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How should ‘use by’ dates on vitamins be interpreted? (After the date, do vitamins lose potency? Do they become unsafe?)

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A

Vitamins and dietary supplements are not required to carry expiration dates on their labels. This is one area where supplements differ from prescription drugs and over-the-counter medications, which are subject to more stringent regulations.

If companies want to print a “use by” or “best by” date on their supplement labels, they can do so voluntarily. But they are then required to honor those claims, said Tod Cooperman, the president of ConsumerLab.com, a popular independent testing company.

“If you see some type of expiration date,” he said, “the manufacturer is legally required to have stability data demonstrating the product will still have 100 percent of its listed ingredients until that date.”

The vast majority of ingredients in supplements decompose gradually over time, which makes them less potent, but not necessarily unsafe — unless, for example, they happen to grow mold. Dr. Cooperman said that to account for the inevitable disintegration, many companies add more than the amounts of ingredients listed on the label, especially vitamins that decompose quickly, like B12 and C.

If stored away from heat, light and humidity, supplements generally last about two years after the date of manufacture before the concentrations fall below 100 percent of the amounts listed on the label. But the window is only about a year for probiotics, liquids and oils, which are more fragile.

“If a probiotic label suggests refrigeration, do so,” Dr. Cooperman said. “Then return the bottle quickly back to the refrigerator before moisture gets in, as this will activate the organisms, causing them to briefly live and then die.”