8 Supplements That Could Be Ruining Your Gut, Experts Warn: High-Dose Antioxidants & More

Supplements are often taken to boost health, provide essential nutrients, or enhance performance. While many of these supplements can offer great benefits, not all supplements are harmless. In fact, certain supplements can disrupt your gut health, causing imbalances in the digestive system. Things such as excessive or high doses of specific vitamins and minerals can irritate the gut lining , affect gut bacteria, and even lead to digestive issues.

We checked in with various health experts to discover eight supplements that you should be cautious about when it comes to your gut. Some of the culprits include iron supplements, calcium supplements, prebiotics , and more . Read on to discover all eight.

1. Iron Supplements

Believe it or not, high doses of iron can irritate the digestive tract, leading to common side effects such as constipation, nausea, and stomach pain.

Although iron is important, Michael O. McKinney, MD from Healthy Outlook, says large amounts of it can "lead to an altered flora in the digestive system. Intake of large amounts of iron may promote the growth of pathogenic bacteria, thus resulting in upset stomach, constipation, bloating, and inflammation."

2. Calcium Carbonate

Another supplement to take cautiously is calcium supplements. Best known for its bone health benefits, they can also cause constipation, bloating, and gas , as they can slow down the digestive process.

McKinney elaborates on this and notes that "calcium is an essential element for the development of bones; however, calcium carbonate supplements produce a constipating effect and may be uncomfortable in the digestive system. This type of calcium is less soluble and may bring disturbances in the intestines, so it becomes difficult for the digestive tract to become healthy."

3. Magnesium Supplements

Magnesium supplements, especially in higher doses or specific forms like magnesium oxide, can mess up gut health by causing digestive issues such as diarrhea, cramping, and bloating. This could happen because magnesium acts as a laxative by drawing water into the intestines, leading to loose stools and dehydration if taken in excess.

"Too much consumption of magnesium can lead to a laxative effect, causing diarrhea. This can cause an imbalance in the natural gut flora and irritate the gastrointestinal tract, leading to discomfort and disrupting digestive health," says Dr. Kubanych Takyrbashev, MD, Health & Wellness Advisor at NAO .

4. High-dose antioxidants

While antioxidants are generally beneficial in moderate amounts, excessive intake can upset the delicate equilibrium of free radicals and antioxidants in the body.

Dr. Kevin Huffman, CEO & Founder of Ambari Nutrition , sheds more light on this and notes that you should "beware of high-dose antioxidants [because] beta-carotene and high-dose vitamin E supplements might sound harmless, but studies suggest that they can upset the equilibrium of gut bacteria. High doses of beta-carotene appear to increase lung cancer risk in smokers, while high-dose vitamin E supplements have been linked to increased bleeding risk."

5. Prebiotics

Prebiotics are another example of avoiding things in excess even if they benefit your gut microbiome. While generally beneficial for gut health, they can cause problems when taken in excess or in the wrong form for certain individuals. Prebiotics serve as food for beneficial gut bacteria, but overloading the gut with them can lead to excessive fermentation, resulting in, you guessed it, bloating, gas, and discomfort.

Huffman says you should avoid this supplement if you already have gut issues, and "for people with irritable bowel syndrome (IBS), for example, prebiotics can make bloating and gas worse."

6. Multivitamins with excessive zinc

High doses of zinc are another one that can irritate the stomach lining, which in turn leads to discomfort and digestive upset. Too much zinc intake may also disrupt the balance of gut bacteria, potentially harming the beneficial microbes that support digestion and overall gut health.

McKinney states, "It also said zinc forms an important part of the immune system but is toxic in excess; this interferes with the gut lining, making it irritated and inflamed. It also results in an imbalance of the bacteria levels in the stomach, causing digestive issues when taking too much of this metal."

To avoid this, it's important to stick to recommended zinc levels and talk to a healthcare professional before taking high-dose multivitamins.

7. Fish oil supplements

Perhaps one of the most popular supplements on the market, fish oil supplements, while beneficial for heart health and inflammation, can negatively impact your gut when taken in excess or in low-quality forms. High doses of fish oil can cause GI issues such as diarrhea, nausea, bloating, and indigestion. Furthermore, the high fat content in fish oil can be difficult to digest for some individuals, leading to these symptoms.

"I've seen individuals complain of gastrointestinal problems like bloating, acid reflux, and diarrhea after taking large amounts of fish oil. Fish oil supplements can trigger an imbalance in the gut microbiota if not taken in moderation," Takyrbashev reveals.

8. Unregulated weight loss supplements

Weight loss supplements can seem like a convenient and easy way to reach your fat loss goals , but it’s extremely important to be careful with them. These supplements promise many things but can harm your gut in several ways, particularly those containing harsh ingredients like stimulants, laxatives, or unregulated compounds.

Some weight loss supplements can cause rapid and unhealthy changes in gut function, which negatively affects nutrient absorption and leads to gut inflammation and irritation.

Another thing to consider is the lack of regulation in the supplement industry. This increases the risk of consuming harmful additives or contaminants, further compromising your gut state.

Huffman adds, "Avoid weight loss supplements that are not regulated. A few may contain ingredients that aren’t labeled and could negatively impact gut health. Stick with the reputable brands and, due to their potency, consult your doctor before beginning any new supplement, especially if you have diabetes or are following a bariatric diet plan."

For safer weight management, it's a better idea to focus on balanced nutrition and regular exercise rather than relying on supplements.