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The 3 Best Websites for the Science of Nutritional Supplements (plus one website that you should skip)

  • 10 min read

We'll be your guide in the search for science!

This may surprise you: doctors often don’t know much about nutrition or vitamins and supplements. “The reality is that physicians usually receive very little education on this in medical school,” says Dr. Sanders Chae, a cardiac electrophysiologist and a graduate of Harvard Medical School. “If your doctor isn’t motivated to read about nutrition then he or she won’t have that information and can’t advise you.” This is an unfortunate situation. As Dr. Mark Hyman, an author and well-known family physician, observes, "informed self-care — or what I call ‘self-health’ — is actually more effective than disease-based healthcare for many lifestyle-driven chronic conditions.”

So where to find information on the science behind your vitamins and supplements?  The two persistent questions that people research are (1) is it safe and (2) does it work.  How can you hope to answer those for yourself? 

The good news is that there is a LOT of information on the internet.  The bad news is that there is a LOT of information on the internet.  We have not found one perfect site, but this article points you to the best of them.

3 Best Websites for Information on Nutritional Supplements

Here are our top three websites for unbiased supplement information – including one that’s free.

SummaryUS government agency website that draws on scientific studies to assess effectiveness and safety of an exhaustive list of supplements

Cost: Free

ProsData is provided on an extensive list of products; extensive citations to scientific studies Cons: No branded-product reviews or analysis is a consumer-focused resource for supplement science.  It pulls supplement information from the Natural Medicines Comprehensive Database (NMCD) and, in a minority of cases, from the U.S. National Center for Complementary and Integrative Health, the Office of Dietary Supplements or the National Cancer Institute.  It is part of the U.S. National Institutes of Health (NIH).  Its mission is to present high-quality and easy to understand health and wellness information in both English and Spanish. 

The “herbs and supplements” section of the website allows you to browse a long list of vitamins, minerals and other specialty supplements to learn about effectiveness, safety, uses, the usual dosage and known drug interactions.  For each product, MedlinePlus presents an effectiveness rating for various use-cases, as well as a safety rating, all based on the evidence and assessments provided by NMCD.  The possible ratings for effectiveness are: effective, likely effective, possibly effective, possibly ineffective, likely ineffective and ineffective.

The ranking system that NMCD uses is really calibrated for pharmaceutical drugs, which are subject to FDA regulation.   For example, to earn an “effective” ranking a product must have passed “a rigorous scientific review equivalent to a review by the FDA, Health Canada, or other governmental authority” – which is to say, it must have been through large multiple-stage controlled clinical trials -- and been found effective for a specific indication.  This imposes a cost-barrier that most supplement companies simply will not be able to break through. 

MedlinePlus observes that “because a high level of evidence is required for a product to be rated Likely Effective or above, relatively few products achieve this rating.”    In fact, a product will qualify as “possibly effective” for a particular use only if “reputable references” find effectivness “based on one or more clinical trials.”  This is still a relatively high bar, and the most effective supplements generally achieve only a “probably effective” ranking. 

This conservative calibration for the ranking system makes reading the scientific summaries slightly disconcerting.  For resveratrol, for example, MedlinePlus indicates the product is “possibly effective” only for hay fever and obesity.  The screen shot below shows the top of the Omega-3 supplements page, which has the odd statement that Omega-3 supplements don’t reduce the risk of heart disease, but people who eat lots of fish (rich in Omega-3 fatty acids) are less likely to die of heart disease. screen shot of Omega 3 description

Bottom Line:  MedlinePlus is a useful resource for free information on the scientific support for supplement use, but keep in mind the calibration of its ratings system for effectiveness and safety.  Unlike (see below), MedlinePlus does not review or test specific brands and branded products.    Because of that is not a resource for finding the best brands, only for learning about nutritional supplements generally.

SummaryProvides product descriptions, summaries of scientific studies for more than one hundred products and product testing and reviews for dozens of brands

Cost: $47.40 for a one-year subscription or $78 for a two-year subscription

ProsUnbiased testing of branded products, with the results presented in a clear table; good guidance on purity, strength and price of branded products; extensive summaries of scientific studies on claims for health benefits Cons: The roundup of scientific studies is sometimes too sprawling to be useful; no summary table that weights the evidence; selection of brands for testing appears somewhat random


Don’t let the mid-1980’s branding and clunky navigation fool you: (“CL”) provides up-to-date product testing information and summaries of scientific research.    

CL is essentially a product-review and testing service, like a wellness-focused Consumer Reports.  It both lab-tests and reviews a dozen or more supplement brands for each product (e.g., Omega 3 fish oil, resveratrol, Vitamin D) and provides explanations of product origins.  These branded-product reviews are its strength and the core of its offering.  There is more, however: CL also provides summaries of the scientific studies on possible use-casese for each product. 

In addition to reviewing and testing vitamins, minerals and other supplements, CL evaluates and ranks functional foods, personal care products (such as air purifiers and water filters), and sports and energy products.  The October 2020 testing and review of water-filter pitchers, for example, revealed that some water-filter pitchers actually increase the amount of microplastic in water!  Yikes!

For dietary supplements, each product page starts with an executive summary: whether a product (e.g., Fish Oil) is effective and for what, how much you should take and in what form, and which brands are best.  Here is a screen shot showing the first two paragraphs from the Fish Oil summary and examples of the “CL Approved” seal that companies can earn. screenshot for fish oil supplements

After the executive summary, the full product page describes what the product is and what it does or claims to do, with references to the relevant scientific studies and assessments of the support for any claims. 

Next, CL provides a table that summarizes the results of tests that it runs on a large number of branded products – approximately 30 brands on the Fish Oil page.  Here’s a screen shot of the table for Fish Oil, showing results for the first tested brand: screenshot supplement lab test results

CL accepts no money from supplement companies, and this shows in the brand-review table.  Some brands earn an “approved” label and some receive the red “not approved” designation.  CL flags its top choices among the branded products it reviews based on what it considers to be the best combination of price, strength and purity.  Helpfully, product pages mention possible side effects and drug interactions, as well as brand warnings and recalls.

Brands that meet the CL quality criteria, based on CL’s own lab testing, are permitted to license the “CL Approved” label to place on products.  A product must be tested and meet the CL criteria every twelve months, with testing based on a random sample purchased on the open market, in order to continue using the seal.

The shortcoming of the CL website is that the summaries of scientific research can be quite sprawling, without any clear weighting of the various studies.  Also, there is no information about how often the scientific reviews are updated, or who is providing the summaries.  Without this it is hard to truly assess the results of all the science.

Bottom Line: If you are searching for branded-product test results, CL is the site for you.  If you’re looking for the science behind supplement products, is likely a better option, and free.  On CL, a subscription that allows you to view all product reviews and detailed scientific summaries is priced at $47.40 for one year or $78.00 for two years.   

TRC Healthcare

SummaryPhysicians and pharmacists are the target clients; not a user friendly design; producers of the Natural Medicines Comprehensive Database (NMCD)

Cost: $177 per year

ProsSite includes all information from the NMCD and a long list of branded products with lists of ingredients for each and notations where a product is USP Verified Cons: Site is not consumer friendly in its organization, and much of the information here is also available on MedlinePlus


The “natural medicines” subsection of the website for TRC Healthcare seems to be targeted primarily at doctors and pharmacists.  The subscription, at $177 per year, is expensive relative to other options.  The excellent information that TRC Healthcare compiles, in the form of the Natural Medicines Comprehensive Database, is largely available for free on the website. 

Like MedlinePlus, the TRC Healthcare site offers information on the relative safety and effectiveness of many supplements.  It also provides, for a very long list of branded products, a description of the ingredients and an indication of whether a product has been USP Verified or is a “Canadian Licensed Product.”  Here is a screenshot of the product page for fish oil.  As you can see, it lists over 6,000 branded products in total, of which 12 are USP Verified and over 1,500 are Canadian Licensed Products. 


Bottom Line: For a doctor being quizzed by a patient about the ingredients and effectiveness of a particular supplement, this website would be quite useful.  Sitting at her computer, the doctor could pull up an explanation of safety, efficacy and drug interactions, and then look up the various other ingredients that might be included in the particular product that the patient has purchased. For most consumers, however, a combination of MedlinePlus and will be more useful and at lower cost.

Not Quite Ready for PrimeTime –

Like ConsumerLab, charges consumers a monthly or annual fee to access its compilations of the scientific research into supplements. Unlike CL, however, Examine does not offer reviews of specific branded products. It is merely an information site that works to collect and analyze the scientific literature on a variety of products.

Behind its paywall the site provides information on many of the most popular supplement, including a description of what the supplement is (or what it’s made from), the benefits, the side effects and drawbacks, when and in what form to take it, frequently asked questions, and finally a “human effects matrix” that sets out in a table format: (a) the possible use cases for the supplement, (b) with the amount of evidence (indicated by the number of bars in a pyramid) that the supplement is effective for that use case, (c) the magnitude of the effect that the supplement will produce, (d) the consistency of study results along with the number of studies and links to those, and (e) explanatory notes.

I noticed a few problems with Examine. First, even after I subscribed to the service, the webpages were so stuffed with advertisements up-selling additional supplement reports that for a while I wasn’t sure that I had properly logged on. I expected that one benefit of the relatively high subscription fee would be an escape from constant upselling.

Second, the “Human Effect Matrix” (HEM) tables seemed to be showing results that are inconsistent with the information from the Natural Medicines Comprehensive Database (NMCD), as presented on MedlinePlus and TRC. I wrote to Examine to ask about the discrepancies I noticed on the resveratrol page. This is the response I received from a researcher at Examine in October 2020: “Unfortunately, our resveratrol page is wildly out of date and you can't take any of the Human Effect Matrix too seriously because it's lacking so many studies. Our pages range from more complete than Medline to much less complete, depending on the page. We're a small team and have had many roadblocks to keeping our pages up to date. Though we're finally on the right path, it will be a long time until they're all up to standard. I apologize for the inconvenience in that regard.”

Points for honesty, but also points lost for incomplete and out-of-date summaries of the science. This is an important issue, and one that should be flagged for Examine subscribers by the business up front. After all, the entire business of is premised on serving as a reliable source of information.

Bottom Line: Because the site, at least as presently populated, is less reliable than the others listed above – and because it’s also more expensive than – I recommend a taking a pass for now.

The Supplement Science Takeaway

Our favorite overall for information on supplement science is For information on the purity and strength of particular branded products, we rely on Some reading is required, but for those interested in supplementation the information on these sites is invaluable.

But if all of this seems too daunting, there is another option: talk with a health coach or a certified nutritionist.

A health coach is trained not only in nutrition, but also in aligning your lifestyle with your health goals. The Health Coach Institute provides recommendations on how to find a coach.

A nutritionist will have studied diet and nutrition and is often recommended to patients if a doctor believes that guidance is required in connection with an illness or surgery.  Ask your doctor or hospital to recommend one. In the U.S. you can also search for a nutritionist on the website of the Academy of Nutrition and Dietetics. 

If you are, instead, undaunted and wanting more, more, MORE science, then consider the additional resources we have included below.

Good luck! And if you think we’ve missed any particularly valuable resources please let us know.

Additional Resources


PubMed is a free resource that is a service of the U.S. National Library of Medicine at NIH. It contains publication information and (in most cases) brief summaries of articles from scientific and medical journals – offering more than 30 million citations and abstracts of biomedical literature. It does not include full-text journal articles, but it does link to the full text when that is available from other sources such as the publisher's website.

U.S. Office of Dietary Supplements (ODS)

Part of NIH, ODS evaluates scientific information, supports research, and shares research results for the benefit of the public. Its resources include publications (such as Dietary Supplements: What You Need to Know), fact sheets on a variety of specific supplement ingredients and products (such as vitamin D and multivitamin/mineral supplements), and the PubMed Dietary Supplement Subset.

U.S. National Center for Complementary and Integrative Health (NCCIH)

Part of NIH, the NCCIH has a variety of general information to help understand health and wellness topics around natural and complementary medicine, including publications and the ability to search U.S. federal databases of scientific and medical literature.

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