A weekly 40,000 IU dose of vitamin D2 (ergocalciferol) for six months was also associated with improvements in vitamin D status, as well as improvements in grip strength and physical performance in 175 osteoarthritis patients, according to findings published in Nutrients.
“[V]itamin D supplementation is a safe and inexpensive way to improve muscle strength and physical function in this population,” wrote scientists from Chulalongkorn University in Thailand.
“Based on these findings, we recommend vitamin D supplementation in knee OA patients that have poor physical function.”
The Sunshine Vitamin
Vitamin D refers to two biologically inactive precursors - D3 (cholecalciferol) and D2 (ergocalciferol). Both D3 and D2 precursors are transformed in the liver and kidneys into 25- hydroxyvitamin D (25(OH)D), the non-active 'storage' form, and 1,25-dihydroxyvitamin D (1,25(OH)2D).
Vitamin D deficiency in adults is reported to precipitate or exacerbate osteopenia, osteoporosis, muscle weakness, fractures, common cancers, autoimmune diseases, infectious diseases and cardiovascular diseases. There is also some evidence that the vitamin may reduce the incidence of several types of cancer and type-1 and -2 diabetes.
While our bodies do manufacture vitamin D on exposure to sunshine, the levels in some northern countries are so weak during the winter months that our body makes no vitamin D at all, meaning that dietary supplements and fortified foods are seen by many as the best way to boost intakes of vitamin D.
Interest in the potential health benefits of the sunshine vitamin has increased significantly over the last decade or more (see Google Trends figure below), while the 2015 Dietary Guidelines Advisory Committee classed the vitamin as a nutrient of concern.
The new study adds to the body of evidence supporting the potential health benefits of vitamin D, with six months of supplementation with D2 associated with significant decreases in LDL cholesterol levels, as well as decreases in levels of protein carbonyl (a marker of oxidative stress) and parathyroid hormone (PTH).
“[H]igh levels of PTH are related with the risk of fall, fracture, and poorer outcomes in terms of frailty,” explained the researchers. “PTH action stimulates the transformation of pro-osteoclasts into mature osteoclasts, which leads to increasing bone turnover. Consequently, optimal vitamin D levels may help to reduce the risk of fall, fracture, and osteoporosis.”
The researchers also found significant improvements in self-assessed scores of “quality of life” and pain, according to the visual analog scale (VAS), after six months of vitamin D2 supplementation compared with baseline values. In addition, improvements in grip strength and physical performance were observed, but no changes to knee extension force were recorded after six months.
“[O]ur results suggest that 40,000 IU of vitamin D2 supplementation reduced oxidative protein damage, improved quality of life, and improved grip strength and physical performance,” wrote the researchers. “It remains unclear whether vitamin D supplementation relates to musculoskeletal pain or not. Accordingly, vitamin D treatment decreases current pain using VAS, but does not reduce pain during physical activity, as determined by WOMAC score.”
2017, 9(8), 799; doi:10.3390/nu9080799
“Vitamin D Supplementation Improves Quality of Life and Physical Performance in Osteoarthritis Patients”
Authors: P. Manoy et al.