Moderate iron intake linked to lower colon cancer risk

A new study reveals that moderate consumption of total and non-heme iron may reduce colorectal and colon cancer risk in South Korea, highlighting the role of plant-based iron in cancer prevention.

Study: Iron Consumption and Colorectal Cancer in Korean Adults: A Prospective Cohort Study. Image Credit: Shutterstock AI Generator / Shutterstock.com

A recent Nutrients study investigates the association between iron consumption and the incidence of colorectal, colon, and rectal cancer in South Korea.

Rising rates of colorectal cancer in Korea

Colorectal cancer (CRC) is the third most common type of cancer to affect both men and women. Since 2019, the prevalence of CRC has risen by 2.6% in South Korea, thus emphasizing the crucial need to identify modifiable risk factors that can support the development of preventive strategies.

Previous studies have reported the multifactorial etiology of CRC that can involve excessive alcohol intake, physical inactivity, smoking, obesity, and dietary habits. In 2018, the International Agency for Research on Cancer (IARC) and World Cancer Research Fund (WCRF) identified red and processed meat consumption as a risk factor for the development of CRC, which may be attributed to increased heme iron intake.

Heme iron catalyzes the synthesis of hydroxyl free radicals, mostly total N-nitroso compounds, and lipid peroxide radicals, which increase the risk of CRC. However, multiple population-based studies have contradicted this observation while reporting that heme iron consumption reduced the risk of colon and colorectal cancers.

To date, the association between heme iron consumption and CRC risks has been primarily studied in Western populations. Since dietary patterns and genetic predispositions significantly differ between Western and Asian populations, it is essential to independently investigate the impact of heme iron intake on CRC risk in a wide range of ethnic populations.

About the study

Study participants were recruited from the Korean Genome and Epidemiology Study’s Health Examinees (KoGES HEXA) study, which included a large-scale population-based cohort. Individuals 40 years of age and younger, as well as those who were 69 years or older, were excluded from the analysis. Any individual with missing mortality, cancer-related, or incomplete dietary data were not considered.

At baseline, information about the participants’ dietary pattern, daily food intake quantity, and types of food consumed were obtained through a semi-quantitative food frequency questionnaire (FFQ). The dietary iron content for each food item was obtained from the KoGES HEXA FFQ database.

Total and non-heme iron intake were classified by quintiles (Q) to ensure the statistical significance of each group. Notably, heme iron was categorized into quintiles due to the insufficient number of observations for absolute levels of heme iron intake.

The number of CRC cases was obtained from the Korea Central Cancer Registry.

Study findings

A total of 109,908 individuals with a mean age of 53.8 years were followed up for 9.1 years. During the follow-up period, 608 new cases of CRC were recorded, which reflected an incidence of 60.5 CRC cases for every 100,000 person-years.

Complex associations between iron intake and colorectal, colon, and rectal cancer were observed. Men, younger individuals, those with high body mass index (BMI), with a history of smoking or drinking, and those with higher levels of education consumed the most amount of iron ranging from 9.49-47.53 mg/Day (Q5), as compared to 1.09-4.97 (Q1).

Study participants in Q1 were more likely to be physically inactive, have a history of diabetes hypertension, or a family history of CRC as compared to those in Q5. The total energy consumption was higher in Q5.

Total daily iron consumption in Q2 was associated with a significantly lower risk of CRC and colon cancer as compared to Q1. However, no significant association between rectal cancer and total iron consumption was observed.

Among men, Q2 participants were significantly less likely to be diagnosed with lower CRC and colon cancer as compared to those in Q1. Among women, the results were statistically insignificant; however, the risk of these cancers was also the lowest in Q2.

Heme iron did not exhibit a linear trend nor significantly affect CRC and colon cancer risk. Relative to Q1, a reduced risk of rectal cancer was observed in Q4; however, these results were not statistically significant. As compared to Q1, significantly lower CRC and colon cancer risk were observed in the Q2 group for non-heme iron consumption.

Nonsignificant associations between non-heme iron consumption and rectal cancer were observed. Men in the Q2 group were significantly less likely to develop colon cancer and CRC as compared to Q1; yet, this association was not observed for rectal cancer.  

Conclusions

Moderate total and non-heme iron intake reduced colorectal and colon cancer risk in Koreans, possible via the displacement of carcinogens and the increased intake of protective micronutrients from plant-based foods.”

CRC and colon cancer risk is reduced by high total and non-heme iron consumption in a population of Korean individuals. Future research is needed to elucidate the mechanisms involved in this association and the impact of diet in modulating cancer risk.