We've all heard that eating fruits and vegetables is healthy for us. But now there's an added incentive to upping your intake of produce: It will put you in a better mood, according to a growing body of research.

In a study published in Molecular Psychiatry, researchers analyzed 41 studies on depression and discovered that people who followed a Mediterranean diet (high in vegetables, fruits, fish and nuts) had a 33 percent lower risk of developing depression compared to those who followed a diet high in processed meats and trans fat. A trial of young adult eating habits published in the journal PLOS ONE reached the same conclusion. The diet may be effective against depression is because produce is front and center, essentially replacing the foods that can cause inflammation.

As researcher Heather Francis, a lecturer in clinical neuropsychology at Macquarie University in Sydney, Australia, told NPR, "Highly processed foods increase inflammation. ... [and] if we don't consume enough nutrient-dense foods, then this can lead to insufficiencies in nutrients, which also increases inflammation."

A separate study from The American Academy of Neurology evaluated 964 participants over the course of six-and-a-half years and discovered those who followed a DASH diet (which includes a lot of produce) may have a lower risk of developing depression compared to those who adhered to a western diet (which heavy on red meat). The risk of suffering from depression was 11 percent lower for DASH diet followers compared to others in the study.

For many, the idea of keeping depression or a dip in mood at bay with food is a lot easier to swallow than taking a pill.

"Making a lifestyle change such as changing your diet is often preferred over taking medications," said DASH diet study author Dr. Laurel Cherian of Rush University Medical Center in Chicago.

Raw produce is even better

apple tree Produce that hasn't been processed in any way, like these apples, could help your state of mind. (Photo: Glysiak [CC BY-SA 4.0]/Wikimedia Commons)

Eating fruits and vegetables raw may help ease symptoms of depression, according to a study conducted by the University of Otago and published in Frontiers in Psychology. Researchers surveyed 422 young adults in New Zealand and the U.S. and found that those who consumed raw produce reported less depressive symptoms and higher life satisfaction and positive outlook compared to those who ate more canned, cooked or processed fruits and vegetables.

"This research is increasingly vital as lifestyle approaches such as dietary change may provide an accessible, safe, and adjuvant approach to mental health," said Dr. Tamlin Conner, lead author of the study.

The study also noted that the following raw fruits and vegetables were related to better mental health: carrots, bananas, apples, dark leafy greens like spinach, grapefruit, lettuce, citrus fruits, fresh berries, cucumber and kiwi.

But just how many fruits and vegetables?

An Australian study published in the American Journal of Public Health found that eating eight servings of fruits and vegetables each day can make you happier. The results won't happen on day one, but over time, many people had significant increased life satisfaction, researchers Redzo Mujcic and Andrew J.Oswald found, writing in their study results:

Increased fruit and vegetable consumption was predictive of increased happiness, life satisfaction, and well-being. They were up to 0.24 life-satisfaction points (for an increase of 8 portions a day), which is equal in size to the psychological gain of moving from unemployment to employment. Improvements occurred within 24 months.

That concrete comparison — the increase in happiness is like "moving from unemployment to employment" — impressed me because it's easy to imagine what that feels like.

But what if eating eight servings seems too lofty a goal? Well even just adding one extra serving of produce to your daily diet can be beneficial.

Analysis of the U.K. Household Longitudinal Study found that eating one extra serving of fruits or vegetables on top of your daily amount has the same mental health benefits as an extra 7.6 days of walking 10 minutes continuously during a four-week period. The real benefit also comes from not just eating more produce here and there but making it a regular habit. Researchers noted that the frequency of eating was just as important as the quantity.

How much is a serving?

Handful of strawberries A serving size might be smaller than you think: Half a cup constitutes one serving. That might be a handful of strawberries or a medium-sized banana. (Photo: Alohaflaminggo/Shutterstock)

Of course, if you want to make it your goal to hit eight servings of fruits or vegetables a day, you need to know how much a serving is.

According to the Australian government site Eat for Health, a standard serving of vegetables is about 75 grams (like 1/2 cup cooked green or orange vegetables or 1 cup green leafy or raw salad vegetables) and a standard serving of fruit is about 150 grams (one medium apple, banana, orange, pear or 1 cup diced or canned no-sugar-added fruit).

Getting in eight servings of fruits and vegetables might seem daunting if you're not used to it, but there's no time like the present to change your ways. It's a lot easier to get in that amount when your choices are abundant. Besides, cementing your new habit now will make it easier to stick with your goal during the winter, when options aren't as plentiful.

Editor's note: This article has been updated since it was originally published in July 2016.

Robin Shreeves ( @rshreeves ) focuses on food from a family perspective from her home base in New Jersey.

Fruits and veggies may keep the blues away
If you're looking to improve your outlook, the produce bin is a good place to start.