Supplements and Nutraceuticals: What’s Really in the Bottle?
Written By Kevin Wallace.
Some product names link to Amazon. I may earn a small commission if you buy through them, at no extra cost to you. That does not change the evidence, and it does not mean you need the product.
In the United States, no one checks a supplement before it goes on sale to confirm that it contains what the label says, and nothing else. Independent testing has repeatedly found products with far more or far less of the active ingredient than stated, heavy metals, and even hidden prescription drugs. Choosing a product verified by an independent program is the single best protection you have. Food still comes first.
People ask me which supplements to take. My first answer is food. My second is that the brand matters as much as the ingredient, because the label and the bottle can be two different things. This article explains why, what the research has found, how the fat-soluble vitamins differ, and how I choose what I take. The list at the end is mine. It will change as better evidence comes out. It is not a prescription for you.
1. How supplements are regulated
Most people assume that anything sold in a pharmacy has been checked by the government. For supplements, it has not.
Under the Dietary Supplement Health and Education Act of 1994, supplements are regulated as a category of food, not as drugs. FDA does not approve them, or their labels, before they are sold, and FDA does not test them before they reach you (1). The company is responsible for safety and for an accurate label. In many cases a product can go on the market without FDA even being notified.
FDA’s role comes mostly after the fact. It inspects some plants, reviews adverse event reports, and can act against a product that is unsafe or mislabeled once it is already for sale (2). A prescription drug has to prove it is safe and effective, and that each batch contains what it claims, before the first sale.
I spent my career prescribing medications whose content I could trust. With a supplement, that trust has to be earned bottle by bottle. It also has to be re-earned. Companies get bought. A new owner can drop the independent testing contract and leave last year’s seal on the picture. When you reorder, look the exact product up on the certifier’s site. The logo on the old bottle is not the check.
2. Does the label match the bottle?
Melatonin is the clean example, because it is cheap, popular, and easy to measure.
A Harvard-led team tested 25 melatonin gummy products sold in the United States. Twenty-two did not match the label. Content ranged from 74 percent to 347 percent of the claimed dose. One product had no detectable melatonin and did contain CBD (3). They tested one bottle of each, so lot-to-lot variation is still open. A child taking a gummy as labeled could receive far more than a nighttime dose.
A 2017 University of Guelph study of 30 melatonin products found content from 83 percent less to 478 percent more than labeled. More than 71 percent missed the claim by over 10 percent. Lots of the same product varied by as much as 465 percent, and about a quarter contained serotonin that was not on the label (4).
A product can be underdosed, so you pay for something that does not work, or overdosed. Overdosing is a real risk with hormones and with the fat-soluble vitamins.
3. Heavy metals, and hidden drugs
Plants pull lead, cadmium, and arsenic from soil. A powder concentrates them. That matters if you eat the way we do, because plant protein and greens powders are what a plant-based kitchen is most likely to buy.
In 2025, Consumer Reports tested 23 protein powders and shakes. More than two-thirds had more lead in one serving than CR’s experts allow for a whole day, and some exceeded that level more than tenfold. Plant-based powders averaged about nine times the lead of dairy-based ones (5). CR’s line, 0.5 micrograms a day, is California’s Proposition 65 figure, and the industry disputes it (6). No safe level of lead is known. A daily powder is still a poor substitute for beans, lentils, tofu, and nuts. If you use one, you want lot-specific metal numbers, not a badge that says passed.
The more dangerous problem is a drug hidden in a “natural” product. From 2007 through 2016, FDA warnings named unapproved drugs in 776 supplements from 146 companies. Most were sold for sexual enhancement, weight loss, or muscle building. About one in five had more than one hidden drug. The usual adulterants were sildenafil, sibutramine, and synthetic steroids (7). Sibutramine had already been pulled for heart risk. Many products stayed on sale after the warning.
I take losartan. A hidden stimulant or sildenafil on top of a blood pressure drug is not theoretical. Be most suspicious of dramatic weight loss, sexual performance, or muscle gain from an unfamiliar online brand. Buy from the maker or an authorized seller. Marketplaces carry counterfeits of legitimate brands too.
4. What the seals mean
| Program | What it verifies | Best for |
|---|---|---|
| USP Verified | Listed ingredients in the declared amounts, limits on specified contaminants, manufacturing practice, and whether the tablet dissolves | Everyday vitamins and minerals |
| NSF Certified, and NSF Certified for Sport | Label accuracy and contaminants. Sport also screens for drugs banned in athletics | Anyone wary of hidden stimulants |
| Informed Sport, Informed Choice, BSCG | Banned-substance screening, often by batch | Athletes |
| ConsumerLab | Independent buy-and-test reviews, by subscription | Comparing products before you buy |
| IFOS and similar oil programs | Potency, oxidation, and contaminants | Fish and algae oils |
“Made in a GMP facility” describes the plant, not the finished bottle. “Third-party tested,” with no lab and no numbers, means little. USP and NSF keep searchable listings. Look up the exact product. Do it again if the company has changed hands.
5. The fat-soluble four
Vitamins A, D, E, and K dissolve in fat. The body stores them. Water-soluble vitamins are easier to flush. These four can accumulate, and they do not accumulate in the same way. Taking them with a meal that contains fat is the shared absorption step. Bile and a working small intestine do the rest.
5.1 Vitamin D: three molecules, not one dose
D3, cholecalciferol, is what skin makes when ultraviolet B hits a cholesterol precursor. It is also the usual supplement, often from lanolin. D2, ergocalciferol, comes from fungi and from mushrooms treated with ultraviolet light. Both are inactive. The liver makes 25-hydroxyvitamin D, the storage form a blood test measures. The kidney makes 1,25-dihydroxyvitamin D, the hormone. At the same labeled dose, D3 raises the storage form more reliably than D2.
Calcifediol is already 25-hydroxyvitamin D. It is a prescription product for some people with liver or absorption trouble. It is not a better daily pill. Sunlight does not cause vitamin D toxicity. Skin shuts production off. A capsule does not.
Absorption needs a meal with fat. Magnesium is a cofactor for the enzymes that activate it. More of a dose parks in body fat, so the same intake can produce a lower blood level in a heavier person. A plant-based reader should read the source line. Ordinary D3 is animal-derived unless the label says lichen. D2 is the vegan form, and it is the weaker raiser of the blood level.
The dose debate is real, and I will not pretend it has been settled.
The official adult intake is 600 to 800 IU a day. In 2014, Veugelers and Ekwaru reanalyzed the data behind that number and argued that a statistical error had set it too low. By their calculation, about 8,900 IU a day from all sources would be needed to bring 97.5 percent of people to 20 ng/mL (8). Another group put the order of magnitude near 7,000 IU (9). I live in upstate New York. Winter sun does not make vitamin D in skin here. I find that argument relevant to my own dose.
The trial evidence is cooler. VITAL gave more than 25,000 older adults 2,000 IU a day for about five years and found no reduction in cancer or cardiovascular events overall (10). A later look at the same trial found fewer new autoimmune diseases in the vitamin D arm (11). In 2024 the Endocrine Society withdrew its own 2011 targets. It no longer calls 30 ng/mL sufficiency, or 20 to 30 ng/mL insufficiency. The panel said trials do not support a disease-prevention blood threshold, advised healthy adults under 75 against doses above the recommended intake, and advised against routine testing (12). Many labs still flag anything under 30. Some clinicians still aim for 40 to 60. There is no new single ideal number.
I am under 75. I still test, because I take two vitamin D products and I want the number, not a guess. That is a personal reason. It is not what the 2024 guideline recommends for a healthy adult. Ask for 25-hydroxyvitamin D through your clinician’s lab, not a finger-stick sold beside the vitamins. Repeat after a dose change, not every month. The adult upper limit is 4,000 IU a day unless a clinician sets a different one (13).
Too much vitamin D shows up as high blood calcium. Nausea, constipation, thirst, frequent urination, weakness, confusion, kidney stones, and in a bad case an abnormal heart rhythm. The pair of tests is calcium and 25-hydroxyvitamin D. Toxicity is uncommon under 10,000 IU a day, and it builds over months, because this vitamin is stored.
5.2 Vitamin K: clotting, and then bone and vessel
K1, phylloquinone, is the form in greens. Its main job is clotting factors in the liver. It is poorly absorbed from a salad unless the meal has fat. K2 is the menaquinones. MK-4 is short-lived, and tissues can make it. MK-7, often from natto, stays in the blood for days rather than hours and reaches proteins in bone and vessel wall, including osteocalcin and matrix Gla protein. That is the theory behind the artery and bone claims. The outcome evidence is thinner than the mechanism. A supplement study found MK-7 lowered uncarboxylated osteocalcin at a much smaller dose than MK-4. That is a lab marker, not proof of fewer fractures.
K3, menadione, is the synthetic form that caused toxicity. It does not belong in a supplement. Natural K1 and K2 have no established upper limit, and they do not have a toxicity picture the way vitamin A and vitamin D do. The harm is a drug interaction. Vitamin K reverses warfarin. I am not on warfarin. Anyone who is should not add K2 because a bottle said it was good for arteries.
5.3 Vitamin A and vitamin E, briefly
Preformed vitamin A, retinol and retinyl esters, is the form that accumulates. Headache, bone pain, dry skin, liver injury, and birth defects. Beta-carotene from food is not that risk. High-dose beta-carotene supplements did raise lung-cancer risk in smokers. High-dose vitamin E increases bleeding tendency. In the SELECT trial, 400 IU a day was linked to a higher prostate-cancer risk in men. Neither is a daily add-on without a reason.
6. How to choose
Start with food. Take a supplement for a specific gap. On a fully plant-based diet, vitamin B12 is not optional.
Prefer USP Verified or NSF Certified, and confirm the listing. Confirm it again when you reorder.
For protein powders, greens powders, beet powders, turmeric, and melatonin, look for published lot-specific numbers.
Skip proprietary blends. They hide the dose.
Be most wary of weight-loss, sexual-enhancement, and muscle-building products from unfamiliar sellers.
Prefer one ingredient, a studied form, and little added sugar. Gummies are where dosing errors hide.
Buy from the maker or an authorized retailer.
Write every product down, with the dose and the reason. Give that list to each doctor, the dentist before a procedure, and anyone who might see you in an emergency. They cannot guess what is in the morning box.
Know which products can skew a blood test, and which only need to be on the list you hand the lab. Biotin is the one that fools the machine. The FDA warned in 2017 that biotin can push some immunoassay results falsely high or falsely low, including thyroid tests and troponin. Quest’s instruction is the practical one: at ordinary supplement doses, draw the blood at least 8 hours after the last biotin. At mega-doses, 5,000 to 10,000 micrograms, wait 72 hours. Our O.N.E. multivitamin has 300 micrograms of biotin. That is ten times the daily intake and far below a hair-and-nail mega-dose. Skip that capsule the morning of the draw. Do not take a separate biotin pill at all in the three days before. Creatine is different. It can raise creatinine on a kidney panel because the body makes more of it, not because the assay is wrong. Do not stop it in secret. Tell the clinician you take it. A morning magnesium or a vitamin D capsule does not need a special hold for a routine panel. If the test is a magnesium level or a 25-hydroxyvitamin D, skip that morning dose so the number is not a peak from an hour earlier. High-dose vitamin C, grams rather than the 180 milligrams in this multi, can interfere with some glucose and stool-blood tests. Food and this multivitamin do not.
Report a bad reaction to FDA’s MedWatch program.
Fermented food is not a supplement. Kimchi, and the soy-milk yogurt we make, belong with the microbiome articles. A capsule labeled probiotic is the item that would belong here. We are not taking one.
7. What we actually do
We eat a whole-food, plant-based diet. Vegetables and fruit from the gardens and the food forest, beans, whole grains, nuts, and seeds. The plate is the foundation. I am 69. I take losartan. This list is how I fill gaps today. I will drop or change a product when the evidence changes.
Food, not capsules, at breakfast: cinnamon and ginger on the oatmeal, every morning. A sprinkle is a food. It is not a concentrated extract. Common grocery cinnamon is usually cassia, which contains coumarin. A large daily dose of cassia powder is the form linked to liver trouble. Ceylon has much less. A sprinkle on oatmeal is not that dose. Ginger at the table has a long food history. A concentrated ginger extract on a blood thinner is the situation to avoid, and it is not ours.
| What I take | When | Why | The limit |
|---|---|---|---|
| Vitamin D3, one product with K2 and one D3 alone | Daily | Winter blood level, guided by 25-hydroxyvitamin D | Add the IU across both bottles. K2 matters if you take warfarin. I do not. |
| Avmacol Extra Strength | Daily | Glucoraphanin plus myrosinase, the sulforaphane precursor in the glutathione article | Not a multivitamin. |
| Pure Encapsulations O.N.E. multivitamin | Once daily, not the morning of a blood draw | Small gaps. The B12 is 500 micrograms, which covers a plant-based diet. A separate B12 pill is not needed unless a blood test says otherwise | The capsule has 300 micrograms of biotin. Skip it the morning of bloodwork, so the draw is at least 8 hours after the last dose. A hair-and-nail biotin of several milligrams needs 72 hours, which this is not. |
| Magnesium L-threonate, 2,000 mg of the compound | Morning | Memory. Promising, not proven | That serving is about 144 mg of elemental magnesium, not 2,000 mg. |
| Bacopa monnieri | Morning | Memory. Modest gains in trials, usually after 8 to 12 weeks (14) | Can upset the stomach. |
| L-leucine powder | Morning, stirred into a little water | The amino acid that most strongly signals muscle-protein building. Plant-based eaters often get less of it | A powder is easy to overscoop. It is not a complete protein, and it does not replace beans or creatine. Dose is whatever the scoop on our jar says. |
| Magnesium glycinate | Evening | Sleep, in my own experience | Supplemental elemental magnesium from all bottles should stay near the 350 mg upper limit, mostly to avoid diarrhea (15). |
| Organic beetroot powder, about 8 g | Several days a week | Dietary nitrate. Trials found about a 4 mm Hg drop in systolic pressure (16) | I already take losartan. Nitrate can lower pressure further. Metal testing matters. |
| Organic turkey tail extract | When inflammation flares | A mushroom I have used for immune support | Human evidence is mostly PSK alongside cancer care in Japan, not a scoop for ordinary inflammation (17). |
| Creatine monohydrate | Daily, in a berry smoothie | Muscle and brain energy. Diet creatine comes mostly from meat and fish | Well studied in healthy people (18). It raises creatinine on a lab slip without meaning the kidney failed. Ask first if you have kidney disease. |
The links above carry my associate tag. If you want the exact bottle I use, the short link from my SiteStripe button is better than a search. Search still attributes the click. It does not guarantee the listing with a seal.
Thea and I both take the creatine in a smoothie that is mostly berries and fruit. The smoothie is the meal. The powder is the gap.
8. Where we land
Food first. B12 is the gap a fully plant-based diet cannot leave open. Cinnamon, ginger, kimchi, and homemade soy yogurt are food, not pills.
No one checks the bottle before it is sold. The label is the company’s claim.
Prefer USP or NSF, and look the product up again after a reorder or a buyout.
Plant powders can concentrate lead. Whole foods first.
Weight-loss, sexual-enhancement, and muscle products from unfamiliar sellers are where hidden drugs cluster.
A, D, E, and K are stored. D3 raises the blood level more reliably than D2. K1 is the clotting form. MK-7 is the long-lived K2. Natural K is not the toxicity problem. Warfarin is.
There is no new official ideal vitamin D number. The 2024 guideline dropped the 30 ng/mL target. I still test, because I take two products. Ask for 25-hydroxyvitamin D, and a calcium, if the dose is high.
Write the whole list down and give it to every doctor. Skip the multivitamin the morning of a blood draw because of its 300 micrograms of biotin. Mega-dose biotin is a three-day hold. Creatine should be named, not secretly stopped. My list will change. Yours should too.
9. References
U.S. Food and Drug Administration. Dietary Supplements. fda.gov
U.S. Food and Drug Administration. Information for Consumers on Using Dietary Supplements. fda.gov
Cohen PA, Avula B, Wang YH, Katragunta K, Khan I. Quantity of melatonin and CBD in melatonin gummies sold in the US. JAMA. 2023;329(16):1401-1402. jamanetwork.com
Erland LAE, Saxena PK. Melatonin natural health products and supplements: presence of serotonin and significant variability of melatonin content. Journal of Clinical Sleep Medicine. 2017;13(2):275-281. PMC
Consumer Reports. Protein Powders and Shakes Contain High Levels of Lead. October 2025. consumerreports.org
NPR. A study found lead in popular protein powders. October 16, 2025. npr.org
Tucker J, Fischer T, Upjohn L, Mazzera D, Kumar M. Unapproved pharmaceutical ingredients included in dietary supplements associated with US Food and Drug Administration warnings. JAMA Network Open. 2018;1(6):e183337. PMC
Veugelers PJ, Ekwaru JP. A statistical error in the estimation of the recommended dietary allowance for vitamin D. Nutrients. 2014;6(10):4472-4475. PMC
Heaney RP, Garland CF, Baggerly CA, French CB, Gorham ED. Letter: A statistical error in the estimation of the recommended dietary allowance for vitamin D. Nutrients. 2015;7(3):1688-1690. PMC
Manson JE, et al. Vitamin D supplements and prevention of cancer and cardiovascular disease. New England Journal of Medicine. 2019;380:33-44. nejm.org
Hahn J, et al. Vitamin D and marine omega 3 fatty acid supplementation and incident autoimmune disease. BMJ. 2022;376:e066452. bmj.com
Endocrine Society. Guideline recommends healthy adults under 75 take the recommended daily allowance of vitamin D. June 2024. endocrine.org
NIH Office of Dietary Supplements. Vitamin D Fact Sheet for Health Professionals. ods.od.nih.gov
Kongkeaw C, et al. Meta-analysis of randomized controlled trials on cognitive effects of Bacopa monnieri extract. Journal of Ethnopharmacology. 2014;151(1):528-535. PubMed
NIH Office of Dietary Supplements. Magnesium Fact Sheet for Health Professionals. ods.od.nih.gov
Siervo M, et al. Inorganic nitrate and beetroot juice supplementation reduces blood pressure in adults. Journal of Nutrition. 2013;143(6):818-826. PubMed
National Cancer Institute. Medicinal Mushrooms (PDQ), Health Professional Version. cancer.gov
Kreider RB, et al. International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation. Journal of the International Society of Sports Nutrition. 2017;14:18. PMC
