Analysis Challenges Link Between Vitamin D Deficiency and Cancer

SAN ANTONIO – A new meta-analysis of 16 studies challenges the notion that breast cancer risk is inversely related to serum vitamin D level.

In 10 studies, vitamin D was measured before diagnosis of breast cancer; in the other 6 studies, blood samples were gathered for vitamin D measurement only after the diagnosis.

When data from all 16 studies were pooled, lower vitamin D levels were linked with a significant 1.5-fold increased rate of breast cancer (P less than .001). Thus, low vitamin D might be causally related to breast cancer, and, by extension, vitamin D supplementation might be an effective option for breast cancer prevention. But a major difficulty with this line of thinking arose when the two groups of studies were analyzed separately, Dr. Eitan Amir said at the meeting.

Only 1 of the 10 studies in which vitamin D was measured before diagnosis of breast cancer showed a significant relationship between low levels of vitamin D and subsequent increased likelihood of the malignancy. But all six studies in which serum vitamin D was measured after the diagnosis showed a significant inverse relationship. In the pooled analysis of these six studies, lower serum vitamin D was associated with a highly significant, 2.63-fold increased likelihood of breast cancer (P less than .001), said Dr. Amir of the University of Toronto.

Breast cancer cells have been shown to express vitamin D catalytic enzymes that may interfere with accurate measurement of serum levels of the vitamin, added Dr. Amir, who said he had no disclosures.

SAN ANTONIO – A new meta-analysis of 16 studies challenges the notion that breast cancer risk is inversely related to serum vitamin D level.

In 10 studies, vitamin D was measured before diagnosis of breast cancer; in the other 6 studies, blood samples were gathered for vitamin D measurement only after the diagnosis.

When data from all 16 studies were pooled, lower vitamin D levels were linked with a significant 1.5-fold increased rate of breast cancer (P less than .001). Thus, low vitamin D might be causally related to breast cancer, and, by extension, vitamin D supplementation might be an effective option for breast cancer prevention. But a major difficulty with this line of thinking arose when the two groups of studies were analyzed separately, Dr. Eitan Amir said at the meeting.

Only 1 of the 10 studies in which vitamin D was measured before diagnosis of breast cancer showed a significant relationship between low levels of vitamin D and subsequent increased likelihood of the malignancy. But all six studies in which serum vitamin D was measured after the diagnosis showed a significant inverse relationship. In the pooled analysis of these six studies, lower serum vitamin D was associated with a highly significant, 2.63-fold increased likelihood of breast cancer (P less than .001), said Dr. Amir of the University of Toronto.

Breast cancer cells have been shown to express vitamin D catalytic enzymes that may interfere with accurate measurement of serum levels of the vitamin, added Dr. Amir, who said he had no disclosures.

SAN ANTONIO – A new meta-analysis of 16 studies challenges the notion that breast cancer risk is inversely related to serum vitamin D level.

In 10 studies, vitamin D was measured before diagnosis of breast cancer; in the other 6 studies, blood samples were gathered for vitamin D measurement only after the diagnosis.

When data from all 16 studies were pooled, lower vitamin D levels were linked with a significant 1.5-fold increased rate of breast cancer (P less than .001). Thus, low vitamin D might be causally related to breast cancer, and, by extension, vitamin D supplementation might be an effective option for breast cancer prevention. But a major difficulty with this line of thinking arose when the two groups of studies were analyzed separately, Dr. Eitan Amir said at the meeting.

Only 1 of the 10 studies in which vitamin D was measured before diagnosis of breast cancer showed a significant relationship between low levels of vitamin D and subsequent increased likelihood of the malignancy. But all six studies in which serum vitamin D was measured after the diagnosis showed a significant inverse relationship. In the pooled analysis of these six studies, lower serum vitamin D was associated with a highly significant, 2.63-fold increased likelihood of breast cancer (P less than .001), said Dr. Amir of the University of Toronto.

Breast cancer cells have been shown to express vitamin D catalytic enzymes that may interfere with accurate measurement of serum levels of the vitamin, added Dr. Amir, who said he had no disclosures.