There is indeed evidence that some supplements can enhance health in different ways. The most popular nutritional supplements online are multivitamins, calcium, and vitamins B, C, and D. Calcium helps with bone health, and vitamin D helps the body absorb calcium. Vitamins C and E are antioxidants - molecules that prevent cell damage and help keep you healthy.

Women need iron during pregnancy, and breastfed babies need vitamin D. Folic acid - 400 micrograms per day, whether in supplements or fortified foods - is important for all women of reproductive age.

Vitamin B12 keeps nerves and blood cells healthy. "Vitamin B12 comes primarily from meat, fish and dairy products, so vegetarians may want to consider a vitamin B12 supplement to ensure they are getting enough," Haggans said. .

Studies have shown that fish oil can boost heart health. Of the non-vitamin and mineral supplements, Hope said, "fish oil probably has the most scientific evidence to support its use."

More research is needed on the health effects of some other common supplements. These include glucosamine (for joint pain) and herbal supplements such as echinacea (immune health) and flaxseed oil (digestion).

Many supplements have mild effects and little risk. But be careful. Vitamin K, for example, reduces the ability of blood thinners to work. Ginkgo can increase blood thinning. St. John's Wort is sometimes used to relieve depression, anxiety, or nerve pain, but it can also speed up the breakdown of many medications, such as antidepressants and birth control pills, and reduce their effectiveness.

Just because a supplement is advertised as "natural" doesn't necessarily mean it's safe. For example, comfrey and kava can seriously damage the liver.

"It's important to understand the chemical composition, how it's prepared, and how it works in the body - especially for herbs, but also for nutrients," Haggans said. . "Seek advice from your healthcare provider on whether you need the supplement in the first place, the dosage, and possible interactions with medications you're already taking."

For vitamins and minerals, check the percentage of daily value (DV) for each nutrient to make sure you're not getting too much. "It's important to think about DV and upper limits," Haggans said. Taking too much of certain supplements can be harmful.