PDF Summary:Keep Sharp, by Sanjay Gupta

When it comes to taking care of your brain, the best time to start is now. Many people don’t consider dementia or cognitive decline until later in life, but neurodegenerative diseases like Alzheimer’s begin developing decades before symptoms appear. Fortunately, you can take steps to prevent cognitive decline and keep your brain strong and resilient throughout your life. In Keep Sharp, neurosurgeon and medical reporter Sanjay Gupta explains how we can best look after our brains in five key areas: exercise, sleep, nutrition, discovery, and social connection.

In our guide, we’ll examine how the human brain works, the potential causes of cognitive decline, and things you can do to promote a healthy brain. We’ll also explain why certain things are helpful or harmful to your brain, like why the Mediterranean diet is so beneficial and what a lack of sleep does to your brain. Throughout the guide, we’ll delve into the ever-evolving science of human cognition so you can better understand how to develop a healthier, happier brain.

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1. Exercise controls blood sugar: When you exercise, the sugar in your blood is used to fuel the muscles in your body instead of staying in your bloodstream. This prevents consistently high blood sugar and keeps your insulin levels stable.

(Shortform note: Although exercise generally lowers blood sugar levels, it can also have the opposite effect. Some workouts, like heavy weightlifting, sprinting, and competitive sports, can increase hormones such as adrenaline, which raises glucose levels. Also, consuming too many carbs before a workout can lead to high blood sugar. To avoid this, experts recommend you choose moderately intense aerobic exercises or light weight training and that you avoid too many carbs before exercising.)

2. Exercise reduces stress: When you’re stressed, your body releases a hormone called cortisol, which has been linked to changes in the brain. People who experience chronic stress early in life are much more likely to suffer from mental problems and mood disorders later in life.

(Shortform note: How does exercise reduce stress? Research shows it’s through a release of hormones. Exercise, especially aerobic exercise, increases your body’s production of endorphins, or chemicals that naturally boost your mood and reduce pain. They are responsible for the “runner’s high” some feel after a long aerobic workout.)

Physical inactivity, on the other hand, sharply increases the risk of cognitive decline. Gupta points to a study that states that lack of exercise is the most significant risk factor in developing dementia. Prolonged sitting (sitting for eight or more hours a day) can be especially harmful. Not only does prolonged sitting increase blood sugar levels, but it also negatively affects blood fats, cholesterol, blood pressure, and leptin (the hormone that tells you when to stop eating). When your muscles are dormant for too long, they begin to break down and atrophy, and your body’s ability to break down calories is weakened.

(Shortform note: Gupta claims that prolonged sitting, even with regular exercise mixed in, can lead to an early death, but some studies refute this claim. A 2015 study of over 5,000 people found there were no associations between prolonged sitting and increased mortality rates. Another study examined the link between sitting and diabetes and came to a similar conclusion. The researchers from both studies recommend regular exercise, as no significant health effects were seen in participants who both exercised and sat for long periods of time.)

Exercise Tips

Knowing how important exercise is, how much do we need to do? Gupta says the good news is that it doesn’t take a lot to counteract the negative effects of inactivity. Aim for at least 30 minutes of exercise a day, five times a week. However, Gupta claims that if you want to get the most out of exercise, exercising more than an hour a day is now recommended. This is because, from an evolutionary perspective, humans have usually spent most of their day moving.

(Shortform note: Most health experts and doctors agree that you should exercise at least 30 minutes a day or 150 minutes a week. As Gupta points out, though, ideally you should get more than that. A 2011 study found that the optimal amount of moderate aerobic exercise is around 90 to 100 minutes a day, or around 700 minutes a week. Alternatively, 350 minutes of intense exercise (as opposed to moderate) will also suffice. This may seem like a lot, but to achieve this, researchers recommend two things: Start at a young age, and find what motivates you.)

To get the most out of exercise, also aim for a mix of three forms of exercise: aerobic, strength, and interval training.

• Aerobic exercise: Aerobic exercise, also known as cardio (like jogging, swimming, biking, or even brisk walking) involves getting your heart rate and breathing up.
• Strength training: Strength training involves using weights or your own body weight to gain muscle mass. It’s important because muscles are crucial in burning calories and maintaining overall metabolic health.
• Interval training: Interval training involves alternating between various levels of speed and intensity in your workouts. This helps challenge the muscles and prevent them from plateauing.

Developing a Balanced Exercise Routine

In Awaken the Giant Within, Tony Robbins advises finding the proper balance between aerobic and anaerobic exercise. Anaerobic exercise (like strength training and interval training) helps build muscle and improve flexibility, but it can also be harmful when done incorrectly. Too much anaerobic exercise can burn through your body’s glucose and lead to anxiety, circulation problems, fatigue, headaches, and injuries. To avoid this, Robbins recommends building an aerobic base, as this trains your body to burn fat instead of glucose.

If you are starting from scratch, build an aerobic base by running, swimming, or biking for at least 30 minutes a day, three times a week for two to three months. Then, you can begin adding anaerobic exercises like weightlifting or high-intensity interval training.

Sleep

Gupta claims that chronic inadequate sleep leads to higher risk of many health issues including dementia and cognitive decline. Extensive research on the effects of sleep shows that sleep is more than just the body’s chance to relax: It’s a vital phase of neural activity and regeneration. In this section, we’ll first look at what happens in our brains when we sleep. Once we understand this, we’ll go over some of Gupta’s tips for consistently getting a better night’s rest.

Our Brains During Sleep

Gupta claims that our brains perform billions of molecular tasks while we sleep. Because of this, sleep keeps us sharp, creative, and able to process information. Sleep keeps our brains healthy in three key ways, says Gupta:

1. Sleep controls our hormonal cycles: Our circadian rhythms revolve around our sleeping habits, and these rhythms dictate our hormonal patterns. These hormonal patterns help regulate our appetites, stress levels, and cellular recovery. People who don’t get enough sleep on a regular basis are likely to have issues with their metabolism and stress levels—and thus, their brain’s function.

(Shortform note: Sleep also appears to reduce stress by mitigating the stress from our daily lives. Research indicates that during REM sleep, our stress neurochemicals weaken while the brain processes emotional experiences. This suggests that this dream stage of sleep acts as a sort of therapy, potentially taking the edges off difficult experiences of the day. This insight may also explain why people with post-traumatic stress disorder (PTSD) have a difficult time with flashbacks: They often have disrupted sleep patterns, so they aren’t effectively removing the emotional impact of their memories during sleep.)

2. Sleep helps us encode memories and process information: A recent theory suggests that our brains consolidate our memories during sleep. Essentially, while we sleep, our brains move information from our short-term to our long-term memory. Furthermore, when we don’t sleep enough, our brains lose the ability to process information at all. In other words, not only do we struggle to remember things later on, but we also struggle to even take in the information in the first place.

(Shortform note: In Why We Sleep, Matthew Walker explains that during sleep, our brains move information from the hippocampus to the cortex. This not only transfers memories from the short to the long term but also clears out short-term memories that are deemed unnecessary. In other words, sleep helps you remember things and make room for new information.)

3. Sleep helps our brain’s cleansing process: Recent studies show that our brains remove excess waste through something called the glymphatic system. When we sleep, this system greatly increases its output. Sleep helps get rid of the waste from our metabolic system, which includes the amyloid plaques that have been linked to dementia.

(Shortform note: The glymphatic system was first discovered in 2012, and some researchers suggest the biological need for sleep across most of the animal world may be because of our need to remove neurotoxic waste. Also, recent research has linked sleep position to changes in the glymphatic system. Patients with dementia were found to spend a much longer time sleeping in the supine position (face up). For most efficient glymphatic transport, sleeping on your side is recommended.)

Problems Associated With Sleep Deprivation

Gupta goes over several studies that exhibit the different effects sleep deprivation has on the body. They are all related to each other, and they all can lead to brain impairment.

• A study showed that people who sleep less than six hours a night after a major coronary event were 29% more likely to suffer a second one.

(Shortform note: A recent study found that too little and too much sleep can increase your risk for a heart attack or stroke. People who slept less than six hours or more than seven hours a night were more likely to die from a heart attack or stroke.)

• Another study revealed that sleeping less than six hours a night increases the chance of prediabetes developing into diabetes by 44%. Less than five hours of sleep and this number goes up to 68%.

(Shortforn note: Why does this happen? Sleep can affect blood sugar for several reasons. Even one night of sleep deprivation can lead to increased insulin resistance, the main factor behind Type 2 diabetes.)

• One study found that just one night of inadequate sleep is enough to activate the inflammation process in the body. For unknown reasons, this is especially true for women.

(Shortform note: One study found that poor sleep increased inflammatory biomarkers in women 2.5 times more than in men. A possible explanation is that testosterone somehow helps to limit the inflammatory effects of sleep deprivation.)

Tips for Better Sleep

Gupta provides some easy-to-follow advice on getting more consistent rest:

Stay on schedule: Irregular sleep patterns are harmful to your health. Try to get up and go to sleep at roughly the same time every day. It can also help to establish bedtime rituals in which you take time to unwind and do something you find relaxing.

Pay attention to diet: What you eat and drink can affect your sleep. Caffeine after 2 p.m. can make it harder to fall asleep. Too much water before bed can cause you to wake up in the night to use the bathroom. Late meals and alcohol use can also disturb normal sleep cycles.

Keep your room dark at bedtime: Most forms of light, including sunlight and artificial light from lightbulbs or electronic devices, contain blue wavelengths. These wavelengths suppress melatonin, the hormone that makes you sleepy, and stimulate other areas of the brain that keep you alert.

Sleeping Pills: Why to Avoid Them

Why We Sleep echoes Gupta’s advice in many ways. Walker also recommends maintaining a sleep schedule, reducing light, and eating a healthy diet. One thing Walker adds to the discussion is the use of sleeping pills. Sleeping pills are bad for you for several reasons:

• Most sleeping pills are sedatives that affect the quality of sleep. Although you might get seven or eight hours of sleep when taking sleeping pills, you won’t get enough deep, restorative sleep.

• Sleeping pills lead to a brutal cycle. Sleeping pills may cause drowsiness in the daytime, which leads to more caffeine use or long naps, which makes it harder to fall asleep at night, which makes you more dependent on the sleeping pills. As you use the sleeping pills more and more, you build up a tolerance, making them both less effective and harder to quit.

• There is a correlation between sleeping pill use and mortality. People who take sleeping pills are more likely to get in a car accident, get cancer, and have a weaker immune system.

Nutrition

Gupta claims a healthy diet is a vital part of brain health. As we’ve discussed, metabolic disorders are thought to be a leading factor in cognitive decline. While there is no general consensus on the perfect diet for brain health, there is plenty of evidence to suggest that you should eat certain foods regularly and avoid other foods as much as possible. In this section, we’ll look at why certain foods are good for your brain and why others can be potentially harmful.

Foods to Eat

Most of the foods that are good for your brain should not come as a surprise. Gupta claims that, although it’s difficult to know exactly how foods interact in our bodies, recent studies point to certain diets as being particularly healthy. For example, a Mediterranean diet is extremely beneficial to brain health. This diet consists largely of olive oil, nuts, fish, and a wide variety of fruits and vegetables.

Of these foods, Gupta mentions that berries and leafy green vegetables are especially good for the brain. One reason for this is that they are high in fiber. Fiber is beneficial because it changes the way your body metabolizes food. If you don’t have enough fiber in your diet, the carbs you consume will be absorbed more quickly, which increases your blood sugar and insulin levels, contributing to cognitive decline. Gupta also points out the benefits of omega-3 fatty acids, which are found in fish, nuts, seeds, and plant-based oils like olive oil. Omega-3 fatty acids are crucial in the maintenance of neurons.

Why the Mediterranean Diet Is Healthy

Gupta cites several studies that show the benefits of a plant-based Mediterranean diet. But why, other than being rich in fiber, are leafy greens and berries so good for us? What exactly are omega-3 fats doing in our brains? What other nutrients does a Mediterranean diet provide?

Leafy greens, such as kale, spinach, romaine lettuce, and cabbage, contain many essential nutrients. Vitamin K, magnesium, B vitamins, and calcium are found in leafy greens and are essential for cell function as well as bone density. Leafy greens are also high in vitamin A, which improves the immune system. Studies show that increasing your intake of greens by one serving a day can lower your risk of diabetes by up to 9%. This is due not only to the low sugar content but also to the high levels of magnesium, which helps regulate blood sugar levels.

Like greens, berries contain many nutrients. Berries also contain antioxidants, which help reduce oxidative stress. Oxidative stress has been linked to brain aging and neurodegenerative diseases such as Alzheimer’s. Berries also have strong anti-inflammatory properties. Dark-colored berries are especially helpful in fighting chronic inflammation.

Furthermore, getting omega-3 fatty acids from your diet is important because the body can’t make them from scratch, and they play an integral role in the function of cell membranes. Omega-3 fats also help make hormones that regulate blood clotting, blood flow, and the inflammatory process.

But the Mediterranean diet is good for your brain for other reasons, too. One study examined the substances that a Mediterranean diet provides, and identified eight nutrients linked to healthier cognitive functions. These include omega-3 fatty and omega-6 fatty acids, lycopene, vitamin D, and the B vitamins riboflavin and folate. The researchers also mention that it’s not just the individual nutrients that affect brain health, but the way they are collectively processed, which is why a varied, balanced diet is so important.

Foods to Avoid

In a typical Western diet, there are three ingredients we consume too much: sugar, salt, and saturated fats. We’ll go through each one and discuss why Gupta feels they are bad for the brain.

Sugar: The average American consumes 163 grams of sugar per day. Most of this usually comes in liquid form or from processed foods. Earlier in the guide, we discussed why high levels of sugar in the blood can be bad for the brain: They can make us insulin resistant, leading to diabetes. They can also lead to high levels of inflammation, which can lead to cognitive decline.

(Shortform note: Insulin resistance can be especially harmful to the brain because of the way the blood-brain barrier works. The brain requires a lot of glucose, so much that the level of glucose in your cerebrospinal fluid (the fluid surrounding your brain) is 60% higher than in your bloodstream. As glucose levels rise, however, the blood-brain barrier can also become resistant to insulin and restrict it from entering the brain. It’s not too much insulin that is the problem here, but too little. Without insulin, brain cells can’t convert glucose into the energy they need to function.)

Salt: Although Gupta doesn’t go into much detail about why salt is bad for you, he does recommend limiting your intake of it as it has been linked to higher levels of heart disease, stroke, and dementia.

(Shortform note: The main reason high sodium diets are harmful is because of the effects on the vascular system, which, as Gupta points out, also harm the brain. Too much salt in the bloodstream leads to high blood pressure. As sodium builds up in the blood, the body dilutes it with water. This leads to a higher volume of blood in the bloodstream, which means more work for the heart and higher blood pressure.)

Saturated Fats: Saturated fats are in foods that are typically solid at room temperature, like cheese, butter, and full-fat yogurt. They can also be found in fatty red meats and milk. Saturated fats raise cholesterol and blood pressure levels and, like salt, have been linked to higher levels of chronic diseases.

(Shortform note: There is much debate surrounding saturated fats in the scientific community. Some researchers suggest that the fight against saturated fats, especially in America, is based on flawed data. The argument against saturated fats comes from a 1952 study that linked them to heart disease. While diets high in saturated fats do seem to raise cholesterol levels, the link to heart disease is now in question. Sugary, carb-rich, and processed foods are now considered to be more harmful when it comes to heart health.)

Learning and Discovery

Gupta argues that keeping your brain active is a vital part of maintaining its health. Learning or discovering new things stimulates the brain, and this stimulation builds a brain more resistant to disease by creating new neural connections (and strengthening existing ones). With stronger neural connections, you are less susceptible to cognitive disruption. With a greater quantity of neural connections, you can offset the disruption through the use of the other networks. This may be how some people whose brains show all the physical signs of Alzheimer’s don’t manifest any symptoms of the disease.

Can the Brain’s Adaptability Be Harmful?

Gupta argues that increasing neural networks through learning can help the brain offset disrupted communications. This neuroplasticity is a vital function, but some suggest that it can also have harmful long-term implications, especially when related to a brain injury.

After a head injury, the brain can rewire itself to maintain the connection between two regions of the brain. In the short term, this is extremely beneficial, as the brain can keep performing at a high level after sustaining damage. In the long-term, however, it may be harmful. Neural networks are usually designed to be as efficient as possible. When alternative routes are used, the brain may use more energy and be less efficient. In other words, it may take your brain slightly more time and energy to process and transmit information. Over time, the consistent use of more energy in the brain may lead to neurological disorders, such as Alzheimer’s.

Ways to Stimulate the Brain

Gupta says that the best way to stimulate the brain is through challenging and novel activities. Doing this will increase the brain’s ability to adapt to damage or other challenges (or what scientists call your “cognitive reserve”). When many people think of brain stimulation, they think of brain games or puzzles. While these are helpful for working memory, they aren’t as beneficial for things like problem-solving or reasoning, which are also a big part of cognitive reserve. For this reason, you are much better off taking a class on something you enjoy, learning a language, or doing some other complex skill that gets you out of your comfort zone.

Tips for Stimulating the Brain

As Gupta indicates, many activities can stimulate the brain—like learning a new language or visiting a museum. However, stimulating the brain isn’t a one-time thing: We develop cognitive reserve through a lifetime of learning and curiosity. Gupta’s tips for stimulating the brain are a good start, but to keep the momentum going, seek out activities with the following characteristics that have been shown to increase cognitive reserve:

Slightly challenging: Perform tasks that are difficult and challenging without being frustrating. These are great for your brain and strengthen neural connections.

Absorbing: Seek out tasks in which you feel actively engaged and interested for maximum benefit.

Varied: To make sure you’re growing new neural connections, mix up activities periodically.

Social Connection

Gupta claims that social interaction is crucial to our psychological well-being and thus our brain health. There is lots of evidence to support this, as strong social connections are a better predictor of long, happy lives than social class, intelligence, or genetics. Lack of social connection has been linked to disrupted sleep patterns, higher levels of inflammation, and higher levels of stress, all of which contribute to cognitive decline.

From an evolutionary perspective, the importance of social connection makes sense. Humans are a very social species. Throughout history, we’ve survived through communal living and reliance on others for food, water, shelter, and protection. In the modern world, as Gupta points out, social isolation is on the rise. Despite being connected to many people through digital media, many people lack real, close connections. If we wish to counteract this and preserve brain health, we must focus on building community with others and establishing meaningful relationships.

Social Connections and Depression

Another reason to strengthen your social connections is to prevent depression. In Lost Connections, Johann Hari argues that one of the leading causes of depression is a disconnection from meaningful relationships. Depression can be a vicious cycle: As you become socially isolated, you may become more depressed, which leads you to further isolate yourself. Like Gupta, Hari argues that online connections, while sometimes helpful, are not enough. Experts say this is because online relationships are more about communication than real connection. To get the most out of relationships, you need to feel you are truly connecting with others.

Avoiding depression is important for your overall cognitive health because depression can cause or exacerbate many of the risk factors for dementia that Gupta presents, including insomnia, weight fluctuations, and constricted blood vessels. This can also be seen in the link between diabetes and depression. Those with clinical depression are 60% more likely to develop diabetes. Therefore, avoiding depression can help avoid many of the predictors of cognitive decline.

Tips for Social Engagement

Gupta provides some ideas for building and maintaining social connections:

First, focus on things you enjoy: Try to spend time with people you enjoy being around and doing the activities you like the most.

(Shortform note: In The Happiness Project, Gretchen Rubin notes that many people participate in activities they believe they should enjoy instead of ones they actually enjoy. One way to avoid this is to ask yourself if you truly look forward to certain activities. If you don’t, you may just be trying to project a certain image of yourself rather than do something because you enjoy it.)

Second, volunteer: Giving back to the community can help you form and strengthen social connections. You can do this through a local school, community center, or charity.

(Shortform note: As pointed out in Lost Connections, group volunteering is often recommended to people struggling with depression. Volunteering not only provides a structured support system and social reconnection, but it can also give people a sense of purpose and increase their self-esteem.)

Third, build and maintain at least one strong relationship: Having one person in your life you can truly count on is extremely important. If possible, try to communicate with them routinely. Gupta recommends going on a walk with a close friend and talking about your anxieties.

(Shortform note: In just the past few decades, social connectedness has decreased at a steady rate in the United States. In 1985, the average person had three close confidantes. By 2004, that number had dropped to one, with a quarter of all Americans claiming that they didn’t have a single person they could confide in.)