As a physician interested in brain health, I’ve been struck by how little we consider the impact of food. We think of our bodies, but we put minimal thought and focus into how food choices relate to our brains, or how the state of our brains can affect so many important aspects of our overall health and mood.

Our brains are both our greatest asset and the home of the hungriest cells in our body. It’s crucial to feed these cells well—and that’s important across the board, whether or not you are a patient on my couch. No matter your personal background, genetics, or situation, the core of your personal wellness is your food.

As the science continues to advance, it’s become easier to see the impact food has on our brain health. Our brains consume 20 percent of everything we eat; this nourishment provides the energy and nutrients to create and sustain the quadrillions of connections that construct the brain, and the electricity that courses between those connections.

Your brain is the organ of connection, and you depend on these connections for all aspects of your life: Your work. Your relationships. Your memories. Your intentions. Your dreams.

You have in your possession the most complex structure in the known universe, a human brain—but most of us, myself included, were never taught how to optimally fuel it.

Prescribing Healthy Food

In my practice, I was prescribing medications and doing talk therapy, but it seemed clear that food presented a unique opportunity to further help my patients. It would certainly be my most delicious prescription.

Better food choices would ensure that my patients’ brains were optimally nourished with “building block” nutrients such as omega-3 fats, vitamin B12, and zinc. It would also make their brains more resilient by enhancing brain growth—the latest brain science tells us that human brains continue to grow through adulthood, creating new brain cells and also new connections.

On top of that, eating better food would decrease my patients’ risk of obesity, diabetes, and heart disease, all diseases that wreak havoc on mental health.

The key to a healthy brain and body—and therefore optimal health—is to “eat complete.” Eating complete means that you get all of the nutrients your brain and body need from the food you eat.

But for many people, it’s challenging to focus on nutrition in a way that is feasible, convenient, and delicious. Instead, it’s easy to make poor choices, fall into bad food habits, and often leave out the very foods we need most in our diets.

3 Barriers to Eating Well

As I began addressing food and nutrition with the patients in my clinical practice, I found myself running into three common barriers.

The first is that it is complicated for people to eat in a way that optimizes nutrients. How do you know what to do, and who can you trust about food?

Another barrier comes from concerns about time and money. Many people feel they lack the skills and time to cook every night, and healthy food can be expensive.

Finally, in order to work around these other two barriers, people often put blind trust in a bad insurance policy: the daily multivitamin.

The data on supplementation are mixed at best—but either way, there is no insurance policy for eating poorly.

The more I ran into these barriers, the more I focused on helping my patients overcome them. Over the years of assessing people’s food habits, a pattern of missing nutrients became apparent to me.

In conjunction, there has been a surge in the scientific evidence about brain health and nutrition. Recent studies have looked at dietary patterns and the risk of brain-based illnesses such as depression and dementia, and the results are showing strong correlations between those illnesses and what we eat.

Coupled with the modern discovery that the human brain is growing even in adulthood, the conclusions are startling. The very nutrients many people are missing are those most important to human brain health. And without these nutrients, your brain and body will not operate as they should.

Take, for example, the brain chemical serotonin, which regulates critical physiology such as mood, weight, and sex drive. For your brain to produce this chemical, you must eat foods that contain the amino acid tryptophan (such as pumpkin seeds, cod, and beef) as well as foods high in iron, folate, and vitamin B12 (such as lentils, mussels, and kale).

3 Rules For Brain Food

There are three rules that can help you spot an important brain food, and kale actually provides a great framework for these three lessons.

The first rule is nutrient density, which focuses on eating with efficiency so that every calorie brings a bevy of nutrients. The foods with the highest concentration of nutrients should be the foundation of your diet.

The second rule is that foods need culinary flexibility so that eaters aren’t bored by the same thing and can instead create diverse feasts with a few foods.

Bring some kale to my house and you could find yourself eating kale and eggs, a kale smoothie, or a kale salad. We might make some kale pesto, or even a “kalejito.” Kale is incredibly versatile and can be added to almost any dish to make it healthier.

The third rule is local access, which encourages people to connect to their food supply, eat with a smaller footprint, and eat seasonal food. Access also means that the food is affordable and available, something that can be a challenge.

Leafy greens form the base of the food supply—they grow almost everywhere, and they are affordable for nearly everyone. Given the spread of farmers’ markets nationally (by last count we have 8,144 in the United States), along with many state programs that double the value of food stamps at farmers’ markets, Americans’ access to fresh, local, nutrient-dense produce is increasing.

Following these three rules helps ensure that your brain is nourished—and it’s easy and affordable to do so.