Many people like to take magnesium at night to promote a sense of calm and support muscle relaxation. However, Erin Stokes, North Dakota, recommends not taking it at the same time as your multivitamin, as it may interfere with the absorption of the smaller minerals found in the multivitamin complex, such as iron and zinc. In addition, he suggests avoiding taking calcium, magnesium or zinc together, as they will “compete for absorption”. These three minerals are common additions to multivitamin supplements that promote the “one-a-day comprehensive philosophy.” The problem with taking magnesium, zinc and calcium together is that they all try to be absorbed by the body in the same way.
They compete and, in that competition, a significant part of each mineral can be lost. Foods that are rich in vitamin A should only be eaten once a week to avoid overeating them. Vitamin E supplements of more than 800 IU can interfere with blood clotting and cause blood to be thinner. Calcium and vitamin D are commonly recommended as tandem supplements because of their beneficial role in bone health.
Studies show that taking these two supplements at the same time can reduce the amount of vitamin B-12 you get. It is not recommended to take any individual mineral at the same time as an MVM or an antioxidant vitamin formula, such as one containing beta-carotene and lycopene. It is important to talk to your doctor to check your vitamin levels before adding any supplements to your regimen. It is possible to build up an unnecessary excess of fat-soluble vitamins, so if you think you're getting enough vitamins A, E, D and K from your diet, you don't need to eat more.
Vitamin B12 helps convert food into energy, helps the body produce red blood cells, and is necessary for the healthy functioning of the nervous system. Unless specifically directed by a doctor, taking individual vitamin or mineral supplements is usually not a good idea. For example, multivitamins try to adjust the amounts of certain vitamins to promote maximum absorption and reduce the chance of a counterproductive interaction between vitamins and minerals, but this is not always the case. Taking a multivitamin that includes niacin or vitamin B3 is generally safe in combination with other nutrients.