Oct. 11, 2012 -- Grumpy and out of sorts? Grab an apple. Or a carrot. Or a banana.
Eating plenty of fruits and vegetables seems to boost life satisfaction, mental well-being, and happiness, according to a new study.
Researchers analyzed the diet habits of 80,000 men and women in Britain.
The more fruits and vegetables they ate, the happier they were. Those who ate seven servings daily were happiest.
"I think it's splendid to know that fruits and vegetables are likely to be good for your mental health as well as your physical health," says researcher Sarah Stewart-Brown, MD, professor of public health at Warwick Medical School in the U.K. "It's not surprising, as the two are related to each other."
The research is to be published in Social Indicators Research.
Fruit, Vegetables, and Well-Being: Study Details
Numerous studies have linked eating lots of fruits and vegetables with health benefits. Among them: a lowered risk for heart disease and cancer, and help with weight management and blood pressure control.
Less attention has focused on fruits, vegetables, and psychological well-being.
Stewart-Brown's team looked at three different sets of data: the Welsh Health Survey of 2007-10, the Scottish Health Survey of 2008-09, and the Health Survey of England in 2008.
Each is a random sample of the population of the countries.
The 80,000 men and women answered questions about their daily intake of fruits and vegetables. They reported on exercise habits, employment, and whether they smoked.
They reported on their levels of life satisfaction, mental well-being, any mental disorders, happiness, nervousness, and feeling low.
The Magic Number: 7
Well-being linked to fruits and vegetables peaked at about seven portions a day, the researchers found.
It appears that ''the more you go from zero to seven or eight, the happier you will be," says Andrew Oswald, PhD, professor of economics at the University of Warwick and a study researcher.
For the surveys, a portion was defined as about 3 ounces. A small apple, for instance, is about 5 ounces.
The study didn't distinguish between types of fruits and vegetables, Oswald says. (No, French fries did not count as a vegetable.)
Quantifying the effect more precisely is difficult, Stewart-Brown says. For example, she says, the effect on the life-satisfaction score for those who ate less than one serving a day is equal to about one-third the effect on life satisfaction reported by those who lose their jobs. That's a substantial effect, she says.
The study was not funded by any produce organizations.
Only about 1 of 10 British people eat seven or more servings of fruits and vegetables daily, the researchers say.
In the U.S., the USDA recommends adults eat at least 1.5-2 cups a day of fruits and 2-3 cups of vegetables, depending on sex and age. But fewer than 1 in 10 people eat the recommended amount, according to the CDC.
Fruits, Vegetables, Happiness: Explaining the Link
The researchers found a link, not cause and effect, Stewart-Brown says.
And it's possible that the link goes in the opposite direction -- happy people may just eat more fruits and vegetables, she says.
How the fruits and vegetables may help well-being is not known, the researchers say.
"Initially, we thought it might give people more energy and they exercise more," Oswald says. But the link held even when they took exercise habits into account.
Fruits, Vegetables, Happiness: Perspectives
The study validates changes that some dietitians see when clients begin eating more fruits and vegetables, says Andrea Giancoli, RD, a spokeswoman for the American Academy of Nutrition and Dietetics. She reviewed the findings for WebMD.
"I can tell you that anecdotally, when they improve their diet, clients tell me, 'I feel good,'" she says.
Even those who say they hate fruits and vegetables can find ones they like, she says. "Usually it's just certain ones they don't like. Once we go through [the list] we find ones they do like."
"When they start to cook them in ways tasty to them, or add them to a meal, they start to like them more."
When eating plenty of fruits and vegetables becomes a habit, people don't feel as well when they skip them, Giancoli finds.
Oswald hopes researchers from the biochemistry field will take up the question of how fruits and vegetables may boost well-being.
Meanwhile, he says he is trying to eat more fruits and vegetables.
"I am keen to stay cheery," he says.