Check it out. Latest concerns about Vitamin D deficiency. BBC News reports that there has been an increase in childhood rickets over the past 15 years. "The chief medical officer for England, Dame Sally Davies, is to contact medical staff about concerns young children and some adults are not getting enough vitamin D. Government guidelines recommend some groups, including the under-fives, should take a daily supplement. However, recent research found that many parents and health professionals were unaware of the advice."
As well as the short video on that webpage, I believe you will find this one from a news report earlier this month even more interesting/alarming. That most health professionals are ill-informed in the matter of the prevalence of vitamin D deficiency is perhaps the most alarming aspect of the problem.
Taking vitamin D3 supplements certainly made a big difference to me: enabled me to rise from a chair without a monumental struggle was perhaps the most noticeable difference, and the ability to climb stairs more easily, and of course to feel stronger, and steadier on my feet. All my life doctors had given me the wrong information about vitamin D. Especially Dr Nigel Bax - now a professor, I believe. Although my chest X-ray at the time I saw him caused him to exclaim with shock that my ribs were almost transparent on the X-ray, he did his damnedest to warn me off taking vitamin D, and said if I did take any supplements, against his advice, the best time to take them was on an empty stomach before breakfast! - That too, was wrong. Fat-soluble vitamins (A, D, E, K) should be taken with or after a meal that contains healthy fat. His confident, strongly expressed, incorrect advice did me immeasurable harm. - I had osteomalacia. No wonder my ribs were hurting.