Properly controlled glycemia reduces the risk of cancer

fEpidemiologic evidence suggests that diabetes is associated with an increased risk of cancer. Many reports describe numerous mechanisms, which can be the basis for the relationship between diabetes and cancer risk. One of them is the promotion of DNA damage through oxidative stress caused by an increased mitochondrial glucose oxidation. Moreover, insulin resistance, hyperinsulinemia, elevated levels of free insulin‐like growth factor and chronic inflammation associated with diabetes may also explain the positive association between diabetes and cancer risk.

The above revelations have led to several hypotheses, e.g. : glycemia markers are likely to be correlated with cancer risk in a dose‐dependent manner and glycemia control through lifestyle changes in people with high HbA1c levels may be important not only to prevent diabetes, but also to prevent cancer. Multiple previous studies have reported an association between high blood glucose levels and cancer occurrence. However, use of blood glucose level as a marker of cancer risk is limited by high intra‐individual variability. Nowadays HbA1c level is a reliable glycemia marker as it reflects the 2‐month average blood glucose level and exhibits less variability.

Researchers in Japan conducted a prospective study to determine whether there is a relationship between the level of HbA1c and the risk of cancer. The study involved 29.629 (11.336 men; 18.293 women) participants 46-80 years old, who were cancer-free at the beginning of the study. Hazard ratios (HRs) were estimated for cancer risk with adjustment for age sex, geographic area, body mass index, smoking status, physical activity, alcohol, coffee, vegetable and total energy consumption, and history of cardiovascular disease. Participants were divided depending on the initial level of HbA1c into 6 groups: individuals without known diabetes and HbA1c < 5.0% 5.0-5.4 % 5.5-5.9 % 6.0-6.4 % , < 6.5 %, and the person with diabetes. After a median follow‐up of 8.5 years, 1,955 (1139 men; 816 women) individuals had developed cancer. Compared to participants with lower HbA1c levels, those with higher levels of HbA1c tended to be older, male, current or past smokers, have higher BMI, have higher energy consumption and have lower coffee consumption. This study showed that higher levels of HbA1c, in both groups, with and without diagnosed diabetes were independently associated with an increased risk of cancer occurrence. Higher HbA1c levels within the non‐diabetic study group were associated with 28% higher risks of all cancers and 51% of colorectal cancer. It is interesting that low HbA1c levels were associated with an increased risk of liver cancer. This study is the first to demonstrate that high HbA1c levels within both non‐diabetic and diabetic individuals are associated with the risk of all cancers.

In summary, these studies provide strong evidence confirming the hypothesis that good glycemia control through lifestyle changes in people with high levels of HbA1c may be important not only to prevent diabetes but also cancer.

Written by: Katarzyna Godzisz, Hubert Opaliński, Michał Godzisz


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