CNN - Eating nutritional foods is one of the best ways to reduce obesity. But following a healthy diet isn't always easy, especially for lower socioeconomic groups.
One of the biggest barriers to buying good food is the cost, many experts say. Now researchers at Harvard School of Public Health have put a dollar amount on the price of healthy eating. By reviewing 27 studies on the cost of healthy vs. unhealthy foods, they've estimated the daily cost of eating better. Their results are published in the British Medical Journal.
"Conventional wisdom has been that healthier foods cost more, but it's never been clear if that's actually true or exactly how much more healthier foods might cost," said lead study author Mayuree Rao. "We found that the healthiest diets cost about $1.50 more per day, and that's less than we might have expected."
Rao and her team looked at studies done after 2000 that compared healthy and unhealthy version of certain foods -- for example, lean beef vs. a fattier cut, and studies that compared healthy and unhealthy diet patterns, such as a diet rich in fruits and vegetables versus a diet without fresh produce.
The studies they analyzed came from 10 countries, including the United States, Canada and several European nations. The food prices were converted to international dollars and adjusted for inflation.
The researchers evaluated the prices based on a specific food's price per serving, as well as the price per 200 calories of that food item. They evaluated the diet patterns based on the price per day (three meals' worth) and the price per 2,000 calories -- the FDA's standard daily intake recommendation for adults. This ensured the researchers were looking at the price variations from all angles.
Some food groups showed more of a difference in price than others. Meat had the highest price difference; healthier versions cost 29 cents more per serving on average than the less healthy option. Grains, snacks and dairy, on the other hand, showed minimal price differences between healthier and unhealthier versions.
On a broader scope, the healthiest diets appear to cost consumers about $1.50 more per day than the unhealthiest diets. This means consumers who eat a diet rich in fruits and vegetables, for example, pay about $1.50 more per day than those who eat a diet made up mostly of processed foods.
This result was consistent across several types of healthy diets, the study authors say, including the Mediterranean-style diet, Harvard's Alternative Healthy Eating Index, and diets focused on eating more energy dense foods.
Every study has a caveat -- something the scientists couldn't control for or didn't analyze that may be affecting the results. In this case, the study authors were limited by data that had been collected by others in the past. The definition of a "healthy" diet varied between each study, and the prices were only evaluated to reflect the price for a typical adult's daily diet.
"Our aim... was not to evaluate whether one specific product costs more than another, but whether healthier foods in a broad class of foods cost more, on average, than less healthy foods in the same broad class," the study authors write.
Rao wants you to consider what $1.50 means to you.
"For many low-income families, that means quite a lot," she said. "It translates to about $550 more per year for one person, and that could be a real barrier to healthy eating."
But for other people, $1.50 is less than they spend on their morning cup of coffee. It's "just a drop in the bucket when you consider the billions of dollars spent every year on diet-related chronic disease like obesity, diabetes and heart disease," Rao said. "When you look at the long-term health impact, the extra $1.50 is a good investment."