Dietary supplements are products that people use to add nutrients or other compounds to their bodies.

From individual vitamins and minerals to blends of nutrients and herbs, there are numerous supplement products on the market that claim to provide specific health benefits.

However, due to limited regulation, it’s not always clear which supplements are high quality, nor which are a waste of your money or even potentially dangerous.

This guide covers all you need to know about what supplements are and how to choose a safe and high quality product.

Supplements are products that are taken by mouth and contain a “dietary ingredient,” such as vitamins, minerals, herbs and botanicals, amino acids, enzymes, probiotics, antioxidants, or other nutrients (1).

Available in numerous forms, including capsules, gummies, tinctures, powders, and liquids, dietary supplements are typically marketed as an easy and efficient way to boost your physical or mental health.

Other important definitions to understand when looking at supplements include (2, 3, 4):

  • Vitamins. Vitamins are essential nutrients that your body needs to function properly and stay healthy. Many help regulate vital metabolic functions, including growth, nerve function, and digestion.
    • Fat-soluble vitamins. These vitamins dissolve in fat and can be stored in your body. They include vitamins A, D, E, and K.
    • Water-soluble vitamins. These vitamins dissolve in water and are not stored by the body. They include vitamin C and B vitamins.
  • Minerals. Minerals are inorganic elements that are essential for specific bodily functions, such as growth, bone health, and fluid balance.
  • Proprietary blend. A proprietary blend is a unique combination of ingredients that’s created by a supplement manufacturer. Oftentimes, it’s hard to tell from the label how much of each ingredient the blend contains.

For most healthy individuals, it’s possible to consume all the vitamins and minerals you need through diet alone. However, there are certain conditions, medications, and circumstances when supplements may be needed to meet nutritional needs.

Still, a key point to make when talking about dietary supplements is that they’re designed to supplement — not replace — nutrients or other compounds in your diet.

This means that even if you’re taking a supplement, it’s still important to consume a varied and balanced diet if possible.


Supplements are products containing ingredients like vitamins, minerals, and botanicals. They’re taken by mouth to support or improve some aspect of health.

Eating a variety of foods is the best way to ensure that you’re meeting your vitamin and mineral needs.

After all, different foods contain varying amounts and combinations of nutrients. For example, citrus fruits are known for being high in vitamin C, while leafy greens are an excellent source of vitamin K (5, 6).

In addition to vitamins and minerals, foods contain other essential nutrients, including protein, healthy fats, and fiber — all of which are needed for overall health and optimal bodily functioning (2, 7).

Furthermore, plant-based foods, in particular, are rich in antioxidants and phytochemicals, two classes of compounds that are linked to benefits reduced inflammation and protection against chronic disease (8, 9, 10).

In contrast, supplements do not offer the same nutritional benefits. As they’re meant to supplement — not replace — a healthy diet, they generally provide only concentrated amounts of specific nutrients (11).

One observational study in 30,899 adults in the United States found that adequate intake of certain nutrients through food sources was associated with a reduced risk of death from heart disease, as well as death from any cause (12).

However, consuming the same nutrients in supplement form did not reduce the risk of death from heart disease or any cause (12).

Individuals with nutrient deficiencies or those at increased risk of inadequate nutrient intake, such as women who are pregnant, can benefit from taking supplements as recommended by a medical professional.


Whole foods contain more than just vitamins and minerals. A varied and balanced diet also provides other essential nutrients and important plant compounds for health. Supplements are meant to help fill gaps in your nutrient needs.

In general, taking vitamin and mineral supplements is not necessary for healthy adults with adequate intakes of these nutrients. While it’s preferred to get these essential nutrients through your diet, some may struggle to do so.

There are also certain instances in which supplements may be indicated. Individuals who may benefit from supplements include (13, 14, 15, 16):

  • women who are pregnant or breastfeeding
  • exclusively or partially breastfed infants
  • adults or children with diagnosed nutritional deficiencies
  • individuals with conditions causing nutrient malabsorption
  • those who have undergone bariatric surgery, such as gastric bypass
  • adults or children with restricted access to foods
  • some vegans and vegetarians

Some nutrient deficiencies are also more common, for example, vitamin D (17).

Unlike other vitamins, it’s difficult to get enough vitamin D from your diet alone. While your body can make vitamin D from exposure to sunlight, it’s estimated that one billion people worldwide have low levels of this vitamin (18).

Frequently wearing sunscreen, living far north or south of the equator, staying indoors, and having darker skin are all risk factors for being deficient in vitamin D (19).

Furthermore, older adults may not be as effective at synthesizing vitamin D due to biological changes in the skin that naturally occur with age (20).

As a result, vitamin D supplements are commonly recommended.

If you’re concerned about getting adequate vitamins and minerals from food alone, talk with your healthcare provider for personalized recommendations regarding the type of supplement you may need, as well as the appropriate dose.

Additionally, while prenatal vitamins are recommended during pregnancy and sometimes while breastfeeding, these populations should avoid herbal supplements unless a medical provider suggests otherwise (21).

Supplements for kids

Healthy children are generally able to meet their nutritional needs through a varied diet alone (22).

However, there are certain age groups and circumstances in which supplements may be recommended.

For example, the American Academy of Pediatrics recommends that partially and exclusively breastfed infants receive approximately 400 IU of vitamin D daily through supplements until the baby starts consuming vitamin-D-fortified milk (15).

Additionally, children or teens who follow a strictly plant-based diet may be at an increased risk of deficiency in several critical nutrients, including vitamin B12, calcium, iron, zinc, and vitamin D (23).

While it’s possible for kids on a plant-based diet to get enough of these nutrients from food alone, it requires careful planning. As a result, depending on the types of foods the child is consuming, supplements may be indicated (23).

As teens and kids have different nutritional needs than adults, it’s important to speak with a pediatrician for recommendations on the types of supplements — and dosages — that are safe.


While supplements are generally not necessary for healthy adults and kids, some populations may benefit from dietary supplements. Always consult a medical professional before taking supplements.

The Food and Drug Administration (FDA) does not evaluate the effectiveness, safety, or quality of dietary supplements — or the ingredients in them — before they enter the marketplace (1).

This is important to realize, as it means that there is no guarantee the product contains what it claims to. Furthermore, a product may even contain varying amounts of the ingredients from batch to batch.

While the FDA requires supplement manufacturers to adhere to Current Good Manufacturing Practices (CGMP), which are intended to ensure the quality and safety of these products, compliance is not always enforced (24).

The best way to ensure the quality of a product is to look for one that has been certified by a third-party company.

Third-party testing

Third-party testing is not required by law.

However, some supplement manufacturers voluntarily choose to undergo testing to show their commitment to producing high quality products.

One objective indicator of product quality is a Certificate of Analysis (COA), which is awarded by an independent third-party company, such as NSF, USP, Banned Substances Control Group (BSCG), or ConsumerLab.

Most products that have been certified by one of these third-party companies have been tested for one or more of the following (25):

  • The supplement contains what’s stated on the label and in the amounts listed
  • Products are standardized from batch to batch.
  • The supplement is free of harmful levels of contaminants or other potential drug contaminants.
  • The product doesn’t contain any undeclared ingredients.

Additionally, if you’re an athlete, it can be helpful to look for products that are NSF Certified for Sport. This certification ensures that the product is free of more than 270 substances that are banned or prohibited by most major sports organizations (26).


Vitamin and mineral supplements are subject to fairly limited regulation by the FDA. To ensure the safety and accuracy of a product, look for supplements that have been certified by a third-party testing organization.

While supplements contain ingredients that are found in foods, there are potential safety concerns to consider before taking concentrated amounts of these ingredients in supplement form.

Possible interactions

In addition to talking to your healthcare provider about the type of supplement you’re interested in taking, it’s critical to ask about any potential interactions.

The ingredients in supplements, including vitamins, minerals, herbs, and other botanicals, can have unintended negative consequences when combined with some medications, other supplements, foods, and alcohol (27).

For example, vitamin E supplements may increase the risk of bleeding in those on blood-thinning medications, while calcium supplements may limit the effectiveness of antibiotics and reduce the absorption of iron from foods and supplements (28, 29).

Some supplements may also affect the accuracy of lab results.

For example, the FDA issued a warning that supplements containing biotin (vitamin B7) can falsely lower troponin-based lab results, an important biomarker that’s used to help diagnose heart attacks (30).

Supplements containing herbs and botanicals can be particularly concerning, as many have been shown to interact with various medications. Additionally, many herbs have insufficient research in humans to confirm potential interactions and side effects (31, 32).

Ingredients that may become toxic over time or at high doses

One concern with consuming vitamins and minerals through supplements rather than from foods is the increased risk of consuming an amount that’s too high or could become toxic over time.

In addition to recommended amounts, many vitamins and minerals have what’s called a Tolerable Upper Intake Level (UL). The UL is the highest intake amount of the nutrient that’s unlikely to cause negative side effects in the general population (33).

The UL for vitamins and minerals varies based on age and gender. There are also separate UL recommendations for women who are pregnant or breastfeeding (34, 35).

Fat-soluble vitamins are particularly concerning in regards to toxicity risk, as excessive amounts can accumulate and be stored in your body.

In particular, overconsuming vitamins A, D, and E can be toxic, leading to side effects like irregular heartbeat, organ damage, hemorrhages, hemorrhagic stroke, and in extreme cases, even coma and death (36, 37, 38, 39).

As water-soluble vitamins are not stored in your body, they’re less likely to cause toxicity from an overdose.

That said, consistently taking very large doses of water-soluble vitamins may still cause digestive upset, liver damage, and even potentially irreversible neurological damage (36, 40, 41).

Unless under the supervision of a medical professional, it’s important not to exceed the UL of vitamins or minerals. While some side effects may be mild, others can be more serious.

Additionally, as the UL for kids is often much lower than for adults, kids are particularly at an increased risk of overdose and toxicity (34).

For safety purposes, make sure to always store supplements out of reach of children. This is especially important for gummy vitamins, as their sweet flavor may appeal to kids (42, 43).

May have negative side effects

Dietary supplements may cause negative side effects, even when taken at the recommended doses.

Reported side effects are often mild, such as nausea, diarrhea, or headaches. In particular, iron supplements are known for causing digestive distress (44).

However, some ingredients in supplements, especially herbs, may have more serious side effects, such as allergic reactions, increased blood pressure, and elevated or irregular heartbeat (45, 46).

May not be effective

As dietary supplements are subject to fairly limited regulation, there’s also the risk that the product contains less of an ingredient than it claims to.

In addition to not getting your money’s worth, this can be potentially dangerous in individuals who are relying on the supplement to help meet their essential nutrient needs.

It’s also important to be cautious of claims on the product. Due to FDA regulations, manufacturers cannot claim that their product cures, treats, or reduces the risk of a specific disease or condition unless it has been proven by research to do so (47).

However, they can include structural or functional claims, which describe how the ingredients in the product may affect systems or organs in your body (47).

For example, a supplement can say that it supports energy levels. Yet, this claim does not require that the product was scientifically proven to help improve energy levels. As a result, there’s no guarantee that taking the supplement will result in this desired benefit.


Taking supplements carries some risks. Depending on the type and level of ingredients, there are risks of side effects, toxicity, and interactions with drugs, foods, and alcohol. Additionally, supplements are not guaranteed to be effective.

The demand for health and wellness products continues to grow, and one of the results of this demand has been an increase in multi-level marketing (MLM) supplement companies.

While there are variations in the exact structure, MLMs operate using a business model in which independent, non-salaried representatives earn affiliate income by selling a specific company’s products.

Some companies also use a pyramid-shaped commission system in which the representative makes additional money by recruiting and selling to new representatives.

Due to the popularity of vitamins, minerals, and other supplements, many MLM companies offer a variety of supplement products, many of which are often advertised as ways to boost various aspects of health or support weight loss.

Some common MLM companies you’re likely to come across include Herbalife, Shaklee, Amway, and Plexus.

While some products may be perfectly safe, many products sold by MLMs are not third-party tested for safety or accuracy. As a result, you could end up spending a lot of money on an ineffective or low quality product (48).

Additionally, these products often contain a mix of herbs and other botanicals, many of which haven’t been proven to be safe for long-term use. These supplements can also contain potentially dangerous levels of vitamins and minerals (48).

Finally, the ingredients used in these products are not always of high quality and may include artificial colors, flavors, and additives.

Overall, when buying supplements from an MLM company, it’s still important to look for indicators of safety and quality, including the ingredient list, dosage, and certification from third-party testing.


Many multi-level marketing companies sell dietary supplements, which are often advertised to support various aspects of health. Products produced by these companies are not always third-party tested nor guaranteed to be safe or effective.

Safety and quality are the most important factors to consider when shopping for vitamins and supplements. However, there are other aspects to think about as well.

For example, some coatings and added ingredients in supplements may be derived from animal products. As a result, if you’re following a vegan diet, you’ll want to look for products that are certified vegan.

Similarly, supplement products may contain gluten or other common allergens, such as soy or dairy.

Under the Food Allergen Labeling and Consumer Protection Act, foods and dietary supplements are required to explicitly state the presence of any of the eight major allergens (49).

Those with celiac disease or gluten intolerance should choose a product that’s certified gluten-free.

Read our guide for more information on what to look for on supplement labels.

Other aspects to consider include how often you have to remember to take it and what form you prefer, such as a liquid, tablet, powder, or gummy.

Finally, even if it’s a high quality product, it’s important to buy from a reputable source. Most supplements should be stored in a cool, dry place, and some even need to be refrigerated.

As a result, you’ll want to choose a retailer that you trust to handle products properly.


You’ll want to look for supplements that adhere to any dietary restrictions you may have. How often you need to take the supplement, as well as its form, such as capsules or chewable gummies, should also be considered.

It’s recommended that healthy individuals primarily meet their nutritional needs through diet.

However, there are instances in which supplements may be indicated, such as nutrient deficiencies, conditions causing malabsorption, inadequate access to food, and certain life stages like pregnancy.

As supplements are subject to fairly limited regulation by the FDA, it can be confusing to figure out which supplements are safe and effective.

When shopping for vitamins and other supplements, look for products that have been third-party tested and contain safe levels of vitamins and minerals.

Due to potential interactions and safety concerns, always talk with your doctor before taking any vitamin or supplement product — especially if you’re pregnant, breastfeeding, taking any medications, or have or suspect that you have a medical condition.