Multivitamins
The multivitamin is the most-purchased supplement category in America — and one of the most debated. Large trials (like the COSMOS study) show modest benefits for cognitive aging, while others show little measurable impact on cardiovascular disease or cancer. The truth is nuanced: multivitamins are most useful when they fill genuine nutrient gaps, and least useful when they're taken as insurance by people who already eat well.
What Actually Matters in a Multivitamin
Most multivitamins are formulated for label appeal, not clinical relevance. Here's what to prioritize:
- Vitamin D3 (2000-5000 IU): The nutrient most people are deficient in. Most multivitamins contain only 400-800 IU — nowhere near enough. You may need a separate D3 supplement.
- Methylfolate (400-800mcg): Superior to folic acid for ~40% of the population with MTHFR variants. Check if your multi uses 5-MTHF or folic acid.
- Methylcobalamin B12 (500-1000mcg): Better absorbed than cyanocobalamin. Essential for vegans and adults over 50 (who lose intrinsic factor for B12 absorption).
- Magnesium (100-200mg): Usually underdosed in multivitamins because it's bulky. You'll likely need a separate supplement.
- Zinc (15-30mg): Important for immune function and testosterone. Zinc picolinate or bisglycinate are better absorbed than zinc oxide.
- Iodine (150mcg): Critical for thyroid function, especially if you don't use iodized salt.
What Doesn't Matter (But Looks Good on Labels)
- Biotin at mega-doses: 5,000-10,000mcg is common but unnecessary unless you have a documented deficiency. The RDA is 30mcg. Excess biotin can also interfere with lab tests for thyroid and cardiac troponin.
- Vitamin C at 1000mg+: Your body maxes out absorption around 200mg. High-dose C creates expensive urine. Adequate vitamin C from food is easy to achieve.
- Calcium in a multivitamin: Usually underdosed (50-200mg) because calcium is physically large. If you need calcium, take it separately.
- "Superfood blends": 50mg of spirulina or acai in a multivitamin is nutritionally meaningless. It's a marketing ingredient, not a clinical dose.
Forms and Formats
- Capsules vs. tablets: Capsules generally dissolve faster and contain fewer binders/fillers. Tablets can be compressed so hard they pass through without fully dissolving.
- One-a-day vs. multi-dose: Splitting across 2-3 doses per day improves absorption of water-soluble vitamins (B, C) that your body can't store. One-a-day is a convenience tradeoff.
- Gummies: Usually lower doses, higher sugar, and missing key nutrients (iron, minerals) because they don't survive the gummy manufacturing process. Fine for children; suboptimal for adults.
- Third-party testing: Look for USP, NSF, or ConsumerLab verification. Multiple investigations have found multivitamins that don't contain what's on the label.
Best For
Do You Even Need a Multivitamin?
If you eat a varied diet with adequate vegetables, protein, and whole grains, you may not need one — with the likely exceptions of vitamin D and magnesium, which are hard to get from food alone. A multivitamin makes the most sense for: people with restricted diets (vegan, keto, elimination), adults over 50, women of reproductive age (folate), and anyone who knows they eat inconsistently. The best approach is to get baseline bloodwork, identify actual deficiencies, and supplement those specifically.
How It Works
Test Before You Buy
A basic nutrient panel (vitamin D, B12, iron/ferritin, magnesium) tells you what you actually need. Don't guess.
Check the Forms
Methylfolate, methylcobalamin, chelated minerals (glycinate, citrate, picolinate) are markers of quality. Folic acid, cyanocobalamin, and oxide minerals are markers of cutting costs.
Ignore the Ingredient Count
A multivitamin with 40 ingredients is not better than one with 15. What matters is whether the important nutrients are at meaningful doses in bioavailable forms.
Fill Gaps Separately
Most multivitamins underdose vitamin D, magnesium, and omega-3. These are the three nutrients most worth adding as standalone supplements.