TOPLINE:

A long-running cohort study has revealed that higher calcium intake from both dietary sources and supplements is consistently associated with a reduced risk of colorectal cancer (CRC). This finding suggests that increased calcium consumption could benefit individuals who do not get enough of this essential mineral, offering a potential strategy for cancer prevention.

METHODOLOGY:

• Researchers from the National Institutes of Health (NIH) analyzed the NIH-AARP Diet and Health Study, initially finding that dairy food and calcium intake were inversely associated with CRC after an average of 7 years of follow-up. However, the study did not report on associations by tumor site or by source of calcium.
• With over 20 years of follow-up, the researchers addressed outstanding questions, including whether associations between calcium consumption and CRC differ by source of calcium, tumor site, or population subgroups.
• The study included 471,396 adults free from cancer at baseline, with a mean age of 62 years and 59.5% being men. Participants reported good health at the start of the study.
• Baseline dietary calcium intake was assessed via a 124-item food frequency questionnaire. Total calcium intake was calculated by combining intake from dietary sources (dairy and nondairy) with that from supplements. Incident cases of CRC were identified using cancer registry data, and risk was analyzed using multivariable Cox proportional hazards models.

TAKEAWAY:

• During more than 7.3 million person-years of follow-up (median, 18.4 years), there were 10,618 first primary CRC cases.
• Participants in the highest quintile of total calcium intake (2056 mg/d for women, 1773 mg/d for men) had a 29% lower risk for CRC (hazard ratio [HR] 0.71) than those in the lowest quintile (401 mg/d for women, 407 mg/d for men).
• The inverse association was observed across all tumor sites, including the proximal colon (HR, 0.75), distal colon (HR, 0.73), and rectum (HR, 0.61).
• Dairy, nondairy, and supplemental calcium sources all contributed to risk reduction.
• Overall, for each additional 300 mg/d in total, dietary, and supplemental calcium intake, there was an 8%, 10%, and 5% decrease in CRC risk, respectively. In Black individuals, there was a 32%, 36%, and 19% decrease in CRC risk, respectively.

IN PRACTICE:

Increasing calcium intake, particularly among groups with lower consumption, may be associated with reductions in avoidable differences in colorectal cancer risk, the authors concluded.

According to the National Cancer Institute, colorectal cancer is the third most common cancer diagnosed in both men and women in the U.S. This study provides a compelling case for increasing calcium intake as a preventative measure. For instance, a diet rich in dairy products, leafy greens, and fortified foods can help meet the recommended daily intake of calcium. Additionally, calcium supplements can be considered for those who struggle to get enough calcium through diet alone.

“Increasing calcium intake, particularly among groups with lower consumption, may be associated with reductions in avoidable differences in colorectal cancer risk,” the authors concluded.

LIMITATIONS:

Calcium intake was assessed at baseline only, with no consideration for changes over time. The study relied on self-reported dietary data, which may introduce recall bias. The number of CRC cases in certain racial/ethnic subgroups was limited, reducing statistical power for subgroup analyses.

DISCLOSURES:

The authors reported no conflicts of interest. The study was supported by the Intramural Research Program of the National Cancer Institute at the National Institutes of Health.

RECENT DEVELOPMENTS AND PRACTICAL APPLICATIONS:

Recent developments in cancer research continue to emphasize the importance of dietary interventions in cancer prevention. The findings of this study align with other research highlighting the role of calcium in maintaining overall health. For example, a 2022 study published in the Journal of the American Medical Association (JAMA) found that higher calcium intake was associated with a lower risk of bone fractures, further underscoring the multifaceted benefits of adequate calcium consumption.

In practical terms, these findings can be integrated into public health guidelines and nutritional recommendations. The U.S. Department of Agriculture’s Dietary Guidelines for Americans already emphasize the importance of calcium-rich foods, but this study provides additional evidence to support these guidelines. Health professionals can use these findings to educate patients about the benefits of calcium and encourage them to incorporate more calcium-rich foods into their diets.

For individuals at higher risk of colorectal cancer, such as those with a family history or certain genetic predispositions, these findings offer a potential preventive strategy. Regular screenings and a balanced diet rich in calcium can work together to reduce the risk of colorectal cancer. For example, the American Cancer Society recommends regular colonoscopies for individuals over 45, and this study suggests that increasing calcium intake could complement these screening efforts.

ADDITIONAL INSIGHTS:

The study’s findings also raise questions about the optimal sources of calcium. While dairy products are a common source, nondairy sources such as leafy greens, fortified plant-based milks, and supplements can also contribute to overall calcium intake. This is particularly relevant for individuals with lactose intolerance or those following plant-based diets.

For instance, a case study involving a 55-year-old woman with a family history of colorectal cancer and lactose intolerance showed that she was able to meet her calcium needs through a combination of fortified almond milk, leafy greens, and calcium supplements. Her regular health check-ups and colonoscopies, along with her balanced diet, have helped her maintain good health and reduce her risk of colorectal cancer.

POTENTIAL COUNTERARGUMENTS:

Some critics may argue that the study’s reliance on self-reported dietary data introduces significant bias. However, the large sample size and long follow-up period help mitigate this concern. Additionally, the consistency of the findings across different tumor sites and population subgroups adds to the study’s credibility.

Another potential counterargument is the lack of consideration for changes in calcium intake over time. Future studies could address this limitation by assessing calcium intake at multiple time points and examining how changes in intake affect CRC risk.

CONCLUSION:

The findings of this study provide strong evidence for the role of calcium in reducing the risk of colorectal cancer. By increasing calcium intake through dietary sources and supplements, individuals can take proactive steps to lower their risk of this common cancer. Public health initiatives and nutritional guidelines should continue to emphasize the importance of calcium-rich diets, particularly for high-risk populations.