Female birds frequently copulate with extra-pair males, but the adaptive value of this behaviour is poorly understood. Some studies have suggested that 'good genes' may be involved, where females seek to have their eggs fertilized by high-quality males without receiving any material benefits from them. Nevertheless, it remains to be shown that a genetic benefit is passed on to offspring. Here we report that nestling bluethroats, Luscinia svecica, sired by extra-pair males had a higher T-cell-mediated immune response than their maternal half-siblings raised in the same nest. The difference could not be attributed to nestling body mass, sex or hatching order, but may be an effect of paternal genotype. Extra-pair young were also more immunocompetent than their paternal half-sibs raised in the genetic father's own nest, which indicates an additional effect of maternal genotype. Our results are consistent with the idea that females engage in extra-pair copulations to obtain compatible viability genes, rather than 'good genes' per se.
Recent studies have shown a decreased risk of colon cancer with consumption of fish. However, most studies on fish consumption do not distinguish between lean and fatty fish, or between poached and fried fish. The aim of this study was to investigate any association between fish consumption and colon cancer in The Norwegian Women and Cancer (NOWAC) study. We focused mainly on lean fish, which was further divided into poached and fried fish. A total of 63 914 women were included in the analysis, 254 of whom were found to have colon cancer during followup. Since fish consumption was one of the main topics of interest in the NOWAC study, there is a predominance of women from northern Norway due to higher fish intake in this area; hence the study is not representative of the whole of Norway. The participants completed a semi-quantitative FFQ between 1996 and 1999, and were followed-up for incidence of colon cancer until 2004. No association between fish consumption and risk of colon cancer was seen, except for the third tertile of poached lean fish consumption (relative risk (RR) 1·46, 95 % CI 1·04, 2·06). This association disappeared when excluding women with less than 1 year of follow-up. In conclusion, the present study does not support the hypothesis of a protective effect of fish against colon cancer risk. Fish consumption: Colon cancer: NOWAC: DietColon cancer is the second most common cancer among women in Norway, with 1217 new cases in 2004 (age-adjusted incidence rates per 100 000 women was 23·9), and colorectal cancer is the most common cancer in men and women combined (3482 new cases in 2004) 1 . Norway has the highest incidence of colorectal cancer of the Nordic countries 2 . It is estimated that a third to half of colon cancers may possibly be avoided if different diet-related factors were controlled for 3 .Norway has a long coastline, and thus a long tradition in harvesting fish, and using fish in the diet. Lean, white fish such as cod, haddock and saithe, and fish products made from these, are most commonly eaten 4 . Fish products, such as fish balls, puddings and cakes, are mainly made of minced lean fish, starch, milk and spices. Fish served for dinner is prepared from fresh/frozen, smoked, salted and/or dried fish, and is often served with melted fat or fatty sauces 4 .Recently, results from the European Prospective Investigation into Cancer and Nutrition (EPIC) showed a decrease in colon cancer risk with higher intake of fish 5 . However, like most studies on fish consumption and cancer risk, only total fish consumption was analysed. No distinction was made between lean and fatty fish. It is also quite common in analyses of fish consumption to combine intake of fish and poultry (white meat), or fish and meat 6 . Fatty fish has been analysed in terms of n-3 fatty acids, but lean fish has not been investigated as much 6 .Heterocyclic amines and polycyclic aromatic hydrocarbons formed during preparation of the fish at high temperatures cause cancer in rodents 7 , and may also be harmful for humans. I...
Combined estrogen-progestin menopausal therapy (HRT) and combined estrogen-progestin contraceptives (OC) both increase breast cancer risk during current use and a few years after. We investigated risk of breast cancer in women who were users of HRT dependant on former history of OC use in a large, national population-based cohort study, the Norwegian Women and Cancer study (NOWAC). Exposure information was collected through postal questionnaires. Based on follow-up of 30,118 postmenopausal women by linkage to national registers of cancer, deaths, and emigration we revealed 540 incident breast cancer cases between 1996 and 2004. Compared to never users of either drugs current use of HRT gave a significant (p 5 0.002) higher risk of breast cancer in former OC users, RR 5 2.45 (95% CI 1.92-3.12), than among never users of OCs, RR 5 1.67 (1.32-2.12). Relative risk of current use of HRT was similar for estrogen only and combinations with progestin added in ever users of OCs. The increased risk of breast cancer in current HRT users with a history of former OC use could have potential great impact on postmenopausal breast cancer risk as the proportion of postmenopausal women with former OC use will continue to increase. ' 2007 Wiley-Liss, Inc.Key words: breast cancer; OCs; HRT; consecutive use; NOWAC Combined estrogen-progestin menopausal therapy and combined estrogen-progestin contraceptives have both been classified as carcinogenic to humans (Group 1). 1 The increased risk of 30-40% for breast cancer related to OC use is mainly connected to present and recent use, while for HRT use the risk also increases with duration of use. [2][3][4][5] For HRT use the increased risk of 1.26 was somewhat lower in the clinical trial of Women's Health Initiative 6 than in most epidemiological studies with relative risks around 2. This could partly be due to the use of different combinations of hormones. During the last decade an increasing number of former OC users have reached the menopausal age, estimated to around 300 million worldwide and exceeding 80% in some moredeveloped countries. 1 Use of treatment with HRT peaked around 2000 with about 20 million women in more-developed countries using this therapy, including as much as half of the women in US aged 50-64 years. 1 Since then use has been substantially reduced. With 1 million cases diagnosed in the world annually, breast cancer is by far the most common female cancer, comprising about 20% of all new cancers in women. 7 Among the few studies that have looked at risk related to combined use of both OCs and HRT, most studies have limited the analyses to ever use of HRT. [8][9][10][11] One French study looked at current HRT use in relation to previous OC use. 12 They found an additive effect of OC and HRT use on breast cancer risk with no significant interaction. The primary objective of this analysis was to investigate the risk of breast cancer in HRT users taking into account information on former OC use, based on the Norwegian Women and Cancer study (NOWAC). Material and meth...
The aim of the study was to investigate the hypothesis that consumption of fish liver increases cancer risk in humans due to increased intake of persistent organic pollutants (POPs). This study is based on data from the Norwegian Women and Cancer Study (NOWAC). The study has a prospective cohort design with questionnaire data from 64 285 randomly selected Norwegian women (aged 40-70 at baseline) and linkage to the Norwegian Cancer Registry. Cox proportional hazards regression was used to calculate risk ratios associated with consumption of fish liver and total cancer and cancer in breast, uterus, and colon. Fish liver consumption was, after adjusting for known risk factors, associated with a significant reduced risk for total cancer (RR = 0.92, 95% CI: 0.85, 0.99), and non-significant reduced risk for breast cancer (RR = 0.90, 95% CI: 0.78, 1.04), and colon cancer (RR = 0.82, 95% CI: 0.63, 1.07). Relative risk for uterus cancer was 0.82 (95% CI: 0.61-1.12). No significant dose-response effect was found for frequency of fish liver consumption (when divided into three intake groups) and total cancer, nor for any of the other cancer sites.We have concluded that in Norwegian women, fish liver consumption was not associated with an increased cancer risk in breast, uterus, or colon. In contrast, a decreased risk for total cancer was found.
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