Combining several supplements or taking doses higher than recommended may increase the risk of them causing harm. Most people don't need to take vitamin supplements and can get all the vitamins and minerals they need if they eat a healthy, balanced diet. However, it's surprisingly easy to overdo it. Any ingredient in a multivitamin supplement can be toxic in large quantities, but the most serious risk comes from iron or calcium.
Omega-3 pills and antioxidants are believed to reduce the risk of heart disease and cancer respectively, and millions of women take calcium to protect their bones. However, recent evidence casts doubt on whether these supplements are as safe or effective as they are supposed to be. Most people can get enough omega-3s by eating fatty fish at least twice a week. The American Heart Association says that people who have coronary artery disease may want to talk to their doctor about taking omega-3 supplements. Data from the National Health and Nutrition Examination Survey (NHANES) indicate that people can continue to consume supplements.
Vitamins A and D can cause symptoms when you take large doses every day but a single large dose of these vitamins is rarely harmful. Even if none of the supplements separately exceeds the maximum limit for a given nutrient combining several pills such as a multivitamin and an additional vitamin D capsule for example can result in higher doses than recommended. Science shows that taking a lot of supplements doesn't seem to have real health benefits and in some situations could be harmful. Based on current evidence vitamins C and E have not been found to protect people from cancer; vitamin E beta-carotene and vitamin C do not appear to protect against cancer or death from it; selenium does not prevent prostate cancer; and there is no convincing evidence that beta-carotene or vitamin A C or E supplements prevent gastrointestinal cancers. Large clinical trials have repeatedly shown that multivitamins do not improve the health of the average person. If you're exposed to the sun at noon during the warmer months and regularly eat foods rich in vitamin D such as fatty fish eggs and fortified dairy products you probably don't need to take a supplement.
The reports alone don't prove that the supplements caused the problems but the raw numbers are a cause for concern. David Jenkins also said that when taken in moderation most vitamin and mineral supplements cause no harm. Kitchin also recommended calcium and vitamin D supplements to some patients at risk of osteoporosis but he always analyzes their diet first before prescribing them. Some population groups are at greater risk of not getting enough vitamin D and are recommended to take a supplement every day of the year. There is some evidence that 200 milligrams or more of vitamin C a day may improve cold symptoms in smokers and older people although they won't prevent colds. In conclusion, it is important to remember that while taking more than one type of vitamin supplement in a week is generally safe, it is important to be aware of potential interactions between different types of vitamins, as well as potential risks associated with taking too much of any one type of supplement. It is also important to remember that most people can get all the vitamins and minerals they need through their diet, so it is best to consult with your doctor before taking any type of supplement.
