Comment by neetdeth | Hacker News Reader

Comment by neetdeth | Hacker News Reader

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This study was peer reviewed, and neither the researchers nor the reviewers are drooling morons as you seem to imply. From the article:

"Based on prior research, we included a rich set of commonly observed predictors of well-being as control variables (see Dolan et al., 2008 for a review of this literature). These include socio-demographic variables such as age, household income, gender, relationship status, number of children and education. Such controls are important as it is possible that fruit and vegetable consumption would co-vary with, for example, income – someone becoming richer and as a result enjoying higher well-being scores and changing their food related behaviours. We also controlled for the presence of long-standing health conditions as well as health and lifestyle related behaviours such as walking frequency and smoking behaviour – again potential confounders that could bias any estimates of the relationship between fruit and vegetable consumption and well-being."

While I do think a lot of research in the social sciences is of questionable value, there's no need to shoot from the hip just for the snarky HN comment.

It's in the summary too:

>They took account of many potential confounding factors, including age, income, marital status, number of children, employment status, smoking status, exercise levels (measured by days each week on which they walked for at least 10 minutes at a time) and whether they had a longstanding health condition.

>The study has limitations, however. The most important is that this type of observational study can't tell us whether the fruit and veg consumption actually causes improved mental wellbeing.

While the longitudinal design and the adjustment for potential confounding factors helps to make the results more robust, there may be something else unaccounted for at play here. The possibility that people who feel happier are more likely to choose healthier food, for example, cannot be ruled out.

Its a responsible and cautious summary.

Is it fair to assume that one cannot just eat more of something without changing anything else? If yes, eating more fruit and veg can be accomplished by eating less of something else and/or increasing caloric requirement through increased physical activity. It would be very interesting to find out what that is, because that could be turned into actionable recommendation about how to eat more fruit and veg.

It could just be focussing on cooking. Less junk food. Taking longer meals. Spending more time on the toilet. Better bowel health.

A litany of secondary factors. But they're all direct effects of eating more veg. That's more than correlation.

It doesn't really matter if it's peer-reviewed or how many variables they controlled for. It's still an observational study and not a randomized controlled trial.

Observational studies are not completely devoid of value. They are in many cases the only way we can practically learn about certain aspects of our world.

Randomized controlled trials are better, of course.

Nutrition epidemiology studies are not scientific experiments; they are wildly inaccurate, questionnaire-based guesses (hypotheses) about the possible connections between foods and diseases. This approach has been widely criticized as scientifically invalid [see here(1) and here(2)], yet continues to be used by influential researchers at prestigious institutions.

Even if you think epidemiological methods are sound, at best they can only generate hypotheses that then need to be tested in clinical trials. Instead, these hypotheses are often prematurely trumpeted to the public as implicit fact in the form of media headlines, dietary guidelines, and well-placed commission reports like this one.

Tragically, more than 80%(3) of these guesses are later proved wrong in clinical trials. With a failure rate this high, nutrition epidemiologists would be better off flipping a coin to decide which foods cause human disease.

(1) https://www.frontiersin.org/articles/10.3389/fnut.2018.00105... (2) https://jamanetwork.com/journals/jama/fullarticle/2698337 (3) https://rss.onlinelibrary.wiley.com/doi/full/10.1111/j.1740-...

Ref: https://www.psychologytoday.com/us/blog/diagnosis-diet/20190...

Although, potentially interesting: Self reported mental well being is correlated with self reported belief of eating more fruits and vegetables. Though a much weaker claim than the headline, I think this is still useful information. Without looking at the study, you can't rule out that there was something about the surveys that caused this correlation, but if there wasn't, it certainly would be interesting to try to find out why this correlation exists.

John Ioannidis, the guy behind "Why Most Published Research Findings Are False" has recently gone after nutrition research. Turns out that nutritional studies are basically devoid of value. After decades of nutrition research we know almost nothing about how to eat healthy.

That's a very bold statement to make.

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