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


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.

  • I rolled back your edit because votes on meta are used for agreement or disagreement. 2 votes were already cast and your edit leads to them being suddenly reversed.
    – YviDe
    Mar 15 '16 at 0:03
  • @YviDe not necessarily. Mar 15 '16 at 0:08
  • A downvote on "is X on-topic" and a downvote on "is X off-topic" are not necessarily different?
    – YviDe
    Mar 15 '16 at 0:09
  • @YviDe votes on meta are not necessarily used for agreement or disagreement. They can simply indicate whether the question is interesting (i.e., worth answering), e.g., meta.softwarerecs.stackexchange.com/q/2457/903 Mar 15 '16 at 0:10
  • Well, without knowing what the two downvoters meant, I think reversing the question isn't a good idea
    – YviDe
    Mar 15 '16 at 0:13
  • 1
    @YviDe ok I edited the question so that the phrasing is unambiguously neutral. Mar 15 '16 at 0:15

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.

  • After reading your PSA, I found this question. I'm trying to imagine a question on nutrition that 1) does not have direct impact on a person's health, and 2) would be a good question on any SE site. So far I'm only coming up with system wide/economic/production questions, which look like they would be off topic on the A51 site as well. Can you give an example of what is off topic here, but on topic there? I'm just not seeing it.
    – Atl LED
    Apr 13 '16 at 13:49
  • 1
    "How do I determine calories/serving size for meals I make at home", "Does Calcium intake decrease iron absorption", "What is a paleo diet", "What does nutritionally empty mean" - All more academic questions rather than immediate health impacts. All of which would be off topic on cooking, fitness, here, the absorption question might be on topic at Biology. All the existing sites stipulate that it must be related to the main topic. Agreed, nutrition impacts health, but you can have nutrition questions that are not health related except peripherally.
    – JohnP Mod
    Apr 13 '16 at 13:59
  • Got it. I understand now.
    – Atl LED
    Apr 13 '16 at 14:00

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.


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.

  • "common sense is the answer" -> so according to your common sense, how does the loss curve looks like? Mar 14 '16 at 23:02
  • This is mostly an aside, but diet and nutrition are not synonyms - most diet questions also have the nutrition tag.
    – YviDe
    Mar 14 '16 at 23:36
  • @YviDe Out of a sample of 50 questions with the nutrition tag, 28% also had the diet tag, so it's not "most" but I do agree there's a significant overlap. But that is kind of an aside. If I edit my post to remove that total of 308 it doesn't change my point.
    – Carey Gregory Mod
    Mar 15 '16 at 0:17
  • @CareyGregory oh I know. I just remembered that the diet tag guide even says questions should also be tagged nutrition. (and I meant the other Way around - questions asking about diet should also get the nutrition tag. 23 out of the newest 50 diet questions have that)
    – YviDe
    Mar 15 '16 at 0:18
  • @FranckDernoncourt I have no idea but I don't think it matters much health-wise. Yes, if you boil potatoes until they're mush then I expect much of their nutrition content will be destroyed or left behind in the cooking water. But that won't matter because most cooks don't do that.
    – Carey Gregory Mod
    Mar 15 '16 at 0:19
  • @CareyGregory Well I think it matters, hence the question. Mar 15 '16 at 0:21
  • @FranckDernoncourt You know what would probably be a much more relevant question health-wise? What happens to the nutritional content of potatoes when they're fried in oil? These days in western societies potatoes are far more often deep fried than boiled, so there would at least be a public health aspect to the question.
    – Carey Gregory Mod
    Mar 15 '16 at 0:22
  • @CareyGregory I agree such efficient would be of higher impact in terms of public health. But as far as I'm concerned, I only boil potatoes :) Mar 15 '16 at 0:24
  • @FranckDernoncourt Okay, fine, and how would knowing this curve change your behavior? Boiling potatoes the minimum time necessary to render them palatable and then reserving the cooking water for other dishes will maximize vitamin retention no matter what that curve looks like. That's why I suspect no one has ever determined that curve.
    – Carey Gregory Mod
    Mar 15 '16 at 0:42
  • @CareyGregory I'm quite lazy in terms of cooking, and I'm pretty good at eating dog food, so I simply wonder to what extent I should be careful about cooking time. Mar 15 '16 at 0:43
  • @FranckDernoncourt If you were even a little bit concerned about nutrition, you would not eat dog food unless you're buying super-premium brands that cost more than human food. You don't even want to know what's in grocery store brands of pet foods.
    – Carey Gregory Mod
    Mar 15 '16 at 0:46
  • @CareyGregory sorry I meant dog good in term of how it tastes, not in term of nutrition content. I am careful about nutrition. Mar 15 '16 at 0:49
  • @FranckDernoncourt Then quit boiling your potatoes and bake (or microwave) them instead. :-)
    – Carey Gregory Mod
    Mar 15 '16 at 0:52
  • @CareyGregory Agreed, microwaving looks like a better option, from what I have read. Mar 15 '16 at 0:55

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .