Vitamins are essential for our health, but taking too many can be dangerous. Any ingredient in a multivitamin supplement can be toxic in large quantities, and the most serious risks come from iron or calcium. High or toxic doses of calcium, vitamin D, and vitamin A can cause nausea, diarrhea, and stomach cramps. Excess selenium can lead to hair loss, gastrointestinal disorders, fatigue, and mild nerve damage. It's important to understand the difference between water-soluble and fat-soluble vitamins.
Water-soluble vitamins are less likely to cause harm since they can be removed from the system with water, while fat-soluble vitamins are slowly absorbed and stored longer. Unless you exercise all the time and use up those fat stores, you're more likely to build up toxic levels. You may have seen tips on which vitamins can help us achieve certain health goals. For example, there are vitamins to increase energy and others that help hair growth. While vitamins are beneficial for our health, it's important to remember that too much of a good thing can be bad.
Some vitamins can build up in the system and cause unwanted side effects such as nausea and headaches. Vitamin A is important for vision, cell division, immunity and growth. It also has natural antioxidant properties that may provide cellular protection. However, it is fat-soluble so it can cause toxicity problems. Studies have linked excessive levels of iron stored in the body to an increased risk of heart disease, cancer and type 2 diabetes.
It can also increase the risk of death and lung-related problems in people who have a history of smoking, especially in women who smoke. Supplements such as fish oil and garlic may increase the risk of bleeding in people who take warfarin (Coumadin) or aspirin, or anticoagulant supplements such as ginkgo, policosanol and high doses of vitamin E. ConsumerLab tests have revealed that many vitamin supplements contain much more (or less) amount of a vitamin than what appears on labels, which could increase the risk of toxicity. To partially offset these risks, it is generally considered advisable to take copper at a dose of 1 to 3 mg per day when taking doses of zinc higher than the UL in the long term.