Dietary Supplements: What Practitioners Need to Know

November 15th, 2021

A whole-foods, plant-based diet provides all the nutrients a body needs, right? In a perfect world this would be true, but not so fast!  For one thing, most people across the globe are not consuming a nutrient-dense diet with micronutrient deficiency affecting an estimated two billion people (1). The United States is no exception, Americans are great at consuming calories, but not so great at consuming nutrient-dense calories. In addition, the Dietary Reference Intakes (DRIs) and the American agricultural system are flawed. So, while food should be the foundation, dietary supplements are often an important piece of the puzzle when it comes to disease prevention, reversal, and the promotion of optimal health.

Many nutrition professionals have been trained to focus mainly on healthy food choices and to leave dietary supplements out of the discussion. But with greater than 70 percent of all US adults using dietary supplements, it’s important for practitioners to educate themselves on all things supplement-related (2).

What is a Dietary Supplement?

Technically, a dietary supplement is any product intended to supplement the diet that contains one or more dietary ingredients or constituents to be taken by mouth as a pill, capsule, tablet, or liquid. In addition, the front package label must identify the product as a dietary supplement (3).  

Are Dietary Supplements Safe?

Dietary supplements may seem innocuous, but it’s important to remember that not all dietary supplements are created equally. The supplement industry is riddled with tainted products, especially those targeting weight loss, sexual enhancement, and bodybuilding (4). Aside from potentially harmful additives, supplements can also be contaminated with mold, yeast, glass, colors, fillers, heavy metals, pesticides, chemicals, and potential allergens. In addition, inconsistent quality and lack of raw material testing are common. Supplement companies are required to have evidence that their supplement is safe and any label claims must be truthful, but with the overwhelming number of products on the market, this is difficult to enforce (5).

There are several independent organizations that offer quality supplement testing to ensure a supplement was manufactured properly, does in fact contain the listed ingredients, and does not contain harmful levels of contaminants. However, this third-party testing cannot promise the safety or effectiveness of a product. Consumer Lab, NSF International, and United States Pharmacopeia are three independent organizations providing this important service (5).

How are Dietary Supplements Regulated?

The Food and Drug Administration (FDA) is involved in the regulation of dietary supplements once they are on the market and the Federal Trade Commission (FTC) monitors product marketing.  There is no law requiring supplement manufacturers to obtain FDA approval to produce or sell a supplement unless it includes a new dietary ingredient (6).

In 2007, the FDA created Good Manufacturing Practices (GMPs) and periodically inspects supplement manufacturing facilities. GMPs are in place to prevent contamination as well as the incorrect labeling or packaging of supplements. In addition, GMPs help confirm a product is what is claimed on the label with regard to purity, strength, and composition (6).

Are Dietary Supplements Necessary?

Dietary supplements are an often-necessary component of an integrative and functional nutrition care plan for a variety of reasons:

  1. Dietary Reference Intakes (DRIs) are meant to assess the nutrient status of healthy people (7).

The average American is not healthy. Almost 70 percent of the adult population is either overweight or obese and moreover, only one in eight Americans display optimal levels of the top five cardiometabolic risk factors without medication (8,9).

  1. Preventing all-out nutrient deficiency is far removed from maintaining optimal nutrient status.

Many of the standard recommendations are based on preventing nutrient deficiency, but nutrient status exists on a continuum from deficiency to insufficiency to normal to optimal to toxic (10). Simply preventing a deficiency will not support patients in attaining optimal health status.

  1. One size does not fit all.

Each patient is unique and will likely require different amounts of nutrients based on their medical history, genetics, environmental exposure, and lifestyle factors.

  1. Medications affect nutrient absorption.

Prescription medication use is common in the US. Between 2015 and 2018, 48.6 percent of Americans had used at least one prescription drug during a 30-day period, 24 percent used three or more, and 12.8 percent used five or more (11). Over time, many medications can lead to nutrient deficiency, for example, metformin can deplete vitamin B12, statin drugs can deplete CoQ10, and oral birth control pills can deplete B vitamins.

  1. Triage theory.

Triage theory suggests the lack of optimal micronutrient intake creates an environment in the body whereby short-term survival is prioritized over less critical body functions. time, this restriction of nutrients increases the risk of chronic disease and diseases of aging (12).  This concept is difficult to study through randomized controlled trials, but vitamin K1 and selenium are two examples. Vitamin K1-dependent proteins were studied in a Knockout mouse model. The researchers determined when vitamin K1 is limited, there is a preferential allocation of dietary vitamin K1 to the liver to sustain proper coagulation. Over time, this vitamin K1 inadequacy leads to bone and cardiovascular consequences (12).  Likewise, one review found that modest selenium deficiency leads to the loss of nonessential selenoprotein activity and concentration. Since the genetic dysfunction of nonessential selenoproteins and modest selenium deficiency are associated with cancer, cardiovascular disease, and immune dysfunction, inadequate selenium intake over time could be a causative factor (13).

  1. The agricultural system is not focused on the nutrient density of plants.

Food has dramatically changed over the past several decades and diet-related diseases are the number one cause of death in the world. Many farmers have gone from growing local, diverse crops to genetically modified crops that require toxic fertilizers, pesticides, and herbicides. Many of these additives wipe out the biodiversity of the soil creating less nutrient-dense plants (14).

While dietary supplements can be an important component of the treatment plan for many disease conditions, let’s look at one powerful example. Depression is one of the most common mental health disorders and affects millions of people worldwide. While conventional treatments such as anti-depressants and cognitive behavioral therapy can provide some relief, depressive symptoms often persist. Magnesium is an important co-factor for hundreds of reactions in the body, yet nearly 70 percent of Americans do not consume even the minimum recommended amount (15). In one randomized clinical trial reported in Plos One, patients with mild to moderate depression experienced statistically significant improvement in depression and anxiety scores after six weeks of receiving 248 milligrams of magnesium chloride daily (16).

Choosing and Recommending Dietary Supplements

Navigating the world of dietary supplements can be challenging!  IFNA offers two comprehensive modules dedicated to this topic presented by expert Kelly Morrow, MS, RDN, FAND. Kelly reiterates the importance of practice and accessing accurate information. As of 2019, the FDA estimated there were up to 80,000 different dietary supplements on the market but a very small percentage of those products have been studied closely (17).  Since 70 percent of dietary supplement companies are not in compliance with regard to testing, record keeping, and contaminants, practitioners need to remain vigilant when choosing and recommending supplements.

While both professional and retail supplement lines can be reputable, Kelly recommends close inspection of the company website or better yet, calling the company to inquire about their process. If the company is unwilling to discuss their quality assurance standards and testing methods, it should likely be avoided.

Kelly encourages practitioners to take a food-first approach, remain up-to-date on the latest evidence, practice within their knowledge limits, and document in the medical record appropriately. Coordination of care and remaining within the scope of practice, which may vary by state and at the national level, are also two important factors.  In addition, Kelly explains the importance of choosing the appropriate supplement form for a specific patient, as well as considerations when choosing between the synthetic versus the natural form of a nutrient.

If you are new to recommending dietary supplements, Kelly recommends learning about foundational supplements like multivitamins, essential fatty acids, probiotics, calcium, magnesium, and vitamin D. Her very detailed lectures address where to find credible supplement information, regulation standards, assessing safety and quality, practitioner scope of practice, and how to integrate advanced nutraceuticals for specific conditions into practice.  While nutritional supplements should never take the place of a well-balanced diet and lifestyle,

IFNA members who open a new account with the IFNA supplement partners receive a 20 percent discount on their first order and as integrative providers can enjoy significant discounts on quality dietary supplements.

By Kellie Blake, RDN, LD, IFNCP


  1. Bailey, R. L., West, K. P., Jr, & Black, R. E. (2015). The epidemiology of global micronutrient deficiencies. Annals of nutrition & metabolism66 Suppl 2, 22–33.
  2. Council for Responsible Nutrition. Dietary Supplement Usage Up Dramatically During Pandemic, New Ipsos-CRN Survey Shows | Council for Responsible Nutrition ( Accessed on 09/17/2021.
  3. National Institutes of Health Office of Dietary Supplements. Dietary Supplements. Retrieved from: Accessed on August 31, 2021.
  4. The Federal Trade Commission. Dietary Supplements. Retrieved from: Accessed on November 10, 2021.
  5. National Institutes of Health. Dietary Supplements: What You Need to Know. Retrieved from:  Accessed on 09/15/2021.
  6. Food and Drug Administration Compliance Program Guidance Manual. Retrieved from: CP 7321.008, Dietary Supplements – Foreign and Domestic Inspections, Sampling, and Imports ( Accessed on September 15, 2021.
  7. National Institutes of Health. Nutrient Recommendations : Dietary Reference Intakes (DRI) ( Accessed on 09/16/2021.
  8. Centers for Disease Control and Prevention. DNPAO Data, Trends and Maps: Explore by Location | CDC Accessed on 09/15/2021.
  9. Araújo J, Cai J, Stevens J. Prevalence of Optimal Metabolic Health in American Adults: National Health and Nutrition Examination Survey 2009-2016. Metab Syndr Relat Disord. 2019;17(1):46-52. doi:10.1089/met.2018.0105
  10. Bailey R, L, West Jr. K, P, Black R, E: The Epidemiology of Global Micronutrient Deficiencies. Ann Nutr Metab 2015;66(suppl 2):22-33. doi: 10.1159/000371618
  11. Centers for Disease Control and Prevention. Therapeutic Drug Use. Retrieved from: FastStats – Therapeutic Drug Use ( Accessed on 09/17/2021.
  12. McCann JC, Ames BN. Vitamin K, an example of triage theory: is micronutrient inadequacy linked to diseases of aging?. Am J Clin Nutr. 2009;90(4):889-907. doi:10.3945/ajcn.2009.27930
  13. McCann JC, Ames BN. Adaptive dysfunction of selenoproteins from the perspective of the triage theory: why modest selenium deficiency may increase risk of diseases of aging. FASEB J. 2011;25(6):1793-1814. doi:10.1096/fj.11-180885
  14. Hyman, Mark. Food Fix. Little, Brown Spark. 2020.
  15. Boyle, NB, Lawton C, Dye L. The effects of Magnesium Supplementation on Subjective Anxiety and Stress – A Systematic Review. Nutrients. 2017; 9(5):429.
  16. Tarleton EK, Littenberg B, MacLean CD, Kennedy AG, Daley C. Role of magnesium supplementation in the treatment of depression: A randomized clinical trial. PLoS One. 2017;12(6):e0180067. Published 2017 Jun 27. doi:10.1371/journal.pone.0180067
  17. Food and Drug Administration. FDA 101: Dietary Supplements | FDA Accessed on 09/15/2021.