Dietary calcium intake and osteoporosis in postmenopausal women living in Sarajevo area

Introduction: Osteoporosis is a multifactorial polygenetic disease of which the genetic determinants are modulated by hormonal, environmental and nutritional factors. Identifi cation of the risk factors for osteoporosis related to nutrition is important in the prevention and treatment of this disease, considering that these factors can be modifi ed. The aim of this study was to examine infl uence of dietary calcium intake on bone mineral density in postmenopausal women who hadn’t a defi cit of estrogen in their menstrual history. Methods: A total of 100 postmenopausal women living in Sarajevo area, aged 50-65 years, without estrogen defi ciency in menstrual history were included in the study. Mineral bone density was measured at the lumbar spine and proximal femur by Dual–Energy X–ray Absorptiometry using Hologic QDR-4000 scanner. Examination and control group were formed based on mineral bone density values. The women in the examination group had osteoporosis. The women in the control group had osteopenia or normal mineral bone density. Estimates of daily dietary calcium intake were performed based on a Food Frequency Questionnaire. Results: The average daily intake of dietary calcium among women who had osteoporosis was 967.32 mg, and in women who hadn’t osteoporosis 1195.12 mg. The difference between two groups was statistically signifi cant (p<0.001). There was registered signifi cant correlation between intake of dietary calcium and mineral bone density in examination (p<0.01) and in control group (p<0.01). Conclusion: The results of this study have shown that adequate daily intake of dietary calcium in postmenopausal women aged 50-65 years living in Sarajevo area, which hadn’t estrogen defi ciency in their menstrual history (in the group of women without osteoporosis amounted to 1195.12 mg) has a positive impact on bone mineral density. © 2012 All rights reserved


Introduction
Osteoporosis is a systemic skeletal disease characterized by low bone mass and micro-architectural deterioration of bone tissue with a consequent increase in bone fragility and higher fracture risk (1).It is considered a multifactorial polygenetic disease of which the genetic determinants are modulated by hormonal, environmental and nutritional factors (2).Postmenopausal osteoporosis is related to the loss of gonadal function.Th e quantity and quality of the bone aft er menopause decreases rapidly resulting in an increased risk of fractures (3,4).Estrogens are known to play an important role in regulating bone homeostasis and preventing postmenopausal bone loss (1).Research results regarding the eff ect of nutritional, environmental and lifestyle factors on bone mineral density and on the risk of bone fractures are not consistent, implying the need for further research which would contribute to providing relief for this problem.Calcium and vitamin D have received most of the attention directed to diet and bone health, but there are continuing questions about their benefi ts for bone health (5).People in some geographical areas with low calcium intakes (Japan) have a low incidence of osteoporotic frac-tures, in contrast to some populations (Scandinavian countries) where average calcium intakes are high, have a high incidence of osteoporosis (5,6).Th e recommendations for calcium intake vary widely among regional agencies.Variability in calcium intake recommendations can be explained partly by the discrepant results obtained in observational and interventional studies (7).Identifi cation of the risk factors for osteoporosis that are related to nutrition is important in the prevention and treatment of this disease, considering that these are factors that can be modifi ed.In addition to diff erences in the incidence of osteoporosis and osteoporotic fractures among racial groups, diff erences within the same race have also been determined as well as diff erences in conjunction with age and gender (8)(9)(10)(11)(12)(13).Th erefore, the importance of conducting research on osteoporosis within certain population groups has been confi rmed.Th e aim of this study was to examine infl uence of dietary calcium intake on bone mineral density in postmenopausal women who hadn't a defi cit of estrogen in their menstrual history.

Methods
A total of 100 postmenopausal women living in Sarajevo area (Sarajevo Canton), aged 50-65 years, without estrogen defi ciency in menstrual history were included in the study.Examination and control group were formed based on mineral bone density values.Th e women in the examination group had osteoporosis.Th e women in the control group had osteopenia or normal mineral bone density.Mineral bone density was measured at the lumbar spine and proximal femur by Dual-Energy X-ray Absorptiometry using Hologic QDR-4000 scanner.Estimates of daily dietary calcium intake were performed based on a Food Frequency Questionnaire.Statistical processing and analysis of data was conducted.Th e diff erence in results was tested by using appropriate statistical tests of signifi cance diff erence (Chi square test, t-test).Th e coeffi cient of linear correlation between dietary calcium intake and bone mineral density was calculated.

Results
Th e average age of women without estrogen deficiency in their menstrual history, in the examination group was 58.64 years, and in the control group was 57.9 years.Th ere was no statistically signifi cant diff erences between these two groups, t = 0.746.Average daily intake of dietary calcium among women without estrogen defi ciency in menstrual history was, in the examination group 967.32 mg, and in the control group 1195.12mg.Th e diff erence in the average daily intake of dietary calcium between the two groups was statistically signifi cant, p < 0.001 Th e coeffi cient of linear correlation between T scores and daily intake of dietary calcium among women without estrogen defi ciency in menstrual history in the examined group was statistically signifi cant, r = 0.677, p < 0.01.Th e coeffi cient of linear correlation between T scores and daily intake of dietary calcium among women without estrogen defi ciency in menstrual history in the control group was statistically signifi cant, r = 0.615, p < 0.01.

Discussion
Th e female reproductive system plays a major role in regulating the acquisition and loss of bone by the skeleton from menarche through senescence (14).Estrogen defi ciency (e.g., aft er menopause) increases the rate of remodeling and the volume of bone that is resorbed and decreases the volume of bone that is formed resulting in bone loss and structural decay aft er menopause (15).Kapetanović et al. found a signifi cant association between menstrual factors (years between menarche and menopause, years since menopause) and bone mass loss in Bosnian postmenopausal women (16).Research results regarding the eff ect of calcium intake on bone mineral density and on the risk of bone fractures are not consistent.Park et al. found in their research that a high intake of dietary calcium, especially calcium from plant foods reduces the risk of osteoporosis and increase bone mineral density in Korean postmenopausal women (17).Napoli et al. studied the importance of sources of calcium intake on estrogen metabolism and bone mineral density in healthy postmenopausal women of white race.Intake of calcium form dietary sources was associated with higher bone mineral density than suplement calcium intake.Th e authors concluded that calcium from dietary sources may produce more favorable eff ects in bone health in postmenopausal women than will calcium from supplements (18).Ilic et al. have shown that there is signifi cant correlation between bone mineral density in healthy Caucasian postmenopausal women and certain nutrients including calcium (19).Although the antifracture eff ect of calcium alone is questionable, several observations justify the recommendation to avoid calcium defi ciency in this age (20).Results of the Feskanich et al. study showed that total calcium intake in postmenopausal women (through diet and supplementation) was not associated with risk of hip fracture and that consumption of milk is not associated with lower risk of hip fracture (compared was intake of 1200 mg / day or more with calcium intake below 600 mg / day), and that consumption of milk is not associated with lower risk of hip fracture.Conclusion of their study is that neither milk nor a high-calcium diet appears to reduce risk of hip fracture in postmenopausal women (21).Fardellone et al. have not found a diff erence in the average daily calcium intake between women with and without a diagnosis of osteoporosis or with and without fractures.Th e study involved postmenopausal women aged 45 years and over (22).Th e results of this study have shown that adequate daily intake of dietary calcium in order to preserve and promote bone health in postmenopausal women, aged 50-65 years, living in the Sarajevo Canton, which hadn't estrogen defi ciency in their menstrual history, was 1195.12 mg (the group of women without osteoporosis).Average daily intake of dietary calcium in postmenopausal women which hadn't estrogen defi ciency in their menstrual history in the group of women with osteoporosis was 967.32 mg.

Conclusion
Th e results of this study have shown that adequate daily intake of dietary calcium in postmenopausal women aged 50-65 years living in Sarajevo area, which hadn't estrogen defi ciency in their menstrual history (in the group of women without osteoporosis amounted to 1195.12 mg) has a positive impact on bone mineral density.

FIGURE 1 .FIGURE 2 .
FIGURE 1.The average age of women without estrogen defi ciency in menstrual history.t = 0.746, no statistically signifi cant FIGURE 2. Average daily intake of dietary calcium among women without estrogen defi ciency in menstrual history.p< 0.001 Authors declare no confl ict of interest

TABLE 1 .
The coeffi cient of linear correlation between T score and daily intake of dietary calcium among women without estrogen defi ciency in menstrual history