Vitamins are substances your body requires in small doses in order to function and remain healthy. While most vitamins can be obtained through diet alone, some individuals require additional supplements as part of their health regimen.
Multivitamins typically provide the Recommended Dietary Allowances (RDAs) of various vitamins and minerals. When choosing a multivitamin supplement, look for one with the United States Pharmacopeia seal to verify it contains what it promises on its label.
Vitamin A
Vitamin A is an essential fat-soluble vitamin essential for overall body health. It aids in keeping the skin, eyes and immune system functioning optimally as well as playing a crucial role in cell division and reproduction.
Vitamin A should be obtained through food sources when possible; however, when this isn’t sufficient, taking dietary supplements may provide enough Vitamin A.
Vitamin A comes in two forms, preformed (retinol) and proformed (carotenoids). Animal products contain preformed vitamin A while plant foods provide proformed versions which your body then converts to retinol. High doses of preformed vitamin A can be toxic; however, for adults the acceptable upper intake level is relatively low.
Vitamin C
Vitamin C is an antioxidant that supports your natural defenses while helping reduce inflammation, potentially decreasing risk for chronic conditions like heart disease. (2)
This water-soluble vitamin can be found in many food items, including citrus fruits, strawberries, kiwi fruit, cantaloupe tomatoes and leafy vegetables. As vitamin C cannot be stored by our bodies it is vital that enough of it be consumed in our daily diet in order to stay healthy.
Clinical studies have not proven that taking vitamin C supplements reduce cardiovascular disease or mortality; however, it may help shorten duration and alleviate symptoms associated with colds. High doses may interact with certain cancer treatments such as chemotherapy and radiation therapy therapies.
Vitamin D
Vitamin D is an essential nutrient, essential to bone health. Studies have also demonstrated its effect on blood pressure reduction, intestinal health promotion and cancer prevention. At recommended dosage levels, vitamin D does not produce adverse side effects; however taking too much can result in elevated 25(OH)D levels which cause nausea, vomiting, confusion and excessive thirst.
Observational studies have not consistently established that vitamin D supplementation reduces cancer incidence; however, the VITAL clinical trial demonstrated a 13% decline in cancer mortality rates among participants with adequate or higher serum 25(OH)D concentration [132].
Vitamin D can be purchased as a dietary supplement and produced endogenously when UV rays reach the skin. In addition, certain foods and fortified dairy products also contain it.
Vitamin E
Vitamin E is an essential nutrient for maintaining a strong immune system and healthy eyes and skin. With antioxidant properties to defend cells from free radical damage caused by free radicals, Vitamin E also offers vital protection.
Research has also demonstrated the efficacy of vitamin E as a means of lowering cholesterol and avoiding high blood pressure, as well as protecting eye health by helping prevent age-related macular degeneration and cataract formation.
Studies have found that taking large doses of vitamin E (over 2,000 IU/day of synthetic d-alpha tocopherol) may increase your risk for heart disease and death; thus it should not be supplemented for healthy individuals who do not already have cardiovascular diseases.
Vitamin K
Vitamin K is essential for blood clotting and bone strengthening, as well as helping prevent blood clots that could block arteries.
Vitamin K1 (phylloquinone) can be found mainly in plant foods and is absorbed through digestion; bacteria produce vitamin K2 (menaquinone). The RDA for vitamin K per day is 120 micrograms.
One small clinical trial linked high phylloquinone intake with reduced hip fracture risk among women, but more research needs to be conducted on this correlation and to see whether vitamin K helps protect coronary heart disease risks by making arteries less likely to harden. Unfortunately, vitamin K interacts with certain medications including warfarin (Coumadin). Therefore it’s advisable to check with your healthcare provider before taking supplements containing vitamin K.
Vitamin B
The B-complex vitamins include eight water-soluble vitamins that cannot be stored by your body, so they must be consumed on a regular basis as part of a healthy diet. They include thiamine, riboflavin, pantothenic acid, niacin, biotin pyridoxine and folic acid (vitamin B12).
Vitamin B12 is the hero of this group – it plays a pivotal role in producing red blood cells and DNA as well as being essential to brain functioning.
According to Wick, food-based B vitamin intake is generally better than taking supplements unless a doctor or dietitian has identified an actual deficiency, because some B-group vitamins can interact negatively with medications and cause side effects if overdosed.
