How Supplement Brands Decide What Counts as One Serving

A "serving" sounds like a standard unit of measurement. It is not. On supplement labels, a serving is whatever amount the brand chose to put in the recommended daily dose — and brands choose it with several goals in mind.

The first goal is honesty about the formula. A capsule can only hold so much powder, so concentrated formulas often need one capsule while bulkier blends need two or three. The second goal is psychology: a bottle of 60 capsules sounds better when it is "60 servings" than when it is "30 days at the recommended dose". A few brands set generous serving sizes to make the price per serving look smaller.

Then there is the nutrient math. Daily values are calculated per serving, so a two-capsule serving can show "100% of your daily vitamin D" while a one-capsule serving of the same formula would show only 50%.…