Nearly three-quarters of Americans take supplements to help fill nutrient gaps or support overall wellness. But some commonly used products may come with an unintended side effect: disrupted sleep. Here are three to keep in mind.
Some pre-workout supplements, as well as those marketed for weight loss or energy, contain caffeine, said Pieter A. Cohen, MD, an associate professor of medicine at Harvard Medical School and an Internal Medicine doctor at the Cambridge Health Alliance. As a result, they may interfere with sleep if taken too close to bedtime.
While some supplements list caffeine as an ingredient, many do not disclose the amount. Others may contain caffeine without clearly labeling it at all. “It’s often very difficult, if not impossible, for consumers to see how much caffeine is in a product by looking at the label,” Cohen told Health.
Vitamin B12 is essential for nerve function, red blood cell formation, and energy production. It may also play a role in regulating melatonin (the hormone involved in the sleep-wake cycle), which could help support sleep and daytime functioning for people with a deficiency, Grace Derocha, RDN, spokesperson for the Academy of Nutrition and Dietetics, told Health.
That said, vitamin B12’s relationship with sleep appears to be complex—with some evidence suggesting it may actually reduce your nightly shuteye. For example, one small study in healthy adults found that vitamin B12 influenced melatonin levels, and that one form—methylcobalamin—was associated with less sleep, though not with poorer sleep quality overall.
But whether the supplements actually disrupt sleep—and why they might do so—remains unclear. “Overall, the research is mixed,” Fariha Abbasi-Feinberg, MD, a member of the board of directors of the American Academy of Sleep Medicine, told Health. “Additional cross-sectional studies are needed to fully understand the relationship between sleep, circadian rhythm, and vitamin B12.”
While there isn’t strong evidence that multivitamins interfere with sleep, there are a couple reasons why they might. Many multivitamins contain vitamin B12, a nutrient linked to sleep disruption, and one study found that people who took multivitamins reported higher rates of insomnia and more nighttime awakenings than those who did not.
However, Abassi-Feinberg cautioned against making too much of those findings. “It’s important to remember that one study is not indicative of a definitive trend or causation,” she said. The study also had important limitations, including a relatively small sample size, a nonrandomized design, and reliance on self-reported sleep data.
