Should you be taking that Vitamin D supplement you’ve had on your kitchen counter for the past 2 years? What if it’s past its expiration date? Many supplement users will wonder what the aging process does to supplements – “will they still be effective a few years down the line? Can it cause more harm than good?” – at some point during their supplementing tenures. In this article, we explain what happens to your vitamins as they age, if you should be taking them past their expiration date, and how to maximize their potency over time.
Generally, vitamins should be stable for four or five years if they are stored properly, according to a New York Times interview with Glen M. Shue, previously a chemist and nutritionist for the Food and Drug Administration (FDA). After vitamins have been sufficiently degraded – whether from oxidation, exposure to humidity and/or light, or other factors – it is generally thought that they are still safe to consume but have simply lost potency. Signs of vitamins past their due dates vary, but changes in color, physical appearance, taste or smell provide some clues, according to Dr. Steven Strauss, author of “Your Prescription and You,” a pharmacy handbook. He also notes that these aren’t definite tells, simply warning signs of spoilage. Lisa Mauer, an associate Professor of Food Science at Purdue University, warns that browning – the appearance of brown spots – on your multivitamin may be a sign of moisture uptake and, more importantly, diminished biological activity.
So how should we store vitamins to maximize their potency over time? As a general rule, keep your vitamins in a cool, dry place, away from light, and make sure they are sealed in an air-tight container. Not all vitamins, however, are created equal. According to Dr. Mauer, water-soluble substances (vitamin C, B-complex vitamins) are susceptible to a process called deliquescence, in which humidity causes a compound to break down. Vitamins (especially water-soluble ones) that come in contact with moisture and high heat will begin to dissolve – and, although they will re-solidify as temperatures drop – the degradation is irreversible. Exposing water-soluble vitamins to humid environments becomes an especially important consideration. Vitamin C, for example, may be lose all biological functionality within a week after it has begun deliquescence, according to Dr. Mauer. In practice, bathrooms and kitchens – rooms in which humidity and temperature are in regular flux – are not ideal options for vitamin storage. What about the refrigerator? If you’re planning on storing supplements for a long time, the refrigerator may be a good option. However, if you use a given supplement regularly, opening and closing the container often may cause condensation build-up at those temperatures – exposing those vitamins to moisture and hastening their breakdown.
A separate consideration is packaging. Generally, “pressed tablets” – like aspirin tablets, for example – are more porous than their coated counterparts and allow a greater influx of oxygen once the vitamins are exposed to air. Oxygen will go on to oxidize the active ingredients, alter their chemistry, and ultimately limit their biological functionality. For this reason, it is thought that capsulated or sugar-coated vitamins last longer than pressed formulations under similar conditions.