Many people take supplements to increase their daily consumption of particular nutrients and improve their overall health and well-being. For example, if you’ve ever taken a multivitamin, probiotics, fish oil, or melatonin, you’ve used dietary supplements.
Often sold over-the-counter at pharmacies and drugstores or online, supplements are typically taken orally as capsules, pills, gummies, liquids, or powders. They may include vitamins, minerals, herbs, amino acids, enzymes, and more. Some dietary supplements contain ingredients derived directly from food sources, while others are synthetically produced.1
Before taking a supplement, it’s important to know its function, potential risks, and how to take it safely.
What Do Supplements Do?
Dietary supplements are primarily used as a way to, literally, supplement—add to—your diet. Some people take supplements to make sure they get enough of a particular important nutrient each day.
For example, someone who follows a vegetarian, vegan, paleo, or keto diet may not consume the daily recommended amounts of certain nutrients, like B vitamins.2 They may take supplements to bridge this gap. Others might use supplements to address a known vitamin deficiency.
Many adults in the United States take supplements to boost their daily consumption of key nutrients like:3
Some people also take supplements to relieve the symptoms of a diagnosed health condition, prevent health problems, or provide certain health benefits. A few common examples include:1
- Using melatonin to treat insomnia
- Taking fiber supplements to regulate bowel movements
- Taking vitamin D or calcium to prevent bone loss
Types of Supplements
There are many different kinds of dietary supplements. Common types of supplements include:1
- Multivitamins. These supplements contain a mix of several vitamins and minerals in the recommended amounts. Often, they are once-daily pills for general health. Some multivitamins may be marketed as having a specific benefit, such as increased immunity or energy, and can include additional ingredients.4
- Individual vitamins. Supplement forms of one vitamin, such as vitamin C and vitamin D, may be used to target a specific deficiency.
- Minerals. Similarly, supplement forms of a particular mineral, such as potassium and calcium, can be used to manage a deficiency.
- Botanicals. Herbs and botanical compounds, such as ginger and caffeine, are often used for their purported health benefits, such as reducing inflammation or increasing energy.5
- Probiotics. Also known as live microbials, probiotic supplements are meant to support the growth of beneficial bacteria in your gastrointestinal tract.6
- Amino acids. These supplements can contain any of the nine essential amino acids or other non-essential amino acids. As the building blocks of protein, amino acids may offer several benefits. For instance, supplements to support athletic performance and recovery may contain amino acids.7
Benefits of Supplements
Vitamins and minerals are involved in many of your body’s most essential functions, meaning supplements have a wide variety of potential health benefits.3 Here are some of the purported benefits associated with some popular dietary supplements:
- Calcium: Increases bone density, prevents fractures among older adults (especially women who have gone through menopause), and prevents preeclampsia during pregnancy8
- Vitamin D: Improves the body’s ability to absorb calcium and preventing osteoporosis9
- Magnesium: Reduces blood pressure and migraine frequency10
- Folate/folic acid: Reduces the risk of certain birth defects when taken during pregnancy, makes antidepressants more effective, and reduces the risk of stroke (when taken alongside B vitamins)11
- Iron: Prevents iron deficiency anemia and prevents the risk of premature birth and low birth weight during pregnancy12
Do Supplements Work?
The available clinical evidence about whether or not dietary supplements work is mixed. Studies suggest some dietary supplements do what their manufacturers claim, while others indicate they don’t work as advertised.
For example, there’s no evidence the herbal supplement gingko biloba works to prevent the effects of cognitive decline, despite its popular use for this benefit.13 And while many researchers believe fish oil (omega-3 fatty acids) can help to improve heart health, the results of available studies are conflicting.14
Although the U.S. Food and Drug Administration (FDA) regulates dietary supplements, they don’t require manufacturers to demonstrate their products’ effectiveness and safety before putting them on the market. This means the health claims on a supplement label don’t have to be verified or vetted before they’re sold for human consumption.13
However, some research about the health benefits of dietary supplements is promising. Here are a few study findings about the efficacy of select supplements:
- Daily iron supplementation has been shown to reduce the risk of anemia in pregnant women.15
- Taking folate (folic acid) lowers the risk of some neural tube defects, such as spina bifida, in infants.16
- Fiber supplements have been shown to relieve chronic constipation and lower cholesterol.17
Risks of Supplements
For most people, taking common dietary supplements (such as multivitamins) is safe and doesn’t pose serious health risks.
However, anyone can have an adverse reaction to a supplement—particularly if you take a large dose. The side effects of taking too much of a given supplement vary widely. Possible health complications include, but are not limited to, liver damage, excessive bleeding, and stroke.1813
Signs of a serious adverse reaction to a supplement may include:18
- Stomach pain
- Nausea or vomiting
- Lightheadedness or fatigue
- Chest pain
- Difficulty breathing
- Rapid heart rate
- Difficulty urinating or dark urine
- Diarrhea or bloody stool
- Loss of appetite
- Unintended weight loss
If you are allergic to a supplement or supplement ingredient, you may experience an allergic reaction. This can present as a rash or hives, itching, and swelling in your throat, tongue, or lips.18
Seek emergency medical help if you experience any of the above symptoms or reactions.
Certain supplements may also have harmful interactions with medications and other supplements. Taking multiple supplements or combining supplements with prescribed medications may increase the risk of side effects or make your medication less effective.19
For example, the herbal supplement St. John’s wort can make antidepressants and birth control pills less effective. Certain antioxidant supplements like vitamin C and vitamin E can reduce the impact of chemotherapy treatments.19
Several supplements also interact negatively with blood-thinning medications, either increasing or reducing their effectiveness. For instance, vitamin K may reduce the effectiveness of the blood-thinner Warfarin (Coumadin).19
How to Use Supplements Safely
There are steps you can take to make sure you are using supplements safely and appropriately. If you are taking a supplement or thinking about starting a supplement, try to follow these guidelines:13
- Talk to your healthcare provider before taking any supplements. Let them know about any other supplements and medications you’re taking.
- Take supplements exactly as directed on the product label.
- If you experience any side effects from a supplement, stop taking it immediately and seek medical help.
- Contact your healthcare provider before starting (or continuing to take) any supplements if you are pregnant or breastfeeding. Many dietary supplements on the market have not been tested for safety in people who are pregnant or breastfeeding.
- If you’re scheduled for surgery, let your healthcare provider know about any supplements you’re taking. Some can interfere with the effectiveness of anesthesia and increase your chance of abnormal post-operative bleeding.
Most experts do not recommend using supplements in place of food sources to fulfill your daily consumption of certain essential nutrients. There is also not enough research to support the benefit of taking an excess of certain nutrients through supplements, and some nutrients can be harmful in very high doses. When possible, it’s often better to get the nutrients your body needs through food rather than supplements.20
Supplements also cannot replace the medications you’ve been prescribed to treat any particular health condition. If you are interested in the potential benefits of supplements, make sure to discuss the uses and risks of the supplement with a healthcare provider.21
A Quick Review
Dietary supplements can be used to correct vitamin and mineral deficiencies and ensure that you get “enough” micronutrients each day. There is also some evidence certain supplements can provide health benefits and alleviate the symptoms of some medical conditions.
However, research on the efficacy of supplements is limited and ongoing. It’s important to seek medical advice from a qualified professional if you want to take a dietary supplement. Before you start taking one, talk to your healthcare provider about potential side effects and drug interactions.