Humans run on a fuel called food. Yet economists and other social scientists rarely study what people eat. We provide simple evidence consistent with the existence of a link between the consumption of fruit and vegetables and high well-being.
In cross-sectional data, happiness and mental health rise in an approximately dose-response way with the number of daily portions of fruit and vegetables. The pattern is remarkably robust to adjustment for a large number of other demographic, social and economic variables. Well-being peaks at approximately 7 portions per day.
We document this relationship in three data sets, covering approximately 80,000 randomly selected British individuals, and for seven measures of well-being (life satisfaction, WEMWBS mental well-being, GHQ mental disorders, self-reported health, happiness, nervousness, and feeling low).
Reverse causality and problems of confounding remain possible. We discuss the strengths and weaknesses of our analysis, how government policy-makers might wish to react to it, and what kinds of further research -- especially randomized trials -- would be valuable.
- David G. Blanchflower, Andrew J. Oswald, Sarah Stewart-Brown, "Is Psychological Well-being Linked to the Consumption of Fruit and Vegetables?" (Abstract), NBER Working Paper No. 18469 (October 2012) (emphasis added) (hat tip to Marginal Revolution).
Commentary
Hurray for abstracts that genuinely summarize the key findings of the research, as this one does! The dose-response relationship after controlling for economic variables is particularly convincing.
Query if the relationship is unduly strengthened by the fact that the social safety net in Britain doesn't permit large numbers of people to suffer the kinds of deep privation that are possible in the United States (e.g. lack of health care for serious chronic medical conditions, high murder rates, very long periods of incarceration, truly dire sustained poverty, etc.) in statistically significant numbers?
Does Britain have the kinds of "food deserts" that are common in low income neighborhoods in the United States (i.e. neighborhoods with no local full service grocery stores)?
Fruits and vegetables as a source of happiness seems a rather more persuasive way to market them than under the theory that they are "good for you."
Diet Will Not Change Through Food Alone.
There in anecdotal evidence, for example, from food channel reality shows, that simply providing "healthy food" to people who aren't eating it isn't sufficient. People who don't have health diets often also don't know what to do with these kinds of food. Eating habits are part of a larger lifestyle and set of "food folkways", rather than a raw input that can be viewed in isolation. Until the people in a household who prepare meals and buy food integrate fruits and vegetables into their menu planning and set of recipes and snack options that they are comfortable with and in the habit of using, making the food available isn't enough. One rule of thumb is that it takes three weeks to develop a habit.
Notably, many professional dieticians don't follow their own advice very well and are heavier than one might hope themselves.
On the other hand, the benefits of developing these habits is great and has the potential to be relatively inexpensive. Another recent study has shown that changing diet is quite effective at addressing youth obesity in practice, while exercise programs as actually implemented are virtually worthless at doing so despite the fact that this reality is rather counterintuitive.
Current home economics education currently doesn't and never has met this need in most schools. In my own experience in junior high school, I was taught how to make casseroles and jello dishes. My daughter was taught how to make meals with Hamburger Helper(r) at Hamilton Middle School, although both of my children leaned much more about healthy eating lifestyles from the Chez Panisse movement garden to table food program at Steele Elementary School in Washington Park (both are schools in the Denver Public Schools district in Colorado).
The Ethics and Practice of Cultural Imperialism
Of course, any daily living instruction risks running afoul of cultural objections from parents in a multi-ethnic population from diverse social classes. It smacks of cultural imperialism. Parents expect their kids to learn facts and academic knowledge, not to have them abandon the cultural roots of their families, of which food is often a core manifestation.
I'm not necessarily against cultural imperialism even in public schools, however, because it works. The most successful schools of choice in terms of value added academic outcomes (like KIPP, the Denver School of Science and Technology, and D'Evelyn in metropolitan Denver) all engage in concerted and conscious efforts to not merely impart knowledge but also culturally shape their students at a very personal level that may break with folkways and cultural modes of dealing with life that they have learned at home. All of these schools make an serious effort to inculcate successful upper middle class Yankee habits and instincts in students who lack them when they start attending these schools. Japanese public education, aided by a strong societal consensus on these matters, also takes this approach.
The reality is that social class has cultural components that can be taught, and that meeting the sometimes expressly stated objective of public education to allow people to overcome social class barriers can only be mass produced with a teaching approach that fundamentally changes the cultural come from of its students.
Ataturk was less insane than he seemed when he mandated that modern Turks where bowler hats and suit jackets in a clime far more balmy than England or Northern Italy where those fashions were invented. The exact means were a bit over the top, the his recognition that modern culture is a package deal with insightful for its time and partially explains why Turkey is the most socially liberal of almost all of the predominantly Islamic countries in the world (although other factors, such as the large Alevi population of Turkey whose culture is quite different from that of the Sunni Arabs of places like Saudi Arabia is also a factor).
Often, the best way to address the cultural imperialism issue is to have these innovations come from inside a community, in its own way, rather than being imposed from the outside. Even the device of school choice, by bringing a voluntary element to the table on the part of the child and family, can make a big difference in how acceptable cultural imperialism in schools is for those involved.
N.B.
A few meta style points at this blog by way of reminder to newbies:
(1) Since I'm a lawyer, I routinely cite to scholarly sources in a reasonable approximation of the Bluebook form (secondary title, "A Uniform System of Citation") used by legal academics regardless of the citation custom in the discipline I reference, unless I am being lazy and cutting and pasting from another source.
(2) I routinely add or remove paragraph breaks in quoted material so that it reads better in a blog format.
(3) When time and presence of mind permit, I credit the source that directed me to the quoted material with a hat tip, but I do not feel an absolute moral obligation to do so. This is an extra. I also feel I have adequately credited a source if I merely include a hyperlink rather than a full citation, and if I include a hyperlink to another source that contains either a hyperlink or reference sufficient to locate the original source.
(4) I frequently edit, with editorial indication through brackets and ellipsis, omissions and editorial additions. I usually, unless I am very harried, indicate when emphasis is my own, but a reader should not automatically assume that emphasis in the quoted material without acknowledgement is not added editorially. Sometimes, I get in a rush and fail to note this, although it is usually obvious.
(5) I avoid inverting the order of quoted material in a single block quote, but often do so in multiple block quotes.
(6) A block quote not immediately followed by a hyperlink is from a previously linked source in the post.
(7) I sometimes make typos as I don't have a professional copywriter for my blog. Sometimes I fix them, sometimes I don't. Unless an omission is in a title or otherwise truly glaring, or reverses the meaning of a phrase, feel no obligation to correct me in the comments. See also the general disclaimer page for this blog regarding gremlins and so forth. This blog is prone to regular gremlin infestations.
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