The influence of lactose consumption on the association of oral contraceptive use and ovarian cancer risk

Milk, yogurt, and lactose intake and ovarian cancer risk: a meta-analysis

Inconclusive information for the role of dairy food intake in relation to ovarian cancer risk may associate with adverse effects of lactose, which has been hypothesized to increase gonadotropin levels in animal models and ecological studies. Up to now, several studies have indicated the association between dairy food intake and risk of ovarian cancer, but no identified founding was reported. We performed this meta-analysis to derive a more precise estimation of the association between dairy food intake and ovarian cancer risk. Using the data from 19 available publications, we examined dairy food including low-fat/skim milk, whole milk, yogurt and lactose in relation to risk of ovarian cancer by meta-analysis. Pooled odds ratio (OR) with 95% confidence interval (CI) were used to assess the association. We observed a slightly increased risk of ovarian cancer with high intake of whole milk, but has no statistical significance (OR = 1.228, 95% CI = 1.031-1.464, P = 0.022). The results of other milk models did not provide evidence of positive association with ovarian cancer risk. This meta-analysis suggests that low-fat/skim milk, whole milk, yogurt and lactose intake has no associated with increased risk of ovarian cancer. Further studies with larger participants worldwide are needed to validate the association between dairy food intake and ovarian cancer.

Association of Reproductive Factors, Oral Contraceptive Use and Selected Lifestyle Factors with the Risk of Ovarian Borderline Tumors: A Danish Case-control Study

OBJECTIVE

The aim was to examine risk factors for ovarian borderline tumors overall, and according to histological subtype (serous vs. mucinous), in a large Danish population-based case-control study.

METHODS

Ovarian borderline cases and controls were recruited from 1995 to 1999, and personal interviews were conducted. In all, 202 cases and 1,564 randomly selected controls were included. The analysis was performed using multiple logistic regression models.

RESULTS

The risk of ovarian borderline disease decreased with increasing parity (OR=0.79 per birth, 95% CI: 0.63-0.98) and older age at first birth (OR=0.67 per 5 years, 95% CI: 0.53-0.84). Both a history of breastfeeding and use of oral contraceptives reduced the risk of borderline tumor, the effect being most pronounced for serous tumors. Increasing body mass index (BMI) was associated with elevated risk of serous borderline tumor (OR=1.05 per BMI unit; 95% CI: 1.00-1.10), whereas current smoking was a strong risk factor only for mucinous tumors (OR=2.10; 95% CI: 1.22-3.60). Finally, increasing consumption of milk (all types) was found to increase the risk of borderline disease (OR=1.04 per glass milk per week; 95% CI: 1.02-1.06), and increasing intake of total lactose also increased the risk significantly (OR=1.16 per 50 gram lactose per week; 95% CI: 1.06-1.26).

CONCLUSION

The risk profile of ovarian borderline tumors is similar to that of ovarian carcinomas, and we observed significant etiological differences between serous and mucinous borderline tumors.

Dairy products and ovarian cancer: a pooled analysis of 12 cohort studies

BACKGROUND

Dairy foods and their constituents (lactose and calcium) have been hypothesized to promote ovarian carcinogenesis. Although case-control studies have reported conflicting results for dairy foods and lactose, several cohort studies have shown positive associations between skim milk, lactose, and ovarian cancer.

METHODS

A pooled analysis of the primary data from 12 prospective cohort studies was conducted. The study population consisted of 553,217 women among whom 2,132 epithelial ovarian cases were identified. Study-specific relative risks and 95% confidence intervals were calculated by Cox proportional hazards models and then pooled by a random-effects model.

RESULTS

No statistically significant associations were observed between intakes of milk, cheese, yogurt, ice cream, and dietary and total calcium intake and risk of ovarian cancer. Higher lactose intakes comparing > or = 30 versus <10 g/d were associated with a statistically significant higher risk of ovarian cancer, although the trend was not statistically significant (pooled multivariate relative risk, 1.19; 95% confidence interval, 1.01-1.40; P(trend) = 0.19). Associations for endometrioid, mucinous, and serous ovarian cancer were similar to the overall findings.

DISCUSSION

Overall, no associations were observed for intakes of specific dairy foods or calcium and ovarian cancer risk. A modest elevation in the risk of ovarian cancer was seen for lactose intake at the level that was equivalent to three or more servings of milk per day. Because a new dietary guideline recommends two to three servings of dairy products per day, the relation between dairy product consumption and ovarian cancer risk at these consumption levels deserves further examination.

Milk, milk products and lactose intake and ovarian cancer risk: a meta-analysis of epidemiological studies

It has been proposed, on the basis of animal models and ecological studies, that consumption or metabolism of dairy sugar may increase the risk of ovarian cancer. Case-control and cohort studies of the association between lactose and dairy food consumption and ovarian cancer risk, however, have yielded varied findings. We summarized the available literature on this topic using a meta-analytic approach. Random-effects models were used to estimate the summary relative risks (RR(summary)). A linear regression analysis of the natural logarithm of the RR was carried out to assess a possible dose-response relationship between lactose intake and ovarian cancer risk. Eighteen case-control and 3 prospective cohort studies were eligible for inclusion in the meta-analysis. The findings of case-control studies were heterogeneous, and, except for whole milk (RR(summary) for highest vs. lowest category = 1.27, 95% confidence interval [CI] = 0.97-1.68), do not provide evidence of positive associations between dairy food and lactose intakes with risk of ovarian cancer. In contrast, the 3 cohort studies are consistent and show significant positive associations between intakes of total dairy foods, low-fat milk, and lactose and risk of ovarian cancer. The RR(summary) for a daily increase of 10 g in lactose intake (the approximate amount in 1 glass of milk) was 1.13 (95% CI = 1.05-1.22) for cohort studies. In conclusion, prospective cohort studies, but not case-control studies, support the hypothesis that high intakes of dairy foods and lactose may increase the risk of ovarian cancer.

Lactase persistence and ovarian carcinoma risk in Finland, Poland and Sweden

Ovarian carcinoma is the fourth most common cause of cancer death in women. The cause and pathogenesis of this disease has remained obscure. Galactose, the hydrolyzing product of the milk sugar lactose, has been hypothesized to be toxic to ovarian epithelial cells and consumption of dairy products and lactase persistence has been suggested to be a risk factor for ovarian carcinoma. In adults, downregulation of lactase depends on a variant C/T-13910 at the 5' end of the lactase gene. To explore whether lactase persistence is related to the risk of ovarian carcinoma we determined the C/T-13910 genotype in a cohort of 782 women with ovarian carcinoma. The C/T-13910 genotype was defined by solid phase minisequencing from 327 Finnish, 303 Polish, 152 Swedish patients and 938 Finnish, 296 Polish and 97 Swedish healthy individuals served as controls. Lactase persistence did not associate significantly with increased risk for ovarian carcinoma in the Finnish (odds ratio [OR]=0.77, 95% confidence interval [CI]=0.57-1.05, p=0.097), in the Polish (OR=0.95, 95% CI=0.68-1.33, p=0.75), or in the Swedish populations (OR=1.63, 95% CI=0.65-4.08, p=0.29). Our results do not support the hypothesis that lactase persistence increases the ovarian carcinoma risk. On the contrary, lactase persistence may decrease the ovarian carcinoma risk at least in the Finnish population.

Milk/dairy products consumption, galactose metabolism and ovarian cancer: meta-analysis of epidemiological studies

Ovarian cancer is the fifth most common cause of cancer death among women and the leading cause of gynaecological cancer death in the United States. Milk/dairy products consumption was considered to be a risk factor for ovarian cancer mainly because milk carbohydrate-lactose and galactose metabolism is toxic to oocytes. However, recent evidence does not support this hypothesis completely. We collected epidemiological studies related to the association between milk/dairy products consumption or galactose metabolism (lactose, galactose, galactose-1-phosphate uridyltransferase, lactose/transferase) and ovarian cancer published between January 1966 and August 2003 and found 27 items from 22 independent studies. Twenty studies were case-control studies and the other two were cohort studies. A meta-analysis method was conducted to estimate relative risk combining all relative data. In general, we did not find any association between milk/dairy products or galactose metabolism and ovarian cancer risk in this meta-analysis. The consumption of whole milk and butter, which contain relatively high amounts of fat, was positively (relative risk > 1.2), but not significantly, associated with an increased risk.

Milk and lactose intakes and ovarian cancer risk in the Swedish Mammography Cohort

BACKGROUND

High intakes of dairy products and of the milk sugar lactose have been hypothesized to increase ovarian cancer risk, but prospective data are scarce.

OBJECTIVE

We examined the association between intakes of dairy products and lactose and the risk of total epithelial ovarian cancer and its subtypes.

DESIGN

This was a prospective population-based cohort study of 61 084 women aged 38-76 y who were enrolled in the Swedish Mammography Cohort. Diet was assessed in 1987-1990 with the use of a self-administered food-frequency questionnaire. During an average follow-up of 13.5 y, 266 women were diagnosed with invasive epithelial ovarian cancer; 125 of those women had serous ovarian cancer.

RESULTS

After adjustment for potential confounders, women who consumed >/=4 servings of total dairy products/d had a risk of serous ovarian cancer (rate ratio: 2.0; 95% CI: 1.1, 3.7; P for trend = 0.06) twice that of women who consumed <2 servings/d. No significant association was found for other subtypes of ovarian cancer. Milk was the dairy product with the strongest positive association with serous ovarian cancer (rate ratio comparing consuming >/=2 glasses milk/d with consuming milk never or seldom: 2.0; 95% CI: 1.1, 3.7; P for trend = 0.04). We observed a positive association between lactose intake and serous ovarian cancer risk (P for trend = 0.006).

CONCLUSIONS

Our data indicate that high intakes of lactose and dairy products, particularly milk, are associated with an increased risk of serous ovarian cancer but not of other subtypes of ovarian cancer. Future studies should consider ovarian cancer subtypes separately.

A comparison of selected nutrient intakes derived from three diet assessment methods used in a low-fat maintenance trial

OBJECTIVE

In the vast majority of surveys and research in humans, dietary data are obtained from self-reports: recalls; records; or historical methods, usually food frequency questionnaires (FFQ). This study provides a rare opportunity to compare data derived from all three methods.

DESIGN

A crossover study of dietary fat in which data were collected using an average of 11.4 food records and 11.7 24-h diet recalls. Using simple subtraction and correlation, energy and nutrient intakes derived from the three methods were compared to each other and with those derived from a single FFQ. Analysis of variance was used to evaluate sources of variability in nutrient intakes estimated from the individual days of records and recalls.

SETTING

An independent, free-standing medical research institute.

SUBJECTS

13 men who were compliant with study procedures.

RESULTS

FFQ-derived estimates of energy and nutrient intake were highest (e.g. 1967 kcal versus 1858 kcal and 1936 kcal for the records and recalls, respectively). Mean differences in energy and nutrient intakes and their variances were lowest and correlation coefficients highest in comparing the records and recalls (e.g. for fat the mean difference was 5.0 g, and r = 0.85). Analysis of variance of individual days of record- and recall-derived data (n = 300) revealed that there was no effect due to either method (record or recall) or the sequence of administration.

CONCLUSIONS

Results of this study indicate that the FFQ overestimated dietary intake. Energy and nutrient results obtained from the records and recalls were interchangeable. However, based on smaller SDs around the means, it appears that the recalls may perform slightly better in estimating dietary intake in groups such as these well-educated, highly compliant men.

Dietary lactose intake, lactose intolerance, and the risk of epithelial ovarian cancer in southern Ontario (Canada)

A case-control study of dietary factors and cancer of the ovary was conducted during 1989-92 in metropolitan Toronto and surrounding areas of southern Ontario, Canada. Four hundred and fifty women aged 35-79 years, with newly diagnosed, histologically verified, primary epithelial ovarian-cancer were interviewed concerning reproduction and diet. Over the same period, 564 randomly-selected population controls, frequency-matched to the cases within three 15-year age groups, also were interviewed. From information obtained by quantitative diet history, average daily macro- and micronutrient intake values were calculated through use of the United States Department of Agriculture Food Composition Databank, which was extended and modified for Canadian items and recipes. Analysis was performed with continuous, unconditional logistic-regression methods, adjusting for age at interview, number of full-term pregnancies, total duration of oral contraceptive use, and total daily caloric intake. Neither reported history of lactose intolerance, nor average daily consumption of lactose or free galactose, were found to be associated with risk of ovarian cancer. Lactose intake or intolerance did not appear to modify the protective effects of parity and oral contraceptive use. Nevertheless, other studies suggest that ovarian galactose metabolism still may have a relationship with risk of ovarian cancer, though more evidence is needed.

Genetic epidemiology of epithelial ovarian cancer

BACKGROUND

Aside from age, family history is the strongest predictor of ovarian cancer risk. Genetic components of risk for ovarian cancer have been evaluated by a number of designs, including case-control studies of family history and other risk factors, segregation and genetic linkage studies, and studies of biomarkers and tumor-specific cytogenetic abnormalities.

METHODS

Data were extracted from all available case-control studies that included family history. Cytogenetic, biomarker, segregation, analytic, and genetic linkage studies were reviewed.

RESULTS

Family history of ovarian cancer confers a 3.6-fold increased risk for this disease. Segregation studies of breast and ovarian cancer in five large families were consistent with dominant inheritance. Low levels of alpha-L-fucosidase confer mildly increased risk for ovarian cancer. Low galactose-1-phosphate uridyl transferase and type A blood group may increase risk for ovarian cancer. Cytogenetic and oncogene studies have identified regions that may be important in tumorigenesis and metastasis, but discriminating between early and late changes is difficult from these studies. Presence of a genetic susceptibility locus for breast and ovarian cancer has been confirmed on chromosome 17q21.

CONCLUSIONS

Family history is an important predictor of ovarian cancer risk. In rare families, a specific dominantly acting gene can be identified, but in the vast majority of familial ovarian cancers the underlying mechanism remains unclear. Specific studies are needed for women with a family history of ovarian cancer because evidence suggests modification of the effects of oral contraceptive use and reproductive patterns in this population of women.