Taking different vitamin capsules at a time may or may not be safe, depending on a number of factors. The exact formulation of the capsule, how it is made, and your dietary intake all can affect how the body uses and reacts to the vitamins. Your current medical status also matters, as this sometimes means that other treatments you may be using will interact with the capsule ingredients.
RDAs and Vitamin Use
In conjunction with medical professionals, agencies such as the U.S. Food and Drug Administration (FDA) set daily recommended allowances (RDAs) for how much of each vitamin a person should get each day. Manufacturers explain how close their products come to these RDAs through percentages, such as 35% of the RDA. These numbers are supposed to help individuals figure out whether their vitamin and overall nutritional intake is sufficient.
When capsules are formulated with more than one ingredient — as multivitamins are — you might exceed some RDAs if you take more than one because of varying manufacturer formulations. For instance, one multivitamin might pair vitamin D and K, while another might combine vitamin D and calcium. If a person took both capsules, he would get vitamin D from both products and might exceed the recommended daily allowance. To control this “doubling,” many people safely take different vitamin capsules with only one ingredient, such as one capsule of vitamin E and one of C.
Even though individuals who take more than one multivitamin may exceed RDAs, this is not necessarily a problem, depending on the exact vitamins involved. The body cannot always break down a vitamin completely, and if the vitamin is water soluble, some of what you take typically ends up excreted in your urine. Manufacturers compensate for this by formulating the capsule with higher vitamin percentages when necessary, with some ingredients exceeding 100% of the RDA.
Another consideration that makes it hard to figure out if taking different vitamin capsules at a time is safe is that RDA values are not an exact science. They are based on the bare minimums a person needs to prevent certain diseases, such as scurvy, which is caused by a lack of vitamin C. For your best health and body function, you might need to get much more than this minimum amount.
The Influence of Diet
The foods you eat naturally provide some vitamins. If you eat an orange every morning for breakfast, you'll get a daily dose of vitamin C, for instance. You might not need as much from a vitamin capsule to meet the RDA as a result. Consider not only how the capsules repeat ingredients, but also how much the ingredients appear again in your everyday snacks, meals, and beverages.
Making the matter more complex is the fact that different vitamins are best taken with certain foods, and that some cause problems with the absorption of each other. For instance, vitamins D, A, and E are all fat soluble, so it’s best to take them with a meal that has some fat in it, which makes it easier for your body to use them. You won’t always reap the full benefit of all the capsules you take unless you knows how the foods you eat react with each ingredient. Most people do not study nutrition to the degree that they are able to put interaction principles into practice, although many individuals who take vitamin capsules do make an effort to keep their diet balanced.
Although you might be able to take different vitamins in conjunction with a healthy diet with no harmful effects, quality is a concern. Some studies have found that many products have compositions that are different from what manufacturers advertise. A vitamin capsule might say it has 75% of the RDA for vitamin K, for example, when in fact it contains 90%. An even greater worry may be contaminants, such as lead, that may be in products. The more vitamin capsules you take, the more at risk you are for ingesting more contaminants, or contaminants at higher levels.
Certain medications can interact with or devalue vitamins. Retinoids are chemically similar to vitamin A, for instance, and are a common prescription for psoriasis. Too much vitamin A can be toxic, so medical professionals often tell people on retinoids to watch the amount of this vitamin that they get from other sources. Individuals who normally could take more than one vitamin might not be able to do so if they develop a medical condition that requires a certain prescription, so it’s always advisable to tell your healthcare provider what vitamins and supplements you take.