Dietary Factors and SES

Summary prepared by Mary Fran Sowers in collaboration with the Allostatic Working Group. Last revised in 1997.

An essay:

Dietary factors have been implicated as causes of chronic diseases because these factors are common, subtle and persistent overtime. It has been speculated that dietary factors may be a differentiating factor in the relatively greater disease burden among the social classes and the economically disadvantaged. There have been numerous relationships described between dietary factors and SES.

It has been assumed that because food costs disproportionately impact the total budget of the economically disadvantaged, they are less likely to be able to buy foods or to buy foods of appropriate quality. It is assumed that the educationally disadvantaged do not have the intellectual resources to select and appropriately prepare nutritionally-appropriate foods.

Secondly, it is well-recognized that groups of lower SES in affluent countries are more likely to be obese than those of higher SES. It is assumed that this obesity is a physical presentation of poor dietary and nutritional practices.

Indeed, it is a frequent observation that as populations evolve from a more agrarian society and/or less affluent society to either a more affluent and/or more urbanized position, there is an adoption of the dietary patterns of that more affluent (and usually more urbanized) society. Attendant to that adoption is a dramatic increase in obesity, greater longevity and manifestation of chronic diseases. Simultaneously, it is also noted that there is a tendency for the more affluent to alter their dietary patterns which tend to resemble a return to the carbohydrate-based diet of the more agrarian state, supplemented by access to fruits, vegetables and other modified foodstuffs which are too costly for the more impoverished.

It was noted in a recent publication by Popkin et al. (NEJM 335:716-720, 1996) that there appear to be convergence in the past 15 years of overall dietary quality between whites of higher SES and the black and whites of lower SES. Whether that convergence should be considered positive or not depends upon our view of the dietary quality of blacks and whites of lower SES. Studies conducted in the 1970's reported that diets of lower SES blacks and whites in the US was of higher quality than had previously been appreciated, albeit, they were not optimal. Furthermore, the diets of white higher SES residents of the US was actually inferior to those of the lower SES.

These observations should help sensitize us to the complexity of addressing and interpreting the relationship of dietary factors as a causal mechanism for the disease burden of those of lower social class. For example, in the US, the Poverty Index is determined by the cost of securing a mythical adequate diet. Thus, a measure of social class is defined by dietary factors including quality, quantity, and cost of foodstuffs. Methods to assess dietary factors (with the exception of the 24hour recall) are notoriously demanding from an educational perspective and are typically culturally-insensitive. Food frequency demands rapid decision-making (usually 400 decisions in less than 20 minutes) and in many instances are self-administered and require literacy. Food record keeping requires literacy and high motivation for record-keeping. Rarely do the assessments consider not only the issue of dietary quality but also the obvious relationship of energy input and energy outlay in physical activities of work and non-work time. Differences may separate on rural/urban lines as well as educational and economic lines. To factor in these elements means assessment of the impact of change in access to storage (refrigeration), the national food distribution system, to distance to food supplies and stores, and the common information sources (such as TV) that influence the food decision process.