It's a funny thing. As much as we're focused on achieving our goals, many of us are also focused on trying to develop healthy habits that can lead to greater happiness, too.

Now it turns out there's  one such habit lying right there in front of you. We all know of course that eating healthy is good for you, but now there's scientific proof that a few small healthy changes in your diet can measurably improve your happiness, too.

There's more good news. First, the changes to your diet are things you'll actually enjoy, if you're not eating them already. And second, the researchers were able to offer a useful metaphor for just how much happier they believe this dietary change can make some people.

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Eight servings of fruit and vegetables

I won't leave you in suspense. The change all has to do with the number of servings of fruit and vegetables that you eat every day. The more of them you eat, the happier you are. (Boom. Science.)

Scientists tracked the food intake of more than 12,000 Australian adults over several years. At the extreme, there were some in the study who had been consuming almost no fruit or vegetables, and they were persuaded to take in the full eight recommended servings of fruit and veggies per day.

Result? It's really quite amazing. To get the full picture, imagine a person who is out of work--stressed, worried, and suffering under crushing self-doubt. Now imagine that you get to go tell that person he's been selected for a great, high-paying job in his field.

Now put a number on how much better the person's mood becomes from the nadir of the job search to the moment he learns about the new job. That's how much researchers calculated the participants' moods improved--just from eating more fruit and vegetables.

Is happy more important than healthy?

The study was conducted by scientists at the University of Warwick in England and the University of Queensland in Australia, and it will be published shortly in the American Journal of Public Health.

And as excited as the scientists are about the happiness angle--who wouldn't be?--they're equally hopeful about something else. If people learn that eating healthy can make them measurably happier, maybe they'll be more likely to make healthy dietary choices than if they "only" know it improves their health, scientists hope.

In other words, avoiding cancer or a heart attack years from now is great--but not as great as feeling better today.

"There is a psychological payoff now from fruit and vegetables--not just a lower health risk decades later," said Redzo Mujcic, an Australian research fellow who was one of the leaders of the study.