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Vitamin K2 reduces uncomfortable nighttime leg cramps in a clinical trial
Last reviewed: 02.07.2025
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Study shows that vitamin K2 supplements reduce the frequency and severity of nighttime leg cramps in older adults.
Nocturnal leg cramps (NLCs) can suddenly interrupt sleep, causing painful spasms in the calf muscles that leave sleepers waking up and struggling with an invisible enemy. Researchers from the Third People's Hospital of Chengdu in China found that vitamin K2 supplements reduced the frequency, intensity, and duration of nocturnal leg cramps in older adults.
Approximately 50%–60% of adults experience NLCs (sometimes called “horse cramps”) in their lifetime, with about 20% experiencing significant discomfort and sleeplessness, leading them to seek medical help. There is currently no medical treatment without a significant list of unpleasant side effects.
In the article, "Vitamin K2 in the Management of Nocturnal Leg Cramps: A Randomized Clinical Trial," published in JAMA Internal Medicine, researchers assessed whether vitamin K2 was more effective than placebo in managing nocturnal leg cramps.
A multicenter, double-blind, placebo-controlled, randomized clinical trial was conducted in China and included 199 participants aged 65 years and older (mean age 72.3 years) who had two or more episodes of NLCs during a two-week screening period. Participants were randomly assigned in a 1:1 ratio to receive either vitamin K2 (menaquinone 7) 180 mcg or placebo daily for eight weeks.
The primary outcome of the study was the mean frequency of NLCs per week between the vitamin K2 and placebo groups. Secondary outcomes were seizure duration measured in minutes and seizure severity assessed on an analogue scale from 1 to 10.
At baseline, the mean number of NLCs per week was comparable in both groups: 2.60 seizures in the vitamin K2 group and 2.71 in the placebo group.
Over the course of the eight-week intervention, the vitamin K2 group experienced a reduction in the average weekly seizure frequency to 0.96, while the placebo group's seizure frequency remained at 3.63. The difference of 2.67 fewer seizures per week between groups was statistically significant and was evident as early as week one.
The vitamin K2 group also significantly reduced the severity of NLC, with an average reduction of 2.55 points compared to 1.24 points in the placebo group. The duration of NLC decreased by 0.90 minutes in the vitamin K2 group compared to 0.32 minutes in the placebo group. No adverse events associated with vitamin K2 were identified.
Based on their findings, the researchers conclude that vitamin K2 supplementation significantly reduces the frequency, intensity, and duration of nocturnal leg cramps in older adults without any adverse effects. They recommend future clinical trials to confirm the efficacy of vitamin K2 and examine its impact on quality of life and sleep in patients with frequent NLCs.