Early menopause, defined as the cessation of ovarian function before the age of 45, affects roughly 10% of women in Western populations. Current research suggests that women who experience early menopause are at increased risk for cardiovascular disease and other adverse health outcomes. Early menopause may also have substantial financial and psychological consequences for family planning, particularly as women increasingly delay childbearing into the later reproductive years. Emerging research suggests that modifiable lifestyle factors such as diet may play an important role in ovarian aging. According to our review of the current biologic and epidemiologic literature in Chapter 1, vitamin D, calcium, and dairy consumption may be related to the physiologic processes involved in ovarian aging. However, no prior epidemiologic studies have evaluated these exposures with regard to risk of early menopause. Thus, the aim of this dissertation was to evaluate these associations in the prospective Nurses’ Health Study II (NHS2) (n=112,429).
In Chapter 2, we evaluated how intakes of vitamin D and calcium are associated with risk of early menopause. Results of this study suggest that high versus low intakes of vitamin D and calcium from food sources, particularly dairy foods, are associated with 17% and 13% lower risk of early menopause, respectively.
In Chapter 3, we evaluated how total and free plasma 25-hydroxyvitamin D (25(OH)D) and vitamin D binding protein levels (VDBP) are associated with risk of early menopause. According to our findings, total and free 25(OH)D levels are not associated with risk of early menopause, and VDBP may be positively associated with risk.
In Chapter 4, we evaluated how intakes of total, low-fat, high-fat, and individual dairy foods are associated with risk of early menopause. Findings indicate that high versus low intake of low-fat dairy foods is associated with 23% lower risk of early menopause. In particular, intakes of skim milk and yogurt intake were associated with lower risk of early menopause.
In conclusion, vitamin D and calcium are not importantly related to early menopause risk. Intake of low-fat dairy foods is associated with lower risk of early menopause, but findings should be replicated in future studies
