Of course, it is important for bones as it is central to the metabolism of calcium to promote bone growth and formation and maintain bone strength. There is also interesting work showing that Vitamin D is associated with depression and this perhaps makes sense if you think that it comes from sunshine and if you spend more time out in the sun there is a reasonable chance you are reducing your risk of depression by being out and about. There is also some interesting work suggesting that Vitamin D has a role in immune modulation and certainly there are links that have been observed between the frequency of the development of multiple sclerosis and the amount of sun exposure a region is subject to such that the incidence of multiple sclerosis is even greater as you move further and further north or south of the equator. From a cardiac perspective there is some work that suggests that Vitamin D is also associated with the modulation of the lipid profile but also has a role in potential deposition of calcium within the arteries during the development of atherosclerosis. In this situation not having enough Vitamin D is the problem. Making sure you have good supplies of Vitamin D is a sensible thing to do.
Lastly, there has been some work talking about the side effects of statins and the condition called myalgia. This is the term given to the general aches and pains felt in the muscles not dissimilar to a flu-like illness that some people report in association with statin therapy. Though there is no conclusive evidence that Vitamin D has an impact on this there is certainly some suggestion that it might reduce the risk of statin-related aches and pains. With all these impacts and effects it's probably a good reminder that we all make sure we get our dose of Vitamin D by sensible exposure to the sun on a regular basis. Sun block, hats and gloves out in the garden won't do it for you. You need to make a concerted effort to present back, chest, abdomen or legs to the sun to allow exposure but avoid burning. Of course, there are plenty of Vitamin D supplements available and Vitamin D levels can also be checked by your doctor.
At the end of the day Vitamin D is free, so make the most of it.