In some cases, supplements can be fantastic additions to your health regimen. They can help fill nutrient gaps in your diet, support a healthy gut and improve your energy levels, or help you get a better night’s sleep. But on the other side of things, it’s important to remember that all supplements come with potential downsides—and some can be especially dangerous when taken in excess. Better Health warns that, “When you artificially remove one [vitamin] and provide it completely out of context, it may not be as effective and, in the case of some vitamins, can have negative effects.”
We spoke to health experts Dr. Michael Lahey, physician from My Weight Loss Partner, and Dietitian Krutika Nanavati to learn about a few potentially dangerous supplements that you should take with caution. They warned against vitamin B6, iron, and calcium. Learn about the risks of each below.
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1. Excessive Vitamin B6 Could Lead To Nerve Damage
Nanavati cautions that overconsumption may cause damage to the nervous system. “Excessive intake of vitamin B6 can result in nerve damage, leading to symptoms such as numbness and problems with balance. It is important to be mindful of the potential consequences of prolonged overconsumption,” she explains.
Unlike water-soluble vitamins that are usually flushed out easily, high levels of Vitamin B6 can build up in the body when supplements are taken in large amounts over time. This can cause neuropathy, a condition that affects the nerves and may lead to tingling, burning sensations, or difficulty walking. In some cases, the damage may become permanent if not addressed early.
The good news? Vitamin B6 deficiency is rare, and most people can meet their daily needs through a balanced diet. Foods like bananas, chickpeas, salmon, fortified cereals, and poultry naturally contain healthy amounts of this nutrient. Supplements should only be taken if recommended by a healthcare provider, especially since the recommended upper intake limit for adults is about 100 mg per day—far above what a typical diet provides.
2. Iron Supplements Can Irritate Your Stomach
Iron supplements, especially when taken in high doses, are known to irritate the lining of the stomach and intestines. High doses of this supplement can also create oxidative stress, which is linked to increased inflammation.
Lahey says, "Even though iron supplements are essential to people with anemia that results from iron deficiency, taking more than recommended or for a very long time may also affect the stomach, causing side effects such as constipation, nausea, and stomach ulcers. Over-intake of this metal can upset the GI tracts, thus causing friction, or in some extremes, it can lead to ulcers."
Lahey also warns that iron supplements “should never be used together with high doses of vitamin C and that these substances should always be taken with food.”
3. Calcium Supplements Can Harm Your Gut
Calcium supplements have been linked to GI problems such as bloating, constipation, gas, and stomach cramps. This is due to the calcium carbonate, which requires stomach acid for absorption.
"Calcium supplements of any kind, and more so the high calcium supplements, lead to constipation and bloating. Prolonged use of the product also has side effects of calcium accumulated in the body, thus causing inflammation of the kidney and increasing chances of formation of kidney stones and other GI complications," he reveals.
Instead, he recommends taking calcium in the form of foods such as dairy or green vegetables. If supplementation is necessary, “they should be prescribed in appropriate doses and in conjunction with magnesium, which will reduce any gut side effects.”
