Are Vitamin Supplements Killing Our Gut Bacteria?

We consume all sorts of things before really knowing how they're going to affect us, including probiotics and dietary supplements. But given how preliminary our understanding of our gut bacteria is, it's very likely that some supplements can work in direct opposition of others. For instance, vitamin A might kill a bacteria hypothesised to promote childhood growth.

Image: CDC/Wikimedia Commons

How supplements impact our microbiome is important, not so much for dodos taking fists full of pills to "stay healthy" as for folks suffering from malnutrition, especially in lower-income countries. The World Health Organisation recommends high doses of vitamin A for children in places where vitamin A deficiency is common. But in a new study in mice, a vitamin A deficiency allowed one potentially beneficial species of gut bacteria to flourish. The unanticipated finding demonstrates that health professionals need to think about the gut microbiome when treating cases of malnutrition.

The gut microbiome is simply the slew of bacteria living inside our guts that play a role in our digestion. Problems with the gut microbiome might lead to illnesses like colitis, or Clostridium difficile. Some researchers think a more diverse microbiome -- more species living inside of us -- could be better for our health, or that certain bacteria could have key roles to play.

A team of American researchers has been studying the effects of diet on the microbiome for a while, by raising human bacterial colonies inside mice guts. In their latest experiments, they fed mice normal diets for two weeks, followed by some nutrient-specific diet for three weeks (they tested iron, folate, zinc and vitamin A deficiencies), followed by a return to a normal diet.

Your Crappy Diet Might Leave Your Gut Bacteria Stunted

Adopting a healthy lifestyle might not seem that hard on the outset. You ate a lot of cheeseburgers and drank a lot of soft drink, and now you're going to stop doing that. But a new study in mice suggests that it takes a while for the gut's bacterial zoo, or microbiome, to adapt to dietary changes. If the results hold in humans, it could mean developing a healthy gut is more than a quick diet fix.

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Analysing the mice's poop samples surprised the researchers, who published their results yesterday in the journal Science Translational Medicine. Most surprisingly, less vitamin A meant more of one bacterium, called Bacteroides vulgatus, and vice versa. In a past study, scientists transplanted a healthy microbiome including this bacteria into malnourished mice, and it helped the mice grow more. As a result, researchers have tried to come up with ways to increase B. vulgatus abundance in malnourished patients. But that's going to be hard to do if vitamin A simultaneously decreases the abundance of B. vulgatus.

This is just a single study and in mice, not humans, so it's important not to oversell its results. "It's hard to say that you can directly relate it [to humans], other than to say in the rodent model, alterations of vitamin A in the diet had an effect on the microbiota," Boston University School of Medicine professor Michael Holick told Gizmodo. Holick studies Vitamin D and is looking at its effects on the microbiome, too, but pointed out that this whole area of study is still evolving. And the other nutrients studied had much less pronounced effects on B. vulgatus. Still, Holick felt the study lends evidence to the fact that specific nutrients might be playing a role in shaping the types of bacteria in our guts.

This doesn't mean much for you -- we already knew that you shouldn't take too much vitamin A if you aren't malnourished. But for those who are malnourished, or those trying to feed the malnourished, it's an important element to consider. It's certainly not a good idea to take a supplement that's simultaneously working against the benefits of another one, after all.

[Science Translational Medicine]

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    Yeah gut biomes play a huge role, much more than most people think.

    For most of my life (if not my whole life), I have had chronic fatigue - when I'm extremely tired (i.e., any period where I have been working 15 hours a week, or more) my digestion suffers, making my fatigue worse.

    A couple of years ago I got really sick - which we believe was lyme disease. There were no tests my doctor could do to confirm it, but she gave me a course of anti-biotics for tick related diseases, and my symptoms went away.

    or, so I thought.... I wouldn't say my gut was great before, but since I got really sick my digestion has deteriorated significantly and now if I' not careful what I eat I feel pretty damn bad - rashes, bloating, burping, soft stool/diarrhoea, pain and discomfort, feeling like I constantly need to go to the toilet, etc. plus I end up feeling completely exhausted and get a really foggy head. It just wipes me out completely until it settles again.

    I've lost heaps of weight (considering I didn't have much to loose, it's quite bad), and even more exhausted than I use to be and even lite work drains me in minutes.

    I am working with a naturopath at the moment to fix my gut, and I see merit and can feel a difference when following what I'm supposed to be doing. Sadly, I am finding it extremely hard to cope with due to the compounding effect of this on top of my chronic fatigue. To actually fix it I have to be very strict with my diet, but by doing so I end up 100% exhausted as the only thing that currently seems to help me is sugar, and it is on the 'no-eat' list. :| if I do eat sugar, well I have at least a little bit of energy, but my gut isn't getting better.

    Anyway, yeah I think a LOT of people have some unbalance and don't realise it.

    It is also god damn expensive to get sorted.
    I'm broke as hell, but what choice do I have!?

    Last edited 19/05/17 6:43 pm

      you've my sympathy and my hopes that you crack the secret. Gut biota and epigenetics are really new areas and fortunately the research is in the hands of microbiologists and not doctors, so there's hope that we'll get there sooner rather than later. have you trialed a low carb, high fat diet at all?

      I know what you mean about sugar helping - I've gone 10 days with no food from chronic fatigue coupled with illness, to weak to even chew .. the gut a bilious mess.. and after that sugar (mars bars) was all I could stomach. It also might be worth your while trying (good luck!) to get a doctor to investigate SIBO. I'm trying to have a GP consider it but it's like pulling teeth grrr. I had cameras shoved in both ends and everything was fine, but at that point they want to declare everything hunky dory, completely ignoring the small intestine because 'oh that's not something you need to worry about'.

        Sorry to hear you are having similar issues finding your solution. It really does suck! :(

        I was tested for SIBO (confimred I had it) and that is actually the diet I was talking about. It's pretty much a stricter FODMAP diet + some herbal mix that kills the bacteria that causes it.

        I was referred by a Naturopath, but you actually have to order it yourself from - she just wanted me to do the basic test, but there are a couple more extensive tests too - of course, ideally you want someone with knowledge about SIBO to go over the results.

        The SIBO diet (plus the herbal mix) in particular has helped with my digestion to a degree (but I've not been very strict yet, for reasons not worth mentioning, they are just making it hard to be strict), which in turn does help with some symptoms (again, to a degree). What I mean by that is, it doesn't help with general fatigue, I'm still extremely tired all the time, but it does help relieve (but not get rid of) my other symptoms such as brain fog, dry/itchy rashes, loose bowl movement, and exacerbated fatigue (where I find it hard to do anything but sit around and switch off).

        Obviously it's going to take time for these diets to fix the issues before I actually get better - and as you know, it's super hard to put in MORE effort in for these diets/treatments when you are already struggling to just get by.

        I haven't tried high fat, but I've kept carbs pretty low overall - currently fat and oil makes me feel quite sick and makes all my symptoms quite bad.

        For me, I also find that my fatigue pretty much overrides all the good being done by the diet. If I am pushed into exhaustion (which takes very little), then it doesn't matter how strict I have been eating, the symptoms smash me. :(

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