How to choose a dietary supplement

Ali McGowan, MS, RD, LDN

Dietary supplements are intended to add to the diet and are not meant to be a replacement for food. While they can certainly improve and maintain overall health (and even help some individuals meet their daily requirements for essential nutrients), supplements can also involve health risks if they’re not used appropriately.

For a high-level overview on how to choose a dietary supplement, skip ahead to the section with 10 factors to consider when choosing a dietary supplement. 

What are dietary supplements?

Dietary supplements are vitamins, minerals, herbs, botanicals, fish oils, probiotics, and other substances that can provide nutrients that may be lacking in the diet or cannot be consumed in amounts that would otherwise prevent nutrient deficiencies.

For example, individuals who follow a vegan or vegetarian diet or those who have life-threatening food allergies may not be able to obtain all essential nutrients through food. In contrast, individuals with gastrointestinal conditions may be able to consume all essential nutrients through food, but may lack the absorptive capabilities to fully process and utilize them. As a result, these individuals may be at increased risk for micronutrient deficiencies and may require a dietary supplement to prevent them.

Dietary supplements are not intended to treat, diagnose, mitigate, prevent, or cure disease. As the name suggests, supplements are meant to add to the diet and are not meant to replace food.

Should I get my nutrients from food or from supplements?

Aiming for a “food-first” approach as often as possible provides the body with benefits beyond obtaining key micronutrients. For example, a meal that contains a sirloin steak and greens like broccoli provides the body with two forms of iron, heme and nonheme iron. This meal also provides protein and fiber that help you feel full and satisfied, promote balanced blood sugar, and support digestion by providing fuel for good gut bacteria. 

Following a foods-first approach also keeps food in the “food matrix.” The food matrix describes how foods are packaged with nutrients that work synergistically in the body to increase their absorption. For example, an egg yolk is naturally packaged with fats that help with the absorption of another micronutrient in eggs called choline.

While food can definitely provide a micronutrient-rich bang for your buck, some individuals still need dietary supplements to meet their nutrition needs. As always, consult with your physician or Registered Dietitian to find out what supplements are right for you.

What should I know about dietary supplements?

The Food and Drug Administration (FDA) does not have the authority to approve dietary supplements for safety and effectiveness or to approve of their labeling before they are sold to the public. So who does?

Under the Dietary Supplement Health and Education Act (DSHEA), manufacturers/distributors are responsible for ensuring that the dietary supplements they sell are safe and properly labeled. In many cases, firms can legally introduce dietary supplements to the market without even notifying the FDA.

The FDA’s role in regulating dietary supplements begins after products enter the marketplace. If the FDA finds a supplement to be unsafe once it is on the market, only then can it take action against the manufacturer and/or distributor by issuing a warning or requiring the product to be removed from the marketplace.

And, with reports showing that there are products on the market that don’t actually contain the ingredients they advertise on the label, choosing the wrong dietary supplements isn’t just risky on your health, it can also be a burden on your wallet.

What are some other misconceptions about supplements?

A common misconception is that if a nutrient deficiency causes a particular set of symptoms, then taking more of that nutrient will not only reverse those symptoms but will also leave you better off. But, if you are already getting enough, getting more doesn’t usually help. And it's possible that over-consuming one nutrient may cause deficiencies in another area since some nutrients compete for absorption (like zinc and copper for example).

This is why working with a licensed healthcare professional is key to understanding the root cause of potential nutrient deficiencies. 

What does %DV mean?

The percent daily value (%DV) refers to the percentage of the Daily Value (DV) for each nutrient in a food or supplement and is based on a 2,000-calorie diet for healthy individuals. The DVs are reference amounts of nutrients to consume or to not exceed each day. The %DV helps consumers determine if a supplement is high or low in a nutrient. When considering food labels for example, individuals may want to look for products that have a high %DV for some nutrients (like fiber, vitamin D, and iron for example) and a low %DV in other nutrients (like added sugars). 

Supplement manufacturers must declare the %DV of all ingredients that have FDA established DVs in order for their supplement label to be considered accurate. 

Here are 10 factors to consider when choosing a dietary supplement:

1. First ask yourself “Do I need the nutrient this supplement is providing?” If yes, ask yourself “Is it possible for me to get this nutrient through food?”

For example, individuals who follow a vegan or vegetarian diet need to supplement with vitamin B12 or ensure their intake of vitamin B12 fortified foods. Although vitamin B12 is found in some plant-based foods like nutritional yeast, it is three times more bioavailable in animal-based products like fish, meat, poultry, eggs, milk, dairy, clams, and liver. Healthy individuals who don’t follow a vegan or vegetarian diet likely get plenty of vitamin B12 and don’t need to supplement. The body excretes excess water-soluble vitamins like B12 in the urine, so more isn’t inherently better. 

2. Check with your healthcare provider.

Before buying or taking a dietary supplement, consult with a healthcare professional like your doctor or Registered Dietitian as some supplements can interact with medications, interfere with lab results, and even have dangerous effects during surgery. For more, check out these educational resources on dietary supplements created by the FDA.

3. Look for third-party testing.

Third-party testing describes the evaluation of dietary supplements by an organization not affiliated with the supplement manufacturer or distributor (i.e., a third party). Third-party certification includes an audit of the manufacturing process, an evaluation of the product’s quality, and an evaluation of labeling to ensure accuracy and compliance. For athletes subject to anti-doping rules, it’s important to know if a supplement is free from banned substances before use. The following companies practice third-party testing: 

  • The United States Pharmacopeia (USP) is an independent, science-based non-profit organization that sets official standards for the quality of drugs and supplements. The USP verification seal ensures that a supplement was 1) made in a facility that employs good manufacturing practices, 2) includes the ingredients that are listed on the label in the declared strength and amounts, 3) does not contain harmful levels of specified contaminants like heavy metals or adulterants, and 4) will dissolve in the body for proper absorption. You can find a list of USP verified brands at
  • Other companies that practice third-party testing include:

Some manufacturers may choose to forgo third-party testing due to logistical reasons, including time and expenses associated with testing. Companies that skip third-party testing can offer products at a more affordable price, making supplements more accessible to consumers. 

4. Check the active ingredients.

Understanding the amount of each active ingredient, as well as its form, can help determine if a supplement is right for you. 

5. Make sure the product doesn’t contain ingredients you’re allergic to.

Supplement manufacturers don’t have to comply with the Food Allergy Labeling and Consumer Protection Act (FALCPA), which regulates the labeling of allergens on food products. Be sure to check the ingredients label for the specific food allergen and its derivative names.

6. Visit the manufacturer’s website.

There are a few clues that can tell you more about whether a manufacturer follows best practices for the supplements they produce. Look for manufacturers that disclose information on the following:

  • How long they’ve been in practice
  • If they have certifications from the FDA
  • If they are current Good Manufacturing Practice (cGMP) compliant
  • If they are US-based and therefore meet local regulations
  • If they list both active and inactive ingredients

7. For sports performance supplements, be wary of fraudulent or adulterated products.

Some products marketed as dietary supplements to improve exercise and athletic performance might contain inappropriate, unlabeled, or unlawful stimulants, steroids, hormone-like ingredients, controlled substances, prescription medications, or unapproved drugs. Using these products can cause health problems and disqualify athletes from competitions. Only buying sports supplements that are third-party tested can prevent these concerns.

8. Look at the expiration date.

Check the supplement’s expiration date and make sure it is far enough in the future to allow you to consume all of the product by that date.

9. Introduce only one supplement at a time and assess how you feel.

Supplements get tested for quality, purity, potency, and composition, but not for efficacy. This means that there’s no way to measure how well a product produces a desired result or to check if a product's claims about how well it works are true.

Use other markers to measure the effectiveness of a new supplement like how you’re feeling or sleeping. Reassess if the supplement is working for you around one week to three months after starting, depending on its intended effects. Getting regular lab work can also show how well a supplement is working over the long-term, like vitamin D levels that move from deficient to sufficient after supplementing with vitamin D3.

Aim to introduce one new supplement at a time to get a clearer picture of how effective it is since adding multiple supplements at once can make it difficult to determine where effects are, or are not, coming from.

10. Remember, a supplement is not a silver bullet. 

Combining lifestyle and nutrition practices with your supplement regimen can increase its effectiveness. For example, individuals struggling with sleep may consider a magnesium glycinate supplement, but should be sure to continue to practice proper sleep hygiene before bed. Supplements are intended to add to your lifestyle practice and are not meant to replace health-promoting behaviors like prioritizing nutrition, movement, sleep, and stress management

If you’d like more personalized support on what dietary supplements may be right for you, reach out to your Care Coordinator to schedule a visit with your Sequence physician or Registered Dietitian. Not a Sequence member? See if you qualify for our program here.

Ali McGowan, MS, RD, LDN

About the Author

Ali McGowan, MS, RD, LDN, is a Registered Dietitian with her Master’s degree in Nutrition, Interventions, Communication, and Behavior Change from Tufts University. A believer in health autonomy, Ali aims to explain both the “what” and the “how” behind key nutrition concepts to help individuals make empowered and personalized health decisions that build confidence and improve their quality of life. Beyond nutrition science, Ali works to identify practical strategies to help members achieve and maintain their desired behavior through all seasons of life. When she’s not working, you can find her spending time in nature, cooking, or finding joy in movement. Follow her on Instagram @sproutoutloud.

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