While a daily multivitamin hasn't been proven to guard against chronic disease in well-nourished individuals, there are good reasons why some people should consider taking one.
If you're time-crunched and eat on the go - or you follow a low calorie diet - you might not be getting all the nutrients your body needs for good health. If you're a menstruating female, it can be challenging to consume a day's worth of iron (18 milligrams) from food alone. (Consider than 3 ounces of red meat, one of the best sources, has roughly 3 milligrams of iron.)
Folic acid is another reason why women of childbearing age should take a one-a-day formula. This B vitamin is vital to preventing serious birth defects called neural tube defects (NTDs) in the developing fetus. Women who could become pregnant, who are pregnant, and who are breastfeeding are advised to take a daily multivitamin with 0.4 to 1 milligrams of folic acid.
If you're an older adult, you may not be absorbing enough vitamin B12 from your diet. With age, we produce less stomach acid which is needed to absorb the nutrient from proteins in food. That's why adults over the age of 50 are advised to get B12 from a supplement or fortified foods.
What to look for in a multi
While a multivitamin and mineral can help bridge nutrient gaps, it won't make up for a diet packed with unhealthy fats, refined sugar and sodium. Nor can it deliver the fibre and phytochemicals found in whole plant foods. A multivitamin is meant to reinforce a healthy diet, not replace it.
Here's a list of important nutrients adults should look for - in milligrams (mg), micrograms (mcg) and international units (IU) - and what to avoid:
Vitamin A. You don't need more than 3,300 IU. Look for multis that contain no more than 2500 IU of vitamin A palmitate or acetate (retinol) since too much has been linked to a greater risk of hip fracture in older men and women. Higher intakes of vitamin A from beta-carotene have not been associated with an increased risk of osteoporosis.
Beta-carotene. Many multis have beta-carotene, some of which the body converts to vitamin A. Look for no more than 15,000 IU. If you're a smoker, avoid high doses of beta-carotene in a supplement since taking more than 30,000 IU daily has been shown to increase the risk of lung cancer. Get beta-carotene from foods like spinach, broccoli, carrots, winter squash and sweet potatoes.
Vitamin D. Choose a product with 400 to 1000 IU. The official RDAs are 600 IU for adults aged 19 to 70 and 800 IU for adults over 70. Some people may need a higher dose to maintain a sufficient amount of vitamin D in their body, especially during the fall and winter months.
Vitamin E. The recommended daily intake is 22 IU. Most multis supply 30 IU which is close to the RDA.
B vitamins. Look for at least 100 percent of the recommended intakes for B1 (1.2 mg), B2 (1.3 mg), B3 (14 - 16 mg), B6 (1.3 - 1.7 mg), B12 (2.4 mcg) and folic acid (0.4 mg).
Iron. If you're a premenopausal women, choose a multi with 10 to 18 mg; men and postmenopausal women don't need more than 8 mg (although products with up to 10 mg are fine). If you have been diagnosed with elevated iron stores, choose an iron-free formula.
Calcium. This mineral is too bulky to fit a whole day's worth into a one-a-day formula. Get what you can from foods first. If you need more to meet your daily requirement, take a separate calcium supplement. Women aged 19 to 50 need 1000 mg per day, older women require 1200 mg. The RDA for men is 1000 mg until age 70 and 1200 mg after 70 years of age.
Magnesium. Men need 420 mg per day; women need 320 mg. It's found in whole grains, legumes, nuts, seeds, dates and leafy greens. To boost your intake, pick a multi with 50 to 100 mg. Taking more than 350 mg of supplemental magnesium can cause diarrhea.
Other minerals. Look for 10 mg of zinc, 2 mg of copper, 25 to 35 mcg of chromium, and 55 mcg of selenium.
What you don't need. Extras like ginseng, ginkgo, lutein and lycopene are not necessary. The amounts added to many multivitamins are too small to be effective. And there's no evidence that "weight loss" multivitamins with green tea extract will help you shed excess pounds.
All research on this web site is the property of Leslie Beck Nutrition Consulting Inc. and is protected by copyright. Keep in mind that research on these matters continues daily and is subject to change. The information presented is not intended as a substitute for medical treatment. It is intended to provide ongoing support of your healthy lifestyle practices.