Ignite Nutrition
Ignite Nutrition
Search Ignite Nutrition Icon

Supplements and your Gut Microbiome

A smiling woman sitting down to eat a healthy green salad.
Supplements and your Gut Microbiome Featured Image

Gut Microbiota for Health Conference Update 2019 – Post Series 2

We’re on week 2 of the Gut Microbiota for Health conference update. You will be seeing 5 different articles on the Gut Microbiota for Health conference coming to Ignite. Mark your calendars and stay tuned for the following topics:

  1. The low FODMAP diet (last week!)
  2. Supplements (today!) 
  3. Probiotics
  4. Personalized nutrition
  5. Taking care of the gut microbiota

I can’t say this has happened often in my 8-year career of being a dietitian. I’ve completely changed my view on ‘casual supplementation’.

When I say casual supplementation – I mean the casual taking of vitamins, minerals, pills, and potions that are sold to use over the counter. My motto is always food first medication second. We can get all our nutrition from food. EXCEPT vitamin D (in Canada, anyway), in certain disease states (ie. osteopenia), and in certain times in our lives (ie. pregnancy).

Every day I get asked ‘what supplements should I take’.

Generally, I take a close look at how a person eats. If they have any signs or symptoms of deficiency, their medical & laboratory history, and what’s going on in their lives. And I can say, for the average person, my recommendation usually comes in the form of food. Vitamin D being the only supplement we can’t get enough of in Canada.

However, at Ignite Nutrition I’ve had many patients insist they’d rather just take a multivitamin or mineral complex. Or, use powders, pills and potions often sold over the counter or in MLM-style supplement companies. These companies tend to make BIG claims about how their products work, with very little research. While they may not put the claims on the label, I often see them pushed by reps with little or no training in health care.

My messaging had always been – if you feel strongly about taking it, as long as it’s not past the ‘upper level’ for recommended daily intakes, and you understand that likely the biggest impact it’s going to have is on your wallet, then I’m going to let ‘you do you’ – as I (previously) doubted any harm to come from it.

Well – suffice to say – I’ve changed my stance. Unless you have a proven deficiency, or are not able to consume adequate nutrients from the foods in your diet, examples being B12 on a vegan diet, folate pre and during pregnancy, iron if you struggle with heavy menstrual cycles and low iron, vitamin D if you live in Canada, or just a poor diet in general (and more! Often patient/condition/diet dependant) then you should NOT be taking an OTC vitamin/mineral supplement that exceeds the upper limit recommendations. Even if it’s ‘water soluble’ or ‘not likely to cause harm’.

In some remarkable research by Joseph Zackular and colleagues out of the University of Pennsylvania, they’ve begun to assess how a single nutrient in excess may alter the microbiota. Especially at times where you may be more susceptible. Like in infections such as C. Difficile.

They looked at zinc supplementation. Many of us take zinc to fight a cold, for acne, chronic fatigue, concentration, hair loss, weight management – and the list goes on.

The majority of supplements available over the counter provide anywhere from 100-1000% the recommended daily intake for zinc. This doesn’t include what you would get from simply eating food, either!

Why is excess Zn (or any micronutrient) a problem?

Bacteria need minerals, like zinc to multiply. Our body has some incredible innate protection mechanisms. Like the ability to bind extra minerals we aren’t using so that they aren’t available for pathogens (bad bacteria) to use. However, when we exceed the amount our body is able to bind, those pathogenic bacteria, which are all floating around in our GI tracts (but in amounts that aren’t harmful) may have the opportunity to use it. Now. The data is only in animal research, with one micronutrient. But it begs the question – can taking too much of any single micronutrient negatively impact the gut microbiota?

I think there’s the potential that it could be harmful, or certain situations – helpful. But the reality is – we don’t know. We need more research. But I’m comfortable enough saying that mega-dosing on supplements is not only unnecessary – but has potential risks that I hadn’t considered before in my practice recommendations!


  • Mega-dosing or getting above the recommended daily amounts of a particular nutrient is often unnecessary. It may also pose risks we’re not even aware of yet
  • In the case of zinc supplements, excess zinc may increase your risk of C.difficle. Which is a dangerous gut infection that causes diarrhea and inflammation of the colon, and is particularly hard to treat
  • If you have C.diff, or have had C.diff and are at risk of recurrence, checking to ensure you’re not receiving above the upper limits of micronutrients (specifically zinc) may help to reduce risk.
  • Choose food first, when able, to get all your micronutrients.
  • Discuss with your dietitian if you follow a limited diet as to what you may need to supplement!
Andrea Registered Dietitian with Ignite Nutrition here in Calgary, Alberta attended the Gut Microbiota 2019 Conference. Here's her takeaway on supplements and your gut microbiome.


Zackular, J. P., Moore, J. L., Jordan, A. T., Juttukonda, L. J., Noto, M. J., Nicholson, M. R., … & Washington, M. K. (2016). Dietary zinc alters the microbiota and decreases resistance to Clostridium difficile infection. Nature medicine, 22(11), 1330.

Categorized: Gut Health & IBS

Leave a Reply

Your email address will not be published. Required fields are marked *


There are no references available for this article.