Vitamin D is an important nutrient for bone health, helping the body to absorb calcium, magnesium, and phosphate. Vitamin D is activated in the liver and kidneys, with 25-hydroxyvitamin D (25(OH)D) being the key form used to assess vitamin D levels in the blood. The risk of vitamin D deficiency (low vitamin D levels) is higher among certain groups of individuals. For example, as people age, their bodies produce and process vitamin D differently. Older adults can often spend more time indoors, which reduces their sun exposure. This makes it harder for them to get the amount of vitamin D they need. Therefore, supplementation may be required to ensure these individuals have sufficient vitamin D to maintain good health.  

This study will compare the effectiveness of two vitamin D supplements—one in spray form and one in capsule form—among people who have low vitamin D levels. The aim of this research is to determine how quickly each supplement raises vitamin D levels and how well participants adhere to taking them.