The report concluded it is biologically plausible that calcium or Vitamin D protects against the development of colorectal cancer,  but results from case-control and cohort studies are inconsistent and indicate that if there is a reduced risk,  it is modest.   Well-designed clinical studies in high-risk populations using intermediate biomarkers of risk also are inconsistent.   Many of these inconsistent findings may be due to factors that influence the relationship between colorectal cancer risk and calcium,  Vitamin D,  or dairy product consumption.   These factors include genetic influences,  differing effects of diet on different types of lesions,  and other dietary constituents such as folate.   Inconsistent findings also may be due to methodological differences and limitations with specific study designs or differences in the populations studied.   Recent findings of a moderate reduction in the risk of recurrent adenomas in a high-risk population are encouraging but these results should be confirmed in other studies.   There are few well-designed clinical studies on the effect of calcium or consumption of dairy products on the intermediate biomarkers of colorectal risk in healthy subjects,  and there are no clinical trials on the effect of calcium or dairy product consumption of the occurrence of colorectal adenomas or cancers in a healthy population.   Although these trials would be extremely expensive,  they would help determine the benefit and risk from high-calcium intakes.   Ongoing calcium supplementation trials,  a European trial and the Women's Health Initiative,  should provide the additional evidence as to whether a high-calcium intake can reduce the incidence of colon or rectal cancers in healthy and at-risk populations.   Studies such as these need to be conducted and previous findings confirmed the before public can be told that increased calcium,  Vitamin D,  or dairy products would lead to a decreased risk of colorectal cancer.