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Despite to high prevalence of osteoporosis, elderly women show overall nutritional deficiency including calcium intake. The DASH diet (Dietary Approach to Stop Hypertension) encourages reducing saturated fat intake and increasing the potassium and calcium intake. The effectiveness of Korean DASH on bone mineral density has been validated. However, the effectiveness of the DASH diet education with calcium and vitamin D supplements women is unknown among Korean elderly. Thus, the purpose of the study was to investigate the impact of the DASH diet education with calcium/vitamin D supplements on the nutritional intake and the bone turnover marker among Korean elderly women.
The DASH (Dietary Approach to Stop Hypertension) that focuses on food high in calcium and potassium was originally designed to regulate high blood pressure. And its positive effects on bone density have been reported in studies conducted in many countries including Korea (Kim et al., 2010; Lin et al., 2003). So if the DASH diet food choices are modified in favor of Korean elderly and provided to them (Korean DASH diet), it would be possible to see increased intake of calcium, potassium and other nutrients that are helpful for bone health. Unlike young people, however, older people may have difficulty increasing calcium and potassium intake from food because they may find their long-lived eating habits hard to and may have some degrees of dental problems.
From the meta-analysis of calcium supplementation effects on bone density, the effects were better for those who had consumed less calcium and who were older(Tang, Eslick, Nowson, Smith, & Bensoussan, 2007). Therefore, elderly women with serious calcium deficiency need to have increased nutrient intake and supplementation of calcium from means other than food to maintain and improve their bone density(Bae et al., 2006).
Methods:
This study is carried out with a non-equivalent control group pre- and post-test and quasi-experimental research design to evaluate the effects of Korean DASH diet education and calcium/vitamin D supplementation on nutrient intake and bone markers in elderly women.
We examined 48 women aged 65 or over who enrolled in a senior welfare center in Seoul, Korea. A total of 108 elderly people were initially recruited through advertisements in the center. At the initial screening, however, 23 participants were excluded due to their sex (male), cognitive disabilities and not filling in questionnaires. The remaining 85 subjects were seen in the first blood sampling, but another 30 were excluded again. In the process of this research, a total of 7(surgery, n=1; start osteoporosis medication, n=4; refuse to participating, n=2) were withdrawn, leaving 26 subjects in experimental group and 22 in control for analysis.
The tools used for data collection were as follows.
General characteristics and health information of subjects were obtained through one-on-one interviews with questionnaires. Participants were interviewed with a questionnaire concerning age, levels of education, living alone or not, monthly expenses(allowance), self-rated economic status, regular exercises, ages at menarche and menopause, parity, history of hormonal replacement treatment, history of fracture after age 50, family history of osteoporosis and dental problems.
Weight and standing height were recorded in light clothing without shoes using the automatic scale(DS-101, Dong Sahn JENIX Corporation, Korea) to produce BMI(Body Mass Index, kg/m2).
DASH diet knowledge and adherence measurement tool (Kim et al., 2010) was used after being adapted partly and reviewed its content validity by an expert group(2 adult nursing professors, 1 nutrition professor and 2 nursing doctors)(CVI=.84, KR20=.70). Dietary knowledge scale comprises of 10 questions with answers of Yes/No/Don’t Know. Correct answer was scored 1 point and incorrect or Don’t Know answers 0 point. Those who get higher totals are interpreted to have more knowledge (Kim et al., 2010). The tool to measure DASH diet adherence consists of 9 questions with 5-point scales(never true/rarely true/ neutral/ usually true/ always true). With higher totals, participants have stronger adherence to the diet(Kim et al., 2010). The Cronbach’s α reliability coefficient of this tool was .68 when it was developed, and is .68 in this study.
Nutrient intake was measured with participants’ 3-day dietary records(2 week and 1 weekend day) using 24-hour recall method. Average daily intake was calculated using CAN-pro 3.0(Computer Aided Nutrition Analysis Program version 3.0)(The Korean Nutrition Society, 2007).
Bone turnover markers were analyzed from blood samples obtained after fasting for more than 8 hours(Eone Reference Laboratory).Electrochemiluminescence Immunoassay(ELISA) was used to assess two kinds of bone markers, CTx(C-telopeptide of collagen cross-links) for bone resorption and osteocalcin for bone formation.
Bone density was assessed with ultrasound measurements using the Achilles Express Ultrasonometer (GE Lunar Healthcare Corporation, USA). The measured site was calcaneus and recorded in stiffness index (Kim et al., 2010).The effectiveness of our program was examined by comparing stiffness indexes taken before and after intervention.
Data collection and intervention programs were executed with following process.
The Institutional Review Board in the Nursing School of S University approved this study. After acquiring approval from the welfare center, we explained the purpose of this study to the elderly who enrolled in the center and obtained consent from them for data collection.
To evaluate the effectiveness of interventions, data were collected pre and post interventions. Five graduate nursing students who had participated in nutrition studies conducted one-on-one interviews with the subject to assess general characteristics and dietary intake records. All the participants were required to write food diaries records at pre and post interventions. The dietary records were collected after food intake on the days of tests and ways of food preparation were evaluated. For those who had trouble writing food diaries, their daughters or in-law daughters wrote the diary. Real-sized food models were used to help subjects recall the foods they had eaten. Anthropometry and bone density were measured by 4 undergraduate nursing students who had been trained beforehand for their assigned areas. Data collection for the two cohorts was conducted on the same day by research assistants who did not know which subjects were in which group. Researchers participated only in providing the intervention program, not directly involved in data collection to avoid any probable impact on study results.
Korean DASH diet is a modified DASH diet for Korean foods that Korean elderly can consume while retaining DASH’s original emphasis on fruits, vegetables, low-fat milk and dairy products together with whole grains, poultry, fish and nuts. Diet education program was developed after advised by two nutrition professors and one nursing professor. Diet counseling was made a total of 12 times through our center visits (6 times) and telephone calls(6 times) over 12 weeks. Individual counseling was made in the center every other week, and in those weeks without our visits, telephone counseling was made to encourage diet and calcium supplementation compliance. In this study, calcium/vitamin supplementation is defined as the provision of white pills containing 1200m of calcium and 800IU(20µg) of vitamin D every other week or 6 times over 12 weeks to the participants. The pills were put into 7-day pill holders for a 2-week use and provided.
Collected data were analyzed using PASW Statistics 18.0. General characteristics were analyzed with frequency, percentage, average, and standard deviation. Homogeneity before interventions and variable differences after intervention between the cohorts were assessed using χ2-test and independent t-test. Reliability of the tools was evaluated with KR20 and Cronbach's α coefficient. Statistical significance was accepted at p<.05.
Results:
Participants in the intervention group showed the higher knowledge score (8.7 ±1.0 vs 7.7±1.3, p=.002) and better compliance to the Korean DASH diet (36.9±4.5 vs 30.8±4.7, p<.001) than the control group. In terms of other nutritional intake, the intervention group showed higher vitamin C intake than control group after the program(p=.026). The intervention group also showed higher intake of vegetable(p=.013), milk and dairy product(p=.041), whereas the control group showed no changes. Consequently animal calcium intake from milk and dairy product was increased in intervention group(p=.023). In terms of biochemical bone turnover marker, the intervention group showed the significant decrease in carboxy-terminal collagen crosslinks(CTx) than the control group (0.30±0.15 vs 0.40±0.16, p=.030) after the intervention. There was no significant difference in osteocalcin and bone mineral density among both groups.
Conclusion:
This study examined the effects of Korean DASH diet education and calcium/vitamin D supplementation on bone health in elderly women ages 65 or over. Based on the results, our interventions are believed to have a positive influence on bone turnover in older women. Nonetheless, the time was limited to fully evaluate changes in bone marker levels and the sample size was small, which raises concerns of selection bias. This limitations warrant the need for extensive research over more than one year. Considering that elderly have difficult to remember and maintain acquired knowledge for a long term and to change dietary habits, we suggest a study that provides Korean DASH diet meals to participants directly and reconfirm its effectiveness on their bone turnover.