Omega-3 and -6 Fatty Acid Intake and Colorectal Cancer Risk in Swedish Women's Lifestyle and Health Cohort

PURPOSE

We aimed to assess the association between the dietary intake of fish-derived omega-3 polyunsaturated fatty acids and the risk of colorectal cancer among Swedish women.

MATERIALS AND METHODS

A total of 48,233 women with information on dietary intake were included in the analysis. Participants were followed for incident colorectal cancer until 31 December 2012. Cox proportional hazard models were used to assess the association between baseline fatty acid intake and colorectal cancer risk. All analyses were stratified by colon and rectal cancers.

RESULTS

During a median of 21.3 years of follow-up, a total of 344 colorectal cancer cases were ascertained. Although there was no overall association between omega-3 fatty acid intake and colorectal cancer risk, high intake of fish-derived docosahexaenoic acid was associated with reduced risk of rectal cancer (hazard ratios for the third and the highest quartiles were 0.59 (95% confidence interval [CI], 0.37 to 0.96) and 0.62 (95% CI, 0.39 to 0.98), respectively).

CONCLUSION

In conclusion, we found only limited support for an association between omega-3 polyunsaturated fatty acids and colorectal cancer in a large Swedish cohort of middle-aged women.

Alcohol consumption, body mass index and breast cancer risk by hormone receptor status: Women' Lifestyle and Health Study

Background

We aimed to estimate the effect of alcohol consumption on breast cancer risk and to test whether overweight and obesity modifies this association.

Methods

We included in the analysis 45,233 women enrolled in the Swedish Women’s Lifestyle and Health study between 1991 and 1992. Participants were followed for occurrence of breast cancer and death until December 2009. Poisson regression models were used, and analyses were done for overall breast cancer and for estrogen receptor positive or negative (ER+, ER-) and progesterone receptor positive and negative (PR+, PR-) tumors separately.

Results

A total of 1,385 breast cancer cases were ascertained during the follow-up period. Overall, we found no statistically significant association between alcohol intake and breast cancer risk after adjustment for confounding, with an estimated relative risk (RR) of 1.01 (95 % CI: 0.98–1.04) for an increment in alcohol consumption of 5 g/day. A statistically significant elevated breast cancer risk associated with higher alcohol consumption was found only among women with BMI ≤25 (RR 1.03, 95 % CI 1.0–1.05 per 5 g/day increase).

Conclusion

An increase in breast cancer risk with higher alcohol consumption was found for breast cancers in women with a BMI ≤25 kg/m².

Alcohol consumption and breast cancer risk by estrogen receptor status: in a pooled analysis of 20 studies

BACKGROUND

Breast cancer aetiology may differ by estrogen receptor (ER) status. Associations of alcohol and folate intakes with risk of breast cancer defined by ER status were examined in pooled analyses of the primary data from 20 cohorts.

METHODS

During a maximum of 6-18 years of follow-up of 1 089 273 women, 21 624 ER+ and 5113 ER- breast cancers were identified. Study-specific multivariable relative risks (RRs) were calculated using Cox proportional hazards regression models and then combined using a random-effects model.

RESULTS

Alcohol consumption was positively associated with risk of ER+ and ER- breast cancer. The pooled multivariable RRs (95% confidence intervals) comparing ≥ 30 g/d with 0 g/day of alcohol consumption were 1.35 (1.23-1.48) for ER+ and 1.28 (1.10-1.49) for ER- breast cancer (Ptrend ≤ 0.001; Pcommon-effects by ER status: 0.57). Associations were similar for alcohol intake from beer, wine and liquor. The associations with alcohol intake did not vary significantly by total (from foods and supplements) folate intake (Pinteraction ≥ 0.26). Dietary (from foods only) and total folate intakes were not associated with risk of overall, ER+ and ER- breast cancer; pooled multivariable RRs ranged from 0.98 to 1.02 comparing extreme quintiles. Following-up US studies through only the period before mandatory folic acid fortification did not change the results. The alcohol and folate associations did not vary by tumour subtypes defined by progesterone receptor status.

CONCLUSIONS

Alcohol consumption was positively associated with risk of both ER+ and ER- breast cancer, even among women with high folate intake. Folate intake was not associated with breast cancer risk.

Endometrial cancer in relation to coffee, tea, and caffeine consumption: a prospective cohort study among middle-aged women in Sweden

This study aimed to add to prospective data on the possible inverse association between coffee consumption and endometrial cancer risk, already supported by several case-control studies. Coffee and tea consumption and possible confounding factors were assessed among 42,270 women aged 30-49 years at enrollment in 1991-1992 in the Swedish Women's Lifestyle and Health cohort study, with complete follow-up through 2009. We calculated caffeine intake per day; Cox proportional hazard models were used to estimate multivariable relative risks (mRR) for endometrial cancer with 95% confidence intervals (CIs). One hundred forty-four endometrial cancers were diagnosed during follow-up. Women with and without endometrial cancer had a similar mean daily coffee consumption (549 vs. 547 g), tea consumption (104 vs. 115 g), and caffeine intake (405 vs. 406 mg). Compared to those consuming <2 cups of coffee per day, women consuming >3 cups had a mRR of 1.56 (95% CI: 0.94-2.59; P for trend = 0.17). Compared with the lowest tertile of caffeine intake, the highest tertile had a mRR of 1.32 (95% CI: 0.87-1.99; P for trend = 0.27). Our study provides no convincing evidence of an association between coffee consumption, tea consumption, or caffeine intake and endometrial cancer risk among middle-aged women.

Fruit and vegetable intake and risk of breast cancer by hormone receptor status

BACKGROUND

Estrogen receptor-negative (ER(-)) breast cancer has few known or modifiable risk factors. Because ER(-) tumors account for only 15% to 20% of breast cancers, large pooled analyses are necessary to evaluate precisely the suspected inverse association between fruit and vegetable intake and risk of ER(-) breast cancer.

METHODS

Among 993 466 women followed for 11 to 20 years in 20 cohort studies, we documented 19 869 estrogen receptor positive (ER(+)) and 4821 ER(-) breast cancers. We calculated study-specific multivariable relative risks (RRs) and 95% confidence intervals (CIs) using Cox proportional hazards regression analyses and then combined them using a random-effects model. All statistical tests were two-sided.

RESULTS

Total fruit and vegetable intake was statistically significantly inversely associated with risk of ER(-) breast cancer but not with risk of breast cancer overall or of ER(+) tumors. The inverse association for ER(-) tumors was observed primarily for vegetable consumption. The pooled relative risks comparing the highest vs lowest quintile of total vegetable consumption were 0.82 (95% CI = 0.74 to 0.90) for ER(-) breast cancer and 1.04 (95% CI = 0.97 to 1.11) for ER(+) breast cancer (P (common-effects) by ER status < .001). Total fruit consumption was non-statistically significantly associated with risk of ER(-) breast cancer (pooled multivariable RR comparing the highest vs lowest quintile = 0.94, 95% CI = 0.85 to 1.04).

CONCLUSIONS

We observed no association between total fruit and vegetable intake and risk of overall breast cancer. However, vegetable consumption was inversely associated with risk of ER(-) breast cancer in our large pooled analyses.

Low carbohydrate-high protein diet and incidence of cardiovascular diseases in Swedish women: prospective cohort study

OBJECTIVE

To study the long term consequences of low carbohydrate diets, generally characterised by concomitant increases in protein intake, on cardiovascular health.

DESIGN

Prospective cohort study.

SETTING

Uppsala, Sweden.

PARTICIPANTS

From a random population sample, 43,396 Swedish women, aged 30-49 years at baseline, completed an extensive dietary questionnaire and were followed-up for an average of 15.7 years.

MAIN OUTCOME MEASURES

Association of incident cardiovascular diseases (ascertained by linkage with nationwide registries), overall and by diagnostic category, with decreasing carbohydrate intake (in tenths), increasing protein intake (in tenths), and an additive combination of these variables (low carbohydrate-high protein score, from 2 to 20), adjusted for intake of energy, intake of saturated and unsaturated fat, and several non-dietary variables.

RESULTS

A one tenth decrease in carbohydrate intake or increase in protein intake or a 2 unit increase in the low carbohydrate-high protein score were all statistically significantly associated with increasing incidence of cardiovascular disease overall (n=1270)--incidence rate ratio estimates 1.04 (95% confidence interval 1.00 to 1.08), 1.04 (1.02 to 1.06), and 1.05 (1.02 to 1.08). No heterogeneity existed in the association of any of these scores with the five studied cardiovascular outcomes: ischaemic heart disease (n=703), ischaemic stroke (n=294), haemorrhagic stroke (n=70), subarachnoid haemorrhage (n=121), and peripheral arterial disease (n=82).

CONCLUSIONS

Low carbohydrate-high protein diets, used on a regular basis and without consideration of the nature of carbohydrates or the source of proteins, are associated with increased risk of cardiovascular disease.

Carotenoid intakes and risk of breast cancer defined by estrogen receptor and progesterone receptor status: a pooled analysis of 18 prospective cohort studies

BACKGROUND

Epidemiologic studies examining associations between carotenoid intakes and risk of breast cancer by estrogen receptor (ER) and progesterone receptor (PR) status are limited.

OBJECTIVE

We investigated these associations in a pooled analysis of 18 cohort studies.

DESIGN

Of 1,028,438 participants followed for a maximum follow-up of 26 y across studies, 33,380 incident invasive breast cancers were identified. Study-specific RRs and 95% CIs were estimated by using Cox proportional hazards regression and then pooled by using a random-effects model.

RESULTS

α-Carotene, β-carotene, and lutein/zeaxanthin intakes were inversely associated with the risk of ER-negative (ER-) breast cancer (pooled multivariable RRs of the comparison between the highest and lowest quintiles): α-carotene (0.87; 95% CI: 0.78, 0.97), β-carotene (0.84; 95% CI: 0.77, 0.93), and lutein/zeaxanthin (0.87; 95% CI: 0.79, 0.95). These variables were not inversely associated with the risk of ER-positive (ER+) breast cancer (pooled multivariable RRs for the same comparison): α-carotene (1.04; 95% CI: 0.99, 1.09), β-carotene (1.04; 95% CI: 0.98, 1.10), and lutein/zeaxanthin (1.00; 95% CI: 0.93, 1.07). Although the pooled RRs for quintile 5 for β-cryptoxanthin were not significant, inverse trends were observed for ER- and ER+ breast cancer (P-trend ≤ 0.05). Nonsignificant associations were observed for lycopene intake. The associations were largely not appreciably modified by several breast cancer risk factors. Nonsignificant associations were observed for PR-positive and PR-negative breast cancer.

CONCLUSIONS

Intakes of α-carotene, β-carotene, and lutein/zeaxanthin were inversely associated with risk of ER-, but not ER+, breast cancer. However, the results need to be interpreted with caution because it is unclear whether the observed association is real or due to other constituents in the same food sources.

Ultraviolet exposure and mortality among women in Sweden

BACKGROUND

Ecological studies have reported possible effects of sunlight on the risk of several diseases. Little evidence is available on the association between mortality and solar and artificial UV exposure by individual level from prospective studies.

METHODS

The Swedish Women's Lifestyle and Health cohort study included women aged 30 to 49 years in 1991-1992. Participants completed a questionnaire and were followed-up through linkages to national registries until the end of 2006. Cox models were used to estimate adjusted HRs and 95% CIs for all-cause mortality and for cancer and cardiovascular disease (CVD) mortality.

RESULTS

During 15 years of follow-up, among the 38,472 women included in the present study, 754 deaths occurred: 457 due to cancer and 100 due to CVD. When combining the information on sun exposure from age 10 to 39 years, women who got sunburned twice or more per year during adolescence had a reduced all-cause mortality, compared with women who had been sunburned once or less. A reduced risk for all-cause and CVD mortality was observed in women who went on sunbathing vacations more than once a year over three decades. Solarium use once or more per month for at least one decade increased the risk of all-cause mortality, when compared with women who never used a solarium.

CONCLUSIONS

Solar UV exposure was associated with reduced overall and CVD mortality, whereas artificial UV exposure was associated with increased overall and cancer mortality among Swedish women.

IMPACT

Moderate sun exposure may protect against cause-specific mortality.

Prospective study of solar exposure, dietary vitamin D intake, and risk of breast cancer among middle-aged women

The relationship between solar exposure or dietary vitamin D intake and breast cancer risk has not been fully elucidated. These associations were studied within the Women's Lifestyle and Health Cohort Study, a cohort of 49,259 Swedish women ages 30 to 50 years at baseline (1991-1992). Women were asked about solar exposure and completed a food frequency questionnaire and were followed-up through linkages to national registries until December 2004. In the current analyses, 41,889 women were included, 840 of whom were diagnosed with breast cancer during follow-up. Breast cancer risk was not related to solar exposure variables, including sun sensitivity, annual number of sunburns, time spent on sunbathing vacations, or solarium use at any age period of exposure. There was also no association with dietary vitamin D intake or supplementary multivitamin use. These relationships were not modified after stratifying by estrogen or progesterone receptor status.

Dietary fat intake and gestational weight gain in relation to estradiol and progesterone plasma levels during pregnancy: a longitudinal study in Swedish women

Background

Elevated pregnancy hormone levels, such as oestrogen and progesterone, may increase the risk of developing breast cancer both in mothers and offspring. However, the reasons for large inter-individual variations in estrogen and progesterone levels during pregnancy remain unknown. The objectives of this study were to investigate whether a) intakes of total dietary fat, types of fat (monounsaturated: MUFA, polyunsaturated: n-3 and n-6 PUFA, and saturated) and b) gestational weight gain are associated with estradiol and progesterone levels in plasma during pregnancy.

Methods

We measured body weight as well as estradiol and progesterone in plasma among 226 healthy pregnant Swedish women on gestation weeks 12, 25 and 33. At the same time points, dietary intake of total fat and types of fat (MUFA, PUFA, SFA, n-3 and n-6 PUFA) were estimated using 3-day food diaries.

Results

A large variation in estradiol and progesterone levels was evident.

Nulliparous women had 37%, 12% and 30% higher mean estradiol levels on gestation weeks 12, 25 and 33 compared to parous women (P = 0.008). No associations were found between dietary intake of total fat or fat subtypes (including n-3 PUFA and n-6 PUFA) and plasma estradiol or progesterone levels. Gestational weight gain was associated with progesterone levels (P = 0.03) but the effect was very small (20% increase in progesterone levels between gestational weeks 12 and 33 per kg body weight/week).

Conclusion

No associations among gestational weight gain, maternal dietary fat intake (total or subtypes including n-3 PUFA and n-6 PUFA) and plasma estradiol levels were found. However, pregnancy progesterone levels correlated with weight gain during pregnancy. Identification of other possible determinants of pregnancy estradiol and progesterone levels, important for the development of breast cancer in both mothers and offspring, are needed.

Longitudinal study of the maternal insulin-like growth factor system before, during and after pregnancy in relation to fetal and infant weight

BACKGROUND

The maternal insulin-like growth factor (IGF) system is considered to be involved in fetal growth regulation. However, available data linking this system to fetal growth are contradictory and incomplete.

AIMS

To measure components of the IGF system before, during and after pregnancy in healthy women and to relate these results, and their changes during pregnancy, to fetal weight (gestational week 31) and birth weight.

METHODS

Serum concentrations of IGF-I, IGF-II, IGF-binding protein (IGFBP)-1, IGFBP-3 and IGFBP-3 protease activity were assessed in 23 women before conception, at weeks 8, 14, 20, 32 and 35 of pregnancy and 2 weeks postpartum. The data were analyzed using simple and multiple linear regression.

RESULTS

One third of the variability in fetal weight was explained by IGF-I in combination with IGFBP-3 protease activity, both assessed at gestational week 32 (p = 0.013). Birth weight was negatively correlated (r = -0.43 to -0.59) with IGFBP-1 at gestational week 20 (p = 0.041), 32 (p = 0.012) and 35 (p = 0.003).

CONCLUSION

We propose there is a finely tuned balance among the components of the IGF system, providing a means for fetal growth regulation.

Activity pattern and energy expenditure due to physical activity before and during pregnancy in healthy Swedish women

Human pregnancy is associated with increased requirements for dietary energy and this increase may be partly offset by reductions in physical activity during gestation. Studies in well-nourished women have shown that the physical activity level (PAL), obtained as the total energy expenditure (TEE) divided by the BMR, decreases in late pregnancy. However, it is not known if this decrease is really caused by reductions in physical activity or if it is the result of decreases in energy expenditure/BMR (the so-called metabolic equivalent, MET) for many activities in late pregnancy. In the present study activity pattern, TEE and BMR were assessed in twenty-three healthy Swedish women before pregnancy as well as in gestational weeks 14 and 32. Activity pattern was assessed using a questionnaire and heart rate recording. TEE was assessed using the doubly labelled water method and BMR was measured by means of indirect calorimetry. When compared to the pre-pregnant value, there was little change in the PAL in gestational week 14 but it was significantly reduced in gestational week 32. Results obtained by means of the questionnaire and by heart rate recording showed that the activity pattern was largely unaffected by pregnancy. The findings support the following conclusion: in a population of well-nourished women where the activity pattern is maintained during pregnancy, the increase in BMR represents approximately the main part of the pregnancy-induced increase in TEE, at least until gestational week 32.

Changes in basal metabolic rate during pregnancy in relation to changes in body weight and composition, cardiac output, insulin-like growth factor I, and thyroid hormones and in relation to fetal growth

BACKGROUND

The total energy cost of pregnancy is largely due to an elevated basal metabolic rate (BMR). Large variations in the BMR response to pregnancy have been reported, but the factors associated with this variability are incompletely known.

OBJECTIVE

The objective was to identify factors associated with variability in the BMR response to pregnancy.

DESIGN

In 22 healthy women, BMR, body weight (BW), total body fat (TBF), fat-free mass (FFM), circulatory variables, serum concentrations of insulin-like growth factor I (IGF-I), and thyroid hormones were measured before pregnancy and in gestational weeks 14 and 32. BMR and BW were also measured in gestational weeks 8, 20, and 35. Fetal weight was estimated in gestational week 31.

RESULTS

In gestational week 14, the increase in BMR correlated significantly with the corresponding increase in BW and with the prepregnancy percentage of TBF. Together these variables explained approximately 40% of the variability in the BMR response. In gestational week 32, the increase in BMR correlated significantly with the corresponding changes in BW, TBF, FFM, IGF-I, cardiac output, and free triiodothyronine. The increase in BW in combination with fetal weight or with the elevated concentration of IGF-I in serum explained approximately 60% of the variability in the increase in BMR.

CONCLUSIONS

Weight gain and the prepregnancy percentage of TBF-ie, factors related to the maternal nutritional situation-are important factors with regard to the variability in the BMR response to pregnancy. Thus, it is important to consider the nutritional situation before and during gestation when assessing pregnancy energy requirements.

Validation of energy intake by dietary recall against different methods to assess energy expenditure

OBJECTIVES

To compare the validity of dietary recalls and physical activity recalls and investigate some factors influencing this validity. To provide an example showing how procedures based on recalls of physical activity can assess the validity of dietary recalls and identify subjects constantly underreporting their energy intake (EI).

DESIGN AND SUBJECTS

Thirty-seven women were studied using three 24-h dietary recalls, two kinds of physical activity recalls, indirect calorimetry and the doubly labelled water method.

RESULTS

The EI obtained using dietary recalls were biased with respect to body mass index (BMI) and attitudes towards body weight and dieting, whereas results obtained using a physical activity recall were not. Eighteen women produced underreports (UR), i.e. their average EI was below 76% of total energy expenditure (TEE), whereas 24 women reported an EI that was lower than TEE on all three recall days, i.e. constantly underreporting subjects. A physical activity recall identified 13 URs and 20 of the constantly underreporting subjects.

CONCLUSIONS

In contrast to estimates of EI, TEE assessed using physical activity recalls was not biased with respect to BMI or attitudes towards body weight and dieting. Recalls of physical activity represent potentially useful procedures for identifying URs and constantly underreporting subjects but are not accurate enough for individuals.

Hydration of fat-free mass in healthy women with special reference to the effect of pregnancy

BACKGROUND

Knowledge of the biological variability of the hydration factor (HF), ie, the ratio between total body water and fat-free mass, is important when calculating total body fat by means of the commonly used two-component model, which is based on estimates of body weight and total body water. The effect of pregnancy on the biological variability of HF, and consequently on the precision of the two-component model, is unknown.

OBJECTIVE

Our goal was to assess the effect of pregnancy on HF and its biological variability.

DESIGN

HF was assessed in 33 women planning pregnancy and in 17 of these women during gestational weeks 14 and 32 and 2 wk postpartum. HF was calculated by using estimates of body weight, total body water obtained by means of deuterium dilution, and body volume measured by using underwater weighing.

RESULTS

In the 17 women who became pregnant, HF was 0.718 +/- 0.023, 0.723 +/- 0.031, 0.747 +/- 0.017, and 0.734 +/- 0.020 before pregnancy, in gestational week 14, in gestational week 32, and 2 wk postpartum, respectively. The biological variability represented approximately 2% of average HF in the nonpregnant state. The corresponding figure was >3% in gestational week 14 but </=1.7% in gestational week 32.

CONCLUSION

The two-component model for assessing body fat is as appropriate during late gestation as it is in the nonpregnant state, although its precision may be impaired when applied during the first part of pregnancy.

Evaluation of bioimpedance spectroscopy for measurements of body water distribution in healthy women before, during, and after pregnancy

Bioimpedance spectroscopy (BIS) is a technique of interest in the study of human pregnancy because it can assess extracellular (ECW), intracellular (ICW), and total body water (TBW) as ECW plus ICW. The technique requires appropriate resistivity coefficients and has not been sufficiently evaluated during the reproductive cycle. Therefore, in a methodological study, we estimated ECW, ICW, and TBW, by means of BIS, and compared the results with the corresponding estimates obtained by using reference methods. Furthermore, results obtained by means of population-specific resistivity coefficients were compared with results obtained by means of general resistivity coefficients. These comparisons were made before pregnancy, in gestational weeks 14 and 32, as well as 2 wk postpartum in 21 healthy women. The reference methods were isotope and bromide dilution. Average ICW, ECW, and TBW, estimated by means of BIS, were in agreement with reference data before pregnancy, in gestational week 14, and postpartum. The corresponding comparison in gestational week 32 showed good agreement for ICW, whereas estimates by means of BIS were significantly ( P < 0.001) lower than the corresponding reference values for ECW and TBW. Thus the BIS technique, which was based on a model developed for the nonpregnant body, estimated increases in ICW accurately, whereas increases in ECW and TBW tended to be underestimated. Estimates obtained by using population-specific and general resistivity coefficients were very similar. In conclusion, the results indicated that BIS is potentially useful for studies during pregnancy but that further work is needed before it can be generally applied in such studies.

Comparison of commonly used procedures, including the doubly-labelled water technique, in the estimation of total energy expenditure of women with special reference to the significance of body fatness

According to the report of the World Health Organization (1985), total energy expenditure (TEE) in human subjects can be calculated as BMR x physical activity level (PAL). However, other reports have pointed out limitations in the suggested procedure related to the % body fat of the subjects. The purpose of the present study was to evaluate the World Health Organization (1985) procedure in thirty-four healthy women with BMI 18-39 kg/m2. BMR and TEE were measured using indirect calorimetry (BMRmeas) and the doubly-labelled water method (TEEref) respectively. When assessed using the doubly-labelled water and skinfold-thickness methods, the women had 34 (SD 8) and 33 (SD 6) % body fat respectively. On the basis of guidelines provided by the World Health Organization (1985), 1.64 was selected to represent the average PAL of the women. Furthermore, PAL was also assessed by means of an accelerometer (PALacc), heart-rate recordings (PAL(HR)) and a questionnaire (PALq). These estimates were: PALacc 1.71 (SD 0.17), PAL(HR) 1.76 (SD 0.24), PALq 1.86 (SD 0.27). These values were lower than TEEref/BMRref, which was 1.98 (SD 0.21). BMR assessed using equations recommended by the World Health Organization (1985) (BMRpredicted) overestimated BMR by 594 (SD 431) kJ/24 h. However, when TEE was calculated as BMRpredicted x PALacc, BMRpredicted x PAL(HR) and BMRpredicted x PALq respectively, average results were in agreement with TEEref. Furthermore, TEE values based on BMRpredicted and PALacc, PAL(HR), PALq as well as on PAL = 1.64, minus TEEref, were significantly correlated with body fatness. When the same PAL value (1.64) was used for all subjects, this correlation was particularly strong. Thus, the World Health Organization (1985) procedure may give TEE results that are biased with respect to the body fatness of subjects.