Do vitamins lose their potency when exposed to the elements?

That’s the central question behind a long-running argument in my otherwise happy marriage. I say yes. He says no.

You see, my husband routinely dumps a week’s worth of his vitamins and nutritional supplements into a little glass bowl, which he keeps in the kitchen cupboard. When he takes his vitamins in the morning, he just picks them out of the bowl instead of opening each vitamin bottle individually.

“It’s more efficient,” he says.

“It’s crazy,” I say. “The warning on the label says KEEP IN A DRY PLACE, TIGHTLY CLOSED, AND AVOID EXCESSIVE HEAT.”

“You’re making a big deal out of nothing,” he replies.

“You’re squandering our investment,” I counter.

To settle this argument—and to learn the facts about vitamin potency—I turned to Julia Gullotti, N.D. (Doctor of Naturopathy), a fellow contributor to this blog who is also a nutraceutical researcher and formulator.

“It really depends on what the products are,” says Julia. “Some are more light- and heat-sensitive than others.”

Julia says relative humidity and temperature both significantly impact vitamin stability. For example, humidity can cause water-soluble vitamins like C and B to dissolve. “In high heat and humidity, it can take as little as a day to lose potency, and you can tell if your vitamins are in danger if there are wet droplets in the container or brown spots starting to appear on them,” she says.

So now the question is, how hot and humid is our cupboard? Probably not very humid, since our South Florida home is air-conditioned most of the time. But the cupboard in question is located just a few feet from the stove, which heats up our tiny kitchen in no time. And then there’s the question of oxidation.

“Tablets outside of their containers are more susceptible to oxidation than encapsulated products (i.e., capsules) because they are more porous,” Julia says. “Herbs in particular should be kept away from exposure to air as well as heat and humidity since those things stimulate enzyme activity of the plant and destroy the beneficial properties.”

So, I win, right? Well… not exactly.

Julia says in general, vitamins should be capped properly in an opaque or darkly colored container, away from bright sunlight and the excessive heat of the kitchen. Then she throws in the kicker:  “Typically, though, keeping supplements in a cupboard open for a week is not going to do anything to reduce their potency. My mother does the same thing. And because she wouldn’t take her supplements otherwise, I say it’s better than nothing.”

Then she adds: “I’ll let you decide if you want to tell your husband that.”

- Paula Detwiller,  All Vitamins Plus Contributor