Start with the Ingredient, Not the Brand

The most effective way to use DSLD data is to research the specific ingredient you need, then find products that contain it, rather than starting with a brand and hoping it has what you want. PlainVitamins organizes the NIH DSLD by ingredient, so you can browse all 4,622 ingredients and see every product that includes each one.

On each ingredient page, you can see: how many products contain it, the range of amounts per serving found across those products, and which brands offer it. This lets you quickly identify whether a specific dose is typical or unusually high or low for that ingredient in the market.

How to Normalize for Serving Size

The single most common mistake when comparing supplements is ignoring serving size. Two products may list different milligram amounts, but if one serving is 1 capsule and another is 3 capsules, the per-capsule dose may be identical.

To compare correctly:

1. Identify the ingredient amount per serving in both products.
2. Check the serving size (number of capsules, softgels, tablets, or scoops).
3. Calculate the amount per single unit (capsule/tablet/softgel) by dividing amount per serving by units per serving.
4. Compare cost per milligram (or per IU, CFU, etc.) rather than cost per bottle or per serving.

This arithmetic is especially important for products where servings range from 1 to 6 units. Browse the supplements database and check serving size carefully on every product page.

Evaluating Ingredient Forms

The chemical form of an ingredient affects how well your body absorbs it (bioavailability). DSLD label data often includes the form as declared by the manufacturer. Some notable differences:

• Magnesium: Magnesium oxide is the most common form in supplements and is cheapest to manufacture, but has lower absorption than magnesium glycinate, citrate, or malate. Labels listing only "magnesium" without specifying the form often contain oxide.
• Vitamin B12: Methylcobalamin and adenosylcobalamin are the active forms used directly by the body. Cyanocobalamin is a synthetic form that requires conversion. Both are widely used; research on differences in humans is ongoing.
• Folate: Methylfolate (5-MTHF) is the active form, relevant for people with MTHFR gene variants. Folic acid is the synthetic form. Labels distinguish these if the manufacturer specifies them.
• Omega-3s: Fish oil triglyceride form vs. ethyl ester form, triglyceride form generally has better absorption with food. EPA and DHA amounts (not total fish oil weight) are what matter for dosing.

Using Brand Data to Evaluate Product Catalogs

The brand pages on PlainVitamins show each brand's full catalog in the DSLD, how many products they have listed, how many are currently on market, and the range of categories they cover. This data is useful for:

• Checking whether a brand you've found is a specialist (e.g., focused only on probiotics) or a generalist with hundreds of products across categories.
• Verifying that a product is currently on market rather than discontinued.
• Finding other products from the same manufacturer to compare formulations across their line.

Brand catalog size in the DSLD is not a quality metric, it reflects how many products have submitted labels to the NIH database, which varies by company size and policy, not product quality.

Quality Indicators Beyond Label Data

The DSLD records what labels say. For independent verification of actual content, look for these quality signals in addition to DSLD data:

• Certificate of Analysis (COA): A document from a testing lab confirming that a specific batch meets label specifications. Reputable brands make COAs available on request or on their website.
• Third-party certification seals: NSF Certified for Sport, USP Verified, Informed Sport, or Banned Substances Control Group (BSCG) seals indicate independent batch testing.
• GMP compliance: FDA GMP regulations (21 CFR Part 111) require manufacturers to test raw ingredients and finished products. GMP certification from NSF, NPA, or similar bodies confirms third-party auditing.
• Transparent manufacturing disclosures: Products that disclose the manufacturing facility and country of origin for ingredients allow for deeper verification.

You can also review the supplement safety basics guide for more on what FDA oversight covers and does not cover.

A Step-by-Step Comparison Workflow

Here is a practical process for using PlainVitamins data to compare supplements:

1. Go to the Ingredients page and find the ingredient you need.
2. Note the range of amounts per serving across products, is your candidate product low, average, or high for that ingredient?
3. Check the ingredient form disclosed on the label (e.g., magnesium glycinate vs. magnesium oxide).
4. Open the product page and review the full ingredient list, is this ingredient standalone or part of a multi-ingredient formula?
5. Check the serving size and calculate the per-unit dose and cost-per-milligram.
6. Visit the brand page to see the full catalog and on-market status.
7. Look up the brand externally for third-party certifications (NSF, USP) and available COAs.

Frequently Asked Questions