Vitamin K2 Is Effective to Decrease Nocturnal Leg Cramps

Is vitamin K₂ effective in decreasing nocturnal leg cramps in older people?

Vitamin K₂ (menaquinone-7), 180 mcg in the evening, halves the average number of nocturnal leg cramps per week in people with frequent bouts. (Level of Evidence = 1b)

The researchers enrolled 199 participants 65 years and older from the community (ie, rather than from a nursing home or hospital) who reported at least two episodes (average 2.6) of nocturnal leg cramps in the previous 2 weeks. The patients were randomized using concealed allocation to receive placebo or vitamin K₂, specifically menaquinone-7, 180 mcg in the evening for 2 months. The average number of cramps dropped to 0.96 per week in the treatment group vs an increase to 3.63 per week in the placebo group (P < .001), with the difference reported in the first week of treatment and continuing to widen over time as the number of episodes decreased in the treatment group. Over 2 months, the patients who received vitamin K₂ had more than 21 fewer episodes of cramps. In addition, duration and severity were reported as lower with treatment, although the difference was not statistically analyzed. Sleep quality and overall quality of life were not assessed.

Vitamin K₁ is found in green leafy vegetables; vitamin K₂ is found in fermented products, such as fermented soybean products and hard cheeses. Menaquinone-7 is a specific type of vitamin K₂ and is sold as a nonprescription vitamin. It has few adverse effects, but it has the potential to reduce warfarin action; therefore, it should not be taken by patients who receive warfarin.

Study design: Randomized controlled trial (double-blinded)

Funding source: Foundation

Allocation: Concealed

Setting: Outpatient (any)

Reference: Tan J, Zhu R, Li Y, et al. Vitamin K2 in managing nocturnal leg cramps: a randomized clinical trial. JAMA Intern Med. 2024;184(12):1443-1447.

Editor’s Note: Dr. Shaughnessy is an assistant medical editor for AFP.