Eating nuts, berries and leafy greens is good for brain health. Most of what people usually eat isn't.

You are what you eat. That goes for both your body and mind. Your diet can have a profound impact on neuroplasticity -- the ability of your brain to work better. It can also affect your energy levels throughout your workday.

Many busy business leaders and entrepreneurs too often grab the most convenient packaged food or caffeine drink to fuel their workday. Yet, this food often does not provide the nutritional value to maintain a consistent energy level and a productive mind.

A few years ago I began training for a half marathon, which launched my journey on changing what I ate throughout the day and how often. I found that eating small, healthy snacks throughout the day kept me from reaching for a diet soft drink or grabbing something from the vending machine. I discovered I no longer had the energy crashes I once had when I monitored how and when I ate throughout the workday.

My mind was clearer, my thought processing was crisper and I was much more productive in my work.

Fortunately, much research has been devoted to how nutrition impacts brain health, especially in terms of improving certain brain regions linked with intelligence, learning, and working memory -- the skills you rely on every day for business success.

So which foods provide the biggest brain boost? Here is a look at four that stand out. What's great about these is that you can use them in a variety of ways -- as part of your everyday meals or as power snacks.

1. Walnuts

Walnuts are one of the richest foods in a type of omega-3 fatty acid called alpha-linolenic acid (ALA), which may help protect brain tissue. One study found that people who ate high amounts of walnuts scored higher on cognitive tests that measured story recall, response speed, sustained attention and visual spatial memory.

You don't need much either. One-quarter cup of walnuts contains 113 percent of the daily value of omega-3s. Enjoy a palm-sized serving as an afternoon snack, sprinkle some into a salad, or stir one or two tablespoons of chopped walnuts into your oatmeal or yogurt.

2. Berries

Want to hold onto your memories? Eat more berries. Researchers found that berries like strawberries and blueberries can delay memory decline. A study on older adults showed that those who consumed at least a half-cup of blueberries or one cup of strawberries per week delayed their cognitive aging by as much as 2.5 years.

Berries are one of the top foods with high levels of anthocyanidins, which are antioxidants that have been shown to stimulate brain regions like the hippocampus, involved in learning and memory. This part of the brain is extremely important for busy business leaders who run from meeting to meeting, and rely on their memory skills to recall details later in the day when it's time to put together product specs or a customer proposal or service program.

3. Green Tea

Drinking more green tea can enhance your working memory. In one study, people drank either a drink containing green tea extract, or a placebo drink, and then tried to solve several working memory tasks while their brain activity was monitored with an MRI. Researchers found that compared with the placebo group, the tea drinkers had more activity in their parietal and frontal lobes -- areas involved in language processing and short-term memory.

It's not clear why green tea might have this effect, but it may be related to its high levels of thiamine (vitamin B-1., which plays a role in brain function maintenance. Try switching your morning coffee for green tea or enjoy a cup as a mid-day refresher. However, keep in mind that bottled green tea beverages contain smaller amounts of tea, so it's best to brew green tea yourself!

4. Green leafy vegetables

Green leafy vegetables, such as spinach, kale, collards and mustard greens, may help preserve what researchers call "crystallized intelligence," the ability to use the skills and knowledge a person acquires over time. These also have omega 3's, but a key ingredient may be their rich amounts of lutein.

A study looked at people's dietary habits and found that those with high levels of lutein tended to do better on tests to measure crystallized intelligence. Besides green leafy vegetables, lutein is abundant in egg yolks and vegetables like broccoli.

While much of this research is ongoing, there is no downside to adding more to your daily diet -- as well as stocking your workplace with better snacks -- since they have other potential health benefits, too. Think of nutritious food as a no-risk investment in your brain, business, and employees to create a healthier and more productive workplace overall.

This post was originally published on Entrepreneur on December 27, 2017.