Relationship between Lifestyle, Body Mass Index, and Dietary Factors with the Equol Production

INTRODUCTION

Equol is a daidzein isoflavones metabolite with the help of intestinal microflora, has a similarity in chemical structure with 17β-estradiol so that it has an estrogenic activity, and was able to stimulate gene transcription via estrogen receptors.¹ There are several factors that are known affecting the metabolism of daidzein into equol, including the specific strain of intestinal bacteria, which is able to metabolize daidzein into equol.^2,3 Lifestyle factors, such as, smoking, physical activity, and obesity are also known to influence the composition of the microflora in the gastrointestinal tract, which reduce the diversity of the intestinal microflora and reduce the population of bacteria that are able to convert daidzein into equol.^4,5 Dietary components like carbohydrates, fats, protein, and fiber also can determine the bacterial population which can grow predominantly in the gastrointestinal tract. Equol production has correlation with the intake of carbohydrates and high fiber. Carbohydrates and fiber that are not digested by the small intestine will undergo fermentation process, which selectively will stimulate the growth and the activity of beneficial intestinal bacteria after entering the colon. Protein and fat intake is known to inhibit the production of equol. They can produce harmful metabolites, which are toxic and carcinogenic, and can inhibit the growth of beneficial bacteria.⁶ There are two phenotypes in the human population, namely, the equol-producing and nonequol-producing. In this study, soy milk was given for three days, for the substrate additional isoflavones in daily diet, as a challenge test to distinguish the two phenotypes of the subjects. Equol levels can be detected in plasma, feces, and urine. However, equol levels in urine are lower than the levels of equol in plasma, and equol detection by using urine is easier and less invasive.

MATERIALS AND METHODS

This study was an observational study with cross-sectional method, analyzing the correlation of lifestyle factors (smoking habits and physical activity), body mass index, and dietary components with the equol-producer phenotype. Research samples were obtained from the study subjects who met the inclusion criteria, which were reproductive, perimenopausal, and postmenopausal women who were healthy and were voluntary to be the subject on the study. The exclusion criteria were those subjects who did not follow the whole steps of the study, including those who did not drink soy milk >1 day prior to the examination of urinary equol concentration and those who were known based on their history had allergic to soy milk.

The method that was used to differentiate equol-producing and nonequol-producing status on the subjects was by giving the subjects 2 cups (250 mL) daily morning and evening of soy milk in addition to their daily dietary consumption for 3 consecutive days, and then on the third day, 24 hour urine samples were collected for urinary equol concentration examination. Urinary equol concentration is stable at room temperature up to 14 days. Equol examination was conducted by using electrospray ionization mass spectrometry (ESI-MS). Equol-producing groups were determined if the urinary equol concentration was >20 ng/mL.

Dietary intake of specific compound was obtained by using semiquantitative food frequency questionnaire method so their daily intake of carbohydrates, protein, fat, and fiber could be determined, and then the result was analyzed by using Food processor II version 3.

RESULTS

This research was conducted from January to June 2015. During the period, 140 subjects met the inclusion criteria. The subjects were reproductive age, perimenopausal, and postmenopausal healthy women. Some were RSHS staffs and group of women from Posbindu Teratai Komplek Bukit Cimindi Raya, Pasirkaliki, Posyandu, and Posbindu in Cileunyi area.

Most of the subjects in both groups were in the perimenopausal age (45–55 years). The previous report says that age and menopausal status have no influence on the ability to produce equol. Age only became substantial factor among newborns in the first month of life, compared to infants or adults, due to the absence of intestinal flora in newborn infants (Table 1).

From Table 2, only smoking habit factor had a significant correlation with the equol-producing and nonequol-producing groups. The higher the number of cigarettes consumed, the lower the percentage of equol production. Physical activity did not have a significant correlation between equol-producing and nonequol-producing groups. Body mass index variable tended to give effect that if there is higher BMI for a person, the person’s ability to produce equol will be lower, although it was not statistically significant.

Table 3 show higher intakes of carbohydrate and fiber were obtained in the equol-producing group compared to the nonequol-producing group. These variables had positive correlation and statistically significant (p %3C; 0.05), although the strength of correlation was weak (r < 0.4).

DISCUSSION

CONCLUSION

Smoking habit and the intake of carbohydrates and fiber in dietary consumption had an effect on the equol-producer phenotype.

CLINICAL SIGNIFICANCE

Our study may be useful as basic data to modify lifestyle and nutrition to improve the metabolism of equol production, which is needed for women’s health.

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