Academic: Sorry USDA, but more nutrient dense diets do cost more…

In their paper 'Nutrient Intakes Linked to Better Health Outcomes Are Associated with Higher Diet Costs in the US’​,​ Adam Drewnowski, Pablo Monsivais and Anju Aggarwal argue that nutrient-rich diets cost more.

Dr Drewnowski, who is director of the Center for Public Health Nutrition at the University of Washington, Seattle, has hit the headlines several times​ over the past two years after publishing a series of papers highlighting the challenges of meeting the 2010 Dietary Guidelines for Americans​, particularly for consumers on low incomes.

He has also urged policymakers to take a “reality check​​” after repeatedly highlighting the disparity between “aspirational​” diets and hard reality based on actual eating patterns identified from federal nutrient composition and dietary intake databases.

Nutrients associated with a lower risk of chronic disease are associated with higher diet costs      ​

Analysis of dietary intakes in Seattle demonstrated that “nutrients commonly associated with a lower risk of chronic disease were associated with higher diet costs​”, concluded the authors.

“By contrast, nutrients associated with higher disease risk were associated with lower diet costs. The cost variable may help somewhat explain why lower income groups fail to comply with dietary guidelines and have highest rates of diet related chronic disease.”​

Diets higher in sat fats and sugars cost less​

The study, published in the peer-reviewed journal PLoS ONE​ on May 25 and funded by a grant from the National Institutes of Health, examined degrees of nutrient intake for every key nutrient in the diet in relation to diet cost and socio economic status.

The authors used a sample of data from more than 2,000 adults in the Seattle Obesity Study in which dietary intakes were assessed using food frequency questionnaires. Diet costs for each respondent were then estimated using Seattle supermarket retail prices.

Lower cost, lower quality diets more likely to be consumed by lower socioeconomic groups​

The results showed that higher intakes of dietary fiber, vitamins A, C, D, E, and B12, beta carotene, folate, iron, calcium, potassium, and magnesium were associated with higher diet costs, with the cost gradient most pronounced for vitamin C, beta carotene, potassium, and magnesium.

Conversely, higher intakes of saturated fats, trans fats and added sugars were associated with lower diet costs, said the authors.

“Lower cost, lower quality diets were more likely to be consumed by lower socioeconomic groups… The cost gradient might help explain why lower income groups have least nutrient adequate diets and are at higher risk for chronic disease including obesity and diabetes.”​

Potassium and vitamin C a particular challenge​

People in the highest quintile of intakes for saturated fats, trans fats and added sugar had significantly lower diet costs, as compared to those in the lowest intake quintiles, added the authors.

“Based on current eating habits, compliance with dietary guidelines is likely to entail higher diet costs for the consumer.”​

However, not all beneficial nutrients are equally expensive, they noted.

“The most pronounced positive gradient with diet cost was seen for vitamin C, beta carotene, potassium and magnesium – nutrients primarily obtained from fruits and vegetables. By contrast, calcium and vitamin D showed a weaker associations with diet cost, likely because milk and milk products are relatively inexpensive.​

“Iron and folate also showed a weak association with diet cost, which may reflect the ubiquity and relatively low cost of grain products fortified with iron and folate. ​

“There is clearly a need to identify and promote inexpensive food sources of key nutrients in order to improve the dietary quality of lower socioeconomic status groups. ​

More research needed to identify cheaper ways of promoting beneficial nutrients to consumers​

While food frequency questionnaires have certain known biases, they are a useful tool to make comparisons across subjects, they noted.

“Nonetheless, the present findings have implications for future research. First, diet cost variable ought to be taken into account in future studies on diets and disease risk. ​

“Second, further research is needed to identify cheaper ways of promoting beneficial nutrients to the consumer, particularly among lower income and lower education groups.”​

Click here​ to read Drewnowski’s study.    

Click here​ to read more about USDA’s recent study.