Higher Calcium Intake Linked to Reduced Colorectal Cancer Risk

Higher calcium intake was consistently associated with a reduced risk of colorectal cancer (CRC) across calcium sources and tumor sites, according to a cohort study using data from the NIH-AARP Diet and Health Study.

Among over 470,000 participants who were cancer-free at baseline, higher total calcium intake was associated with a lower risk of CRC (HR 0.71, 95% CI 0.65-0.78, P<0.001 for trend), reported Erikka Loftfield, PhD, MPH, of the National Cancer Institute, and colleagues.

Dairy, nondairy, and supplemental sources contributed a mean of 42.1%, 34.2%, and 23.7% of total calcium intake, respectively, they noted in JAMA Network Open.

“Our study is larger than most and has a longer duration of follow-up for CRC incidence,” Loftfield told MedPage Today. “We were able to take a deeper dive and study whether source of calcium, anatomic location of the tumor, or participant characteristics impacted the association between higher calcium intake and lower CRC risk.”

“We observed inverse associations for total calcium with risk of proximal colon, distal colon, and rectal cancer, as well as for subsites,” Loftfield noted.

The authors explained that calcium insufficiency is higher among Asian (48%) and Black (47%) adults compared with Hispanic (30%) and white (24%) adults in the U.S. Of note, Black people have a higher incidence of lactose intolerance and are less likely to use supplements.

“Calcium has preventative potential across population subgroups,” Loftfield said.

She and her colleagues noted that they found a dose-response relationship between higher calcium intake and lower relative risk of incident CRC overall. For each additional 300 mg/day in total, dietary, and supplemental calcium intake, they found an 8%, 10%, and 5% decrease in CRC risk, respectively. In Black participants, there was a 32%, 36%, and 19% decrease in CRC risk, respectively.

“We found no evidence of effect measure differences by sex or race/ethnicity, suggesting that increasing calcium intake in population subgroups with low calcium intake could help reduce avoidable differences in CRC risk,” Loftfield said.

The NIH-AARP Diet and Health Study was launched in 1995 and examines the relationship between diet, lifestyle, and cancer risk. AARP members ages 50 to 71 were mailed a self-administered questionnaire, which asked about demographics, behaviors related to health, and dietary intake.

Any responders who said they had had cancer, poor health, end-stage kidney disease, or a very low or very high calcium intake were excluded, leaving 471,396 participants for this study. Mean age at baseline was 62 years, 59.5% were men, and 91.3% were white. Participants were followed up until the date of their first primary cancer diagnosis, death, loss to follow-up, or end of follow-up (Dec. 31, 2018).

Mean total calcium intake for the lowest quintile was 401 mg/day for women and 407 mg/day for men; for the highest quintile, these values were 2,056 mg/day and 1,773 mg/day, respectively.

For Black participants, the mean calcium intake was 382 mg/day for the lowest quintile and 1,916 mg/day for the highest quintile, with no association of total calcium intake with CRC risk (highest vs lowest quintile: HR 0.60, 95% CI 0.32-1.13, P=0.12 for trend).

Over a median 18.4 years of follow-up, 10,618 first primary CRC cases were identified.

More studies that focus on calcium intake and CRC in population subgroups are needed, the researchers said. Loftfield added that she did not know of any research currently underway, but that “increasing representation of population subgroups that are underrepresented in cohort studies will make this possible in the future.”

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