Evidence for Supplements

Information is Beautiful have produced an infographic on the scientific status of popular food supplements. As there is lots of talk of supplements on this forum, people here might find it interesting.

Seems like the person who put it together, David McCandless, is relatively well respected. So its probably accurate.


I find that a bit confusing and difficult on the eyes, because it’s too visually crowded and things appear multiple times.

If someone is genuinely interested in nutrition, including supplements, I think it’s good to try to find credible authors and read their books. Patrick Holford seems to know his stuff, however he does sell his own brand of supplements so he could be a bit biased. One author I really like is Andrew W Saul because he doesn’t sell any supplements or endorse any particular brand of supplements, so his advice is less likely to be biased.

One thing to stay away from is hypey newspaper articles, both in terms of positive or negative stories. As we all know, newspapers tend to jump on anything and blow it up out of all proportion just to sell papers or get clicks on articles.

When I was listening to a podcast featuring Julian, one of the interviewers made a good point about the placebo effect. He said that even if something achieves its effect via placebo, that’s still a positive effect. I do meditation most days, and I’m pretty sure it makes me feel better. It could just be that I’m expecting it to make me feel better, but it doesn’t actually matter.

The problem occurs when people try to use homeopathy to treat cancer. That’s when things become dangerous.

While I agree that reading a book is the best way to get a deeper knowledge of something, its not practical to be an expert in everything. Trustworthy summaries help patch the weaker parts of our understanding.

Also, did you notice you can filter for health condition or for supplement type? Some supplements are considered for more than one condition, hence, as you noted, they appear twice.

Thanks, yes, that does help to narrow it with the criteria on the right.

I understand what you are saying. However, it’s possible to read a book which gives a general overview of nutrition, such as Patrick Holford’s Optimum Nutrition Bible. I know that not everyone wants to do that, though.

Information on the chart about vitamin C contradicts what Patrick Holford says in his books, as well as what Andrew W Saul says in his book on Vitamin C. I personally find that megadoses of C are great as a preventative measure. I almost never get ill at all these days, whereas I did used to, even with a healthy diet (including juicing). I’ve had situations where everyone in my office has gotten ill except me, whereas I know I would have gotten ill before. Last winter, the two people I live with both got the flu and it didn’t even touch me at all. I know that my experience is not a scientific study, though, so I can’t 100% prove it was the C.

This chart seems to think that vitamin C is of some use - just not a lot.

This is the study they are summarising.

I don’t have access to either of the books you mention, but I would be intrigued to know what their analysis of vitamin C is? Would you summarise for me please?

In that study they only gave them 200mg of Vitamin C. This is nowhere near enough! To prevent or cure a cold, you need a lot more than that, well into multiple grams.

The therapeutic effects of vitamin C are all about reaching bowel tolerance. This level varies according to the severity of the illness your body is fighting, and is also different from person to person. So if someone has an infection, the plan is to take lots of vitamin C frequently throughout the day until gas or loose bowels start to occur, then to cut back. Frequent doses are needed throughout the day in such a situation because vitamin C is water soluble so it only stays in the body for a few hours; so taking frequent high doses keeps the blood level of it elevated.

To give people with colds only 200mg of Vitamin C and say it has no effect on treating colds is a bit like giving someone only 1 scoop per day of Huel and then claiming Huel doesn’t stop people getting hungry. Or it’s a bit like giving thirsty people only a tiny shot glass of water per day and then concluding that water doesn’t get rid of your thirst.

Did you know that many other animals actually have the ability to make their own vitamin C? Their bodies make the equivalent of multiple grams of it per day in terms of body weight. There is a theory that many years ago our ancestors also had this ability, but lost the ability due a mutation, an evolutionary mistake. We lost the enzyme that converts glucose into ascorbic acid. Perhaps we needed the glucose for energy more than we needed the vitaminc C, who knows.


In that study they only gave them 200mg of Vitamin C. This is nowhere near enough! To prevent or cure a cold, you need a lot more than that, well into multiple grams.

I have two points:

  1. I don’t believe there’s any credible evidence that vitamin C can cure a cold. There may be some limited or poor-quality evidence for it shortening the time for which one feels symptoms, however, depending on your lifestyle. Can you provide any sources for the claim?

  2. The human body can absorb less than 500mg into blood within a 24 hour period. As it’s water-soluble, you’ll urinate the rest (and could well give yourself kidney stones due to that much oxalate passing through), so - as far as I understand - ‘megadoses’ are not only pointless, but potentially dangerous.

I’d love to see some sources to explain why multiple grams per day can have some sort of benefit when we can only absorb a fraction of that, as it seems implausible to me.


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I recommend the book Vitamin C: The Real Story by Steve Hickey, Phd, and Andrew W. Saul, Phd. I also recommend the book The Optimum Nutrition Bible by Patrick Holford.

However, I realise those books cost money and take time to read, so if you want free information on the topic, I recommend searching the web for online information by Andrew W. Saul and/or Patrick Holford. Both have a lot of experience in nutrition and really know their stuff. One great thing about Andrew Saul, though, is that he doesn’t sell or even endorse any particular brands of supplements, so his advice is unbiased and therefore just based on his research and experiences.

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Better call Saul.


Thanks, but I was after any actual evidence there may be for the claim - meta-analyses, cohort or cross-sectional studies, etc…

Everyone is biased, including you and me. For any given number of books making assertions, I can doubtless find you an equal number of books asserting the exact opposite - each sounding perfectly logical and reasonable on their own merits. Everyone is biased - authors want to sell books; bloggers want to sell page clicks; and everyone has their own cognitive biases based on the position they have adopted, whether or not they are trying to sell something. Books and blogs asserting a disprovable claim aren’t worth the paper they’re written on unless they present cited, referenced, replicable evidence of the assertion in question - and the current scientific consensus is that it is not possible to cure rhinovirus (the common cold).

I have read some of Patrick Holford’s stuff - I disagree with most of what he says.

Sorry, I don’t have any individual studies to hand. My position was based on what I have read from those nutritionists, combined with my own experiences of following their advice.

I’ve gone down this route and it seems to be working for me in terms of how little I get ill now compared to previously. I can’t 100% prove that my own experiences are anything more than placebo. But we make choices in life based on the information we come across and the experiences we have.

I understand my anecdotal experience is not convincing to another person, though. I can only apologise for letting you down in your search for the truth.

Okay, fair point. So it’s better to say that Andrew Saul is perhaps less biased than Patrick Holford because he’s not connected to any particular products, other than his books. And I take your point that everyone is biased to some extent because that’s how the mind works. I agree with that. [quote=“logicelf, post:10, topic:3117”]
and the current scientific consensus is that it is not possible to cure rhinovirus (the common cold).

But it’s possible that this scientific consensus may have been reached by using too low a dose in the studies. In the study that Quidditch provided a link to above, they only used 0.2g. That dose is far too low. If the claim is that 0.2g doesn’t do anything to prevent of hasten the end of a cold, then I’m in complete agreement and so is probably Andrew Saul and Patrick Holford (as well as most other nutrition experts).

But that’s not what the claim is.

Proponents of vitamin C therapy recommend far higher doses, but because the body can only hold so much as any one time, it needs to be split into multiple doses throughout the day.

Okay, thanks. I’d be tempted to agree on the issue of dose, except we already dealt with that (much more than 200mg is pointless, as the body just can’t absorb it).

It’s all very interesting, but I see nothing to counter the current consensus based on the data to date. If you feel that it works for you, that’s great. Thanks for getting back to me, anyway.

How can vitamin C enter urine without being absorbed into the blood?

It may or may not be urinated out but until you start getting diarreah (indicating no further absorbtion of the vitamin c solution in the stomach) it is surely going into the blood.


Yes, this is the common confusion with vitamin C. People say you just wee it out so it’s not absorbed, but those two things cannot both be true. For a substance to end up in the urine, it has to have been absorbed. The same is true of water. You absorb it, then later urinate it out. But you still needed to absorb it in the first place.

The issue with vitamin C is not lack of absorption, but that it doesn’t stay in the body for long, typically 4 hours.

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