Low‐carbohydrate diet and risk of cancer incidence: The Japan Public Health Center‐based prospective study

Epidemiological evidence on the effects of a long‐term low‐carbohydrate diet (LCD) on cancer incidence remains sparse. We investigate the association between LCD and the risk of overall and specific cancer site incidence in a Japanese population‐based prospective cohort study among 90 171 participants aged 45‐74. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). During a median 17.0 y of follow‐up, we identified 15 203 cancer cases. A higher overall LCD score was associated with increased overall cancer risk (HR = 1.08 [CI: 1.02‐1.14], P‐trend = .012), while it was associated with decreased gastric cancer (GC) risk (0.81 [0.71‐0.93], P‐trend = .006). A higher animal‐based LCD score was associated with higher risk of overall cancer (1.08 [1.02‐1.14], P‐trend = .003), colorectal cancer (CRC) (1.11 [0.98‐1.25], P‐trend = .018), rectal cancer (RC) (1.24 [1.00‐1.54], P‐trend = .025), lung cancer (LC) (1.16 [1.00‐1.34], P‐trend = .042), and lower risk of GC (0.90 [0.79‐1.01], P‐trend = .033). Furthermore, we found that plant‐based LCD score was related to lower GC incidence (0.87 [0.77‐0.99], P‐trend = .031). Additionally, adjusted for plant fat intake amplified the adverse associations (overall cancer: 1.08 [1.02‐1.14] vs. 1.11 [1.05‐1.18]; CRC: 1.08 [0.95‐1.22] vs. 1.13 [0.99‐1.30]; LC: 1.14 [0.98‐1.33] vs. 1.19 [1.01‐1.41]). We conclude that LCD enriching with animal products was associated with increased overall cancer, CRC, and LC incidence. These adverse associations could be attenuated by plant fat consumption. LCD reduces the risk of developing GC. Long‐term adherence to LCD without paying attention to the balance between animal and plant food source consumption might cause adverse overall cancer incidence consequences.