Nocturnal cramps of the lower limbs remain poorly understood, their exact cause still not being identified, and no effective and safe treatment exists to date. The prescription of quinine (muscle relaxant) is very limited due to its adverse effects (allergic reactions, visual and hearing problems, blood disorders). As for magnesium, there is no evidence of its effectiveness.
A randomized, multicenter, double-blind, placebo-controlled Chinese trial — meaning the highest level of scientific evidence — was conducted in people aged 65 and older who had at least two episodes of nocturnal cramps in the legs during the previous two weeks. According to the results, which have just been published in JAMA Internal Medicine, daily supplementation with vitamin K2 would be effective in reducing cramps.
The vitamin K family is essential for several biological functions, including blood clotting, bone health and calcium metabolism.
Less frequent and less severe cramps with vitamin K2
In the trial, vitamin K2 was administered to participants at 180 mcg per day for 8 weeks.
Specifically, this was given in its menaquinone-7 form, which is one of its main variants. MK-7 is often favored in studies and dietary supplements due to its bioavailability and longer duration of action in the body, compared to other forms of vitamin K.
Nearly 200 participants took part in this study. The latter had reported more than 2.5 episodes of nocturnal cramps per week. After the 8 weeks, nothing changed among the people in the placebo group, while those in the vitamin K2 group saw the frequency of their cramps decrease. In addition to frequency, the severity of the cramps eased, as did the duration of each episode.
The authors conclude that vitamin K2 supplementation reduces the frequency, shortens the duration and reduces the intensity of muscle cramps in elderly people suffering from nocturnal cramps, from the first week of intervention, and without adverse effects. Research must be carried out to confirm these results and particularly in people whose intensity of nocturnal leg cramps is severe because the participants here suffered on average from cramps of moderate intensity.
Vitamin K2 in the daily diet
Without being equivalent to daily supplementation, you should know that vitamin K2 is mainly present in meats, eggs and fermented dairy products such as certain cheeses. The consumption of these foods rich in vitamin K2 can be encouraged, in a reasonable manner of course, including in the event of excessively high cholesterol levels in the blood.
How would vitamin K2 work?
In the laboratory, a mechanism explaining the relaxing effect of vitamin K on muscles was observed: this vitamin promotes relaxation of muscle fibers by preventing calcium from penetrating into muscle cells from the outside.
No adverse effects linked to vitamin K2 were observed in this study, which is rather reassuring in elderly people who are most often affected by nocturnal cramps. But be careful because vitamin K2 is not recommended for patients under treatment with warfarin (in the event of heart rhythm disturbances which could expose them to a stroke, pulmonary embolism, etc.). However, this medication is commonly prescribed to the elderly. Warfarin works by inhibiting the action of vitamin K, which plays a crucial role in blood clotting. Therefore, vitamin K2 may reduce its anticoagulant effectiveness.
Source: Tan J, Zhu R, Li Y, et al. Vitamin K, in managing nocturnal leg cramps: a randomized clinical trial. JAMA Intern Med. Published online October 28, 2024; Frequencies of muscle symptoms in the general population, by Eric Bruckert
