Harvard nutritionist says these are the 4 best changes you can make to your diet for a healthy brain

The decades-old saying "you are what you eat" has grown increasingly true as we learn just how important our diets are for immunity, longevity and even mental health.

"Many people don't realize that there's a way in which the food we eat impacts our mental wellbeing," according to Dr. Uma Naidoo, a Harvard-trained nutritional psychiatrist and author of "Calm Your Mind with Food."

"The food we eat, as it gets digested, interacts with the trillions of microbes in the gut microbiome, and gets broken down into different substances, which then subsequently over time impact our mental wellbeing. Some of the foods that are less healthy, if we're eating them, set the gut up for inflammation."

DON'T MISS: 4 simple ways to eat for longevity in the new year, according to a Harvard nutrition expert

Inflammation in the gut can lead to several adverse mental health symptoms, Naidoo says, including anxiety.

"By tweaking your diet back to a healthier norm, you can actually help to relieve some of these symptoms," she notes.

Here are four simple changes you can make to your diet for better brain health.

1. Increase the fiber you eat

"An easy first step is to increase the fiber in your diet," Naidoo says.

"An increased intake of total dietary fiber" was associated with a lower chance of developing depression, according to a study published in "Complementary Therapies in Medicine" in 2021.

The best way to get fiber in your diet is to obtain it from plant-based foods, Naidoo says.

These are a few great food sources that are high in fiber:

• Colorful vegetables like leafy greens
• Beans and other legumes
• Flax seeds
• Healthy whole grains

2. Get more polyphenols

Naidoo refers to this method as getting a "kaleidoscope of color" in your diet by eating colorful foods that are high in polyphenols. Different plants and vegetables of different colors "represent a level of biodiversity needed by the gut microbes," she says.

Aim to eat more foods rich in polyphenols like:

• Carrots
• Blueberries
• Strawberries
• Nuts, especially hazelnuts and pecans
• Black olives

"All of these are hugely important, because they have anti-inflammatory, antioxidant properties [and] fiber, plus multiple micronutrients that our bodies need," Naidoo says.

3. Eat foods rich in probiotics

A healthy gut is great for our brains, and our guts love probiotics. And you can get more of the healthy bacteria from fermented foods.

"A study published in 'Cell,' a very highly reputable journal, done by a research group at Stanford University a couple of years back, showed that adding fermented foods to your diet lowers inflammation," Naidoo says.

Naidoo recommends finding a fermented food that appeals to you, whether it be kefir, kimchi, yogurt or kombucha.

4. Use more herbs and spices

One of the simplest ways to improve your gut health, which can also promote healthy brain health, is by adding more spices and herbs to your diet, Naidoo says. It's "something people often overlook," she adds.

"Spices and different types of fresh herbs are rich in plant polyphenols, high in antioxidants and anti-inflammatory properties," Naidoo says.

You can spice up your meals with:

• Turmeric and a pinch of black pepper
• Capsaicin from chili peppers
• Mint
• Oregano
• Parsley
• Thyme
• Ginger
• Garlic

"They flavor up your food [and] they add depth, whether you make a soup or roast vegetables or a piece of salmon," Naidoo says, but they're also "a powerful part of our kitchen that we can lean into."

Want to land your dream job in 2024? Take CNBC's new online course How to Ace Your Job Interview to learn what hiring managers are really looking for, body language techniques, what to say and not to say, and the best way to talk about pay. Get started today and save 50% with discount code EARLYBIRD.