For Healthy Diet, Learning Level Counts More Than Earning Level

That may seem obvious, but it wasn't the case in 1965. Then, people who had not finished high school, those who were high school graduates and those who went to college all had about the same level of diet quality. But a more recent survey by Barry Popkin, Ph.D., and colleagues from the Department of Nutrition at the University of North Carolina at Chapel Hill found that while dietary quality has improved overall, those with more education now have much healthier diets.

"In fact, the gap in diet between higher educated persons and lower educated persons may explain the large disparity in health between higher and lower socioeconomic groups in the United States," Popkin says.

The research is published in the July issue of the American Journal of Preventive Medicine. Popkin emphasized that this study examined the composition of the diet, not energy intake or obesity.

Comparing dietary habits from 1965 and 1994-96, Popkin and colleagues measured the overall healthfulness of the diets of 6,475 respondents in 1965 and 9,241 in 1994-96. In two telephone calls on different days, respondents were asked to recall what they had eaten in the previous 24 hours. They tabulated results using the Revised Dietary Quality Index, a rating of a diet's overall healthfulness.

The effects of income and education were rarely significant in 1965, Popkin says. There were a few differences back then: College-educated people took in more calcium, iron and servings of fresh fruit than less-educated people did, but they also ate more saturated fats -- which decreased their Dietary Quality Index.

Between 1965 and the mid-1990s, the overall Dietary Quality Index improved for all education groups. But better-educated people not only have better diets today compared to their counterparts 30 years ago, they also eat better than today's high school dropouts.

Thirty years later, the effects of education are more pronounced. For instance, white men with no high school diploma scored 61.9 on the Dietary Quality Index, while their college-educated peers scored 68.3. A similar gap separated black men in the same educational categories. Income variations produced far smaller differences, said Popkin.

"In general," Popkin says, "extra years of schooling related to small upward shifts in diet quality. The highest diet quality level was found among white women who attended college and for those with income far above the poverty line."

Comparison of the two surveys found some anomalies, as well. For instance, race alone did not always predict results. Black male high school graduates saw no change in their dietary quality scores, while black women with the same level of education saw significant gains.

An exception to the general dietary improvement was a drop in calcium intake, which Popkin blames on reduced milk consumption. Other researchers have noticed the same pattern with calcium, which is needed to build and maintain strong bones.

Besides calcium, the most striking dietary shortcoming in the 1994-96 survey came with a disappointingly small shift downward in the use of added sugar, discretionary fat, salt and alcohol.

Popkin said that by the 1994-96 survey, people were consuming less fat and cholesterol and more grains and vegetables. But this good news was overshadowed by the increasing prevalence of obesity in the United States, he said.

The Dietary Quality Index research model reflects proportion, variety and moderation in diet, but does not account for total energy intake, Popkin said. So while it showed a lower percentage of calories coming from fat (a sign of dietary improvement) because the consumption of fats remained constant, total calories increased, leading to a net weight gain.

Exactly why more education is linked to better diets wasn't clear, Popkin says. Previous research showed that, more than income or occupation, lower levels of education were associated with higher disease risk.

"It may be caused by a diffusion of knowledge, skills, attitudes and beliefs that occur while individuals are participating in the educational system," he says. Better-educated people may get better nutritional information or are more likely to act on it than those with less schooling.

"Improving the education system in the United States may help to eliminate disadvantages in diet quality," Popkin concludes.