Food Is Medicine! Regression to the Mean Proves It!

Fruit TreesA sure way to make a good program look bad is to offer up flawed evidence for its benefits. Then call it the biggest and best evaluation ever. So it is with a study of Food Is Medicine, impaired by a problem with regression to the mean.

That little problem does not stop some pretty impressive puffery as the authors tout the strength of their study:

“To our knowledge, this is the largest evaluation of produce prescriptions and health outcomes to date, increasing statistical power to detect impacts on dietary intake, health outcomes, and other clinically relevant endpoints.”

Note the use of “impact.” Its use seems calculated because it also appears in the study title: Impact of Produce Prescriptions on Diet, Food Security, and Cardiometabolic Health Outcomes. An impact is “a powerful effect that something, especially something new, has on a situation or person.”

But No Measurement of “Impact”

Unfortunately, this study does not provide evidence for “impact” attributable to food as medicine produce prescriptions because it lacks a control group and suffers from problems with regression to the mean. The authors know this and get around to mentioning it toward the end of the article.

“The primary limitation is the absence of a control group. Therefore, the observed improvements in health outcomes could be attributable to regression to the mean and to other clinical factors like medication changes.”

Standing on Weak Evidence

It’s nice that they mention this serious limitation, even if they bury it. Sharing this article on X (Twitter’s sad remnant), Kevin Hall is a bit more direct:

“There was no control group and biomarker improvements were only reported in subgroups with poor baseline values. So, was this just regression to the mean?

“Without a control group who did not receive the intervention, we cannot know for sure. So, while I’m all for healthy food prescriptions, I don’t think this study offers strong support for the ‘food is medicine’ program.”

At the end of the day, we believe programs to assure nutrition security are the basis for sound food policy. Food is not medicine. Medicine is. But it sure is important for people to know they can rely on having good, nourishing food to keep them healthy.

Trying to sell this idea with puffed-up non-evidence is a mistake. Credibility matters. Especially now.

Click here for this study and here for more about the problem of regression to the mean.

Fruit Trees, painting by Gustav Klimt / WikiArt

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September 6, 2023

2 Responses to “Food Is Medicine! Regression to the Mean Proves It!”

  1. September 06, 2023 at 8:15 am, Mary-Jo said:

    Food in USA is far from nourishing if I assess after shopping yesterday at 3 different places — 2 supermarkets and a fresh produce stand. I got peaches, melons, tomatoes, peppers, cucumbers at the stand, but it closes in 2 weeks as many other freshstands in Delmarva, acc to proprietor. It was shocking for me to check out food at supermarkets — peanut butter w/sugar, palm oil, salt, and those were the expensive ‘good’ ones. Any ‘purer’ pb sold at health food section at exorbitant premium! Similar story with many other items. Some products ARE improved, like plain yogurt, whole oats, kefir. NO muesli, just granola- my pet peeve here. Overall, I find what’s on shelves here for daily shopping/dietary intake for the public MUCH more ultra-processed than in Europe. It IS possible to get better options here, but in health-food sections of supers or at health-food shops, at a premium. Is it any wonder that ‘prescribing’ produce needed to get people to eat more healthfully?! Re: medicine, ad nauseum TV commercials for drugs are disturbing. UP foods on shelves, medicine TV ads have gotten worse over the years despite attention and efforts for healthier lifestyle habits. Rant over.😣

  2. September 07, 2023 at 5:28 pm, David Brown said:

    Excerpt from the Preface to “Food for Nought” by Ross Hume Hall, PhD, 1973.

    “Nourishment of the American populace has undergone a startling transition since World War II. A highly individual system of growing and marketing food has been transformed into a gigantic, highly integrated service system in which the object is not to nourish or even to feed, but to force an ever-increasing consumption of fabricated products. This phenomenon is not peculiar to the American scene and occurs in every industrialized country. The United States, however, has progressed furthest in the transformation. Man can never be more than what he eats, and one would expect that a phenomenon with such profound effects on health and well-being as a radically changed system of supplying nourishment would be thoroughly documented and assessed by the scientific community. Such is not the case. The transformation has gone unmarked by government agencies and learned bodies. Government agencies, recipients of the public trust charged with protecting and improving the public’s food, operate as if the technology of food fabrication rested in pre-World War II days.”