I found out an interesting thing recently.  I was dieting and working out like crazy and showing barely any progress at all.  After about a month, I developed back and leg pain.  I felt like an arthritic old woman every time I tried to exercise. I went to see my doctor for my physical and mentioned it to her.  I thought I might be hypothyroid because my mom had that issue years before.  She ordered blood tests and talked to me about getting my Vitamin D checked. I agreed to this test.  My level was about half of the normal lower limits despite the fact that I have 2 servings of diary every day.  She put me on some prescription supplements.  After a couple of weeks, the weight started falling off of me. The back and leg pain went away.  I felt happier and more energetic than I have in years.  I even went through 2 period cycles with none of the PMS symptoms that I've had for the last 10 years or so.  After doing some research I found that Vitamin D deficiency can lead to bone pain, osteoporosis, obesity, depression, and heart disease. My doc is still working with me to get my level up.  She has me taking a multivitamin as well as a calcium supplement with D added (you have to take calcium with Vit D.)  After I reach my ideal level she wants me to take the calcium supplement as well as 1000-2000 IU per day of D.

I was so impressed with my results that I have my son taking extra calcium with D as well.  His diet is horrible and I thought it definitely can't hurt.

I just thought I'd share the information I learned.  You can't get sufficient D from dairy unless you drink like 10 cups of milk per day and most of us don't get sufficient sunlight at this time of year.