ICMR Study in Rats Finds Vitamin D3 More Effective Than D2 for Muscle and Heart Health

Vitamin D3 may be more effective than vitamin D2 at maintaining and restoring skeletal muscle and heart function, according to a study on male rats by researchers at the Indian Council of Medical Research–National Institute of Nutrition (ICMR-NIN), Hyderabad. The benefits of vitamin D3 were particularly evident during the animals' recovery from vitamin D deficiency, and the findings were published in Molecular Nutrition and Food Research.

The researchers used weaning male Sprague-Dawley rats given diets containing vitamin D2, vitamin D3, a combination of both, or a vitamin D-deficient diet, and then evaluated body composition, muscle strength, skeletal muscle structure and metabolism, and markers of cardiac function. Vitamin D3 had a stronger effect than D2 on muscle mass, muscle fiber size and grip strength, as well as on markers linked to muscle development and energy metabolism, during both the maintenance phase and the recovery phase after deficiency. It also produced greater improvements in markers of cardiac contractility and heart metabolism, particularly during recovery.

Dr. Ayesha Ismail, Scientist F at ICMR-NIN and the study's corresponding author, said vitamin D3 increased blood levels of 25-hydroxyvitamin D (25OHD) — a key biomarker of vitamin D status — by approximately two-fold compared with D2 at the same dose. Vitamin D deficiency is widespread, affecting more than 1 billion people worldwide, with an estimated 50% to 80% of populations in different countries insufficient or deficient; in India, Dr. Ismail said, nearly 80% of people may have inadequate vitamin D levels.

Vitamin D3 is produced mainly through sun exposure and is found in animal-based foods such as eggs, fish and organ meats, while vitamin D2 comes mainly from mushrooms, UV-B-irradiated yeast and other plant-based sources, and is preferred in some countries for vegetarian or vegan diets. Dr. Bharati Kulkarni, Director of ICMR-NIN, said the findings suggest vitamin D3 may be more effective than D2 for skeletal muscle and cardiac function, but stressed that further studies are needed to determine whether the results translate to humans.