Diet plays an important role in social inequalities in health

Hypertension, obesity, diabetes, cardiovascular diseases and osteoporosis are more prevalent among socio-economically disadvantaged populations than in populations of high socioeconomic status and have a stronger impact on their health. In France, for instance, rates of premature mortality from nutrition-related diseases are 3 times higher for manual workers than for white-collar workers^[1].

Dietary behaviours have been shown to be involved in social inequalities in health^[2]. Most foods recommended for a good health, such as fruits and vegetables, whole grain breads, fish, seafood and lean meats are consumed in low amounts by people of low socioeconomic status, whose diets are mainly based on refined cereals and starchy foods.

The consumption of fruit and vegetables, in particular, is strongly and directly associated with socio-economic status. As a result, there is a marked social gradient for the intake of essential micronutrients found in abundance in fruits and vegetables, such as fiber, vitamin C, ß-carotene, folates, polyphenols as well as calcium and potassium, while macronutrient intakes are poorly related to socio-economic status[^2-6].

Economic constraints orient food choices towards unhealthy options

In households with limited economic resources, cost is often perceived as a barrier to the consumption of fruit and vegetables and to the adoption of healthier diets^[7,8]. This is not surprising since, at a given energy intake, fruit and vegetable-rich diets actually do cost more^[9-11]. Indeed, the cost of dietary energy is inversely related to dietary energy density^[12], while it is positively related to the intake of essential micronutrients^[13]. This has been attributed to the high water content and very low energy density of vegetables and fruit, which makes them expensive sources of energy^[14]. Moreover, diet modelling studies with linear programming have shown that a cost constraint alone orients food choices almost necessarily towards the selection of energy-dense^[15] nutrient-poor^[16] diets. This strongly suggests that unhealthy food choices observed among the poor could be due, at least in part, to economic constraints.

A minimal food budget is required to achieve a healthy diet

Based on linear programming analysis, the lowest cost required to achieve a nutritionally adequate diet in France was estimated to be 3.5 ?/d. and 3.2 ?/d. for adult men and women respectively^[17]. This is lower than the current mean national expenditure for food at home in France (approx. 6.0?/d)^[18], indicating that, for the vast majority of French adults, fulfilling the recommendations would be possible without marked increases in their food budget. It will be more difficult, however, to achieve a healthy diet when the budget for food is just above the minimum required. In this case, nutrition education programs must actively focus on promoting relatively inexpensive nutrient dense plantbased foods, such as legumes, roots and nuts, fresh fruit and vegetables such as oranges, bananas, apples, carrots, cabbage, tomatoes, zucchini, celery and onions, as well as frozen or canned vegetables, citrus juices and dried fruits^[14,17].

The nutritional quality of food aid needs to be improved

Unfortunately, the minimal cost of a healthy diet exceeds the actual budget for food of people living below the poverty level in France^[18], in particular those seeking food aid whose food budget is approximately 2.3 ?/d.^[19]. Since people in these groups can not afford to consume diets that meet current recommendations, food aid of good nutritional quality should be provided to them. However, charitable organizations often face the same economic and structural barriers than those actually faced by the individuals they are helping. Food-aid recipients and charitable organizations both rely on food donation to acquire food and have problems to transport and stock fresh foods. Providing people in the lowest income groups with economic supplements or vouchers to specifically purchase fresh foods of good nutritional quality may overcome such practical difficulties. As described by D. Herman in this issue of IFAVA, this approach was recently shown to be efficient in a population of low-income women^[20].

The nutritional quality of diets has been shown to be directly related to their cost. This probably explains the strong prevalence of obesity and nutrition-related diseases in lowincome populations. Nutritional policies aimed at increasing the economic and physical access to fruit, vegetable and fish for the poorest fractions of the population are required to make the right to eat healthily a reality for all.