It is well established that a healthy diet helps prevent chronic diseases.
Studies consistently find that a diet based on vegetables and fruits, whole grains, a variety of proteins, and healthy fats is associated with a lower risk of heart disease, stroke, Alzheimer’s disease, and some cancers.
However, if your diet isn’t that good, you might consider taking a daily vitamin supplement to protect your health in the long run.
If that’s the case, an updated evidence review suggests you’re wasting your money.
Here’s what you need to know about vitamin and mineral supplements.
Updated add-on guidelines
To update its 2014 supplement recommendation statement, the US Preventive Services Task Force (USPSTF) commissioned an independent panel of experts to review 84 studies, including 52 new studies published since 2014.
Researchers are trying to determine whether taking single-nutrient supplements (eg, folic acid, vitamin D, vitamin E), nutrient-pair supplements (eg, calcium + vitamin D, folate + B12), or multivitamins reduces the risk of heart disease. – vascular disease, cancer or early death.
According to new USPSTF guidelines published June 21 in the Journal of the American Medical Association, there is no evidence that multivitamins, single supplements, or pairs of supplements help prevent cardiovascular disease or cancer in otherwise healthy nonpregnant adults.
For most of the supplements reviewed, there was little or no evidence of serious harm.
However, the USPSTF specifically recommends against taking a beta-carotene supplement because of a possible increased risk of lung cancer and cardiovascular death. The updated guidelines also advise against the use of vitamin E, possibly because vitamin E supplementation has not shown a protective benefit against cardiovascular disease, cancer, or early death.
These findings are not at all surprising to me.
Whole foods contain a mixture of vitamins, minerals, phytochemicals, fiber and other nutrients, dietary components that are thought to work together to offer health benefits. This organized network of beneficial compounds does not exist in isolated vitamin and mineral pills.
However, this does not mean that nutritional supplements are useless. In the right circumstances, they can offer benefits.
When supplements are helpful
While I recommend trying to meet your daily nutritional needs from whole foods, in some cases this is not always feasible.
Some supplements are helpful in bridging nutritional gaps in the diet. They are also needed to treat vitamin and mineral deficiencies.
Women who plan to become pregnant or could become pregnant should take a daily multivitamin that provides 0.4 mg of folic acid to help prevent neural tube defects, birth defects that affect the brain and spinal cord.
If you’re following a vegan diet, taking a multivitamin and mineral supplement is an important way to get your daily iodine, a mineral found in dairy and seafood that’s needed for thyroid hormone production as well as vitamin B12.
Natural B12 is only found in animal foods. It is needed to maintain healthy nerve function and to make red blood cells and DNA.
Vegetarian or not, it is recommended that adults over 50 get most of their daily B12 through supplements, such as a multivitamin or B complex, or fortified foods. This is because many older people do not produce enough gastric (stomach) acid needed to absorb B12 from food.
I also recommend a daily multivitamin for people taking medications that can reduce the absorption of vitamin B12 from the diet (eg, stomach acid inhibitors and metformin).
If you’re on a low-calorie diet to lose weight or eat a very restricted diet, multivitamins and mineral supplements can provide some nutritional coverage.
Daily vitamin D supplementation is necessary to maintain sufficient levels of the vitamin in the blood. Osteoporosis Canada recommends vitamin D supplements for adults year-round, as it is nearly impossible to get enough of the nutrient from food alone.
Vitamin D plays an important role in calcium absorption, bone health, muscle performance and balance.
Bottom row
Vitamin supplements are often seen as completely harmless. However, this is not always the case. When taken in high doses, many nutrients can have adverse effects.
For example, in moderate doses, vitamin A can reduce bone density, and high doses of it can be toxic to the liver. Taking too much iodine can cause some of the same symptoms of iodine deficiency, including an enlarged thyroid gland (eg, goiter).
Supplementing with too much zinc can lead to consequences such as impaired immune function, decreased levels of HDL (“good”) cholesterol, loss of appetite, diarrhea, headaches, and abdominal pain.
To supplement appropriately and safely, consult your healthcare provider.
Leslie Beck, a Toronto-based private practice nutritionist, is the director of food and nutrition at Medcan. Follow her on Twitter @LeslieBeckRD
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