The combination of supplements does not normally interfere with their functioning and, in some cases, may be beneficial; for example, vitamin C helps the absorption of iron. Science shows that taking a lot of supplements doesn't seem to have real health benefits and, in some situations, could be harmful. However, in moderation, some supplements may be recommended if those vitamins or minerals are lacking in your diet. People who eat a lot of nutrient-rich foods live longer and healthier lives, so enjoy lots of fruits, vegetables and whole grains and talk to a healthcare provider if you're not sure if taking supplements would benefit you.
If there are no known interactions between vitamins, it's OK to take multiple vitamins at once, Litt says. If you're not sure if there's an interaction, contact your healthcare provider. For example, if you take your multivitamin first thing in the morning, try to do it every day to maintain consistency. This is because vitamin D is a fat-soluble vitamin that is best absorbed with food, while B-12 is a water-soluble vitamin that should be taken on an empty stomach.
According to Dr. Kitchin, he also recommended calcium and vitamin D supplements to some patients at risk of osteoporosis, but he always analyzes their diet first before prescribing them. Sean Ormond, a doctor specializing in interventional pain at Atlas Pain Specialists in Phoenix, Arizona, fat-soluble vitamins are stored in the body's liver, fat and muscles and must be taken with fat from a meal for the body to better absorb and use them. Research indicates that the two fat-soluble vitamins (vitamin D and vitamin K) work synergistically to ensure that bones absorb calcium instead of accumulating in the arteries.
That said, Kitchin said that a multivitamin can help compensate for some deficiencies in a person's diet, especially if they avoid certain food groups such as meat or dairy products. Scientists know that people who eat a lot of vitamin and mineral-rich foods tend to live longer and healthier lives. While measuring serum levels of several vitamins is widely available, testing for deficiencies is often unnecessary. If you're taking a multivitamin complex that contains 5000 IU, in addition to including foods fortified with A in your diet and foods that contain vitamin A, you're probably fine.
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. A couple of years ago, the Institute of Medicine published a report in which it listed the maximum level of tolerable intake of all vitamins and minerals, the maximum safe amount that anyone should take. Vitamin K1, or phylloquinone, is found in dark leafy vegetables, while vitamin K2 (menaquinones) is found in fermented and animal foods. David Jenkins also said that, when taken in moderation, most vitamin and mineral supplements cause no harm.
In general, water-soluble vitamins can be taken together without food, and fat-soluble vitamins can be taken together with foods that contain healthy fats.