Bottles of supplements line the shelves at your local supermarket. These include vitamins and minerals from A to zinc. You can also find products like probiotics, herbs, and fish oil. But are they needed for good health? And what about their risks?
“For most people, eating a nutritious variety of foods can provide all the nutrients they need,” says Carol Haggans, a registered dietitian and consultant with NIH. But some may need more than they get from their meals. Your needs can vary depending on your age, health, and what you eat.
Many misunderstand what dietary supplements are for, Haggans explains. “Some people might believe or hope that supplements can prevent or treat disease, but that’s not what they’re intended to do,” she says. “They’re intended to supplement the diet.”
Dietary supplements are regulated by the U.S. Food and Drug Administration. “But they’re regulated under the umbrella of food,” says Haggans. “It’s important for people to know that they’re not regulated like medicines.”
That means companies don’t have to prove that a supplement works before selling it. Companies are required to follow good manufacturing practices in making their products. But bottles still may not always contain what the label claims.
A few independent organizations conduct quality tests of supplements and give seals of approval. But these tests only ensure that a product was properly made and contains the listed ingredients. They don’t guarantee that it works or is safe to take.
Who Needs Supplements?
Your body needs different amounts of certain nutrients at different times in your life. For example, the ability to absorb and process some nutrients decreases with age. So older adults may need more of certain vitamins and minerals, such as vitamin D, vitamin B12, and calcium.
People who avoid certain foods may also need a nutrient boost. For example, vitamin B12 is found only in animal products. “So if you follow a vegan diet, you may not get enough B12 from food,” Haggans says.
Women who are pregnant, or may become pregnant, need a certain amount of folic acid. This helps prevent a type of birth defect called neural tube defects. And infants may need more vitamin D than the amount found in breast milk.
People with chronic health conditions also may need more of some vitamins and minerals, says Dr. Patricia Haggerty, who studies nutrition and the immune system at NIH. These conditions include heart disease, diabetes, cancer, HIV/AIDS, and some autoimmune diseases.
But whether you need a supplement—and which one or ones—isn’t something to guess at, Haggerty says. “Which supplements, the dosage, and so on, are things you should work out with your health care provider.” Blood tests often can help determine whether you have a nutrient deficiency.
If you take supplements, tell your health care providers. Some supplements can change how well medications work. Others have risks for specific groups of people. See the Ask Your Doctor box for questions to ask about supplements. You can track information about your supplements and medications using NIH's My Dietary Supplement and Medicine Record chart.
“It’s also important to know the total amount of nutrients you’re getting from both food and different supplements,” Haggans says. “More is not necessarily better, and natural doesn’t necessarily mean safe.”
Many nutrients can be dangerous in large amounts. These have what’s called an upper intake level. Regularly getting more than that level can lead to serious health problems. Vitamins and minerals with an upper limit include calcium, iron, zinc, and vitamins A, B6, C, and D.
Manufacturers aren’t required to keep their products below these upper limits, Haggans explains. So check the labels before you buy. And some nutrients, like vitamin K, can interact with common medications.
Other types of dietary supplements, such as botanicals, can be even more complicated. Botanicals are also known as herbal supplements. They contain one or more parts of a plant. Examples include ginseng, echinacea, and St. John’s wort. Botanicals can come in many forms, such as capsules, dried teas, or liquid preparations.
Botanical products can vary in their ingredients from brand to brand. So their effects in the body can vary. “They can also interact with medications and have side effects,” says Haggans.
Some botanical products may come with health claims that go too far, says Dr. Ikhlas Khan, an NIH-funded natural products researcher at the University of Mississippi. Examples include helping you “sleep better” or “lose weight.”
“If you’re looking for a cure, you shouldn’t be looking in the supplement aisle,” he says.
Boosting Your Immune System
Perhaps the most common claim for supplements is that they boost your immune system. Researchers have been studying whether any can help.
“Many nutrients, like vitamin C, vitamin D, vitamin E, zinc, selenium, and magnesium are important for a healthy immune system,” Haggerty says. But so far, getting more than the recommended amount of any nutrient doesn’t appear to boost the immune system.
Researchers are testing whether certain supplements can lessen COVID-19 symptoms. “But so far, the data are insufficient to support recommendations for or against any vitamin, mineral, or botanical product to prevent or treat COVID-19,” Haggerty says.
Scientists are also looking at supplements for other viruses. Khan and colleagues are studying a botanical extract made from a type of algae, called spirulina. Studies in mice have shown that compounds in it may increase the immune response and protect against viral infection. The team wants to test whether it can be used to protect against the flu.
But a challenge with botanical supplements is that they can vary from bottle to bottle, Khan explains. So the team must first fully characterize the product before they can test it in clinical trials.
You might wonder: If supplements aren’t the answer, what can you do to boost your immune system right now? “The most important thing is to eat a nutritious variety of foods and maintain a healthy weight,” Haggerty says. Obesity can weaken your immune system.
It’s also important to get regular physical activity, enough sleep, and to minimize stress. Don’t smoke. If you drink alcohol, do so in moderation. Keep up with your vaccines. And wash your hands to lower your chances of getting sick.
“These are all things we can do on a daily basis to keep our immune system healthy,” Haggerty says.
Ask Your Doctor
Before taking a supplement, ask:
- Can this supplement help with my health concern? If so, how much should I take?
- Does this supplement have any harms associated with it? What side effects should I look for?
- Could this supplement interact with my prescription medications? What about over-the-counter medications?
- How do I know whether a supplement contains what it says it does? Can you recommend a brand to take?
- Health Capsule: Taking Dietary Supplements Safely
- Dietary Supplements: What You Need to Know
- Dietary Supplements: Frequently Asked Questions
- Dietary Supplements in the Time of COVID-19
- Dietary Supplement Fact Sheets
- Vitamins and Minerals
- Herbs at a Glance
- Nutrient Recommendations and Databases
- Dietary Supplements for Older Adults
- Dietary Supplements(link is external) (FDA)
- Recommended Vitamin and Mineral Intake Calculator(link is external) (USDA)