Abstract
The incidence of colorectal cancer (CRC) has increased among Norwegian women, and is among the highest in the world. In order to understand this increase, country specific dietary exposures have been investigated. The aim of this study was to quantify the association between consumption of brown cheese, a common bread topping in Norway, and colorectal, colon, and rectal cancer in the prospective Norwegian Women and Cancer (NOWAC) Study. Data on brown cheese consumption and adjustment factors was available for 82 527 women. During a mean of 14.6 years of follow-up (1.2 million person-years), there were 1360 cases of colorectal cancer (907 colon; 453 rectal). Multivariable Cox proportional hazards models were used to calculate hazard ratios (HR) with 95% confidence intervals (CI) for colorectal, colon, and rectal cancer sites. We modelled restricted cubic splines with 4 knots, to assess a possible non-linear relationship between brown cheese intake and the investigated cancer sites. In the age-adjusted model, consumption of more than 2 slices (>16 grams) of brown cheese per day was associated with 13% reduced risk of colon cancer (95% CI 4%-21%) compared to women who did not consume brown cheese. The multivariable-adjusted model, however, showed no association between brown cheese consumption and the risk of colorectal, colon, or rectal cancer (colorectal: HR = 0.93, 95% CI 0.76–1.13, p-trend 0.37; colon: HR = 0.83, 95% CI 0.65–1.06; p-trend = 0.10; rectal: HR = 1.16, 95% CI 0.84–1.1.61, p-trend = 0.41). In this large, prospective cohort study of women, consumption of brown cheese was suggestively protective against colon cancer. However, adjustment attenuated the inverse risk association. Brown cheese consumption was not associated with rectal cancer, or colorectal cancer overall.
Highlights
Norway has seen a steep rise in colorectal cancer (CRC) incidence in the past six decades
In the age-adjusted model, consumption of more than 2 slices of brown cheese per day was associated with 13% reduced risk of colon cancer
None of the measures taken during the sensitivity analysis affected the results. In this nationally representative prospective cohort of Norwegian women, consumption of more than 2 slices of brown cheese per day was associated with 13% reduced risk of colon cancer in the age-adjusted model, while multivariable adjusted risk estimates showed no association between consumption of brown cheese and the risk of colorectal, colon, or rectal cancer
Summary
Norway has seen a steep rise in colorectal cancer (CRC) incidence in the past six decades. The rise in CRC incidence has been steeper in Norway than in the neighboring countries[2]. One potential cause of the high Norwegian CRC incidence could be population specific exposures. In this paper we set out to examine the association between one country-specific exposure, brown cheese, and CRC. Brown cheese – a bread-topping specific to Norway – has, to the best of our knowledge, not been studied as a risk factor for cancer. Brown cheese contains all the constituents of whey, and is very high in lactose (35–47%)[5]. We sought to assess whether brown cheese could be a contributing factor to the high incidence of CRC in Norwegian women, by using the Norwegian Women and Cancer (NOWAC) Study, a nationally representative prospective cohort of women with comprehensive dietary information
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