Higher dietary, supplemental calcium intake reduced colorectal cancer risk
Key takeaways:
- Individuals with the highest average calcium consumption were 29% less likely to develop CRC, compared with the lowest consumption group.
- More research in racial and ethnic minoritized groups is needed.
Increased dietary and supplemental calcium intake appeared to reduce the risk for colorectal cancers among adults aged 50 years and older, according to findings published in JAMA Network Open.
“In the U.S., close to 30% of men and 60% of women consume less than 1000 mg of calcium per day, making it a dietary component of public health concern for the general U.S. population,” Semi Zouiouich, PhD, from the division of cancer epidemiology and genetics at the National Cancer Institute, and colleagues wrote. “Additionally, a nationally representative study found that levels of calcium insufficiency were higher among non-Hispanic Asian (48%) and non-Hispanic Black (47%) adults than among Hispanic (30%) and non-Hispanic White (24%) adults in the U.S.”
In 1996, the NIH-AARP Diet and Health Study had recruited 566,398 AARP members aged 50 to 71 years to complete a survey, which included questions about their daily dietary and supplemental calcium intake.
In 2008, findings from a 7-year follow-up study demonstrated that increased dairy and calcium intake were linked to lower rates of CRC. However, at that time, fewer than 3,000 people had been diagnosed with colon cancer and fewer than 1,000 were diagnosed with rectal cancer, which limited the study’s statistical power, according to Zouiouich and colleagues.
In this follow-up study nearly 20 years later, the authors evaluated the outcomes of 471,396 adults (40.5% women; mean age, 62 years; standard deviation, 5.4 years) who were cancer-free and in good health at baseline.
Men and women in the lowest quintile consumed an average of 407 mg and 401 mg of total calcium each day, respectively, whereas men and women in the highest quintile averaged 1,773 mg and 2,056 mg of calcium per day. Most of their daily calcium intake came from food (42.1% from dairy and 34.2% from nondairy foods), and nearly one-quarter was from supplements and multivitamins (23.7%).
After a median follow-up period of 18.4 years (interquartile range, 9.2-22.5 years), 10,618 participants developed primary CRC, the researchers reported.
In an adjusted analysis, participants in the highest quintile for total and dietary calcium intake were less likely to develop CRC, compared with those in the lowest quintiles (HR = 0.71; 95% CI, 0.65-0.78; and HR = 0.84; 95% CI, 0.77-0.92, respectively). The researchers found similar results when they stratified data by tumor location.
Additionally, the authors reported that people who consumed more than 1,000 mg per day of supplemental calcium were less likely to develop CRC, compared with people who consumed less than 400 mg per day (HR = 0.8; 95% CI, 0.72-0.9). Greater supplemental calcium intake was associated with a reduced risk for rectal cancer, but not proximal or distal colon cancers, Zouiouich and colleagues wrote.
According to the authors, every additional 300 mg of total daily calcium consumed reduced participants’ risk for CRC by 8% (HR = 0.92; 95% CI, 0.9-0.95). Similarly, additional calcium from food and supplements reduced the risk by 10% (HR = 0.9; 95% CI, 0.84-0.96) and 5% (HR = 0.95; 95% CI, 0.93-0.97), respectively.
These results were consistent among white participants, who made up 91.3% of the cohort. Black participants, who comprised 1.9% of respondents, experienced a 32% lower risk for CRC with each 300 mg of extra calcium per day (HR = 0.68; 95% CI, 0.56-0.82).
“While calcium intake may vary by race and ethnicity, the potential for calcium to play a role in CRC prevention appeared to be consistent across racial and ethnic groups; still, research in racial and ethnic minority populations is needed,” Zouiouich and colleagues wrote. “Increasing calcium intake, particularly among population subgroups with lower intakes, may be associated with a reduction in avoidable differences in CRC cancer risk.”
Perspective
Back to TopThis cohort study used data from the NIH-AARP study, which sent self-administered questionaries to 3.5 million people aged 50 to 71 years of age. After 20 years of follow up, nearly a half million participants were included in this analysis. The investigators excluded individuals considered to have exceptionally high or low calcium intake, as well as those with prior cancer or end-stage kidney disease, to allow for generalization to the majority of the U.S. population.
Dietary intake made up the majority of calcium intake. Overall, higher daily calcium intake, which includes calcium from diet and supplements, was associated with lower risk of CRC, with a reduced risk for every additional 300 mg of calcium per day. This reduction in risk was seen across population subgroups and site of disease within the colon or rectum.
Further, the percentage risk reduction with each additional 300 mg per day was higher among Black individuals compared with white individuals. However, risk reduction was not statically significant among non-Hispanic Black, Hispanic, American Indian/Alaska Native, Asian or Pacific Islander participants.
There are obvious limitations to this study, including but not limited to, assumption that individual calcium intake remained consistent over time, accuracy of self-reporting calcium intake and lack of diversity of the sample population, with the majority of participants (91.3%) identifying as white.
These data are supportive of increasing calcium supplementation in our diets, but do not prove a causal link between lower calcium intake and the development of colon cancer. Rather, the findings support the potential protective role of higher calcium intake.
This study further illustrates how diet plays an integral role in the risk for CRC development. Still, dedicated prospective trials are needed to assess which dietary factors may play a protective role vs. increase our risk for development of disease.
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