The short version
- Across the 100 best-selling pre-workout supplements, 44.3% of ingredients sat inside a proprietary blend with no amount disclosed, an average of 8.1 hidden ingredients per product.
- Magnesium oxide is about 60% magnesium by molecular weight and magnesium L-threonate about 8%, so 500mg of one supplies roughly 300mg of elemental magnesium and 500mg of the other supplies about 41mg.
- When 30 immune-support supplements bought from a major online marketplace were analysed by mass spectrometry, 17 had inaccurate labels: 13 listed ingredients that could not be detected and nine contained undeclared substances.
- An analysis of 25 melatonin gummies sold in the US found 88% were inaccurately labelled, with actual melatonin ranging from 74% to 347% of the declared amount and one containing none at all.
- Serving size is chosen by the brand, so a 120-capsule bottle at four capsules per serving is a 30-day supply rather than a 120-day one.
44.3%. That is the share of ingredients in the hundred best-selling pre-workout supplements that sat inside a proprietary blend, named on the label but with no amount attached. Jagim and colleagues pulled those hundred labels in 2019 and counted: an average of 18.4 ingredients per product, 8.1 of them hidden in a blend. They also compared the disclosed doses against the amounts used in research. The average beta-alanine serving came in below the dose the studies use.
That is the supplement label problem in one number. The information is legally present and practically useless. Here is how to read the back of a bottle so it tells you what you actually bought — ours included.
1. Serving size is the number that moves every other number
Everything on a Supplement Facts panel is stated per serving, and the brand picks the serving. Two capsules or four. One scoop or two. A product advertising 1,000mg of an ingredient at four capsules per serving is a 250mg-per-capsule product, and a bottle of 120 capsules is a 30-day supply, not a 120-day one.
Do the arithmetic before you compare prices. Divide the container count by the serving size, then divide the price by that. Two bottles that look like they cost the same often don't.
2. Elemental weight versus compound weight
Minerals are never sold as the bare metal. They are bound to something — an oxide, a citrate, an amino acid — and the front of the bottle usually prints the weight of the whole compound. Magnesium is the clearest example, because the arithmetic differs so much between forms.
- Magnesium oxide is about 60% magnesium by molecular weight. 500mg gives roughly 300mg of magnesium.
- Magnesium citrate is about 16%. 500mg gives roughly 81mg.
- Magnesium bisglycinate is about 14%. 500mg gives roughly 70mg.
- Magnesium L-threonate is about 8%. 500mg gives roughly 41mg.
None of those are dishonest numbers. They are just different questions. A well-made label states both: the compound weight and, in parentheses or on a second line, the elemental amount. If a label gives you only the big number, you are being invited to compare 500mg of one thing to 500mg of a completely different thing.
Higher elemental content does not mean better, either — that is the trap on the other side. Magnesium oxide is the most magnesium per milligram and among the least absorbable. Which brings us to why the form line matters as much as the number.
3. Proprietary blends are a pricing decision, not a formulation one
A proprietary blend lets a brand list ten ingredients in descending order of weight and disclose only the total. It is legal. The stated reason is protecting a formula from copying. The practical effect is that you cannot tell whether the interesting ingredient at the top of the blend is 90% of it or 2% of it.
In the Jagim analysis, this was not a fringe practice — nearly half of all ingredients across the top hundred products were inside one. Our position is simple: if a dose is worth charging for, it is worth printing.
4. %DV is a floor, not a target
The percentage in the right-hand column compares the serving against the FDA's Daily Value — a population reference amount, set to cover the needs of most healthy people. It answers "am I likely to be short of this?" It does not answer "is this the dose that was studied?"
Two consequences. First, 2,000% of the DV is not a sign of potency; for several water-soluble vitamins it is mostly a sign of expensive urine. Second, most of the ingredients people actually buy supplements for — creatine, ashwagandha, lion's mane, probiotics — have no Daily Value at all, so the column is blank. A blank %DV tells you nothing about whether the dose is right. Only the research does.
5. "Other ingredients" is where the rest of the capsule lives
Below the panel is an unglamorous line listing everything that is not an active: the capsule shell, flow agents, fillers, sweeteners, colours. It is worth thirty seconds. It is where you find out whether a "vegan" capsule is actually gelatin, whether there is a bulking agent doing most of the work, and whether the gummy you are taking for sleep is mostly sugar.
Why any of this matters more than it should
Because labels are frequently wrong. In a 2022 case series in JAMA Network Open, researchers bought 30 immune-support supplements from Amazon and ran them through liquid chromatography–mass spectrometry. Thirteen of the 30 had accurate labels. Of the 17 that did not, 13 listed ingredients that could not be detected at all, and nine contained substances that were never declared. Not one of the 30 carried a third-party certification seal.
It is not confined to obscure products. When Cohen and colleagues analysed 25 melatonin gummies sold in the US in 2023, 22 of them — 88% — were inaccurately labelled, with actual melatonin ranging from 74% to 347% of the declared amount. One contained no detectable melatonin at all.
What we'd actually tell you
Read four lines and you will out-read most of the market: serving size, form, elemental amount, and whether anything is hidden in a blend.
Apply this to us too. If our label doesn't answer one of those four questions to your satisfaction, that is our failure, not your misreading.
Good questions
What is a proprietary blend and should I avoid it?
A proprietary blend lists ingredients in descending order of weight but discloses only the total, so you cannot tell whether the interesting ingredient is 90% of the blend or 2% of it. It is legal. Across the 100 best-selling pre-workouts, 44.3% of all ingredients sat inside one. Our position: if a dose is worth charging for, it is worth printing.
Why does the front of the bottle say 500mg but the panel says 70mg?
Because those are two different measurements: the weight of the whole compound versus the weight of the mineral inside it. Magnesium bisglycinate is about 14% magnesium by weight, so 500mg of it supplies roughly 70mg of magnesium. Citrate is about 16%, threonate about 8%, oxide about 60%. Compare elemental amounts, never headline numbers.
Does a high percent Daily Value mean a supplement is stronger?
No. The Daily Value is a population reference amount set to cover the needs of most healthy people, so it answers whether you are likely to be short of something, not whether the dose was the one that was studied. For several water-soluble vitamins, 2,000% of the DV is mostly a sign of expensive urine.
Can I trust what is printed on a supplement label?
Often not. When 30 immune-support supplements bought from a major online marketplace were analysed by mass spectrometry, 17 had inaccurate labels: 13 listed ingredients that were undetectable and nine contained undeclared substances. A separate analysis of 25 melatonin gummies found 88% inaccurate, with actual content between 74% and 347% of the declared amount.
How do I know your labels are any better than anyone else's?
Hold us to the same four lines: serving size, form, elemental amount, and whether anything is hidden in a blend. If our label fails one of those checks, that is our failure.
Sources
- Jagim AR, Harty PS, Camic CL. Common Ingredient Profiles of Multi-Ingredient Pre-Workout Supplements. Nutrients, 2019. View study
- Crawford C, et al. Analysis of Select Dietary Supplement Products Marketed to Support or Boost the Immune System. JAMA Netw Open, 2022. View study
- Cohen PA, Avula B, Wang Y-H, Katragunta K, Khan I. Quantity of Melatonin and CBD in Melatonin Gummies Sold in the US. JAMA, 2023. View study
- US Food and Drug Administration. Dietary Supplement Labeling Guide. View study
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
