Effects of a low-fat high-carbohydrate diet on plasma sex hormones in premenopausal women: results from a randomized controlled trial. Canadian Diet and Breast Cancer Prevention Study Group.
Study Goal
The researchers aimed to determine if a low-fat high-carbohydrate diet reduces breast cancer risk by examining its effects on serum sex hormone levels in premenopausal women.
Results Summary
After 2 years, the intervention group showed significantly lower oestradiol (20%) and progesterone (35%) levels and slightly higher FSH levels (7%) compared to controls, suggesting potential breast cancer risk reduction via reduced ovarian hormone exposure.
Population
Premenopausal women with extensive mammographic densities.
Effective Dosage
Dietary fat reduced to 15% of calories (specific carbohydrate intake not detailed).
Duration
2 years.
Interactions
None mentioned.
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
low-fat high-carbohydrate diet | decrease | breast cancer risk | - | - | reduces | #1 |
dietary intervention (intensive individual counselling aimed at reducing total dietary fat to 15% of calories) | decrease | oestradiol levels | premenopausal subjects | 20% (70 pmol l(-1)) | were 20% lower | #2 |
dietary intervention (intensive individual counselling aimed at reducing total dietary fat to 15% of calories) | decrease | progesterone levels | premenopausal subjects | 35% (1.0 nmol l(-1)) | were 35% lower | #3 |
dietary intervention (intensive individual counselling aimed at reducing total dietary fat to 15% of calories) | increase | follicle-stimulating hormone (FSH) levels | premenopausal subjects | 7% (1 IU) | were 7% higher | #4 |
dietary intervention (intensive individual counselling aimed at reducing total dietary fat to 15% of calories) | increase | FSH-oestradiol ratio | premenopausal subjects | 13% | was 13% higher | #5 |
dietary intervention (intensive individual counselling aimed at reducing total dietary fat to 15% of calories) | decrease | oestradiol and progesterone levels | subjects with blood samples taken more than 30 days after the last menstrual period | - | were lower | #6 |
dietary intervention (intensive individual counselling aimed at reducing total dietary fat to 15% of calories) | increase | FSH levels | subjects with blood samples taken more than 30 days after the last menstrual period | - | higher | #7 |
low-fat high-carbohydrate diet | decrease | risk of breast cancer | - | - | may reduce | #8 |
low-fat high-carbohydrate diet | decrease | ovarian hormones that are a stimulus to cell division in the breast | - | - | reducing exposure to | #9 |
We are conducting a long-term randomized controlled trial to determine if intervention with a low-fat high-carbohydrate diet reduces breast cancer risk. The present study examines the effects of 2 years of dietary intervention on serum sex hormone levels in premenopausal women. Subjects with extensive mammographic densities were enrolled in a dietary intervention trial. The intervention involved intensive individual counselling aimed at reducing total dietary fat to 15% of calories. Control subjects received general advice about diet but were not counselled to change their fat intake. Serum sex hormone levels were measured in 220 premenopausal subjects at entry and 2 years after randomization. Two years after randomization oestradiol levels were 20% (70 pmol l(-1)) lower (P = 0.04) and progesterone levels were 35% (1.0 nmol l(-1)) lower (P = 0.004) and follicle-stimulating hormone (FSH) levels were 7% (1 IU) higher (P = 0.38) in the intervention group than in the control group. The FSH-oestradiol ratio was 13% higher in the intervention group (P = 0.18). Samples analysed accounting for the timing of the blood sample in relation to the menstrual cycle showed that, in the intervention group, oestradiol and progesterone levels were lower and FSH levels higher in subjects with blood samples taken more than 30 days after the last menstrual period. Because of the strong evidence linking ovarian hormonal activity to breast cancer risk, these results suggest that a low-fat high-carbohydrate diet may reduce risk of breast cancer by reducing exposure to ovarian hormones that are a stimulus to cell division in the breast.