Dietary Supplements – The Wild West of Good, Bad, and a Whole Lot of Ugly

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Dietary Supplements – The Wild West of Good, Bad, and a Whole Lot of Ugly

My dear friend, Dónal O’Mathúna, PhD, and I co-authored a review article in the September 2022 edition of the Medical Clinics of North America, titled, “Dietary Supplements – The Wild West of Good, Bad, and a Whole Lot of Ugly.” The publisher, Elsevier, has graciously granted me permission to post it here for you.

By the way, if you like this article, you can learn more in my newest book on the topic, for which Dónal wrote the introduction, The Natural Medicines Handbook: The Truth about the Most Effective Herbs, Vitamins, and Supplements for Common Conditions.

Order the book or learn more

Dietary Supplements – The Wild West of Good, Bad, and a Whole Lotta Ugly

Copyright © 2023 Elsevier Inc. Used with permission; however, no part of this particular posting may be reproduced, in any form or by any means, electronic, photocopying or otherwise, without permission in writing from Elsevier Inc, which cautions that their content “is intended for healthcare professionals.”

Dónal O’Mathúna BSc(Pharm), MA, PhD (College of Nursing, Helene Fuld Health Trust National Institute for Evidence-based Practice in Nursing and Healthcare, The Ohio State University, Columbus, OH 43210, USA) and  Walter L. Larimore MD (UCHealth Occupational Medicine Clinic, 13445 Voyager Pkwy, Colorado Springs, CO 80921, USA)

Med Clin N Am 106 (2022) 881–898.  (


None of the authors have any commercial or financial conflicts of interest. No funding source was used. Drs Larimore and O’Mathüna indicated they do not nor ever have had any financial relationship with any commercial publications mentioned in this article. Dr Larimore does serve as a volunteer physician peer-reviewer for Prescriber’s Letter.


The popularity of and market for natural medicines (herbal remedies, dietary supplements, and vitamins) is accelerating. At the same time, evidence for their effectiveness (both in general and for specific conditions) and safety remains poor in many instances. Independent evaluations have identified products that are poorly manufactured, contaminated, or mislabeled. We examine data on cannabidiol (CBD) to exemplify these problems. Yet consumers often are unaware of these concerns and problems and continue to believe that “natural” means “safe.” The current U.S. regulatory framework founded in the 1994 Dietary Supplement Health and Education Act (DSHEA) does not adequately protect the health of U.S. consumers and urgently needs to be revised. At the same time, clinicians should update themselves regularly with the best available evidence on the natural medications most relevant to their areas of practice. We recommend some evidence-based resources that will help clinicians and their patients remain current in this area.

Key Points:
  • Dietary supplements, herbal remedies, and vitamins (natural medicines) remain extremely popular with consumers.
  • Evidence for the effectiveness, safety, and quality of many natural medicines is often lacking.
  • Consumers often have both inaccurate beliefs and incomplete knowledge about natural medicines. For example, most believe “natural” means “safe.”
  • Regulation of and advertising about natural medications in the United States urgently needs revision to better protect public health.
  • Clinicians and consumers need independent and trustworthy information about natural medicines along with independent lab testing of products identifying those inaccurately labeled or contaminated.
Clinics Care Points:
  • Clinicians are often surprised to learn how many natural medicines (herbal remedies, dietary supplements, or vitamins) their patients are taking.
  • Each patient’s history should include all the natural medicines they take either regularly or as needed.
  • Patients should be advised verbally and/or via handout of the potential benefits, side effects,, and risks, including interactions with conditions, foods, lab tests, and/or other prescribed or over-the-counter medications they may be taking.
  • If there is evidence supporting the recommendation of a natural medication for a particular patient, recommendations should also be made of specific products that have been passed or approved by an independent quality testing organzation.

Keywords: dietary supplements, natural medicines, herbal remedies, herbs vitamins, evidence, advertising, quality, effectiveness, safety, cannabidiol, CBD, vitamin C


The market for herbal remedies, dietary supplements, and vitamins (what are collec-tively called “natural medicines”) continues to grow. For decades now, the interest in and purchasing of these products has not decreased. But neither have the concerns that we have been writing about for more than 20 years. Foremost among these is the myth that just because something is “natural,” it must be safe.1 The natural world con-tains many poisonous and dangerous things. Just because it’s “natural” or has “nat-ural” on the label, does not make something safe, and it also doesn’t necessarily mean it will do any good.

Questions that health professionals and their patients should all ask before recom-mending or taking any remedy or treatment include: What’s the evidence that this works? If it works, will it work for my condition? What sorts of side effects might it have? Was it manufactured to the highest possible standards? Was it tested to make sure that what’s on the label is in the bottle? And does it contain anything it shouldn’t have in it?


Natural medicines are trendy across most of the developed world. According to a 2019 report, the global natural medicines market was valued at about $140 billion US dollars (USD) in 2018 and could reach over $216 billion USD by the year 2026, at a compound annual growth rate (CAGR) of 5.5%.2 Another report estimated that the global dietary supplements market is expected to reach over $220 billion USD in 2022 while growing at a CAGR of 8.8%.3

Unfortunately, much of the advertising for these products is inaccurate, with the marketing claims far exceeding scientific data on safety and effectiveness. In a sys-tematic review for the lay public, one of us (WL) evaluated about 1300 natural medi-cines or lifestyle interventions for about 550 conditions or indications. Two-thirds did not have evidence of safety or effectiveness—not only being a waste of time and money but in some cases even dangerous (Table 1).4

Table 1

Evidence available on the safety and effectiveness of 1300 natural interventions or medicines

w1300 Natural Medicines or Interventions Evaluated for w 550 Conditions/Indications
*****                        83                    6%                     150                   11%

****                         67                    5%

***                           88                    7%                     269                   22%

**                            69                    5%

*                              103                  10%

☹                             888                  67%                    888                   67%
***** Effective and Likely Safe
**** Likely Effective and Likely Safe
*** Effective and Possibly Safe
** Likely Effective and Possibly Safe OR Possibly Effective and Possibly Safe

* Possibly Effective and Possibly Safe

☹ Insufficient Evidence, Possibly Ineffective, Possibly Unsafe, Ineffective, OR Unsafe


Our best-selling books on alternative medicine and natural medicines5,6 did very well with the public because the use of natural medications was hugely popular. It still is is, being approximately a $30 billion industry in the US, with over 90,000 products on the market in 2018.7In 2020, Natural Medicines listed over 185,000 products in the US and Canada.8 Four out of five Americans regularly take a natural medicine.

A 2021 consumer survey by the Council for Responsible Nutrition (CRN) announced, “Supplement usage among Americans has steadily increased in the more than twenty years CRN has conducted the survey,” adding, “With 80% of Americans now using supplements, these products are now mainstream and broadly accepted by the American public. Just as important, 79% of Americans believe the dietary supplement industry is trustworthy, a jump of 5 percentage points from 2020.” Ac-cording to CRN, “50% of supplement users report a change to their supplement routine since the COVID-19 pandemic started, and 55% of those who reported a change indicated that it included adding new supplements to their existing routine.”9

A 2019 national survey reported 86% of Americans took natural medicines, espe-cially vitamins and dietary supplements10 – with 48% of adults taking vitamins and 39% taking minerals—most to “maintain health and prevent disease.”11 Another na­tional survey showed that 52% of US adults reported the use of at least 1 natural med-icine a day7 while 10% reported using at least 4 such products daily.7Although these percentages vary from source to source, depending upon who and how they sur-veyed, the point is that natural medicines are very popular.


What are the top reasons people provide for taking supplements? It varies by age group, but some themes run across the generations(Table 2).12

Table 2

Top reasons why people take supplements by age groups

18–34 y 35–54 y 55D y
Overall Wellness (42%) Overall Wellness (47%) Overall Wellness (49%)
Energy (37%) Energy (33%) Fill Nutrient Gaps (33%)
Hair, Skin, Nails (28%) Fill Nutrient Gaps (32%) Bone Health (31%)
Immune Health (25%) Immune Health (31%) Heart Health (29%)
Fill Nutrient Gaps (22%) Hair, Skin, Nails (23%) Healthy Aging (28%)
Weight Management (21%) Digestive Health (21%) Joint Health (23%)

What are the most popular natural medicines? Different surveys give different pic-tures, but some similar patterns are visible. ConsumerLab, in its “2022 Survey of Vita­mins & Supplement Users,”13 reported on the responses of 8049 US adult subscribers (with over 80.6% taking at least 4 different supplements daily). Among the top 50 sup-plements, only 8 declined in popularity, while 42 showed an increase (Table 3).

Table 3

Top supplements taken by consumers ( survey)

1.  Vitamin D Vitamin D (-0.4 pts) remained the most popular supplement, purchased by 72.6% of respondents.
2.  Magnesium With a continued rise in popularity, magnesium secured its place as the second most popular supplement and is used by 51.8% of respondents.
3.  Fish oil Was surpassed by magnesium for third place.
4.  CoQ10: Remained in fourth place.
5.  Multivitamins 43.3% of respondents, +1.0 pts
6.  Vitamin C (including Rose Hips) 41.9%, -0.1 pts
7.  Probiotic (eg, Acidophilus, Lactobacillus) 38.7%, +2.3 pts
8.  Zinc 36.9%, +1.2 pts
9.  Curcumin/Turmeric (as Supplement) 35.9%, +2.3 pts
0.    Vitamin B12 (Cobalamin) 33.3%, +4.0 pts

Data from survey.

In contrast, a CRN survey of 2006 adults in the US, of whom 1529(76%) considered themselves supplement users, reported different findings (Table 4).12

Table 4

Top supplements taken by consumers (CRN survey)

1.  Multivitamins 58%
2.  Vitamin D 31%
3.  Vitamin C 28%
4.  Protein 21%
5.  Calcium 20%
6.  Vitamin B or B complex 20%
7.  Omega 3 fatty acids or fish oil 16%

Data from CRN survey.

Again, the disparate results reflect different populations surveyed and the use of different survey tools.


The Nation Center for Complementary and Integrative Health (NCCIH) writes, “A lot of people believe that when it comes to medicine, natural’ is better, healthier, and safer than unnatural’ or synthetic drugs.” They add, “Some people also believe that natu-ral’ products are safe because they believe these medicines are free of chemicals.”14 Around the world, people seem sold on the marketing claims that these products will allow them to avoid the ”toxic” drugs foisted upon them by “the evils of Big Pharma” that “seeks enormous profits over the health and well-being of the humans it serves.”15

An article in Science-Based Medicine adds, “Supplements are marketed as safe, natural, and effective, and there is no question that messaging has been effective.”16 CRN states, “85% of Americans are confident in the safety and quality of supplements

overall—and, unsurprisingly, in vitamins and minerals especially, which received an 88% confidence response.” Additionally, CRN added, “76% of Americans perceive the dietary supplement industry as being trustworthy.”12

Unfortunately, false advertising, inflated claims, poor manufacturing practices, inac-curate labeling, and contaminated products are far more common than most health professionals and consumers suspect.


JoAnn Manson, MD, chief of the Division of Preventive Medicine at Brigham and Women’s Hospital in Boston, states, “Most supplements on the market are not tested for either efficacy or safety.”17 In contrast with “pharmaceuticals, which undergo extensive testing to prove they’re effective and safe before they can be sold, dietary supplements can be sold without proof of effectiveness or safety. Moreover, supple-ment makers can claim their products enhance health, despite a dearth of evidence in most cases.”18 A 2018 editorial in the Journal of the American Medical Association (JAMA) added, “Clinicians and patients should also be aware that the US Food and Drug Administration is not authorized to review dietary supplements for safety and ef-ficacy prior to marketing.”19


Natura! Medicines explains, “Most dietary supplements cannot legally claim to treat, cure, or prevent a disease. Doing so makes them legally unapproved drugs.”20 Unfor-tunately, the FDA and the Federal Trade Commission (FTC) often must issue warning letters to companies because of “advertisements and labels touting the supplements’ ability to treat or cure Alzheimer’s, cancer, and myriad other diseases. The warning let-ters specifically call out the manufacturers for making unapproved drug claims and deceptive statements.”21 Natura! Medicines explains that “many supplement com-panies bank on the ignorance of consumers and continue to skate this line. It can sway those with serious medical conditions away from using proven therapies.”20


In 2010 testimony before the US Congress, Tod Cooperman, MD, the President and Founder of, cited common problems with natural medicines sold in America (Box 1).22

Unfortunately, the situation has not improved greatly. In early 2020, ConsumerLab reported that about one in 5 supplements in the US and Canada that they tested did not meet one or more quality parameters. This is true even though ConsumerLab’s testing tends to focus on the more popular and established brands that would be ex-pected to have the best findings.

SURPRISING FAILURE RATES IN FOLLOWING GOOD MANUFACTURING PRACTICES also reported on information from the FDA (obtained by a Freedom of Information Act request) revealing that 51% of 598 US dietary supplement manufacturing facilities audited from October 1, 2018, through September 30, 2019, failed inspections and received letters of noncompliance with good manufacturing practices (GMP).23

The situation has been worse. The failed inspection rate in US facilities peaked at 70% in 2012. “Although an improvement over past years,” says Dr Cooperman, “the most recent FDA audits show that, overall, dietary supplement manufacturers need to do a lot better.” He added, “Consumers often express concern about supplement ingredients from China, but the US is doing no better than China based on this limited sampling. People may also be surprised that four out of five facilities were noncompliant in Germany, where many herbal supplements have drug status, although our own tests have also shown issues with some products from Germany.”23

The FDA noted a median of 4 infractions at facilities that received notices, although they did not release a list of the specific violations of each facility. Nevertheless, the most common breaches have each been observed at more than 15% of noncompliant facilities (Table 5).23

Table 5

Common infractions found during FDA inspections at facilities producing natural medicines

1.  Not establishing product
specifications for the identity,
purity, strength, or composition
of the finished dietary
25% of facilities inspected
2.  Not establishing or following
written procedures for quality
control operations.
3.  Not producing batch records,
which include the complete
information relating to the
production and control of each

A 2015 study by the New York Attorney General concluded, “DNA testing . shows that, overall, just 21% of the test results from store brand herbal supplements verified DNA from the plants listed on the products’ labels—with 79% coming up empty for DNA related to the labeled content or verifying contamination with other plant material.”24 In other words, they found that if a consumer purchased one of the tested herb-al supplements, they had a four-in-five chance of being duped.

In February 2019, FDA Commissioner Dr Scott Gottlieb said, “The growth in the number of adulterated and misbranded products—including those spiked with drug ingredients not declared on their labels, misleading claims, and other risks—creates new potential dangers.”25


Science-writer Markham Heid reported, “Despite recent studies that find supplements are frequently contaminated or that the best way to get nutrients is through food, Americans’ interest in supplements is only growing. And experts say many supple-ment users don’t recognize or appreciate the risks that accompany the use of these products.”17 Dr Manson compares “the current regulatory environment to ‘the Wild West.’”17 In 2018, a study in JAMA Network Open reported, “From 2007 through 2016, 776 adulterated dietary supplements were identified by the FDA and 146 different dietary supplement companies were implicated.”26


A recent example surrounds the growing popularity of cannabidiol (CBD). The market size is soaring at about 27% CAGR globally27 with projections that “the collective market for CBD sales in the US will surpass $20 billion [USD] by 2024.”28The New York Times reports, “We are bombarded by a dizzying variety of CBD-infused products: beers, gummies, chocolates and marshmallows; lotions to rub on aching joints; oils to swallow; vaginal sup-positories for soothing,’ in one company’s words, the area that needs it most.’”29

According to the New York Times, even CVS and Walgreens have announced plans to sell CBD products in certain states. It adds, “Many of these products are vague about what exactly CBD can do. … Yet promises abound on the internet, where numerous articles and testimonials suggest that CBD can effectively treat not just ep-ilepsy but also anxiety, pain, sleeplessness, Crohn’s disease, arthritis, and even anger…. The FDA…. sent out a flurry of letters warning companies not to make medical claims.”29

In 2015, an academic study reported that it found that many CBD-labeled products contained very little CBD.30 Two years later, another study published in JAMA found that in 84 CBD products sold online, 36(43%) had more CBD than advertised, and 22 (26%) had less. Also, 18 of the 84 products (21%) contained THC (the psychoactive component of marijuana), with none listed on the label, making it potentially illegal to purchase in some jurisdictions.31


Besides the many regulatory difficulties with natural medications, many other potential dangers exist for consumers. For example, one group of independent pharmacy professionals wrote, “Although many people don’t realize it, dietary supplements can cause serious health concerns when taken incorrectly. In fact, they are a common reason for calls to U.S. Poison Control Centers, and dietary-supplement-related calls are on the rise.”32

For example, from 2000 to 2012, US Poison Control Centers received nearly 275,000 calls related to dietary supplements (or one call every 24 minutes) with an almost 50% increase between 2005 and 2012. One in 20 calls reported a serious med-ical outcome, including, in rare cases, death. The majority of the calls involved miscellaneous dietary supplements, followed by botanicals and hormonal products. Of these, 70% related to dietary supplement use in children younger than 6 years old.33The pharmacists added, “These exposures were mostly accidental, so it’s important to store dietary supplements out of the reach of children.”32


Another critical issue is the possibility of the interactions and direct toxicities of natural medicines. The NCCIH warns, “Although there is a widespread public perception that herbs and botanical products in dietary supplements are safe, research has demon-strated that these products carry the same dangers as other pharmacologically active compounds. Interactions may occur between prescription drugs, over the counter drugs, dietary supplements, and even small molecules in food — making it a daunting challenge to identify all interactions that are of clinical concern.”34

In 2019, researchers from Harvard’s T.H. Chan School of Public Health found that of the single-supplement-related adverse event reports in children and young adults, “approximately 40% … involved severe medical outcomes, including death and hos-pitalization; supplements sold for weight loss, muscle building, and energy were asso-ciated with almost three times the risk for severe medical outcomes compared to vitamins; and supplements sold for sexual function and colon cleanse were associ-ated with approximately two times the risk for severe medical outcomes compared to vitamins.”35


Despite ubiquitous advertising claiming that natural medicines (as a broad category) are effective, very little reliable evidence supports most of these claims. “With a few exceptions, the research done on dietary supplements is unconvincing and largely negative.”16 The National Institute on Aging (NAI) adds, “Some advertisements for dietary supplements in magazines, online, or on TV promise that some of these prod-ucts will make you feel better, keep you from getting sick, or even help you live longer. It’s important to know that often, there is little, if any, science supporting these claims.36


Health professionals and consumers in America can rely on prescriptions and FDA-regulated over the counter medications to be high-quality, safe, and effective. The same is not true for natural medicines. Scott Gavura, writing for Science-Based Med-icine, explains how this situation arose:16

“It’s a consequence of legislation deliberately designed to weaken the FDA’s ability to regulate and provide oversight of supplements. The Dietary Supplement Health and Education Act of 1994 (DSHEA) was an amendment to the US Federal Food, Drug, and Cosmetic Act that established the American regulatory framework for dietary supple-ments. It effectively exc!udes manufacturers of these products from many of the re-quirements that are in place for prescription and over-the-counter drugs. Amazingly, it puts the requirement to demonstrate harm on the FDA, rather than the onus on the manufacturer to show a product is safe and effective.”

Natura! Medicines adds: “One of the biggest differences between drug regulations and dietary supplement regulations is the approval process. There is NO approval process for dietary supple-ments. As long as supplements contain dietary ingredients that were either already used in supplements before DSHEA (1994), or established as reasonably safe since then, they can be sold to consumers lawfully. This is very different from drugs, which must go through an extensive approval process BEFORE entering the market. Basically, drugs are assumed unsafe until proven safe, whereas supplements are assumed safe until proven otherwise.”37


Unless Congress repeals or revises the DSHEA Act, the only hope for the average health professional or consumer considering recommending or using a natural medi-cation is to ask the questions we’ve adapted from the PBS 2016 Frontline special, “Supplements and Safety” (Table 6).38

Table 6

Questions to ask and answer before recommending or using a natural medicine

1.  Has the product triggered any health warnings or sanctions? . Search the FDA’s website for a list of all recalls (

. notifies its

subscribers of significant warnings and recalls.

. Given the few resources put into monitoring supplement safety issues, a lack of notices is no assurance of quality or safety.

2.  Does the product sound too good to be true? Supplement makers cannot legally make unfounded claims of efficacy; however, these sorts of claims regularly appear on products or the Internet. Extraordinary claims should not be believed.
3.  Is there evidence that the supplement does what it promises? Look to reputable peer-reviewed resources that summarize evidence without bias. If good evidence supporting efficacy and safety claims is not readily available, that is a giant red flag that the product may be bogus.

In general, the Internet is an unreliable place for people to do research on natural med-icines. One Scientific American blog reported that among health websites, retail web-sites presenting information on products they were selling had the lowest level of medical accuracy (only 9%). On the other hand, government websites (.gov) and web-sites of national organizations (.org) had the highest level of accuracy (81 and 73%, respectively). It is problematic that even these “reputable” sources were not 100% accurate.39

Surprisingly, the same blog reported that educational websites (.edu sites, e-books, peer-reviewed articles) only had 50% accurate medical information. Most of the books found by search engines either provided outdated or irrelevant information. Blogs and websites of individuals are even worse, having low rates of accuracy (26 and 30%, respectively).39


Several trustworthy, medically accurate, unbiased, and evidence-based sources of in-formation are available at no cost and can be recommended:

  1. The National Institutes of Health (NIH) has summaries about the most consumed supplements—vitamins and minerals—in a series of fact sheets.40
  2. The US National Library of Medicine’s MedlinePlus has similar information about drugs, herbs, and supplements.41
  3. Resources are also available for specific groups. For example, the Department of Defense offers information about the safety of specific supplements for service members.42 Older adults can find resources specifically designed for them by the FDA,43 FTC,44 and NIA.36
  4. The NIH’s National Center for Complementary and Integrative Health (NCCIH) pro-vides information about complementary health products and practices—including many natural medicines.45

These sites can give general information on natural medicines but are of very little help when it comes to choosing specific products for specific diagnoses, especially in a highly unregulated environment.


How does a busy health professional keep up with this often-hard-to-find information about natural medicines that are safe and effective for common conditions—and affordable (another relevant factor)? The only real protection health professionals and consumers have from inaccurate information, unscrupulous manufacturers, untrained salespeople, and fraudulent, contaminated, or dangerous products is to recommend or use products that have been tested by an independent lab which makes the data available to the public.

Labs such as, the National Sanitation Foundation (NSF Interna­tional),, and the United States Pharmacopeia (USP) purchase products from the marketplace (big box stores, health food stores, pharmacies, the Internet, etc.) and test them or have them tested for quality.

The two largest and oldest organizations for evidence-based information on natural medicines, including details on specific brands, and Natura! Medicines. uses a variety of labs for its tests to evaluate products, while Natura! Medicines highlights products that are USP-Verified. Both organizations are independent of the natural medicine industrial and sales complex and make their findings and recommendations publicly available via Internet subscription. You can also get free online information from NSF, USP, about the products they have evaluated.

For over 2 decades we’ve recommended the constantly updated and evidence-based information from the experts in natural medicines and Natura! Medicines. In our opinion, these 2 groups provide the most up-to-date, accu-rate information on safe, effective, and economical options to consider. Furthermore, they help people avoid potentially dangerous, unproven, and money-wasting natural medicines.a, LLC, founded in 1999, has been a leading provider of indepen­dent test results and information to help consumers and health professionals identify the best quality health and nutrition products. It publishes results of its tests in comprehensive reports at a subscription website,, along with expert answers to many common questions about natural medicines and integra­tive medical practices. They frequently post news reports and information about re-calls and warnings. claims to have “perhaps the highest testing standards of any third-party group certifying the quality of dietary supplements” and “are also the only third-party verification group that freely publishes its testing methods and quality criteria/standards.” Their standard is to test products for at least 5 characteristics (Box 2). Products that pass all the tests are “Approved” and are eligible to bear the ConsumerLab “Seal of Approval” on their label, which “guarantees consumers the specific product carrying the Seal has met ConsumerLab’s standards and passed all of ConsumerLab’s tests for ingredient quality.”

The ConsumerLab Seal also indicates the specific ingredients of the product that were laboratory tested by experts. In addition to the products it selects to review, Con-sumerLab enables companies of all sizes to have the quality of their products tested for potential inclusion in its list of “Approved” products.

ConsumerLab gives the typical cost (in USD) of each product they review, which helps with price comparisons and helps consumers determine which products offer the best value. ConsumerLab also provides their “Top Picks” for each natural medi-cine tested.

Since 1999, ConsumerLab has tested more than 5600 products, representing over 850 different brands and nearly every type of popular supplements for adults, children, and pets. We consider to be the Consumer Reports of natural medicines.


For example, ConsumerLab tested 31 vitamin C products in February 2020. Three failed, and 28 were “Approved.” Of those “Approved,” ConsumerLab chose 3 prod-ucts as their “Top Picks.” The cost to obtain 500 mg of vitamin C from each product they tested, based upon the price they paid, ranged from as little as 1 cent to as much as $2.80.

However, among these products, the suggested daily doses ranged from 63 mg to 5000 mg. Such a broad range provides another reason why someone should not just follow the instructions on a natural medicine label. People should choose a product that will provide the amount of vitamin C they need. Consum-erLab’s “Top Picks” help do that. Their reviews also list vegan and kosher products.


Natural Medicines, formerly known as The Natura! Medicines Comprehensive Data-base, is also a subscription website and is published by independent pharmacy pro-fessionals who also publish Prescriber’s Letter. They provide authoritative, independent, evidence-based information and resources on natural medicines as well as complementary, alternative, and integrative therapies which provide health professionals and the public with interactive tools and over 1250 monographs on the safety, effectiveness, and cautions for food, vitamins, herbs, and supplements and an additional 150 monographs on health and wellness topics. For each condition or diagnosis, Natura! Medicines advises about each substance or therapy with 2 ratings:

  1. SAFETY, which is broken into: “Likely Safe,” “Possibly Safe,” “Insufficient Evidence for Safety,” “Possibly Unsafe,” “Likely Unsafe,” or “Unsafe.” Meredith Worthington, PhD, the former Senior Editor at Natura! Medicines, writes, “Our ‘Likely Safe’ rating means that an ingredient has good evidence of safe use and would generally be considered appropriate to recommend.”46
  2. EFFECTIVENESS: “Effective,” “Likely Effective,” “Possibly Effective,” “Insufficient Evidence for Effectiveness,” “Possibly Ineffective,” “Likely Ineffective,” or “Ineffective.”

All ratings are based upon evidence-based, peer-reviewed, objective standards. One caution about the Natura! Medicines ratings when it comes to their term “Possibly Effec-tive” is, “A product might be rated ‘Possibly Effective’ for one condition but be rated ‘Likely Ineffective’ for another condition, depending on the evidence.” Furthermore, by “Possibly Effective,” they mean, “This product has some clinical evidence support-ing its use for a specific indication; however, the evidence is limited by quantity, quality, or contradictory findings. Products rated ‘Possibly Effective’ might be beneficial, but do not have enough high-quality evidence to recommend for most people.”46

Natura! Medicines also has extensive information on “Health and Wellness” topics (ie, everything from “Acupressure” to “Zero Balancing”), including many complementary and alternative medicine (CAM) therapies. Their NMBER (Natura! Medicines Brand Evidence-based Rating) rating is provided for over 185,000 commercial brand products. NMBER provides an objective, scientific rating for most commercially available natural medicines and rates each from 1 to 10, with 10 being the highest. We do not recommend any product unless it has an NMBER rating of 8 or higher. Natura! Medicines licenses its content to WebMD. We think of Natura! Medicines as the PDR of natural medicines.

Both organizations make most of their information available via subscription and their reviews are continually updated. Having access to one or both can provide health professionals with the latest information on these topics or products as well as other content such as the latest recalls and warnings, answers to common questions, inter-actions with tests or other medications, and more.


In Box 3, we’ve adapted the cautions NCCIH gives health professionals and con-sumers when it comes to natural medications.47

For health professionals, having easy-to-find, objective, evidence-based, and up-to-date information on natural medicines is critical to providing quality patient care. This information must include the evidence for the safety, effectiveness, interactions, adverse effects, and appropriate condition-specific dosing for any natural medicine that is recommended to patients. At this point in time, it seems that ConsumerLab.-com and Natura! Medicines are the best sources for clinicians.


David S. Seres, MD, ScM, PNS, FASPEN.

Dönal O’Mathüna, BSc(Pharm), MA, PhD.

Walter L. Larimore, MD, FAAFP, DABPS.

Vitamin D has received enormous attention in the medical literature, and supple-mentation has been touted for prevention of cardiovascular disease, cancer, respira-tory illness, improving outcomes in the critically ill, and most recently for the prevention and treatment of COVID-19. In the aggregate, and despite the thousands of observa-tional studies and reviews showing clear correlations, randomized trials do not sup-port a role for vitamin D in primary or secondary prevention,48,49 other than in the presence of deficiency. In a Cochrane systematic review and meta-analysis of ran-domized controlled trials (RCTs) that reported mortality, a potential for decreased mortality was seen in the elderly, likely due to a higher risk for deficiency in that pop-ulation.49 In an RCT of older adults, high dose supplementation did not prevent acute respiratory infections.50 Moreover, there is potential for harm. In a large cohort study from the Centers for Disease Control and Prevention’s (CDC) National Health and Nutrition Examination Survey (NHANES), vitamin D supplement use was associated with all-cause mortality.51

A true deficiency occurs only when the lack of a substance causes a pathology that is reversed or prevented when the substance is replaced or supplemented. Low levels of numerous nutrients often occur because of disease activity, and do not represent deficiency. Take, for instance, the relationship between calcium and albumin. Since much of the calcium in the bloodstream is bound to albumin, a decrement in albumin causes a decrement in calcium. But this is not a deficiency, and adjustment of calcium based on albumin is taught to every medical student.

Similarly, vitamin D binding protein (VDBP), onto which most of the vitamin D in the bloodstream is bound, drops because of acute illness and systemic inflammatory response.52 This is thought to be due to the same mechanism by which albumin drops, that is capillary leak. The sicker the patient, the greater the capillary leak and the lower the carrier protein levels. It is no surprise and indisputable, therefore, that there are strong correlations between vitamin D levels and length of stay and mortality in the critically ill,53,54 just as there are strong associations between albumin and outcome. But only VDBP, and not free vitamin D, is correlated with ICU survival when both are measured.55 Moreover, supplementation has failed to result in benefit in RCTs.56,57 Thus, these reductions in vitamin D levels are disease epiphenomena, and do not represent deficiency in the critically ill.

Within the first few months of the SARS-CoV-2 pandemic, theoretic and observa-tional studies reporting a relationship between vitamin D and COVID-19,58 and health experts touting the potential benefits of vitamin D supplementation for the prevention and treatment of COVID-19 were making national news.59–61 Of note, the first of these studies58 made national news after it was made available as a preprint prior to peer review at the British Medical Journal (BMJ). It was subsequently rejected by the BMJ, and (to the best of our knowledge) has never been published in a peer reviewed journal. The growing popularity and acceptance of preprints has been a problematic development during COVID-19.62 Evidence-based reviewers, such as the pharma-cology experts at Natural Medicines, continue to say, “There is insufficient reliable ev-idence to rate” vitamin D for the prevention or treatment of COVID-19.63

Despite the clear pathophysiology for low vitamin D levels in these patients, and RCTs showing no benefit from supplementation in critical illness or COVID-19, authors continue to promote supplementation as primary prevention for these conditions and refer to low levels as “deficiency.”64

Nevertheless, given the myriad immune mechanisms dependent on vitamin D,65 it is highly likely that patients with true vitamin D deficiency are more likely to have worse outcomes from critical illness or COVID-19, and there may be benefit for them from supplementation.66 But the role for population-wide supplementation with vitamin D to prevent or treat COVID-19 is far from established.


Dönal O’Mathüna, BSc(Pharm), MA, PhD, is Associate Professor in the College of Nursing, The Ohio State University (OSU), Columbus, Ohio, the director of the OSU Cochrane Affiliate at the Helene Fuld Health Trust National Institute for Evidence-based Practice in Nursing and Healthcare, and is on the Executive Committee, Cochrane US Network.

Walter L. Larimore, MD, FAAFP, DABPS, is a family physician, medical journalist, and best-selling author who has been listed in “The Best Doctors in America,” “Distin-guished Physicians of America,” “Who’s Who in the World,” and “International Health Professionals of the Year,” and who practices in Colorado Springs, Colorado.

David S. Seres, MD, ScM, PNS, FASPEN, is director of medical nutrition and associate professor of medicine in the Institute of Human Nutrition, Columbia Uni-versity Medical Center, New York, NY; directs the nutrition support service, the medical school nutrition curriculum, and one of the few clinical nutrition fellowships for physicians in the US; serves as a clinical ethicist and a Columbia University/ OpEd Project Public Voices Fellow; and was honored with the prestigious Excel­lence in Nutrition Education Award from the American Society for Nutrition.

  • Clinicians are often surprised to learn how many natural medicines (herbal remedies, dietary supplements, or vitamins) their patients are taking.
  • Each patient’s history should include all the natural medicines they take either regularly or as needed.
  • Patients should be advised verbally and/or via handout of the potential benefits, side effects, and risks, including interactions with conditions, foods, lab tests, and/or other prescribed or over-the-counter medications they may be taking.
  • If there is evidence supporting the recommendation of a natural medication for a particular patient, recommendations should also be made of specific products that have been passed or approved by an independent quality testing organization.

None of the authors have any commercial or financial conflicts of interest. No funding source was used.

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© Copyright WLL, INC. 2023. This blog provides healthcare tips and advice that you can trust about a wide variety of general health information only and is not intended to be a substitute for professional medical advice, diagnosis, or treatment from your regular physician. If you are concerned about your health, take what you learn from this blog and meet with your personal doctor to discuss your concerns.

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