Luckily the issue of vitamin D deficiency is easily resolved. Blood tests don't lie. If your test shows you don't have enough Vitamin D, it could be diet, it could be aging (as we get older, everyone generates less Vitamin D). I agree with Cheryl that you should not just start popping Vitamin D pills
Few individuals would allow their clinician to simply guess an cholesterol level before placing him/her on some type of medication. Clinicians have access to an accurate lipid test that provides guidance. The same is true for vitamin D levels.
What counts is your blood level, not your intake.