Modest changes in dietary intake across the menstrual cycle: implications for food intake research.

Food intake varies across the menstrual cycle in mammals, energy intake usually being greater in the premenstrual phase compared with the postmenstrual phase. Premenstrual increments in energy intake and a preferential selection of carbohydrate have been suggested to be greater in women with premenstrual syndrome (PMS), who may be more sensitive to cyclical hormonal or neurotransmitter fluctuations. This has direct implications for research within populations of women, especially where the primary outcome is diet or a change in energy balance. We aimed to determine whether: the premenstrual intake of energy and macronutrients differed from the postmenstrual intake; the change in intake across the menstrual cycle differed in women with PMS compared with controls; and the change in intake was related to the severity of premenstrual symptoms. We collected 3 d dietary intake data during the postmenstrual and premenstrual phases of the menstrual cycle in thirty-one women with PMS and twenty-seven control women. The consumption of energy and macronutrient intake were similar between the phases of the cycle in women with PMS. Conversely, intakes were usually greater premenstrually in control women, although not all differences were statistically significant. Exceptions were with non-milk extrinsic sugars and alcohol, which were both consumed in greater amounts in the premenstrual phase in women with PMS. Significant correlations were observed between the severity of symptoms and the change in the consumption of these nutrients. These data suggest that a consideration of the menstrual cycle phase and PMS in diet may not be warranted, especially in cross-sectional analysis, although it may need to be taken into account when examining change in intake during dietary interventions.