Vitamin D3 may be more effective than vitamin D2 in maintaining and restoring skeletal muscle and heart function, according to a recent study by researchers at the Indian Council of Medical Research–National Institute of Nutrition (ICMR-NIN), Hyderabad. The study, conducted on male rats, found that the benefits of vitamin D3 were particularly evident during recovery from vitamin D deficiency. The findings were published in Molecular Nutrition and Food Research.
Vitamin D3 Improves Muscle Mass and Strength
Researchers found that vitamin D3 had a stronger impact than vitamin D2 on several indicators of skeletal muscle health. These included muscle mass, muscle fibre size and grip strength, as well as markers associated with muscle development and energy metabolism. Moreover, vitamin D3 produced greater improvements in markers linked to cardiac contractility and heart metabolism, particularly when the animals were recovering from vitamin D deficiency.
Dr Ayesha Ismail, Scientist F at ICMR-NIN and corresponding author of the study, said vitamin D3 increased blood levels of 25-hydroxyvitamin D (25OHD)—a key biomarker of vitamin D status—by approximately two-fold compared with vitamin D2 when administered at the same dose. She noted that vitamin D3 was more effective than vitamin D2 for certain muscle- and heart-related parameters.
Study Compares Vitamin D2 and D3
To examine the differences between the two forms of vitamin D, the researchers used weaning male Sprague-Dawley rats. The animals were given diets containing vitamin D2, vitamin D3, a combination of both, or a vitamin D-deficient diet. The researchers then evaluated body composition, muscle strength, skeletal muscle structure and metabolism, along with markers associated with cardiac function. The study showed that vitamin D3 had a greater effect on skeletal muscle size and function during both the maintenance phase and the recovery phase following vitamin D deficiency.
Vitamin D Deficiency Remains a Major Concern
Vitamin D deficiency is widespread globally, affecting more than 1 billion people. Estimates suggest that between 50% and 80% of populations in different countries may have insufficient or deficient vitamin D levels. In India, Dr Ismail noted that nearly 80% of people may have inadequate vitamin D levels. Based on the study’s findings, she suggested that supplements containing vitamin D3 could be a more effective option than those containing vitamin D2. Vitamin D occurs naturally in two major forms: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol).
How Vitamin D2 and D3 Differ
The body produces vitamin D3 primarily through exposure to sunlight or ultraviolet (UV) radiation. It is also found in animal-based foods such as eggs, fish and organ meats, as well as in supplements. Vitamin D2, meanwhile, is mainly obtained from mushrooms, UV-B-irradiated yeast and other plant-based sources, in addition to certain supplements. Both forms are used in food fortification. However, vitamin D2 is preferred in some countries because it is suitable for people following vegetarian or vegan diets.
D3 May Have an Advantage Beyond Bone Health
Vitamin D is widely recognised for its role in maintaining bone health. However, it also contributes to the regulation of skeletal muscle mass, structure and function. The researchers pointed out that the differences between vitamin D2 and D3 in their effects beyond bone health have remained unclear. Their findings now indicate that vitamin D3 may have a stronger influence on muscle size, muscle function and cardiac parameters, particularly during recovery from deficiency.
More Research Needed
Dr Bharati Kulkarni, Director of ICMR-NIN, said the findings suggest that vitamin D3 may be more effective than vitamin D2 in maintaining and restoring skeletal muscle and cardiac functions. However, the researchers stressed that further studies are necessary to determine whether these findings translate to humans. More research is also needed to understand the implications of vitamin D2 and D3 for supplementation and food-fortification programmes. According to the World Health Organization–Food and Agriculture Organization (WHO-FAO), micronutrient supplementation is among the fastest ways to improve the nutritional status of populations. Food fortification, meanwhile, can provide a cost-effective intervention with a sustained public-health impact. As reported by newindianexpress.com, the ICMR-NIN study suggests that vitamin D3 may offer greater benefits than vitamin D2 for skeletal muscle and heart function, especially during recovery from vitamin D deficiency. However, further human studies are required before the findings can be directly applied to supplementation recommendations.