What is our stance on questions about nutrition?

Question

What is our stance on questions about nutrition? Are they on-topic or off-topic?

Example:

Question: To what extent does the cooking time impact the nutritional content when boiling potatoes?

Body: I wonder to what extent the cooking time impacts the nutritional content when boiling unpeeled potatoes with unsalted water.

http://www.livestrong.com/article/340060-does-boiling-potatoes-reduce-their-vitamins/ says:

Boiling potatoes whole in their skins minimizes the amount of vitamin C that is lost. According to the Food and Agriculture Organization of the United Nations, boiling unpeeled potatoes results in losses of up to 30 percent of vitamin C, but boiling peeled potatoes can cause losses of up to 40 percent. About 2 percent of the vitamin B-6 is lost due to boiling potatoes, as well as about 23 percent of the thiamine. A 3.5-ounce serving of potato boiled in the skin provides 22 percent of the daily value for vitamin C, but boiled peeled potatoes provide only 12 percent. Peeling potatoes before boiling can also increase vitamin B-6 losses, with unpeeled boiled potatoes containing 15 percent of the DV per 3.5-ounce serving and peeled boiled potatoes containing only 13 percent of the DV. There is no difference in thiamine content between peeled and unpeeled boiled potatoes.

but does not mention the impact of the cooking time.

In case nutrition is off-topic here, here is a Area 51 proposal on nutrition.

Answer 1

Nutrition questions that have a direct impact on a persons health or health situation can be on topic, much as nutrition questions on Fitness.SE are on topic if they are directly related to their impact on a fitness/weight management program.

However, such questions as the above are not really health related in my opinion, as they are not really related to a health condition or problem being experienced, it's an academic food question.

I would need to go through the questions tagged with nutrition, but I would suspect that at least a portion of them should be closed for that reason, and others are inappropriately tagged.

Answer 2

It should be on topic, there are high quality peer reviewed journals devoted to nutrition, e.g. The American Journal of Clinical Nutrition. Some questions may yet have to be answered by scientists, but you'll be surprised about the many questions that have already been answered using rigorous research. E.g. the fact that calcium in spinach is not going to be absorbed as well as calcium from kale (which had been theorized on the grounds that oxalates in spinach should interfere with calcium absorbtion) has been confirmed in experiments involving growing kale and spinach with different isotope ratios of calcium compared to the natural environment. By measuring the isotopes of calcium in the urine and blood of volunteers who eat that kale or spinach one can measure how much of the calcium they absorb.

Now nutrition can be argued to not be directly health related. I believe that this attitude taken by the medical profession has led to the obesity epidemic. Not enough research has been done in the last century or so, nutrition was traditionally treated as something trivial, but it's a highly non-trivial subject.

Answer 3

Here are the top 10 tags:

Tag, No. of Questions, Unanswered %

1. Nutrition 198, 30%
2. Diet 110, 35%
3. Dermatology, 83, 39%
4. Medications, 82, 30%
5. Sleep, 71, 32%
6. Dentistry, 59, 37%
7. Pain, 49, 22%
8. Side-effects, 49, %18
9. Eye, 46, 34%
10. Cancer, 42, 31%

As you can see, the Nutrition tag has the highest question count and Diet is a close second. They're largely synonyms so combining them yields 308, which is higher than the total of the next four tags combined. Surprisingly, the unanswered percentage doesn't change much among the top 10 (except Pain and Side-effects, which I suspect is because they are more often added to concrete questions with other tags).

Unfortunately, that's the end of objective facts I can muster from the stats available to me. What I see subjectively is that a very large percentage of nutrition and diet questions are what I would label frivolous or even downright silly. I vote to close questions almost daily along the lines of "Which is better: A or B?" where A and B are largely irrelevant things, often based on superstition or cultural practices that amount to old wive's tales. In fact, the huge number of such questions has surprised me. I had no idea how many people think that drinking liquids before, during or after a meal will have profound effects on your health, or that such questions have even been studied extensively. Quite often no one has bothered studying them at all so scientific answers aren't possible. (If I could answer with what I consider to be common sense, the answered percentage would quickly approach 100%.)

Unfortunately, I consider the OP's example to be a question where common sense is the answer. Vitamin C, for example, is water soluble so cooking potatoes in water is bound to remove vitamin C, and that effect will increase with cooking time (which the supporting article states). The problem is, can I find scientific support for that answer? No, probably not, or at least not directly. I can probably dig into chemistry or biology research to show the general effect, but boiling potatoes specifically? Not likely. I doubt that anyone has done a definitive study that would yield a cooking time/vitamin retention curve for boiled potatoes. They haven't done that study because the answer is unlikely to have an impact on culinary practices or contribute to future research.

Those questions also attract alternative medicine trolls like flies to dead stuff. Asking nutrition questions is a sure-fire way to get long-winded diatribes from brand new users telling us how eating only this or that type of food will change our lives like winning the lotto, and failing to do so will put us in the grave by next week.

And therein lies the problem with nutrition questions. The signal-to-noise ratio with such questions is very low. It's so low that I would consider dropping the tag entirely. In general, I agree with the requirements specified by JohnP in his answer. For example, the potato-vitamin question would be on-topic if it was asking if boiling potatoes directly affected a specific health concern rather than just the generality of vitamin retention of certain cooking methods. That's a cooking question, but it's not even welcome on cooking.SE for pretty much the same reasons.