The $60 Billion Problem
The U.S. supplement industry generates over $60 billion in annual revenue. The FDA does not approve supplements before they reach store shelves. Manufacturers are responsible for their own quality control. There is no requirement to prove a supplement works before selling it. There is no requirement to prove the bottle contains what the label claims.
Read that again. Unlike prescription drugs, which must survive years of clinical trials and FDA review before reaching consumers, supplements operate under a 1994 law called DSHEA that essentially treats them as food. The FDA can only act after a product has caused harm. By then, you have already bought it.
This creates a market where good products and worthless products sit side by side on the same shelf, wearing nearly identical labels. Some contain exactly what they claim, in clinically effective doses, verified by independent labs. Others contain less than half the labeled amount, use poorly absorbed ingredient forms, hide behind proprietary blends, and have never been tested by anyone outside the factory.
The review sites that should help you tell the difference are mostly making the problem worse. Search "best magnesium supplement" and you will find listicles that rank products they have never tested, cite no research, and earn affiliate commissions on every recommendation. The scoring rubric, if one exists, was bolted on after the affiliate links were already in place.
We built our scoring methodology before we signed up for a single affiliate program. This page explains how to think about supplement evidence and quality so you can evaluate any product - whether you use our scores or not.
The Evidence Hierarchy: Not All Research Is Equal
The supplement industry thrives on vague claims. "Clinically studied." "Research-backed." "Science-based formula." These phrases mean almost nothing because they do not tell you what kind of research exists. A single study in mice is research. So is a systematic review of 30 human trials. They are not remotely the same thing.
Here is the hierarchy of evidence, from strongest to weakest. Understanding this is the single most important skill for evaluating any health claim.
Systematic Reviews and Meta-Analyses
The strongest form of evidence. Researchers collect every relevant study on a question, assess their quality, and synthesize the results - sometimes pooling data mathematically (meta-analysis) to calculate an overall effect size. When a meta-analysis of 15 randomized controlled trials says creatine monohydrate increases lean body mass, that is a conclusion built on thousands of participants across multiple research teams. It is very hard to argue with.
Randomized Controlled Trials (RCTs)
The gold standard for individual studies. Participants are randomly assigned to receive either the supplement or a placebo. Neither the participants nor the researchers know who got what (double-blinding). This design controls for the placebo effect and researcher bias. When we say vitamin D3 supplementation raises serum 25(OH)D levels, that conclusion comes primarily from RCTs.
Not all RCTs are equal. A trial with 20 participants for 4 weeks is far less reliable than one with 500 participants for 12 months. Sample size, duration, funding source, and whether the outcomes were pre-registered all matter.
Cohort and Observational Studies
Researchers follow groups of people over time and look for associations between supplement use and health outcomes. These can reveal patterns, but they cannot prove causation. People who take vitamin D might also exercise more, eat better, and see doctors regularly. The association between vitamin D and better health might have nothing to do with the supplement itself. Observational studies generate hypotheses. RCTs test them.
Animal and In-Vitro Studies
Studies in rodents or in cell cultures. These are useful for understanding biological mechanisms, but they routinely fail to translate to humans. A compound that shrinks tumors in a petri dish may do nothing in a living person. A compound that improves memory in mice may not cross the human blood-brain barrier at achievable doses. When a supplement's marketing cites only animal studies, the honest translation is: "We do not know if this works in humans."
Traditional Use and Expert Opinion
The weakest form of evidence. "Used for centuries in traditional medicine" sounds compelling but tells you nothing about efficacy. Bloodletting was used for centuries too. Expert opinion matters for clinical practice, but it is not a substitute for controlled trials. Many supplements that experts initially endorsed have failed when subjected to rigorous testing.
Why This Matters for Your Wallet
Most supplement marketing relies on the bottom two tiers. A company can truthfully say a product is "backed by research" if a single mouse study exists. Knowing where to look in the hierarchy protects you from paying $40 a month for something that has never been shown to work in a human being.
Our Two-Tier Scoring System
Traditional supplement reviews combine two fundamentally different questions into one grade: does this ingredient work, and did this brand make the product well? That is a mistake. A beautifully manufactured product containing an ingredient with zero clinical evidence is not the same problem as a poorly labeled product containing an ingredient backed by 30 RCTs. Blending them into one number obscures the information you actually need.
We separate them. Read the full methodology for every detail, but here is how the system works.
Tier 1: Evidence Rating (per ingredient type)
Every supplement type gets an evidence tier based on the strength of clinical research supporting its primary claimed benefit. This rating applies to the molecule, not the brand. Whether you buy Thorne or Nature Made magnesium glycinate, the underlying clinical evidence is identical.
| Tier | Label | What It Means |
|---|---|---|
| 1 | Strong Evidence | Multiple large RCTs, systematic reviews, and meta-analyses confirm the benefit. The medical community broadly recognizes it. |
| 2 | Likely Effective | Several RCTs with generally consistent results. Good evidence base with some limitations in study design or sample size. |
| 3 | Mixed Evidence | Limited RCTs, inconsistent results, or primarily observational data. Reasonable people looking at the same research could disagree. |
| 4 | Weak Evidence | Mostly animal or in-vitro studies. Human data is scarce, from small trials, or poorly designed. |
| 5 | Ineffective | No meaningful evidence of benefit in humans, or evidence actively shows it does not work for its primary claimed purpose. |
This tier tells you whether the ingredient is worth taking at all. If something is Tier 4 or Tier 5, it does not matter how well a brand manufactured it.
Tier 2: Execution Score (per product, 0-100)
For ingredients that have meaningful evidence (Tiers 1-3), we score individual products on four equally weighted pillars, each worth up to 25 points:
Dosing & Form (0-25): Does the product deliver the clinically effective dose identified in published RCTs? Does it use the most bioavailable form? A magnesium oxide product scores lower than magnesium glycinate because the research shows dramatically different absorption rates.
Purity Verification (0-25): Has the product been independently tested by a third party - USP, NSF, ConsumerLab, BSCG, or Informed Choice? There is a meaningful difference between a facility following GMP standards and a specific product having its contents verified by an independent lab.
Value (0-25): Cost per clinically effective daily dose. Not cost per pill. Not cost per serving. If a product contains 150mg of an ingredient whose clinical dose is 600mg, you need four servings per day. The true cost is four times what the label math suggests. This is the single metric most review sites get wrong.
Transparency (0-25): Does the label disclose every ingredient and its exact amount? Does it specify the form used? Or does it hide behind a "Proprietary Blend" that lists five ingredients but only tells you the total weight?
A product scoring 85-100 is excellent across all four pillars. A product scoring below 40 has serious problems in multiple areas. Full score interpretation is on the methodology page.
Category-by-Category Evidence Summary
Below is an honest summary of where the evidence stands across the 15 supplement categories we cover. This is not marketing. Some of these categories contain ingredients with strong research. Others are dominated by hype. Browse all categories on the categories index.
| Category | Evidence Landscape | Key Takeaway |
|---|---|---|
| Vitamins & Minerals | Strong for deficiency correction (Tier 1-2). Weak for supplementation in well-nourished populations. | Vitamin D3 is the standout - most adults in northern latitudes are insufficient. Magnesium is close behind. Most healthy adults eating a varied diet do not need a multivitamin. |
| Omega Fatty Acids | Strong for triglyceride reduction at high doses (Tier 1). Mixed for general cardiovascular protection. | Fish oil at 2-4g EPA+DHA has solid evidence for triglycerides. The "take fish oil for heart health" narrative is more nuanced than most brands suggest. EPA-heavy formulas have the strongest data. |
| Protein & Amino Acids | Strong for creatine and protein supplementation (Tier 1). Variable for individual amino acids. | Creatine monohydrate is one of the most researched and effective supplements in existence. Protein supplements work but are unnecessary if dietary intake is adequate. Most BCAA supplements are redundant if you eat enough protein. |
| Herbal & Botanical | Highly variable. Ranges from Tier 2 (ashwagandha for stress) to Tier 4-5 for many popular herbs. | This category has the widest gap between marketing claims and evidence. A few botanicals have genuine research support. Many are sold on tradition and animal data. Check the evidence tier before buying anything here. |
| Probiotics & Gut Health | Strain-specific evidence is moderate (Tier 2-3). Generic "probiotic blend" evidence is weaker. | Probiotics are not interchangeable. Specific strains have evidence for specific conditions. A random multi-strain blend from Amazon is not the same as the strain used in clinical trials. Digestive enzymes have limited evidence outside diagnosed deficiencies. |
| Sleep & Relaxation | Moderate overall. Melatonin is Tier 1-2 for sleep onset. Others are Tier 2-3. | Low-dose melatonin (0.3-1mg) works for falling asleep faster. Most products wildly overdose it. Magnesium glycinate has moderate evidence. L-theanine and 5-HTP show early promise but need more trials. |
| Joint & Bone Health | Mixed. Glucosamine sulfate has moderate evidence (Tier 2-3). Many others are Tier 3-4. | Glucosamine sulfate (not HCl) has the best data, but effect sizes are modest. Calcium + D3 is well-supported for bone density in deficient populations. Collagen for joints is an active area of research with early positive signals. |
| Cognitive & Nootropics | Mostly Tier 3-4. A few exceptions for specific populations. | The nootropics category is heavy on promise and light on proof. Creatine for cognitive performance has emerging evidence. Caffeine + L-theanine is well-studied. Most "brain stack" formulas combine underdosed ingredients with zero evidence for the specific combination. |
| Energy & Performance | Strong for caffeine and creatine (Tier 1). Variable for others. | Caffeine and creatine are proven performance enhancers. Beetroot (nitrates) has moderate evidence for endurance. CoQ10 is well-supported for specific populations (statin users, heart failure). Most pre-workout formulas underdose the ingredients that actually work. |
| Heart & Cardiovascular | Strong for omega-3 at prescription doses (Tier 1-2). Mixed for most OTC heart supplements. | High-dose EPA (prescription Vascepa-level) has cardiovascular event data from large trials. OTC fish oil at typical doses has weaker evidence. CoQ10 is well-supported for heart failure. Garlic extract has modest blood pressure data. Red yeast rice works but carries statin-like risks. |
| Weight Management | Mostly Tier 3-5. This is the most overhyped category in the industry. | No legal supplement produces meaningful weight loss without diet and exercise changes. Green tea extract has a small thermogenic effect. Fiber supplements support satiety. Everything marketed as a "fat burner" should be treated with extreme skepticism. |
| Immune Support | Moderate for deficiency correction (Tier 1-2). Weak for immune "boosting" in healthy people. | Vitamin D, zinc, and vitamin C support immune function when you are deficient. The evidence for "boosting" an already-healthy immune system is thin. Elderberry has some cold-duration data but the studies are small. The concept of "immune boosting" is itself misleading. |
| Skin, Hair & Nails | Limited. Tier 2-3 for collagen, Tier 3-4 for most others. | Collagen peptides have the most promising data for skin elasticity and hydration, though the studies tend to be small and often industry-funded. Biotin is effective for deficiency (rare) but has weak evidence for hair growth in people who are not deficient. |
| Men's Health | Mixed. Tier 2-3 for saw palmetto (BPH symptoms). Tier 3-4 for testosterone-focused supplements. | Saw palmetto has moderate evidence for urinary symptoms from BPH. Supplements marketed for testosterone "boosting" - tongkat ali, fenugreek, tribulus - have limited and inconsistent human data. Zinc matters if you are deficient. Most men's health supplements overpromise. |
| Women's Health | Strong for prenatal folate (Tier 1). Variable for others. | Prenatal folate for neural tube defect prevention is one of the best-established supplement benefits in all of medicine. Iron supplementation is critical for diagnosed deficiency. Most other women's health supplements fall in the Tier 3-4 range. |
Every supplement we cover has a detailed scorecard with the full evidence summary, product comparisons, and cost-per-dose calculations. Browse all 63 profiles on the supplements index.
What 90% of Supplement Buyers Get Wrong
After scoring hundreds of products across dozens of categories, patterns emerge. The same mistakes show up over and over. Here are the most common ones.
1. Comparing price per bottle instead of cost per effective dose
A $15 bottle of magnesium oxide looks cheaper than a $30 bottle of magnesium glycinate. But magnesium oxide has roughly 4% bioavailability. You would need to take a massive amount to absorb what one capsule of glycinate delivers. When you calculate cost per milligram actually absorbed, the "cheap" option is often the expensive one. We calculate cost per clinically effective daily dose for every product we score. It is the only price metric that means anything.
2. Ignoring the form of the ingredient
Not all forms of a supplement are equally effective. Magnesium oxide vs. magnesium glycinate. Cyanocobalamin vs. methylcobalamin. Curcumin powder vs. curcumin with piperine or liposomal delivery. The form determines how much your body actually absorbs and uses. A product with the right dose of the wrong form can be nearly useless. Every one of our scorecards specifies which form the research supports.
3. Trusting "clinically studied" on the label
This phrase has no legal definition. It can mean the ingredient appeared in one tiny pilot study with 12 participants and no placebo group. It can mean the brand funded its own study with a design guaranteed to produce positive results. When we assign evidence tiers, we look at the full body of research - systematic reviews first, then individual RCTs, evaluated for quality, sample size, and independence from the manufacturer.
4. Assuming third-party testing is standard
It is not. Third-party testing means an independent laboratory has verified that the product contains what the label claims and is free from contaminants like heavy metals, pesticides, and undeclared substances. Fewer than 1 in 5 supplements on Amazon carry any form of third-party verification. The ones that do (USP, NSF Certified for Sport, ConsumerLab approved) have invested real money in quality assurance. The ones that do not are asking you to trust them. Our purity verification pillar scores this directly.
5. Buying proprietary blends
A "Proprietary Blend" on a supplement label means the company has combined multiple ingredients into a single listed amount without disclosing how much of each ingredient is included. A blend might say "Proprietary Cognitive Complex: 500mg" and list five ingredients. The lead ingredient could be 490mg or 5mg. You have no way to know. Proprietary blends exist to protect the manufacturer's margins, not to protect a secret formula. Any brand serious about transparency discloses individual ingredient amounts.
6. Supplementing without testing
The most common waste of money in the supplement world is taking something you do not need. Vitamin D is critical if you are deficient. It is unnecessary if your serum levels are already optimal. Iron supplementation is essential for iron-deficiency anemia. It can cause harm if your iron stores are adequate. Before starting any supplement, ask your doctor for relevant blood work. A $30 lab test can save you hundreds in supplements you do not need.
7. Stacking supplements with overlapping ingredients
Many people take a multivitamin, a B-complex, an energy formula, and a stress supplement - not realizing that all four contain B vitamins. Ingredient overlap means you are paying multiple times for the same thing, and in some cases exceeding safe upper limits. Before adding a new supplement, check the full ingredient list against everything else you take.
8. Expecting supplements to fix what lifestyle changes would fix better
Supplements are supplementary. They fill gaps. They do not replace sleep, exercise, a varied diet, or medical treatment. The strongest evidence for most supplements is in populations with a specific deficiency or diagnosed condition. For generally healthy people eating a reasonable diet, the list of supplements with clear evidence of benefit is short: vitamin D in northern climates, creatine for performance, and omega-3 if you do not eat fish regularly. That is close to the entire list.
How to Use This Site
We built Supplement Scored to be the resource we wished existed when we started researching supplements. Here is how to get the most out of it.
If you know which supplement you want
Go to the supplements index and find the ingredient. Each scorecard page opens with the evidence tier (does this ingredient work?) and then scores 8-15 specific products on dosing, purity, value, and transparency. The "Top Pick" and "Best Value" badges are based on the execution scores, not on which brand pays the highest affiliate commission.
If you have a health goal but are not sure which supplement to take
Start with the goals index. Each goal page - sleep, energy, joint health, focus, and 14 others - lists the relevant supplements ranked by evidence strength. This tells you which ingredients are worth considering before you start comparing products.
If you want to browse by category
The categories index organizes all 15 supplement categories with descriptions and links to every scored supplement in each one. Good for exploring what is available in a specific area like probiotics or herbal supplements.
If you want to understand our scoring
The methodology page explains every detail: how evidence tiers are assigned, how the four execution pillars are scored, how cost per effective dose is calculated, and where our data comes from. We publish it because the methodology is the product. If you disagree with a score, you can see exactly how we arrived at it.
If you want to go deeper on the evidence
Our blog covers specific topics in more depth. When You Actually Need a Supplement covers who benefits from supplementation and who is wasting money. Supplement Ingredients Ranked by Evidence is a companion piece to this page that ranks individual ingredients by evidence tier. And every supplement scorecard page includes a full evidence summary with links to primary research on PubMed.
The Bottom Line
The supplement industry makes it hard to make good decisions. The regulatory framework is weak. The marketing is aggressive. The review sites are conflicted. And most consumers are comparing the wrong numbers.
But the underlying research is real, it is publicly available, and it is not that hard to read once you know what to look for. Some supplements work for specific purposes in specific populations at specific doses. Many do not. The difference between wasting $100 a month and spending $20 on something that actually helps comes down to asking three questions: Is the evidence real? Is the dose right? Is the product what it claims to be?
That is what we score. Every supplement, every product, every dollar justified.