The Big Five: How Food, Hydration, Sleep, Exercise, and Caffeine Affect Your Cognitive Function

Your body is one integrated whole, and it’s easy to see that when you take a look at the relationship between the body and the brain. Your brain, which extends into your entire body through the central nervous system, is affected by everything you do — the food you eat, how much water you drink, your caffeine intake, your sleep schedule, and your daily exercise routine. And by optimizing these factors, you can get your brain into the best shape of its life.

Read on to learn how you can optimize your cognitive performance through food, hydration, exercise, sleep, and even caffeine. Or use the table of contents below to skip ahead to the good part.

How Food Affects Your Brain

Like the rest of your organs, your brain is a self-repairing structure. An intricate organic maze of cells, it constantly grows and constantly rebuilds. In order to keep up with the demands of human life, it needs a steady supply of raw materials, and it gets these from the food you eat.

When it comes to the effect of food on your brain, two things are important:

  1. Getting enough vitamins and minerals.
  2. Getting those calories regularly.
  3. Getting the right amount of calories (not too much, not too little).

Slipping up on any of these three things can hurt your cognitive performance. Let’s dive into the details.

Vitamins and minerals: what happens without them?

Essential vitamins and minerals are called “essential” for a reason: without them, the body and brain fail to do essential tasks, and you develop serious diseases. However, certain vitamins and minerals have specific effects on how your brain functions.

For example, thiamine (B1), riboflavin (B2), and niacin (B3), and folates are said to improve abstract thought, and vitamin C improves performance in visuospatial tasks (think hand-eye coordination).

Over the long term, the content of your diet affects the health of your brain. There’s evidence to suggest that a diet rich in berries, nuts, fish oil, and curcumin can protect you from the natural decline in cognitive function that comes with aging. On the opposite end, diets high in refined sugars, saturated fats, or generally high in calories stress your body out and lower cognitive function.

As a general rule, it’s easy to miss a vitamin and mineral here and there. Take a multivitamin to fill in the gaps.

Calories at a regular rate: the ill effects of skipping lunch

If you’ve ever skipped lunch, you understand that going several hours without food affects your ability to do what you need to do. You can’t focus, you can’t think, you can’t plan, and you can’t make decisions. That’s the bad news — the good news is you’re not the only one. It’s normal for cognitive function to drop if you go too long without a meal.

For example, one study looked at how fasting during the day affected people observing Ramadan. During Ramadan, people typically have one meal before dawn and fast until sundown — which leaves a big caloric gap in the middle of the day. The study found two things:

  • Right after breakfast, subjects showed a significant increase in psychomotor function (i.e., brain to muscles) and visual processing.
  • Right before dinner — that is, following at least 8 hours of fasting — subjects showed a significant drop in performance in learning and memory tasks.

Another study looked at the effects of fasting on reaction times after two hard sprints. The results were similar: the subjects who fasted had significantly slower reaction times than the ones who didn’t.

Depriving your body of food not only makes you feel sluggish and lightheaded — which you already know — but also literally makes your brain slower.

Moderation in all things: getting the right amount of calories

One of our core principles at TB12 is moderation and balance, and this applies to the way your brain is affected by your caloric intake. While cutting out too many calories has serious effects on short-term memory, planning, and decision-making (as seen in patients with eating disorders), the brain actually does well with a slight reduction in caloric intake.

In fact, research shows that the best way to maintain cognitive performance through food is through moderate calorie restriction — eating until you’re about 75 percent full. This is what Tom Brady does, and evidence from scientific studies supports it. Long-term caloric restriction promises a host of benefits for your body (like weight loss and a lower risk of heart diseases), but it can also reduce feelings of depression and hunger without hurting your cognitive performance.

Bonus Brain Hack: You Don’t Even Have to Swallow Your Drink to Make Your Brain Happy

Carbohydrates affect your brain as soon as they enter your mouth. Any carbohydrate (solid or liquid) will work, but this trick would work best with a sports drink. Even if you don’t swallow, the carbohydrates send a signal from your mouth to your brain that instantly increases brain activity.

Scientists have observed a second spike in brain activity when carbs make it to your stomach. This spike occurs about 10 minutes after ingestion.

How Hydration Affects Your Brain

Your brain is 75 percent water, so when it doesn’t get enough, it really feels it. The most important effect of dehydration on your cognitive performance is the simplest one: it makes you feel awful. And if you feel bad, you’re not going to play at the top of your game. This effect of dehydration is well-documented — but it’s also easy to understand because we’ve all been there.

In addition to making you feel subjectively worse, dehydration has specific effects on your brain function. Dehydration has been found to impair hand-eye coordination, short-term memory, attention, alertness, and concentration — all of which you need to do what you love.

On the flip side, adding water back into your system has positive effects. For example, you can boost your brain activity instantly by drinking a glass of water, even if you’re not thirsty. Not only will drinking water help you to avoid dehydration, but it also significantly improves your mood for about half an hour after you drink it. This, at least, is the finding of a study of the effect of hydration on young students

bonus: to rehydrate faster, have some carbohydrates with your water and electrolytes

Eating carbohydrates isn’t just a way to help your muscles restore glycogen; it’s also a way to tell your body to absorb water and electrolytes. In other words, your body will benefit more from the hydrating power of your water and TB12 Electrolytes if you couple it with a TB12 Snack. More hydration means even more cognitive benefits of adequate hydration.


How Sleep Affects Your Brain

The strongest conclusions that scientists can make about sleep and the brain come from studies of sleep deprivation, which evaluate test subjects’ cognitive performance (on a variety of tasks) after the subjects have been kept awake for a certain amount of time. These studies have found that sleep deprivation affects your brain in serious ways.

Sleep deprivation makes you slower and sadder — and the worst part is you probably won’t remember why

Sleep deprivation has several effects. First, it makes it harder for you to learn new skills. Specifically, it throws a wrench into the hippocampus, the part of the brain responsible for short-term, long-term, and spatial memory (your memory of where things are and how to get to them). For this reason, long term sleep deprivation can actually lead to psychological disorders and permanent cognitive problems.

In addition to this, sleep deprivation decreases alertness, increases reaction time, impairs decision making, lowers mood, and causes confusion. All of these effects make sleep deprivation one of an athlete’s worst enemies.

Improve your sleep by respecting your circadian rhythm

The most important thing you can do to improve your sleep is to respect your circadian rhythm, which we discuss at length in The Circadian Rhythm: What Is It And Why Is It Important. For the most part, this means sticking to a consistent daily routine. Follow these tips to optimize your rhythm, performance, and overall health.

  1. Stick to one time zone. Wake up and go to bed at the same time every day, including weekends.
  2. Maximize blue light in the morning and limit blue light in the evening. Blue light resets your body’s master clock to think it’s daytime, and even a little blue light at the wrong time of day can throw off your body’s internal rhythm.
  3. Keep all your meals in a 10-hour window during the day. This is called Time-Restricted Eating, and it has been shown to improve sleep quality.
  4. Within that window, eat your meals at the same time each day. Your gut clock, which runs on an independent schedule, expects food roughly at the same times every day.
  5. Respect a 3-hour buffer zone between dinner and bedtime to give your digestive organs time to realize their last meal is done and go into “sleep mode.”

How Exercise Affects Your Brain

Exercise has immediate, short-term, and long-term benefits for your brain. In the short term, exercise can boost your mood and reduce stress, anxiety, and depression. In terms of cognitive function, exercise increases decision speed (without impairing judgment) and boosts focus — both of which are important in sports and in life.

Over the long term, regular exercise has actually been shown to increase the size of the hippocampus, which is responsible for spatial memory. As we age, the hippocampus typically shrinks, and research has shown that this natural decline can actually be reversed if you stay on your feet. Exercise protects against age-related decline in other parts of the brain as well, which means it’s an essential part of pursuing your life passions long term.


How Caffeine Affects Your Brain

Besides food, hydration, sleep, and exercise, you might be wondering about your morning coffee. Caffeine has been shown to improve numerous body functions like airflow in the lungs, blood flow, muscle stimulation, and metabolism, but it also has direct effects on your brain.

Generally speaking, caffeine electrifies your central nervous system by telling your body to produce more serotonin. This hits the fast-forward button on all your cellular activity, and on the macroscopic scale, this makes most people feel less tired, happier, more alert, and more energetic. For athletes in particular, caffeine has been shown to

  • Improve concentration and vigilance
  • Reduce the time it takes to make decisions
  • Lower feelings of fatigue
  • Increase MVC (maximum voluntary contraction or “max strength”)
  • Increase muscular endurance

The benefits vary from person to person, but research suggests the optimal amount is somewhere between 38 to 400 mg per day — 1 to 8 cups of tea or 0.5 to 4 cups of coffee.

Caffeine is often called a diuretic, but there are surprisingly few studies that support this claim. Studies of caffeine intake among cyclists, for example, found no significant increase in urine output between placebo and caffeinated groups. In fact, evidence suggests that if you’re a regular coffee drinker, your body becomes used to the caffeine and adjusts the way it releases fluids to keep you hydrated.

Where you need to be careful, it seems, is when you haven’t had coffee (or caffeine) in a while and then go back to it. For the first 48 hours, you may urinate more, and in that case it will be important for you to take in more water and electrolytes before, during, and after your training.

General Summary: Keep Your Brain Fit with the Big Five

You can use food, water, sleep, exercise, and caffeine to keep your mind sharp day-to-day and protect yourself against the natural cognitive declines that come with aging. Here’s a summary of everything we said above.

  • Eat a lot of fruits, vegetables, whole grains, and legumes, and fill in all the gaps with a multivitamin. This ensures your brain has everything it needs to build and rebuild. 
  • Keep your brain sharp by eating regularly; during the day, don’t go more than 4 hours without a meal or a snack. You’ll start to feel it.
  • Drink half your body weight in ounces of water during the day to stay optimally hydrated.
  • If you’re feeling down, boost your mood with a glass of water.
  • Protect your hippocampus by respecting your circadian rhythm, sticking to a regular sleep schedule, and avoiding late night food.
  • Grow your hippocampus by engaging in regular exercise.
  • If you drink coffee, keep your intake between 38 and 400 mg, depending on your personal tolerance. 
  • If you go back to drinking coffee after not having had it for a while, be sure to take in extra fluids and electrolytes for the first 48 hours after you drink it. (This also goes for other sources of caffeine.)
  • Increase your decision speed and focus by sprinting to your next meeting. 

Ultimately, your brain has a big impact on how you recover. With increased focus, concentration, learning ability, and decision making, you get to be more deliberate about how you live your life. You lean less on your instinct and habit — which might lead to poor choices and a protracted recovery — and more on your knowledge of what’s right for you. By recharging your brain, you take charge of your life.

This blog is part of a series based on Tom Brady’s New York Times Bestseller The TB12 Method. To learn more about the ways you can train your brain and your body, read The TB12 Method and subscribe to the TB12 Newsletter.

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