Multi-Vitamin-Mineral Supplements: Are they necessary and safe?

Taking nutritional supplements is never a substitute for eating whole foods. Fruits and vegetables are the best sources of the vitamins and minerals our bodies need and most adults should eat seven to nine servings each day. (One serving of fruits and vegetables is one half cup, excluding raw leafy greens like lettuce, which require one cup for one serving.)

However, comparing apples to apples and oranges to oranges, some are more nutritious than others. Foods grown in nutrient-rich soils are rich in nutrients and foods grown in nutrient-poor soils are poor in nutrients. After all, plants cannot absorb what is not in the soil. Nutrient depletion largely results from the use of chemical fertilizers that replenish only three of the many nutrients plants need to thrive. But farmers who use natural fertilizers, grow a variety of plants, and rotate their crops actually enrich and improve the soil. Find these farmers and their nutritious fruits and vegetables at your local farmers’ market or join their CSA (community-supported agriculture).

Another benefit of produce from local farms is fresher food. Because fruits and vegetables begin to lose nutrients as soon as they are picked, those that travel hundreds or thousands of miles between farm and plate usually contain less vitamins than their freshly picked counterparts. Healthy adults eating plenty of local, fresh-picked fruits and vegetables – or those preserved at peak ripeness – and a minimal amount of meat or animal products probably do not need to take a daily multi-vitamin-mineral supplement (MVMS).

For some, MVMS can provide extra insurance that nutritional needs are being met. People who benefit most include adults who do not eat seven to nine servings of fruits and vegetables each day, individuals following vegan diets, growing children, couples who plan to conceive, pregnant and lactating women, and older adults whose ability to assimilate nutrients becomes less efficient with age. Individuals with increased needs for nutrients due to chronic medical conditions or prescription medications may also benefit. If it’s not clear, blood tests can measure levels of vitamins and minerals. They can also be used to track progress after supplementation.

MVMS are not standardized and different products contain different combinations and concentrations of vitamins and minerals. People with special nutritional needs should ask their doctor for recommendations to ensure they are getting exactly what their bodies require.

MVMS come in many forms: tablets, chewable tablets, capsules, gel capsules, and liquids. Tablets can hold more ingredients but may also contain more fillers and binders to keep everything together. Some companies use animal-derived gelatin to encapsulate their formulas, so individuals avoiding animal products should seek supplements with cellulose capsules. For individuals with compromised gastrointestinal function, liquids and gel capsules are often easier to digest and absorb. Liquids, however, usually need to be refrigerated and may have shorter shelf lives.

Minerals are sometimes chelated (bound to an amino acid) to increase absorption. Because chelated minerals take up much more volume than minerals alone, formulas containing chelates often require a larger daily dose, up to eight capsules per day. Forms most easily absorbed include mineral aspartates, citrates, malates and picolinates.

In addition to vitamins and minerals, some MVMS may contain ingredients like omega-3 fatty acids, probiotics (healthy intestinal bacteria), green tea and other herbs. These can be helpful for some people, but not for others. For example, many diets are deficient in omega-3 fats and could benefit from supplementation, but fatty acids found in fish oil can interfere with certain medications and high doses may increase the risk of bleeding in some individuals. Green tea is a powerful antioxidant and has been studied for its protective effects against cancer and other illnesses, but it also contains caffeine that can aggravate certain conditions like ulcers, anxiety and insomnia. Herbal medicines, including those added to MVMS, should only be taken under the guidance of a doctor trained in their use.

Other ingredients may be used in the manufacturing process, like fillers and binders, or added to improve flavor, appearance and palatability (especially in chewable and liquid products). Always read the additional ingredients listed on the label and avoid supplements containing sweeteners, colors and artificial flavors. Sensitive or allergic individuals should check for gluten, dairy, yeast, corn, soy and shellfish.

Because MVMS contain nutrients that require fat for absorption, like calcium and vitamins A, E and D, they should always be taken with food. Food stimulates the secretion of stomach acids, so taking these supplements at mealtimes can also improve the digestion and absorption of nutrients. If you can, spread the dose throughout the day unless directed otherwise.

Because dietary supplements are regarded as food, the United States Food and Drug Administration does not have standards for testing and manufacturers are responsible for determining that the ingredients they use are safe. Consumer Lab, an independent company that tests supplements for safety, found problems with more than 30 percent of products they recently tested. Some MVMS contained too much of some nutrients, too little of others, or dangerous ingredients like lead.

Earlier this year, the Archives of Internal Medicine published a study using data from the Women’s Health Initiative to evaluate potential benefits of supplementation in postmenopausal women. After investigating their use of MVMS, researchers found that the supplements made little or no difference in the women’s risk for common cancers, cardiovascular disease, and death. However, there were no standards set for quality or consumption of MVMS and because the women were not all taking the same supplement, variations existed in the potency of the formulas and the frequency of their use. Benefits of MVMS cannot be dismissed by studies such as this.

High quality MVMS may be expensive, but price isn’t always an indicator of quality. When selecting supplements, choose products that list important information on the label: expiration date, lot number or batch number, name and address of the manufacturer, and scientific name, quantity and part (root, leaf, flower) of any plant ingredient. To ensure that products have been tested by an independent lab and found to contain the ingredients listed on the label, look for brands with seals from Consumer Lab, the United States Pharmacopeia (USP), the National Nutritional Foods Association (NNFA) or National Sanitation Foundation (NSF) International. But keep in mind that such certification does not guarantee the manufacturers started with high quality raw ingredients or tested the supplements in clinical trials. Direct questions like these to the manufacturer or ask a knowledgeable practitioner to recommend trusted brands.