough, my recommendation is to try coconut water. Coconut water is Nature’s thirst quencher, being low in sugar while still providing you with the potassium you’re looking for. Most coconut water contains up to 300 mg of potassium and as little as 5 mg of natural sugar per glass, unlike your favorite sports drink that contains only half the potassium you need and five times the amount of processed sugar you don’t want. Be sure to go for unsweetened, organic coconut water to replenish the fluids your body loses during a workout or even just during the course of the day.

In addition to drinking plenty of water (and coconut water when I need it), I rely on a favorite trick: aloe vera juice. Aloe juice is Nature’s own first aid—naturally anti-bacterial, anti-viral, and anti-fungal, this healthful juice contains about 99 percent water and over two hundred active components from vitamins and minerals to amino acids, enzymes, and even fatty acids. Thanks to its well-established properties, drinking aloe juice is a great way to soothe and hydrate all your organs, reduce inflammation, and get the brain ready to spring into action, from the inside out.

Also keep in mind that drinking is not the only way to maintain water balance. According to the recommendations of the Institute of Medicine of the National Academies (the advisors to the nation on food and health), we could actually eat, rather than drink, up to 20 percent of our daily water intake. This means that one to two glasses of our daily fluids can be obtained from water-rich foods rather than water itself. To do so, focus on fruits and vegetables. These fluid-filled foods will support your staying hydrated while also providing healthful nutrients, not to mention natural sugars that the body can actually use to its advantage. Take a look at Table 1 for a list of fruits and veggies boasting the highest water content. Among vegetables, cucumbers and lettuce top the list with a whopping 96 percent. Next are zucchini, radishes, and celery, followed by tomatoes, eggplant, and cruciferous vegetables like broccoli, peppers, and spinach. Perhaps it comes as no surprise that watermelon has the highest water content of all fruit (93 percent water per volume), followed by strawberries, grapefruit, and cantaloupe. By comparison, a banana provides a relatively low 74 percent.

In conclusion, simply drinking more water and eating water-rich foods could be one of the healthiest changes you make to bring about better health as well as greater cognitive power in your life.

FruitsWater contentVegetablesWater content
Strawberries 92%Lettuce96%
Peaches 88%Celery95%

Table 1. Top five fruits and vegetables with high water content