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Correlate the plasma concentrations of estradiol, progesterone and leptin with the food intake, during the follicular and luteal phases of the menstrual cycle.
Thirty female graduate students from the Universidade Federal de Santa Catarina were investigated. The food intake during the follicular and luteal phases was determined from three-day food intake records. In the same phases, blood was collected for the assay of estradiol, progesterone and leptin. Weight and height were used to evaluate the nutritional status. The results were analyzed with SPSS 10.0 for Windows with Student's t test and Pearson correlation.
Leptin correlated with the Body Mass Index and with the percentage of body fat in the follicular and luteal phases. Energy, carbohydrate and fat consumption in the luteal phase was greater than in the follicular phase. Concentrations of estradiol, progesterone and leptin were significantly higher in the luteal phase. Progesterone correlated positively with the energy and carbohydrate consumption in the luteal phase.
It is suggested that the regular fluctuations of the female ovarian cycle can influence the food intake, exerting a central paper in the maintenance of energy balance and in the maintenance of body weight.
The menstrual cycle is regarded as a physiological phenomenon that results from the precise coordination of events that occur in the hypothalamus, the anterior pituitary gland and the female reproductive system. This dynamic interaction allows the reproductive process to proceed in the form of a cycle.
Numerous physical, emotional and cognitive changes over the course of the ovarian cycle have been recorded and, in general, these are directly related to fluctuations in the levels of the hormones estradiol and progesterone.
The menstrual cycle can exert an important influence over food consumption. For example, studies have reported changes in feeding behavior, in terms of the quantity and types of foods consumed, during the phases of the menstrual cycle, especially between the follicular and luteal phases.
In this way, the female steroid hormones, especially estradiol and progesterone, can, by means of regular fluctuations over the course of the ovarian cycle, influence food intake. The control of the cycle thus plays a central role in the maintenance of energy balance and, consequently, over the stability of the body weight.
In the context of the regulation of food intake, leptin is a substance that also has been implicated in the control of appetite and of energy expenditure and, consequently, in the homeostasis of body weight. Leptin is a hormone secreted by several tissues, among them adipose tissue and the ovaries.
Nowadays it is known that the concentration of leptin in the follicular phase of the menstrual cycle is lower than that during the luteal phase, while significant positive correlations have been found between the increased expression of leptin and the increase in the concentration of steroid hormones.
Furthermore, studies have demonstrated that serum levels of leptin in eutrophic women with regular menstrual cycles rise from the follicular period to the luteal period, suggesting that the female sex hormones are involved in the regulation of leptin.
The aim of this study was to investigate the relationship between food intake, the female sex hormones and leptin, in the follicular and luteal phases of the menstrual cycle, with the objective of contributing to the understanding of women's nutrition in the light of these aspects of female physiology.
The sample consisted of 30 women from the full-time post-graduate courses at the Universidade Federal de Santa Catarina – UFSC, aged between 18 and 35 years, with regular menstrual cycles varying from 25 to 32 days and who had not taken any hormonal medication for at least 3 months before data collection.
Women younger than 18 years or older than 35 were excluded from the study, as were those with a Body Mass Index (BMI) other than eutrophic,
women who were pregnant or breast feeding, smokers, those following a special diet, athletes, those with a tendency towards anorexia or bulimia, those who were suffering from a disease, taking any hormonal medication or one with effects on the Central Nervous System.
The weight was obtained using a digital balance and the height was determined using a metric tape appropriate.
For the purposes of standardization, day “1” was taken to be the first day of menstrual bleeding. The follicular phase was considered to last from the 5th to the 9th day following the beginning of menstruation, and the luteal phase was taken to be from the 20th to the 25th day after the onset of bleeding. For those participants who had a cycle of greater than 30 days, the luteal phase was taken to occur between the 23rd and 28th days.
An 8 mL sample of blood was drawn from each participant, all of whom had fasted for 8 h, in both phases of the cycle, for the determination of sex hormones and leptin. The samples were centrifuged and kept frozen at −20 °C until analysis. Progesterone and estradiol analyses were conducted using the chemiluminescence method with the ACS®: 180 equipment (Automated Chemiluminescence System, Bayer Diagnostics New York, USA), and the Bayer kit Healthcare LLC®, Bayer Corporation. Leptin concentrations were determined according to the radioimmunoassay method using the Wallac® radioactivity counter (Linco Research, St Louis, 60MO, USA). Every determination was performed in duplicate at the Clinical Analysis Laboratory from University Hospital – UFSC and at the Central Radioimmunoassay Laboratory of São Paulo.
The participants were instructed to record their dietary intake over three days during the two periods (follicular and luteal phases), comprising 2 weekdays and 1 day at the weekend. The data from the diet records were tabulated using the Software.
The following were assessed: caloric consumption in kilojoules, carbohydrates and lipids in grams/day, and proteins in grams/kg of body weight/day.
Statistical analysis was performed using the Statistical Package for the Social Sciences 10.0 for Windows. Results are expressed as means±standards deviation.
The paired Student's t-test was employed to compare differences between the phases, while for the analysis of correlations between hormonal secretion and food consumption, Pearson's Correlation was used. For all the tests a significance level of 95% was employed (p<0.05).
All of the participants signed a Term of Free and Informed Consent.
The results show that the means±standards deviation age, weight, height and BMI for the sample were 27.7±4.1 years, 58.0±6.4 kg, 1.6±0.0 m, 22±2 kg/m2, respectively. All of the participants exhibited a normal BMI.
Table 1 presents the mean accompanied by the standard deviation for the variables estradiol, progesterone and leptin in the follicular and luteal phases.
Table 1Plasma concentrations of estradiol, progesterone and leptin in the follicular and luteal phases.
The mean values for the plasma concentrations of hormones in the two phases investigated were found to be within reference values. However, there was a statistically significant difference for all the hormones when the two phases were compared, with a greater significance level for estradiol (p<0.0001) and progesterone (p<0.0001), and a lesser one for leptin (p<0.05).
The caloric consumption, as well as that of carbohydrates, proteins and lipids in the two phases of the menstrual cycle are given in Table 2.
Table 2Consumption of energy and of macronutrients in the follicular and luteal phases in the sample.
In absolute values, the consumption of macronutrients in the luteal phase was superior to that of the follicular phase, representing a difference of 67 g of carbohydrates, 26 g of lipids and 0.1 g/kg of weight of proteins.
Fig. 1, Fig. 2 shows the correlation between progesterone and total energy (r=0.38; p=0.036) as well as carbohydrates (r=0.38; p=0.035) ingested by the sample in the luteal phase of the cycle, respectively. The significance of the difference between the correlations was p<0.05. With regard to estradiol and leptin, there was no correlation between these hormones and the variables for food consumption in the sample in the phases investigated.
In relation to the differences between the hormonal concentrations in the phases, there was a significant increase of progesterone and of estradiol in the luteal phase when compared to the follicular phase (Table 1). These increases are physiological, since the levels of progesterone are 12–20 times greater in the luteal phase and the levels of estradiol are around 3–4 times higher in the same period.
in their study of food consumption in 18 healthy women in the different phases of the menstrual cycle, carried out by means of the direct weighing of food and the production of a diet record. The authors noted a significant rise in food consumption in the luteal phase (p<0.05). The same was observed by Barr et al
involving 20 university students, food consumption was determined on 3 days in each phase of the cycle, by means of dietary record, and these authors also found a greater caloric intake during the luteal phase (p<0.05). Some studies have reported a rise in the consumption of one or more macronutrients in the luteal phase, however, these results display less consensus.
In the present study, the consumption of carbohydrates and lipids by the sample was higher during the luteal phase compared to the follicular phase (Table 2). This finding is similar to those of Li et al,
that found significant differences for the ingestion of carbohydrates (p<0.05), lipids (p<0.01) and proteins (p<0.05) in the luteal phase, on investigating the effect of menstrual cycle on food consumption in 18 women. Cross et al
also found similar results to those of the present study, reporting a significant increase in the consumption of lipids and carbohydrates (p<0.05) in the luteal phase.
One hypothesis that attempts to explain the consumption of carbohydrates in the pre-menstrual period is concerned with the reduction in the levels of serotonin in this phase of the cycle. The ingestion of carbohydrate-rich meals increases the production of 3-phosphoglycerate, a metabolite of glycolysis that promotes the synthesis of aromatic aminoacids, among them tryptophan, the main substrate for serotonin synthesis, increasing its concentration during the pre-menstrual phase.
The increase in lipid consumption in the luteal phase has been described in the literature as resulting from the effect of steroid hormones over the metabolism. It is believed that progesterone would promote the accumulation of lipids in the interior of adipose cells, resulting in a reduction in plasma triglycerides and stimulating the consumption of meals containing superior levels of fat. Estradiol, by contrast, would stimulate lipolysis, resulting in a greater quantity of substrate for energy production.
reported that it is the intracellular metabolism of glucose which is in fact altered. As a result, the literature suggests that the probable changes in glucose metabolism brought about by the rise in the concentration of progesterone may lead to an increase in the consumption of carbohydrates by the women, during the luteal phase of the menstrual cycle.
one of the greatest limitations to the investigation of steroid hormones is the difficulty in identifying and recruiting normal individuals who conformed to all of the selection criteria for the sample, especially with regard to the non-use of hormonal contraceptives. In addition, the normal biological variations in hormonal secretion among women increase the variability to such an extent that the sample size needs to be relatively large in order to minimize these differences.
Further investigations of this type with more representative samples are important, with the aim of deepening the understanding of the relationships between female hormones and food consumption during the menstrual cycle.
The results presented here suggest that regular fluctuations in the ovarian cycle can influence food consumption, playing a central role in the maintenance of the energy balance and, consequently, in the stability of body weight.
Conflict of interest
The authors have no conflict of interest.
The authors are grateful to Professor Carlos Alberto Justo da Silva, director of the Hospital Universitário (HU)/ UFSC, and the staff of the Clinical Analysis Laboratory of HU/UFSC, for their assistance with analyses of estradiol and progesterone. Also, we thank the Coordination of the Post-Graduate Program in Nutrition for their support and help with the doses of leptin.
Oliveira H.C. Lembruger I. Tratado de Ginecologia. vol. 1. Revinter,
Rio de Janeiro2000: 231-236