When You Actually Need a Supplement (And When You're Wasting Money)

We score supplements for a living. We also think most people are buying ones they don't need.

That's not a contradiction. It's the whole point. The supplement industry is worth over $60 billion in the US alone, and a significant chunk of that spending goes toward products that do nothing for the people taking them. Not because the products are bad. Because the people don't have the deficiency the product addresses.

Supplements fill gaps. They don't replace a diet. If you eat a reasonably varied diet with vegetables, protein, whole grains, and some fruit, you're covering most of your bases. The word "supplement" is right there in the name.

But some gaps are common enough that they're worth checking for. And a few are so widespread that supplementation makes sense as a default.

The supplements most people actually need

Vitamin D3

This is the closest thing to a universal recommendation. An estimated 42% of US adults are deficient in vitamin D. If you live above the 37th parallel (roughly north of Richmond, Virginia), your skin cannot produce adequate vitamin D from sunlight between October and April. If you work indoors, wear sunscreen consistently, or have darker skin, your risk is higher year-round.

The evidence for supplementation is strong. 1,000-2,000 IU daily is a reasonable baseline for most adults. It's cheap, safe at those doses, and addresses a deficiency that's genuinely difficult to fix through food alone - you'd need to eat fatty fish almost every day.

See our full Vitamin D3 scorecard

Vitamin B12

If you're vegan or vegetarian, you need to supplement B12. No plant food provides adequate B12 in a reliable, bioavailable form. This isn't debatable - it's basic biochemistry.

Adults over 50 should also consider B12 supplementation. The body's ability to absorb B12 from food declines with age due to reduced stomach acid production. Methylcobalamin is the preferred form, though cyanocobalamin works fine for most people.

See our full Vitamin B12 scorecard

Folate

Women of childbearing age should take folate (400-800 mcg daily), especially if pregnancy is possible. The evidence for neural tube defect prevention is among the strongest in all of nutrition science. The critical window is early pregnancy - often before a woman knows she's pregnant - which is why preconception supplementation matters.

Methylfolate is preferred over folic acid for people with MTHFR variants, which affect roughly 25-40% of the population. If you are already pregnant or planning to be, see our ACOG prenatal vitamin requirements checklist for the full nutrient spec - folate is one of six thresholds most prenatals quietly miss.

Iron (with a major caveat)

Women with heavy menstrual periods, endurance athletes, and vegetarians are at elevated risk for iron deficiency. Symptoms include fatigue, weakness, poor concentration, and cold intolerance.

Here's the caveat: do not supplement iron without a confirmed deficiency via blood work. Unlike most vitamins, excess iron is toxic. Your body has no efficient mechanism to excrete it. Iron overload damages the liver, heart, and pancreas. Get tested first. If you're deficient, supplement under medical guidance. Iron bisglycinate causes fewer GI side effects than ferrous sulfate.

See our full Iron scorecard

Omega-3 fatty acids (EPA/DHA)

If you eat oily fish (salmon, mackerel, sardines, anchovies) at least twice a week, you're probably fine. Most Americans don't come close. The typical Western diet provides far more omega-6 than omega-3, and the cardiovascular and anti-inflammatory evidence for EPA/DHA is solid.

Look for supplements that provide at least 500 mg combined EPA/DHA per serving. Many cheap fish oil capsules contain far less than their label suggests per effective dose.

See our full Fish Oil scorecard

Supplements that make sense for specific situations

Magnesium

Roughly half of Americans don't meet the RDA for magnesium through diet. Modern soil depletion and processed food consumption are the main drivers. If you experience muscle cramps, poor sleep, or eat a diet heavy in processed foods, magnesium supplementation is reasonable. Glycinate is well-absorbed and less likely to cause digestive issues than oxide or citrate. If muscle cramping or fibromyalgia-style fatigue is your primary complaint, magnesium malate has a small but distinct evidence niche (the malic acid carrier contributes to the Krebs cycle), though the trial base is much thinner than glycinate's.

See our full Magnesium Glycinate scorecard

Creatine

If you do any form of resistance training or high-intensity exercise, creatine monohydrate is one of the most well-studied and effective supplements available. 3-5g daily. No loading phase needed. The evidence base spans decades of research with consistent positive results for strength, power output, and muscle recovery. It's also remarkably cheap.

See our full Creatine scorecard

Probiotics

After a course of antibiotics, a quality probiotic can help restore gut flora. There's also reasonable evidence for specific strains in specific GI conditions (IBS, antibiotic-associated diarrhea). But the evidence does not support daily probiotic use as a general "wellness" supplement for healthy people with no digestive complaints. Save your money.

See our full Probiotic scorecard

Chromium picolinate (modest blood sugar and craving signal only)

Chromium picolinate shows modest HbA1c reductions in T2DM trials and a cleaner secondary signal in carbohydrate craving (Docherty 2005, 600 mcg/day in atypical depression). It nudges the scale by roughly half a kilogram over placebo across pooled weight-loss trials - real but too small to anchor a strategy around. The 2016 Costello review concluded the overall evidence is limited; treat it as a low-cost adjunct ($0.03-0.18/day), not a primary intervention.

See our full Chromium Picolinate scorecard

Where most people waste money

Multivitamins

The largest and longest studies on multivitamins - including the COSMOS trial and the Physicians' Health Study II - show minimal benefit for well-nourished adults. If you eat a varied diet, a multivitamin is expensive insurance against a problem you don't have. The doses of individual nutrients are often too low to correct an actual deficiency and too scattered to serve a targeted purpose.

See our full Multivitamin scorecard

"Immune boosters"

No supplement "boosts" a healthy immune system. That's not how immunity works. An overactive immune system is called an autoimmune disease. What vitamin C and zinc can do is support normal immune function and may reduce cold duration modestly - but only if you're deficient. Mega-dosing vitamin C beyond what your body can absorb just creates expensive urine.

Same logic applies to echinacea: the Lancet meta-analysis shows a real but modest signal for cold prevention with Echinaforce specifically, while the broader Cochrane review across 24 trials is much more sober. Species and preparation matter more than dose, and most generic dried-root capsules are not the format the positive trials tested.

"Superfood" greens powders sit in the same overpromised category. Moringa is sold as a miracle tree on the strength of impressive in-vitro and animal data, but the human RCTs are small, unblinded, and dominated by populations where baseline malnutrition confounds any supplement effect. A 2025 cardiometabolic meta-analysis found no significant pooled effect on HbA1c or fasting glucose. It is reasonable as an iron-and-vitamin-rich green for people with genuinely inadequate leafy-vegetable intake, but the "general immunity and energy" framing is not supported by trials in well-nourished adults.

Detox supplements

Your liver and kidneys detoxify your body continuously. They're very good at it. No supplement improves on millions of years of evolutionary engineering. "Detox" and "cleanse" products are marketing, not medicine. Chaga mushroom is often slotted into this category alongside chlorella and milk thistle. The chemistry is interesting (extremely high ORAC values, melanin, betulinic acid) but Memorial Sloan Kettering states plainly that "the safety and efficacy of chaga have yet to be evaluated in clinical studies." Worse, chaga is high in oxalates and there are documented case reports of end-stage renal failure in chronic users - exactly the wrong product to take for "kidney support."

Proprietary blends

If a label says "proprietary blend" followed by a list of 15 ingredients and one total weight, you have no idea what you're getting. Most ingredients in these blends are present at doses far below what any study has ever tested. You're paying for label decoration. We factor this into every transparency score on this site.

The decision framework

Before buying any supplement, ask three questions:

1. Do I have a confirmed or likely deficiency? Blood work is ideal. Population-level data (like the vitamin D statistics above) can inform reasonable assumptions.
2. Is there strong clinical evidence that supplementation helps? Not a single study. Not animal research. Multiple human RCTs with consistent results. Check our evidence rankings.
3. Can I address this through diet instead? If you can get what you need from food, that's almost always the better path. Better absorption, additional co-factors, no pill fatigue.

If you answered yes, yes, and no - supplement. If not, put the money toward better groceries.

The bottom line

We built this site because the supplement industry needs honest scoring, not because everyone needs supplements. The five recommendations in the first section of this article cover the most common real deficiencies. Everything beyond that should be targeted, evidence-based, and ideally confirmed by blood work.

When you do decide to supplement, quality matters. Third-party testing matters. Cost per clinically effective dose matters. That's what we score. But the best supplement decision you can make is knowing when you don't need one at all.

Sources

1. Parva NR, Tadepalli S, Singh P, et al. Prevalence of vitamin D deficiency and associated risk factors in the US population (2011-2012). Cureus. 2018;10(6):e2741. PMID 30087817.
2. Forrest KYZ, Stuhldreher WL. Prevalence and correlates of vitamin D deficiency in US adults. Nutrition Research. 2011;31(1):48-54. PMID 21310306.
3. Manson JE, Cook NR, Lee IM, et al. Vitamin D supplements and prevention of cancer and cardiovascular disease (VITAL). New England Journal of Medicine. 2019;380(1):33-44. PMID 30415629.
4. Sesso HD, Rist PM, Aragaki AK, et al. Multivitamins in the prevention of cancer and cardiovascular disease: the COSMOS randomized clinical trial. American Journal of Clinical Nutrition. 2022;115(6):1501-1510. PMID 36449943.
5. Allen LH. How common is vitamin B-12 deficiency? American Journal of Clinical Nutrition. 2009;89(2):693S-696S. PMID 19116323.
6. Institute of Medicine (US) Committee on Use of Dietary Reference Intakes. Dietary Reference Intakes for Calcium and Vitamin D. National Academies Press. 2011. NBK56070.
7. Centers for Disease Control and Prevention. Second National Report on Biochemical Indicators of Diet and Nutrition in the U.S. Population. cdc.gov/nutritionreport.