The effect of the human menstrual cycle on nutrient intake

Physiology & Behavior, Vol. 31, pp. 209-212. Pergamon Press Ltd., 1983. Printed in the U.S.A.

The Effect of the Human Menstrual Cycle on Nutrient Intake I STEPHANIE

P. D A L V I T - M c P H I L L I P S

12764 O p a l o c k a , C h e s t e r l a n d , O H 44026 R e c e i v e d 17 F e b r u a r y 1983 DALVIT-McPHILLIPS, S. P. The effect of the human menstrual cycle on nutrient intake. PHYSIOL BEHAV 31(2) 209-212, 1983.--The dietary intakes of eight human females were obtained by interview each day for 60 days to determine whether the menstrual cycle affected nutrient intake. Analysis showed that over the menstrual cycle there were fluctuations in carbohydrate consumption, but not in protein and fat consumption. The mean post period (preovulation) intake was between 51.6% to 56.4% of the preperiod (postovulation) consumption. The evidence indicates that women eat more carbohydrate per day after they ovulate than before. Menstrual cycle

Carbohydrate

Nutrient intake

IN T H E course of experiments with a variety of animals, it has been observed that a definite relationship exists between blood levels of steroids and patterns of food intake [2, 3, 4, 6]. There is a reduction in food intake at ovulation when estrogen levels are at their peak. In menstruating human females, a cyclic pattern of food intake has also been observed [5]. Food consumption is higher during a ten day interval after ovulation than during a ten day interval before. Other experiments have shown that certain animals regulate not only their energy, but also their intake o f protein, fat and carbohydrate during the menstrual cycle [10,14]. Wurtman observed that rats reduce their total food and carbohydrate intake at estrus but not their protein intake, and that ovarectomized rats injected with estradiol benzoate also decrease food and carbohydrate consumption [ 14]. The relationship between the human menstrual cycle and nutrient intake has not previously been explored. However, based on animal studies, it was logical to suspect that a similar pattern in nutrient selection might exist in humans. The purpose of this paper is to analyze further the food intake data from the author's earlier study [5] to determine whether women significantly change their carbohydrate, protein, and fat consumption during the menstrual cycle. In that sixty day study, food intake data were obtained daily by interview from eight cycling human females. It was demonstrated that these women showed a fluctuation in their caloric intake during their menstrual cycles with their intake ten days prior to the onset of the menstrual period (postovulation) about 500 calories per day higher than during the ten days after (preovulation). METHOD

In the author's earlier study, subjects were obtained by announcing in a college nutrition class that volunteers were needed for a research experiment, that the purpose of the

Estrogen

Serotoninergic transmission

Hypoglycemia

study would not be revealed until the end of the study, and that whoever volunteered would be asked to report her food intake to an interviewer each day for 60 days. Seventeen students volunteered and were given a questionnaire to determine each subject's committment and suitability for the study. Eight women were selected who were between the ages of 18 and 22, were o f normal weight, who menstruated regularly, who were not taking oral contraceptives, and who in the opinion of the instructor would be very conscientious in reporting their serving sizes. It was not considered necessary to include any controls because it was anticipated that the women's menstrual cycles would be asynchronous so that if any other factor were to influence the subjects' food intakes it would occur at midcycle in some women and at the end of the cycle for others, thus causing no systematic error. PROCEDURE

The study was double blind in the sense that the subjects did not know its purpose while the interviewer did not know the timing of the cycles until after aH data were collected. S u b j e c t s were given two questionnaires at the start, one to be turned in before the study, and the other upon its completion. The purpose of the first questionnaire was to eliminate any subjects who might be aware of the purpose of the study. The second questionnaire appeared to ask for a record of major factors arising during the study which might affect food intake, but the only information used from the questionnaire was the dates of the subjects' menstrual periods. During the study, each subject was asked by interview at a prearranged time each day to report her food intake by food and serving size for the previous 24 hours. After the 60tb interview the second set of questionnaires was turned in. The investigator noted menstrual periods and designated

~Supported by the Whitney Fund, Florida State University Foundation, Tallahassee, FL 32306, and Belhaven College, Jackson, MS 39216.

Copyright © 1983 Pergamon Press Ltd.--0031-9384/83/080209-04503.00

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DALVIT-McPHILLIPS TABLE 1 M E A N C A R B O H Y D R A T E , PROTEIN, A N D FAT I N T A K E F O R TEN DAYS PRE- AND P O S T M E N S T R U A L IN G R A M S

Premenstrual Subject 1 2 3 4 5 6 7 8

Postmenstrual

Cycle

Carbohydrate

Protein

Fat

Carbohydrate

Protein

Fat

1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2

340 354 242 285 282 319 239 215 173 199 296 284 210 243 225 204

40 42 55 50 75 49 53 36 59 53 51 56 38 56 44 42

62 44 97 71 84 72 51 51 36 40 77 67 49 66 70 62

129 199 134 124 161 173 123 127 95 97 161 153 ill 104 113 129

40 44 56 49 76 47 56 33 57 52 48 58 32 51 47 40

58 41 98 68 83 74 53 49 39 38 78 64 47 69 73 58

the first day of menses as day 1 of the menstrual cycle. The desired comparison was between preovulatory and postovulatory nutrient intakes (carbohydrate, protein, and fat) but it could not be determined exactly when ovulation had taken place, only that it was approximately at midcycle. Therefore, for the purpose of comparing pre- and postovulatory nutrient intakes, the midcycle days were not used. The ten preperiod days were used, which would be clearly postovulatory, and the ten postperiod days were used, which would be preovulatory. Total carbohydrate, protein, and fat grams ingested per day were calculated by using a nutrient composition table [11]. The average carbohydrate, protein, and fat intake for each subject over the 60 day interval, the average carbohydrate, protein, and fat intake for ten days prior to the onset of menstruation (PRE) and the average carbohydrate, protein, and fat intake for ten days after the onset of menstruation (POST) were calculated. The mean POST/PRE ratio was obtained to determine statistical significance.

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RESULTS Table 1 presents the average carbohydrate, protein, and fat intake of each subject for ten days before menstruation (postovulation) and ten days after menstruation (preovulation) for two menstrual cycles. Because the menstrual cycle for subject 1 began on day 1 of the study and her last cycle began on day 60, preperiod and postperiod data for these two cycles were combined and treated as one cycle. Figure I provides a percentage comparison between the average total carbohydrate variation for ten days pre- and postmenstrual for the two combined cycles of each of the eight subjects. Figure 2 shows the percent of calories represented by carbohydrate, protein, and fat for ten days pre- and postmenstrual for the two combined cycles of each of the eight subjects. A plot of the changes in the means from premenstrual

6

5

4

DAYS PRE-CYCLE

2

1-1

2 3

4

5

6

7

8

9 10

DAYS POST-CYCLE

FIG. 1. Averaged carbohydrate intake in grams for eight subjects for ten days pre- and postmenstrual period. Daily carbohydrate for each subject was first converted to a percentage of that subject's average carbohydrate intake over the 60-day period. Each bar represents a composite average for all eight subjects on a given day of the cycle for both cycles, an average of 16 numbers.

(PRE) to postmenstrual (POST) for carbohydrate showed that the greatest pre-post differences were associated with the largest premenstrual values, a violation of statistical assumptions. Accordingly, the data for all three variables (protein, carbohydrate, and fat) were transformed to POST/PRE, and the null hypothesis was that the population mean ratio was unity. For carbohydrate, t values were -45.2, Period 1, and - 18.5 Period 2 (paired t-test, 7 ds0. To

MENSTRUAL CYCLE AND NUTRIENT INTAKE

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Days Post-Cycle

FIG. 2. Percentage of calories from carbohydrate, protein, and fat for eight subjects for ten clays pre- and postmenstruaJ period. Dally carbohydrate, protein, and fat were first converted to calories and then expressed as a percentage of each subject's total daily caloric intal~¢ for each of the ten days prior to and after menstruation. Each point represents a composite average for carbohydrate, protein, and fat for all eight subjects on a #yen day of the cycle for both cycles, an average of 16 numbers.

estimate the true ratio p, 95% confidence intervals were obtained for carbohydrate for Period 1, 0.516
body is at rest, almost two thirds of the total hepatic glucose output is utilized by the brain [8]. It is as if the production of glucose by liver gluconeogenesis and glycogenolysis were dictated primarily by the brain. A drop in blood sugar would affect the central nervous system and neuronal activity would be immediately altered with personality changes, lethargy, and hunger as a result. Except under conditions of very prolonged fasting, the only fuel used by the central nervous system is glucose conveyed continuously by the blood since the brain is not able to store glycogen [8]. Most data are in accord with the theory that a satiety center in the hypothalamus is activated (depressed) by a rise in glucose and that this center is insulin sensitive [8]. When carbohydrate is eaten in response to a drop in blood sugar, blood glucose levels are raised and insulin is released promoting the passage of glucose into the cells. A correlation between cessation of hunger and an increase in glucose utilization has been observed [1] which occurs five to fifteen minutes after carbohydrate is consumed. In the central nervous system serotonin occurs primarily in the midbrain and the hypothalamus. I f a diet rich in carbohydrate is eaten (which raises blood glucose and insulin) tryptophan levels rise and enter the brain promoting serotonin synthesis [7]. The observed effects of estrogen on food intake in humans seen in this study, are similar to those reported in rats after drugs which enhance serotonergic transmission were administerd to them [14]. This suggests a possible connection between estrogen and activation of a serotonergic mechanism [14], and lends credence to the view that serotonin-containing neural systems play an integral role in the regulation of food in man. Whatever the reasons for the observed changes in nutrient intake and caloric consumption in these subjects, the changes appear to be in response to a complex interplay of physiological processes. More research is needed to explain the relationships among neurotransmitter hormones, hypo-

212

DALVIT-McPHILLIPS

g l y c e m i a , e s t r o g e n , a n d c a r b o h y d r a t e m e t a b o l i s m d u r i n g the m e n s t r u a l cycle. T h e o u t c o m e o f this s t u d y m a y s h e d light o n t h e p r o b l e m s o f w e i g h t c o n t r o l in w o m e n , especially a r o u n d the t i m e o f m e n s e s , a n d m a y b e useful in t r e a t i n g a v a r i e t y o f eating d i s o r d e r s . It w o u l d i n d i c a t e t h a t a m o r e e f f e c t i v e diet strategy w o u l d b e to m o d e r a t e l y i n c r e a s e o n e s c a r b o h y d r a t e a n d caloric c o n s u m p t i o n s e v e n to t e n d a y s p r i o r to m e n s t r u a t i o n ,

r a t h e r t h a n ridigly a d h e r e to a s u b o p t i m a l caloric level at a t i m e w h e n t h e b o d y ' s physiological n e e d s are i n c r e a s e d . ACKNOWLEDGEMENTS The author wishes to thank Dr. Richard Wurtman whose interest in my work stimulated this research, Dr. Duane Meeter for his statistical consultation, Dr. Eleanor Whitney for her help with the design and the obtaining of subjects, and Patricia Dalvit for her help in the preparation of this report.

REFERENCES 1. Bernstein, L. M. and M. I. Grossman. An experimental test of the glucostatic theory of regulation of food intake. J Clin Inves 35: 627-633, 1956. 2. Blaustein, J. D. and G. N. Wade. Ovarian influences on the meal patterns of female rats. Physiol Behav 17: 201-208, 1976. 3. Czaja, J. A. Food rejection by female rhesus monkeys during the menstrual cycle and early pregnancy. Physiol Behav 14: 570-587, 1975. 4. Czaja, J. A. and R. W. Goy. Ovarian hormones and food intake in female guinea pigs and rhesus monkeys. Horm Behav 6: 329--349, 1975. 5. Dalvit, S. P. The effect of the menstrual cycle on patterns of food intake. Am J Clin Nutr 34: 1811-1815, 1981. 6. Gentry, R. T., G. N. Wade and E. J. Roy. Individual differences in estradiol-induced behaviors and in neuronal 3H-estradiol uptake in rats. Physiol Behav 17: 195-200, 1976. 7. Growdon, J. L. and R. J. Wurtman. Dietary influences on the synthesis of neurotransmitters in the brain. Nutr Rev 37: 129136, 1979.

8. Levine, R. and D. E. Haft. Carbohydrate homeostasis. N Engl J Med 283: 237-244, 1970. 9. Morton, J. H., H. Additon, R. G. Addison, L. Hunt and J. J. Sullivan. A clinical study of premenstrual tension. Am J Obstet Gynecol 65: 1182-1191, 1953. 10. Musten, B., E. Peace and G. H. Anderson. Food intake regulation in the ,,4e~mling rat: self-selection of protein and energy. J Nutr 104: 563-572, 1974. 11. Science and Education Administration Federal Research Staff. USDA home and garden bulletin No. 72, Nutritive value of foods. Rev ed Washington, DC: US Government Printing Office, 1978. 12. Snell, A. M., F. Ford and L. G. Rowntree. Studies in basal metabolism. J Am Med Assoc 75: 515-523, 1920. 13. Wakeham, G. Basal metabolism and the menstrual cycle. J Biol Chem 56: 555--567, 1923. 14. Wurtman, J. J. and M. J. Baurn. Estrogen reduces total food and carbohydrate intake, but not protein intake in female rats. Physiol Behav 24: 823-827, 1980.