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I understand that diet, habits and lifestyles differ preposterously across different countries and different people. Of late, there has been an increasing trend among people to take multi-vitamin tablets as a daily dietary supplement.

Is there any actual benefit of taking it? Assuming that people normally eat a balanced vegetarian diet, I think the only justification for taking these could be that they aren't deriving all the essential nutrients from fruits and vegetables alone. Could the gradual degradation of environment over time be a reason for that?

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The answers so far suggest that the evidence in this direction gathered by most studies is inconclusive at best. However, I am still interested to know about any more studies and data, be it for efficacy of supplements or degradation of nutrients in plants, just for the sake of completion.

Prahlad Yeri
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  • Interesting question. Probably yes, the degradation of environment has caused the urgent/immediate need for third party resources to get important vitamins and minerals. – ABcDexter Aug 20 '16 at 17:03
  • A vitamin deficiency objectively lead to a couple of health problems. Taking supplements can off-set a deficiency. Do you accept such a line of reasoning for an answer? – Mast Aug 20 '16 at 19:13
  • @user2318 Most vitamin/mineral deficiencies--when the deficiency is due to low dietary intake--can be effectively treated by vitamin/mineral supplements and this is known for decades. The question contains "Assuming that people normally eat a balanced vegetarian diet"... – Jan Aug 22 '16 at 08:42

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Is there an objective answer to whether or not taking a multi-vitamin dietary supplement is beneficial to health?

No, there is not.

If you dig into the existing research, unless you are looking to experience some confirmation bias one way or the other, you will only continue to find evidence that there is no conclusion.

In this case Wikipedia actually does sum it up nicely, emphasis mine:

Provided that precautions are taken (such as adjusting the vitamin amounts to what is believed to be appropriate for children, pregnant women or people with certain medical conditions), multivitamin intake is generally safe, but research is still ongoing with regard to what health effects multivitamins have.

Evidence of health effects of multivitamins comes largely from prospective cohort studies which evaluate health differences between groups that take multivitamins and groups that do not. Correlations between multivitamin intake and health found by such studies may not result from multivitamins themselves, but may reflect underlying characteristics of multivitamin-takers. For example, it has been suggested that multivitamin-takers may, overall, have more underlying diseases (making multivitamins appear as less beneficial in prospective cohort studies). On the other hand, it has also been suggested that multivitamin users may, overall, be more health-conscious (making multivitamins appear as more beneficial in prospective cohort studies). Randomized controlled studies have been encouraged to address this uncertainty.

I'd love to quote the whole "Research" section here, but if you read through it, and between the lines, you can start to get an inkling of just how all over the place and inconclusive research has been.

For example, the citation for the "randomized controlled studies have been encouraged" bit is simply a paper from 2011 that concludes with "these results highlight the need for more case-control studies or randomized controlled clinical trials to further examine this relationship." In other words, as recently as 5 years ago, at least one researcher was still in the state of realizing that randomized trials may be needed to clear things up.

Every credible source, e.g. Johns Hopkins, periodically releases some article that says "In a recent study, vitamins have shown to be beneficial / unhelpful". If you dig into the methods of these studies you will likely find (very reasonable) initial bias in both directions as well as the introduction of other variables due to the selected sample set.

For example, the title of that that Johns Hopkins editorial linked to in the other answer is "Enough Is Enough: Stop Wasting Money on Vitamin and Mineral Supplements". With a title like that I'm sure that research wasn't neutral to begin with (not that it was bad, it's just this is a really inconclusive topic so it's easy to interpret study results according to initial views, hence the fact that this has been an ongoing conflict for decades).

The abstract of that study concludes with the absurdly inconclusive, and probably biased, "Although available evidence does not rule out small benefits or harms or large benefits or harms in a small subgroup of the population, we believe that the case is closed— supplementing the diet of well-nourished adults with (most) mineral or vitamin supplements has no clear benefit and might even be harmful." -- A sentence which I can't help but laugh at because, you know, what? -- The issue really is so up in the air that anybody can pretty much find any data to support any viewpoint. You can pick anything you want from that abstract and use it as a basis to publish an article with a catchy headline like "The Vitamin Verdict" that supports your view either way, there is very little objectivity involved.

However, there does at least seem to be a general consensus that, massive overdose aside they don't hurt (except for the couple of studies that said they do, which were countered by meta studies that said the studies said they didn't, and so on...).

Note by the way this isn't really "of late", well, at least not in the US where it's been a slowly but steadily increasing trend for at least 30 years. I distinctly remember having a heated conversation with somebody about this exact same topic 20 years ago.

I think personal dietary and health trends are simply too varied to make any kind of general conclusion here. Perhaps they are good for some people in some situations and have no benefit for others, and every study from now until the end of time will continue to be inconclusive and unintentionally (or intentionally!) biased.

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Jason C
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  • Efficacy of multivitamin supplements is just one side of the coin. As @Milo Martinovich's answer suggests, the other important aspect is the gradual degradation of nutrients in plant food over last few decades. At least, this is something that could be objectively proven, and if found true, should at least become a major health concern to us, whether supplements are effective or not. – Prahlad Yeri Aug 22 '16 at 17:40
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    @PrahladYeri You would never to be able to prove/disprove that generally, with a single statement that encompasses all "plant food". You could only show that in small isolated areas (and sure, it's valuable info). And it's the same with "are supplements beneficial/harmful". I contend that all claims of this nature depend on the person and on the environment, and so that is why such "studies" about supplements, plant nutrient quality, you name it, have been and shall remain inconclusive. General conclusions can not be draw, there is just too much variance across the not-so-small planet. – Jason C Aug 22 '16 at 18:12
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    (Plus just trying to define "degradation of nutrients" would be controversial and inconclusive in itself. What would that even mean? "Degradation" can mean anything, not to mention the personal variance of its effects, if any. "Nutrients" is a massive varying category of things, different supplements have different efficacies for different people. It would be just as inconclusive and [un]intentionally biased a set of studies as the supplement question being asked here. There are just too many variables, not to mention too many agendas.) – Jason C Aug 22 '16 at 18:15
  • This is an excellent answer! – Narusan Jun 20 '17 at 14:11
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    I think special mention of pediatric cases and studies is worth mentioning, where the research seems less ambiguous. It's also worth pointing common deficiencies in vegetarian diets to avoid, given the op. Still +1 – Atl LED Jun 21 '17 at 17:39
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In a perfect world, no, a multivitamin wouldn't be needed. However, even with high intake of fruits and vegetables, you have to consider micronutrient degradation in fresh fruits that you buy in the store. As soon as you pick a fruit/veggie, the micronutrients are starting to break down. The longer you wait to eat it, the less it will have.

One way to get around this is to have your own garden and eat what you pick every day. The other way to ensure more micronutrient intake is to take a multivitamin. One thing to consider as well is that the RDA for each vitamin/mineral isn't the upper limit for positive benefits. There are more benefits to be reaped at higher intake with a lot of the vitamins/minerals.

As for the links posted by Jan, the 1st one states that there is no definitive evidence either way, so nothing can be concluded. The 2nd link analyzed multivitamin users and only concluded results of the risk of heart attacks, mental decline, and cancer. That is not the main purpose of a multivitamin in the first place.

If you look at the benefits of each vitamin/mineral(http://www.helpguide.org/harvard/vitamins-and-minerals.htm) you'll see nothing about heart attacks, cancer, or mental decline. Lets see a study on these proposed benefits of each vitamin/mineral with multivitamin users vs non-users. I'm sure that would lead to different results.

Summary: Yes, they can be useful if you are not getting your daily intake of each of the vitamins/minerals. They can also provide benefits beyond the RDA for certain vitamins/minerals. Micronutrient degradation happens and can cause lower intake of micronutrients than you might expect, even with high amounts of fruits and vegetables in your diet. Take a multivitamin for the benefits of the vitamins/minerals, not to try and stop heart attacks, cancer, etc.

Milo Martinovich
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    Yes, your answer makes more sense. Multivitamin supplement's job is to compensate for deficiency in vitamins, minerals and other micro nutrients in our diet. Cancer and Heart disease are hardly any examples of diseases arising from malnutrition of vitamins, so I don't see how those studies are relevant at all to this question. – Prahlad Yeri Aug 20 '16 at 22:09
  • Incidentally, and further supporting the points here, the actual editorial (it wasn't even a proper study, it was just an editorial piece in a journal) behind that 2nd link didn't really seem to conclude anything at all and ended with the authors basically saying "although available evidence tells us nothing, we consider the case closed". – Jason C Aug 21 '16 at 00:45
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    This would be a better answer if it quoted studies about the vitamin/mineral benefits. Right now it offers no evidence that we do not live "in a perfect world" and that people lack those micronutrients. I don't really doubt it, but the question asked for an objective answer, not hand-waving. – Hassassin Aug 21 '16 at 08:33
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    http://www.scientificamerican.com/article/soil-depletion-and-nutrition-loss/ Here is a article referencing a couple studies proving lower amounts of micronutrients in fruits and vegetables produced today versus decades ago. These new findings aren't found with the nutrition facts of foods so you can easily overestimate the micronutrients you intake daily if you follow nutrition labels/facts for fruits and vegetables. – Milo Martinovich Aug 21 '16 at 19:10
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    @MiloMartinovich, that's still only half the premise. Ok, some foods contain less of these micronutrients than they used to. However, is that enough to push the intake below the recommended minimum? – Hassassin Aug 22 '16 at 06:21
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    @MiloMartinovich 1. You said "They can also provide benefits beyond the RDA for certain vitamins/minerals." You did not provide any evidence for this claim. 2. Vitamin degradation in foods that occurs with time is a known thing. This does not automatically mean you do not get enough nutrients by eating foods you can buy in stores. 3. The article (not a study) in Scientificamerican does not prove that foods you can buy today contain so little nutrients that you would need supplements. – Jan Aug 22 '16 at 09:04
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    Jan - I clearly said it was an article referencing studies. And, I'm not going to go out and find hundreds of studies to show that more than the RDA for certain vitamins and minerals is more beneficial. For example, the RDA for Vitamin C is 100-200mg, but Coritsol can be lowered with 500mg+, athletes use 2,000mg+ for immune support, 3,000mg for depression reduction, etc. https://examine.com/supplements/vitamin-c/ Examine is a great place to look at all the micros and benefits at any dose, based on studies only. – Milo Martinovich Aug 22 '16 at 15:32
  • Or you can read about all the studies pertaining to Vitamin D and how the RDA is too low to actually provide the many benefits https://examine.com/supplements/vitamin-d/ The list goes on for all the micros, just because their is a RDA for micros doesn't mean that it's the upper limit for benefits. – Milo Martinovich Aug 22 '16 at 15:44
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Several reviews of studies about multivitamin supplements have been done lately, mostly in 2015:

  1. U.S. Preventive Services Task Force - Vitamin, Mineral, and Multivitamin Supplements for the Primary Prevention of Cardiovascular Disease and Cancer: Recommendation Statement

Multivitamins: no recommendation; Single- or paired-nutrient supplements: no recommendation

Evidence on supplementation with multivitamins to reduce the risk of cardiovascular disease or cancer is inadequate, as is the evidence on supplementation with individual vitamins, minerals, or functional pairs. Supplementation with beta carotene or vitamin E does not reduce the risk of cardiovascular disease or cancer.

  1. John Hopkins Medicine - Is There Really Any Benefit to Multivitamins?:

A recent look at multivitamins by Johns Hopkins researchers shows that there’s no proof of benefit, but there is evidence of possible harm from high doses of certain vitamin supplements.

  1. US Department of Agriculture - Dietary Guidelines for Americans 2015-2020:

In some cases, fortified foods and dietary supplements may be useful in providing one or more nutrients that otherwise may be consumed in less-than-recommended amounts.

^^ This last claim is a direct quote from the Guidelines -- it is an unfortunate sentence structure, which can be misleading. What they are saying is that "in some cases, " which is for individuals with inadequate nutrient intake by regular diet (but not for those with adequate intake), supplements may be beneficial.

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Jan
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  • Interesting. The first two sources reached a conclusion that there isn't any benefit of dietary supplements, whereas the third one reached to the contrary? – Prahlad Yeri Aug 20 '16 at 18:11
  • @PrahladYeri No. The Dietary Guidelines say that "in some cases," which means in individuals with inadequate intake from foods, supplements may be useful. You designed your question for individuals with adequate nutrient intake, which therefore need no supplements according to all 3 reviews. I copy-pasted the exact claim from the Guidelines and I must say it sounds misleading. – Jan Aug 20 '16 at 18:15
  • There is also the question of who decides whether the micro-nutrients you consume are adequate or not? (especially concerning for vegetarians). We don't have electronic meters yet that show you have X amounts of Vit-A or Y amounts of Vit-C in your body. Besides, considering the constant environmental degradation going on since millennia, isn't it probable that a lot of people will be falling short of that nutrient adequacy by consuming plant food alone? – Prahlad Yeri Aug 20 '16 at 18:28
  • The Institute of Medicine (IOM) in the US has suggested "Recommended Dietary Allowance" for vitamins and minerals: https://fnic.nal.usda.gov/sites/fnic.nal.usda.gov/files/uploads/RDA_AI_vitamins_elements.pdf . US Department of Agriculture has a huge list of foods with the content of main nutrients: https://ndb.nal.usda.gov/ndb/foods . I believe the authors of the above 3 reviews designed their recommendations with the currently available foods in mind. – Jan Aug 20 '16 at 18:49
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    Note that the abstract for the actual Johns Hopkins study concludes with the absurdly inconclusive, and probably biased, "Although available evidence does not rule out small benefits or harms or large benefits or harms in a small subgroup of the population, we believe that the case is closed— supplementing the diet of well-nourished adults with (most) mineral or vitamin supplements has no clear benefit and might even be harmful." -- The issue really is so up in the air that anybody can pretty much find any data to support any viewpoint. – Jason C Aug 21 '16 at 00:30
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    And you do kinda have to lol at "does not rule out small benefits or harms or large benefits or harms in a small subgroup ... we believe that the case is closed", because http://i.imgur.com/LinOE3w.jpg. – Jason C Aug 21 '16 at 00:33
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One point that has not been explored is the quality of the supplement. It can vary widely regardless of the percentage of each vitamin. The NIH has done extensive testing on whether vitamins and other supplements are beneficial. In this link, it lists 3 independent organizations that test supplements of all kinds. Another issue is whether or not the vitamins are prescribed by a dr. Mine does want me to take them as well as other supplements, so I do on his advice. NIH Dietary Supplements

Debbie D'Amelio
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  • Thanks, this answer brings a lot of new information. You may ask the Doc what exactly is lacking in your usual vegetarian/non-vegetarian diet for which you should take the supplements, and also whether there are any studies that show any concrete evidence for the efficacy of the supplements? – Prahlad Yeri Aug 23 '16 at 21:16
  • I always do and I know and agree. – Debbie D'Amelio Aug 24 '16 at 18:29