Strength of evidence for Calcium at NLM
http://www.nlm.nih.gov/medlineplus/druginfo/natural/781.html
It seems to consider the benefits of Calcium by itself, and not in combination with vitamin D
'insufficient evidence' seems to indicate insufficient evidence when not combined with vitamin D)
The following is a tiny subset of the information
Effective for...
Raising calcium levels in people who have low calcium.
Preventing low calcium levels.
Reversing high potassium levels, when given intravenously (by IV).
Use as an antacid as calcium carbonate.
Reducing phosphate levels in people with kidney disease.
Likely effective for...
Treating osteoporosis (weak bones).
Preventing bone loss caused by insufficient calcium in the diet. This can reduce the risk of breaking bones.
Reducing symptoms of premenstrual syndrome (PMS)..
Increasing fetal bone density in pregnant women with low calcium intake.
Reducing bone loss in people taking drugs called corticosteroids, when used in combination with vitamin D.
Reducing thyroid hormone levels in people with kidney failure.
Possibly effective for...
Reducing the risk of colorectal cancer. .
High blood pressure.
High blood pressure in pregnancy (pre-eclampsia).
High cholesterol.
Reducing weight and body fat while dieting.
Preventing stroke in women.
Preventing fluoride poisoning in children when taken with vitamins C and D.
Reducing tooth loss in elderly people.
Possibly ineffective for...
Preventing breast cancer in older (postmenopausal) women.
Reducing lead levels in breast-feeding women.
Insufficient evidence to rate effectiveness for...
Preventing falls.
Metabolic syndrome.
Cancer.
Pregnancy-related leg cramps.
Diabetes. .
Lyme disease.
Seizures.
Other conditions.