Tuesday, 2 June 2009

A question (not just an answer): How much does a nutritious diet cost?

How much does a nutritious diet cost?

Some say that the high price of healthy food is making us obese and unhealthy. Others wonder how that could be so, because (even with recent inflation) food of all sorts has been comparatively cheap in the United States for many years, due to government policy and technological change in the food system.

The leading source of disagreement about the cost of an adequate diet is different definitions of "adequate," not different price estimates. Your estimate of the minimal necessary cost depends on your opinion on questions like the following:
  • whether a high level of meat and dairy is necessary for an adequate diet,
  • whether your vision of healthy food includes foods marketed as healthy (organic yogurt, low-fat cereal) or simple basic staples (whole grain rice, cabbage, carrots),
  • whether diets should be judged by their adherence to USDA's Pyramid recommendations,
  • whether diets should be judged by their adherence to the National Academies' nutrient recommendations, and
  • whether you think low-income people can cook at home, or whether instead convenience and restaurant foods are central to your definition of adequacy.
More subtly, your estimate of minimal cost depends on your opinion about whether people can change their diets in order to meet cost and nutrition goals, or whether it is inevitable that any realistic diet closely resembles the current average diet.

Reasonable answers about the cost of a nutritious diet, corresponding to different definitions of nutritious, range from even less expensive than the federal government's Thrifty Food Plan to much more expensive.

No wonder this issue generates a lot of argument! Most people on all sides of this issue leave these key assumptions implicit and unstated. Yet, these assumptions strongly influence conclusions about minimal costs.

In a recent article in the Journal of Consumer Affairs (free abstract, pay site for full article), "Using the Thrifty Food Plan to Assess the Cost of a Nutritious Diet," Joseph Llobrera and I use USDA's Thrifty Food Plan (TFP) framework to clarify the relationship between assumptions and cost estimates for nutritious diets. Let me know by email if your library does not have the journal. There is a related seminar on the Friedman School website. If you would like to play around with these models yourself, see our Thrifty Food Plan calculator. In both the seminar and the calculator, I should have emphasized more strongly that all of the dollars are in 2001 dollars per adult in the household, not adjusted for inflation (if you didn't know this, the amounts would seem unrealistically low).

For some readers, the whole computation will seem beside the point. They may reason that is clearly wrong to set the TFP cost target too low, but harmless to set it too high, so why not just pick the highest estimate? For a number of reasons, I think better food assistance policy comes from trying to choose the right estimate for a minimal cost target, rather than padding the estimate too much.

In the article, we find that the USDA's Thrifty Food Plan cost level can purchase a nutritious diet if (1) you think nutrient constraints (adequate protein, for example) are more important than food category constraints (plenty of meat), or (2) if you think it is reasonable to expect people to drastically change their current consumption pattern. If, instead, you think substantial meat and dairy amounts are essential to an adequate diet and you defer to the current consumption pattern of low-income consumers, you will probably prefer a more generous TFP cost target.

Update: Slate's Daily Bread food business blog has a thoughtful post about this article (gently needling the online presentation as "a little geeky" -- ha!).

No comments:

Post a Comment