Why the gut needs balance
Our digestive tract is not just a tube that food passes through. There lives a huge world of bacteria, fungi, and other microorganisms, which together interact happily (or sometimes less happily). Experts often call this the gut microbiota (microorganisms living in a specific environment). When we take supplements, especially in large amounts, this balance can be disrupted, leading to problems such as bloating, gas, discomfort, and sometimes even constipation or increased sensitivity.
Research has shown that diet and supplements strongly affect the composition of the microbiota. For example: a 2021 literature review showed that nutrients such as vitamins and minerals influence the microbiota and digestive health. Be very careful with some of them ...
- Iron supplements
Iron (Fe) is a mineral that is crucial for the body. It helps carry oxygen and provides energy. But if we take it in large amounts, our gut can experience less friendly conditions. Research from 2020 showed that high doses of iron affect the composition of the microbiota. They reduce beneficial bacteria such as Faecalibacterium and Akkermansia, while increasing those associated with inflammation.
So if you take iron without a real need (for example, if you do not have a diagnosed deficiency), you can cause an overgrowth of less friendly bacteria, leading to bloating, discomfort, and even constipation. Experts emphasize that larger amounts of iron can change the gut flora and enable the growth of harmful bacteria.
What to do?
If you do not have a confirmed need for extra iron (with lab results), it's better to rely on foods such as red meat, legumes, leafy green vegetables ... - Magnesium supplements
Magnesium (Mg) is also a very useful mineral. It is involved in muscle function, sleep, and relaxation. But be careful! If you take it in very large amounts or in a form that is poorly absorbed (such as magnesium oxide), you can experience excessive effects, including diarrhea, cramps, bloating ...
Although many studies about digestion and magnesium don't offer conclusive results, many articles warn that magnesium supplements in high doses act as a laxative (a laxative is a product that causes bowel movements). A report from spring 2025 even states that excessive magnesium intake can cause digestive disorders.
What to do?
If you take magnesium, choose a form with high absorption (for example: citrate, glycinate), and do not overdo the dose unnecessarily. You can find it in food in nuts, seeds, legumes. - Calcium carbonate
Calcium is known as the bone mineral. But many supplements offer it as calcium carbonate, which is harder for the body to break down, meaning it is less soluble. This also means it works slower and this slowness can mean that the abdominal or gut area works longer, which can lead to difficult digestion, bloating, gas, and constipation.
Research from 2022 showed that the composition of the microbiota also affects calcium balance. This determines how calcium is absorbed and used. In terms of supplements, this means: if you take calcium, make sure it's in a form that absorbs well (for example: citrate) and do not overdo it on the quantity.
What to do?
Rather, get enough calcium from food. It is most abundant in dairy products, dark leafy greens, legumes ... Always consider first whether you really need calcium. - Antioxidants in high doses
Antioxidants are substances that help the body fight free radicals (these are molecules that can damage cells). That's why people often think more is better. In reality, it's just the opposite. Studies show that high amounts of antioxidants can disrupt the balance between oxidation and reduction (these are bodily processes where electrons are transferred).
In concentrated form, such as strong doses of vitamins C, E, A, they can disrupt the normal function of the gut microbiota and consequently cause more harm. Unfortunately, for specific studies on the gut, there is not much detailed data, but experts warn that antioxidant supplements are not always risk-free.
What to do?
Instead of taking large doses of antioxidants, rather choose foods rich in them, such as berries, nuts, vegetables ... Only use supplements if they are truly needed. - Probiotics
Probiotics are good bacteria that should help the gut. But be careful! If you take them without a real need or too much, you can experience the opposite effect. Excessive fermentation (meaning that bacteria break down substances and produce gas) causes bloating and discomfort.
Research from 2022 states that taking probiotics often has no effect on the composition of the microbiota, and among people with disease, such as irritable bowel syndrome (IBS—inflammation, cramps, changed digestion), probiotics can even worsen symptoms.
What to do?
If you are considering probiotics, first consult with a doctor or nutritionist. Ensure a natural intake of good bacteria through foods like sauerkraut, yogurt, kefir, fermented vegetables ...
Why we highlight the problem of overusing dietary supplements
Between 2020 and 2025, there has been a noticeable increase in interest in all types of supplements. People are increasingly looking for quick fixes, even for gut health. At the same time, the number of studies warning that supplements are not always safe has also grown, and taking more of them does not mean better health.
For example, an article in Verywell Health from 2024 warns that people take supplements without regulation (in the USA more than 50% of adults use dietary supplements) and it is essential to emphasize the approach of food first, then supplement.
For a homemade and cheap solution, at least regarding gut health, we have very good options without expensive supplements:
- Eat natural foods high in fiber (around 30 grams or more per day).
- Enjoy fermented foods (sauerkraut, kefir), which support the balance of the microbiota without supplement capsules.
- Be moderate with supplements and only use them if you have a confirmed need.
- If you do take supplements, first check if you really need them and stick to dosing instructions.
- And finally, most importantly: sleep enough, be active, move a lot ... Even sleep disturbances and poor physical activity negatively affect gut function.
To conclude
If you thought supplements were always safe, at least be cautious with these 5 supplements (iron, magnesium, calcium carbonate, high doses of antioxidants, probiotics). When taken incorrectly, they can greatly harm your gut, and problems can appear almost immediately. Compromises with the microbiota, bloating, discomfort are very real.
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