In the news: Vitamin D & Glucose Control in Diabetics; Nighttime Leg Cramps & Vitamin K

Vitamin D & Glucose Control in Obese Type 2s

Vitamin D deficiency is associated with reduced insulin release, insulin resistance and type 2 diabetes. Additionally, the results of some prospective studies have found that insufficient levels of the vitamin accelerate the progression of prediabetes to type 2.

However, even with these observed associations, the potential benefits of vitamin D supplementation on glycemic control and insulin sensitivity remain controversial. This led researchers from China’s National Clinical Research Center for Metabolic Diseases to conduct an updated meta-analysis to assess the role of vitamin D in blood sugar control.

The analysis(1) included 39 randomized controlled trials involving 2,982 subjects. Serum vitamin D as well as 4 indicators of glycemic control were measured: fasting blood glucose (FBG), fasting insulin, HbA1c and Homeostasis Model Assessment for Insulin Resistance (HOMA-IR).

The researchers also explored factors such as the dosage and duration of supplementation, baseline serum vitamin D and HbA1c levels, as well as the body mass index (BMI) of type 2 patients – all factors that can impact the outcome of vitamin D interventions.

The study found that vitamin D supplementation increased serum vitamin D levels and provided significant benefits in improving glycemic control, as indicated by marked reductions in FBG, HbA1c, HOMA-IR and fasting insulin levels.

Subgroup analyses showed that vitamin D had the greatest effect in obese diabetics with vitamin D insufficiency and a baseline HbA1c of 8% or higher.

Obese and overweight individuals have a higher risk of vitamin D deficiency for several reasons. Those with subcutaneous fat deposits store a large amount of vitamin D which impedes the transport of vitamin D from the skin into the bloodstream. Also, vitamin D stored in fat tissue isn’t readily mobilized into the circulation. Overcoming this deposition may require higher supplemental doses of vitamin D.

In terms of supplement dosage and duration, the study found that daily doses 2000 IU/d or higher provided significant improvement in glycemic control, while a greater improvement of fasting insulin was observed during long-term vs. short-term interventions.

Since glycemic control is a key factor in preventing and slowing the progression of diabetic retinopathy, it may be prudent for overweight type 2 diabetics to have their serum vitamin D levels assessed and monitored.

Vitamin K: Helpful for Nighttime Leg Cramps?

The exact cause of nocturnal leg cramps (NLCs) is unknown, but muscle fatigue or nerve problems may be the issue for many. Other possible causes include dehydration, electrolyte imbalance, physical inactivity, exercise, and certain medications.

About 50% to 60% of adults experience NLCs in their lifetime, with approximately 20% of those experiencing significant levels of distress and insomnia that lead them to pursue medical intervention. There are currently no treatments for NLCs that have been proven both safe and effective. Thus, seeking safe, effective ways to manage NLCs is important.

This prompted researchers to ask whether vitamin K(2) could significantly reduce the frequency, duration, and severity of NLCs in an older population. In addition to its role in blood clotting and bone formation, vitamin K is thought to inhibit the uptake of calcium into muscle which could lead to muscle relaxation.

In this randomized clinical trial2 involving 199 older participants with NLCs, those who received 180 mcg of vitamin K2 for 8 weeks experienced a significant reduction in the mean frequency of cramps per week – a drop to 1 per week – compared with a placebo group, which increased to 3.6 weekly. While vitamin K may be avoided by those on Coumadin, this trial reported no adverse effects and confirmed the good safety profile of the vitamin.

References

1. Chen W, et al. Efficacy of vitamin D supplementation on glycaemic control in type 2 diabetes: An updated systematic review and meta-analysis of randomized controlled trials. Diabetes Obes Metab. 26:5713–5726, 2024.
2. Tan J, et al. Vitamin K2 in managing nocturnal leg cramps: a randomized clinical trial. JAMA Intern Med. Epub Oct. 28, 2024.