If you've ever woken up in the middle of the night with sudden painful thigh, calf or foot cramping, you'll know just how awful the experience is – and, unfortunately, the frequency of these nighttime disturbances increases with age.
Around 40% of people over 50 experience night cramps – known by many names, such as sleep or nocturnal leg cramps (NLCs) – in which muscles in the lower limbs contract painfully and that can take up to several minutes to recede. However, only a minority of sufferers report them to their doctor.
Now, researchers from the Third People's Hospital in China and several medical colleges have found a promising preventer for these waking nightmares, and a clinical trial of 199 people found that vitamin K2 significantly reduced episodes, pain experienced and the duration of the cramping.
"This study was based on our previous research, which revealed the efficacy of vitamin K2 in relieving hemodialysis-related muscle cramps," the researchers noted. "To our knowledge, this is the first study that explored the use of vitamin K2 specifically for treating NLCs."
Until now, lifestyle interventions – exercise, hydration – have been an imperfect way to reduce the chances of experiencing frequent NLCs, which become more frequent as we age and are often independent of any underlying diseases or conditions. While magnesium supplements have shown some efficacy in relieving cramping in pregnant women, it didn't help NLCs in general.
Overall, while a less active lifestyle and poor diet and lifestyle plays a role in the condition, it's not well understood nor treated.
"Quinine has been shown to be effective in treating NLCs but is not recommended by the US Food and Drug Administration due to severe side effects," the researchers noted in a preliminary study protocol paper last year. "Magnesium supplements are often used as a preventative treatment for NLCs; however, their effectiveness is controversial."
Controversial, because trials have not delivered clinically significant results for older adults who experience NLCs.
In this eight-week study, 199 participants aged 65 or older with a minimum of two NLCs in two weeks were recruited for a randomized, double-blind, placebo-controlled trial to test whether vitamin K2 could be a better intervention.
Splitting the group in two, 103 participants were randomly assigned to take a daily dose of 180 μg of K2, with the remaining 96 people receiving the placebo. Overall, 54% were female and the average age was 72.
So why this particular isoform of vitamin K? K2, a group of menaquinones synthesized by bacteria in the gut, is bioavailable in dairy products like full-fat cheeses, fermented foods such as sauerkraut and other animal products (as opposed to K1, a phylloquinone, which you'll find in leafy greens and certain plant oils). Vitamin K, overall, is important in blood coagulation, as well as general blood and bone health.
While K2 has shown potential in helping reduce the risk and morbidity of certain cancers, it's largely understudied and its broad health benefits are not well understood.
During the clinical trial – patients were assessed weekly for occurrence and severity of NLCs, and both cohorts had a similar baseline number of events, with 2.60 in the K2 group and 2.71 in the control. At the end of the eight-week experiment, weekly scores were analyzed to see if there had been a sustained benefit to the K2 treatment.
What the team found was that over the eight weeks, the participants taking K2 showed a statistically important reduction in NLCs, with a mean of 1.41. The control group, meanwhile, had a mean of 3.63 with a much greater range in number of events than the K2 group.
"The difference in cramp frequency at intervention phase between the vitamin K2 and placebo groups was statistically significant," the researchers noted. "The between-group difference became significant since the first week of the intervention."
The K2 group also had a greater reduction of pain and episode duration than the placebo cohort, and no negative side effects were experienced by those taking the supplement.
"Our results demonstrated that daily vitamin K2 supplementation alleviates muscle cramps in older individuals affected by NLCs, manifested by decreased frequency, shortened duration, and weakened intensity," the researchers added.
They also noted trial limitations, such as not assessing overall quality of life and sleep, and many participants experienced mild NLCs. Future studies should take these into account to confirm vitamin K2's efficacy as a treatment for the condition.
While K2 supplements, when taken within dose range, are considered low-risk when it comes to side effects, some people have reported initial mild digestive issues like bloating or gas, or headaches.
The team cautions that anyone should consult a medical professional before taking new supplements, as K2 could present issues for people on other medications, including anticoagulant treatments.
The study was published in the journal JAMA Internal Medicine.
Source: The Third People's Hospital of Chengdu via Scimex