We are all told that we need plenty of fruits and vegetables in our diets, and, yes, it can cost more money to eat fresh fruit than many of the processed foods out there.

But for most of us, the cost is not the biggest factor in what we stuff in the grocery cart. Those high-calorie corn chips, breakfast doughnuts and ice cream cost as much as or more than the healthier choices. And the more money we make, the more likely we are to get a few of those fresh fruits into our diets anyway.

But when you don't make much money and you live in a food desert, the decision on what to take home with you is more carefully considered.

Food deserts are areas where there is a lack of traditional grocery stores such as portions of North Charleston and rural areas of Berkeley and Charleston counties, and where there are a high number of people who live a mile or more from a grocery store and lack a car.

The cost of food is so much higher in those areas for two reasons: The choice of fresh food is limited, and what is there is much more expensive. Shoppers have to weigh the extra cost of the food locally versus the cost to go to a grocery store and try to get the food home by taxi, a ride from a friend or bus.

Experts have tried to make a correlation between the distance to a grocery store and obesity, but the issue is more complex than that.

The cost of an apple can vary widely across a city, and you can actually get a much better deal in a suburban grocery store on those foods than you can in areas where the stores are scarce.

It turns out that a study conducted in Detroit shows that price may be a better indicator of whether someone on a limited budget is likely to choose fresh food and, thus, be able to control their weight better.

A 2012 study released last month by researchers at Michigan State University and published in Urban Studies, titled “Price and Expenditure Elasticities for Fresh Fruit in an Urban Food Desert,” examines the effect of availability of fruits and vegetables on the demand for these goods.

The researchers compared the amount of money people spent on fresh food relative to their income, and they compared fruit sales between suburban grocery stores and those at an inner-city nonprofit grocery store.

It turns out that when you have less money to spend and the fruit is much more expensive, you are less likely to put it in your cart. But when the cost of an apple at the urban store was the same as the suburban store, there was a greater likelihood that it would be purchased.

According to the study, “When consumers spent more, their purchases of many fruits increased by an even greater amount: A 1 percent rise in spending increased banana purchases by 1.18 percent, oranges by 1.74 percent, apples by 2.15 percent and lemons by 1.26 percent.

“If prices increased, fruit purchases dropped, but not as much as the price increase: For a 1 percent rise in prices, purchases of bananas fell by 0.33 percent, apples by 0.28 percent, and oranges by 0.54 percent. This suggests that demand for these fruits is relatively inelastic, even if prices go up, consumers will make it a special priority to get some amount of fruit in their grocery order.

“Within the fruit group, income plays a much more important role in the purchasing decisions of Detroit food desert residents than price compared with consumers more representative of the average American.”

One of the study's conclusions is that obesity could be greatly helped in those food desert areas by lowering the price of fresh food and vegetables to suburban levels. People will buy apples and bananas if they can get them for a fair price.

Reach Stephanie Harvin at 937-5557.