FAQ
What is a multivitamin?
A multivitamin is a supplement that combines several vitamins and often minerals in one product. Large trials in generally healthy adults have produced mixed results on long term health outcomes. Health authorities generally emphasize a varied diet as the main source of nutrients, while recognizing that some groups, such as people with malabsorption conditions or certain dietary patterns, may have particular nutritional needs that are assessed by health professionals.
Are supplements regulated?
In the United States, dietary supplements are regulated as a category of food under the Dietary Supplement Health and Education Act of 1994. Manufacturers are not required to prove safety or efficacy before marketing, and quality varies between products. Independent organizations offer third party testing and certification programs for supplement quality. Rules differ in other countries.
Can all nutrients come from food?
A varied diet of whole foods supplies most nutrients for most people. Some nutrients are naturally scarce in certain diets, for example vitamin B12 is found almost only in animal foods, and some populations are at higher risk of specific deficiencies. Public health measures such as iodized salt and folic acid fortification of flour were introduced to address deficiencies at the population level.
What is the difference between RDA and AI?
The Recommended Dietary Allowance is a reference intake set to meet the needs of nearly all healthy people in a given age and sex group. An Adequate Intake is used when there is not enough evidence to set an RDA and is based on observed intakes of apparently healthy populations. The Tolerable Upper Intake Level is the highest habitual intake considered unlikely to cause harm. These values are designed for planning diets for populations rather than as individual prescriptions.
Are natural vitamins better than synthetic?
For most vitamins, natural and synthetic forms are chemically identical. Exceptions include vitamin E, where the natural d alpha tocopherol form has higher biological activity than the synthetic mixture, and folate, where naturally occurring food folates and synthetic folic acid are absorbed and metabolized differently.
Why does absorption differ between nutrients?
Fat soluble vitamins A, D, E and K are absorbed along with dietary fat in micelles. Iron absorption depends on its form, with heme iron from animal foods absorbed more readily than non heme iron, which is enhanced by vitamin C and inhibited by phytates and polyphenols. Calcium absorption is regulated by vitamin D. Interactions between nutrients and with medicines are one reason individual questions are best discussed with a health professional.