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There was a comment in this question saying that he was dubious of claims of the Vitamin C benefits of eating an orange. My gut reaction was to respond that Vitamins taken in food are metabolized better than those from a supplement. But I realized I had never seen any real proof of that. I believe this is a fairly common belief, at least among those of us who believe in natural living.

The scenerio I am asking about is this. If I were to take in the vitamin needs for my body through:

A) Naturally occurring (not necessarily organic) foods.

B) Vitamin Supplements

Is there any research to support or refute the belief that the body makes more effective use of the the vitamins from Scenario A than Scenario B.

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    It's not a problem of being metabolized better, a vitamin is a vitamin, whether you take it in a pill or in an orange. The problem is that they may be absorbed differently in the intestine, e.g. due to the presence of other compounds in the fruit. – nico Nov 3 '11 at 19:19
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    @nico - I would include that in the metabolism process. – Chad Nov 3 '11 at 20:28
  • I suspect you're referring to my comment about the Vit.C content of oranges. I did not mean to imply that taking supplement was a good/better idea than eating oranges, simply that there are many natural sources of Vit.C with a much higher concentration of Vit.C. Spinach is a good example. Even so, I think this is a great question. – Flimzy Nov 3 '11 at 21:35
  • contained within a larger mass than a small pill the vitamins might be released more slowly, allowing for a larger percentage of the total dose to be absorbed into the bloodstream before the rest leaves the body as waste. Just applying logic here, no time to look for research into the matter. – jwenting Nov 4 '11 at 12:16
  • My understand was actually that if you consumed (Pulling numbers from darker regions here) 20% RDA of a vitamin in food that it would be used by the body more effectively than a supplement that had 100% RDA of the vitamin. The point of the question was that I realized this belief was based on no rational data. I seem to recall something where vitamins consumed in supplement form were more likely to pass through the digestive tract with out uptake into the metabolic system. But I can not say for sure that it was a study and not a claim from a natural foods sales pitch. – Chad Nov 4 '11 at 12:56
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As far as I can find where Vitamin C is concerned, the controlling factor in how fast it's absorbed is not whether the food is a tablet or an orange, but how much Vitamin C has already been consumed.

The nearest I could find on the subject directly comparing the two is this article saying Orange juice and supplements are equally effective at Reducing Plasma Lipid Peroxidation in Healthy Adult Women http://www.jacn.org/content/22/6/519.full If you look they note that concentrations of Vitamin C in blood remained mostly the same amongst the 2 groups

Objective: To directly examine the contribution of vitamin C to the antioxidant potential of fruits and vegetables, the antioxidant effect of orange juice consumption (8 and 16 fl. oz.) was compared to the antioxidant effect of supplemental vitamin C (dosage equivalent to that supplied by 8 fl. oz. of orange juice).

Methods: Subjects (n = 11; 28.6 ± 2.1 years) received each treatment in a 3 × 3 randomized crossover design, and each two-week treatment was preceded by a two-week washout. During the entire trial, subjects restricted fruit and vegetable consumption to ≤3 servings per day except the vitamin C-rich foods (items containing >20 mg/serving), which were restricted to ≤3 servings per week. A fasting blood sample was collected at the end of each washout and each treatment period.

Results: Following washouts, plasma vitamin C and lipid peroxidation (plasma TBARS) were similar by treatment group and averaged 25.4 ± 3.6 μmol/L and 3.82 ± 0.10 nmol/mL respectively. Plasma vitamin C concentrations were similar following each treatment period, 37.9 ± 8.1, 45.8 ± 9.4, and 38.3 ± 12.4 μmol/L for the 8 and 16 fl. oz. orange juice treatments and the supplement treatment, respectively. All intervention treatments reduced plasma TBARS as compared to pretreatment values: −47% (p = 0.013), −40% (p = 0.083), and −46% (p = 0.015) for the 8 and 16 fl. oz. orange juice treatments and supplement treatment respectively.

Conclusions:These data indicate that the regular consumption of 8 fl. oz. orange juice or supplemental vitamin C (∼70 mg/day) effectively reduced a marker of lipid peroxidation in plasma.

Ofcourse this now relies upon how dependable the study conducted at the Department of Nutrition, Arizona State University East headed by Carol Johnston Phd is.

If you have a choice between a pill and food on a plate, I would advise the food however, as food gives other benefits, the actual act of digestion and satisfaction has other health benefits.

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One of the problems with the question is that it subtly presupposes that vitamin supplementation is good for us. But the evidence that vitamins or other nutritional supplements do anything much at all is weak to non-existent in people who consume a balanced diet and don't suffer specific deficiency diseases. For a good summary with links to the research sources see the Information is Beautiful site's visualisation (indeed one of their more effective ones) of the evidence and internet popularity of a range of vitamins and supplements (and note the lack of relationship between popularity and evidence). Or the existing answer: Should a healthy adult take a daily multi-vitamin?.

So the question is asking us to judge the effectiveness of two forms of something with no demonstrable effectiveness either way (above the baseline nutritional needs). However, there is still a residual claim which I read as relating to bioavailability. So, assuming you choose to think there is a benefit in taking extra vitamins, which way is best for bioavailability?

There is solid science behind the idea that bioavailability or drugs and vitamins are altered by food and by each other. For example, see the BMJ reviews in 1984 and 1981. The first summarises (he counts vitamins as drugs):

When drugs are taken by mouth their bioavailability is determinedly factors in the drug-which include the nature of the molecule, its stability, and the formulation administered- and in the patient-such as a reduced intestinal surface area as a result of coeliac disease or intestinal resection and whether or not the drug is taken with a meal. In addition, drugs may undergo "pre systemic" metabolism in either the intestine, the liver, or, less commonly, the lungs.

So it is perfectly scientifically reasonable to believe that vitamins in foods are differently bioavailable from the same vitamin in pill form. But you could always take the pill with an appropriate meal and get the same effect.

So my summary answer is a qualified maybe. Since few supplements have demonstrable effects, it doesn't much matter how you take them. If that evidence doesn't matter to you and you still want to maximise bioavailability, take your pills with food and there is no good reason to expect a difference.

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    "One of the problems with the question is that it subtly presupposes that vitamin supplementation is good for us" Actually this is the debate I did not want to have. I purposely did not phrase it in such a way. I also am not asking about the benefits of taking in vitamins beyond our needs. And you have no evidence to support the claim "take your pills with food and there is no good reason to expect a difference." which is what the question is asking about. – Chad Nov 7 '11 at 14:13
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    @Chad If you had used the word bio-available rather than effective you would have come closer to a totally neutral question where the issue of effectiveness would be irrelevant. – matt_black Nov 7 '11 at 14:50
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    @Chad I'm not certain whether this is just a language problem but my interpretation of bioavailability is how medics would measure usability. I'm not even sure there is a reasonable way to measure anything if two equal bioavailabilities lead to unequal use. Unless I'm misreading the literature something affecting biological uptake of a drug would be counted as part of the drug's bioavailability rather than as some separate factor. – matt_black Nov 7 '11 at 16:25
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    But the effectiveness would be measured other ways. Maybe increase in white blood cell count, increase in some hormone, etc. – Chad Nov 7 '11 at 16:41
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    @BlueRaja-DannyPflughoeft I think we are reading the references differently. To quote the second "No, you do not need vitamin supplements if you get sufficient levels of vitamins anyway. There is no added benefit to getting more than enough vitamins." And it is hardly off topic if the core issue is measuring benefits or proxies for benefits. – matt_black Nov 7 '11 at 20:19

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