Firm Link Between Calcium Intake and Osteoporosis

Summary
Elderly people, especially women, suffer from decreased bone density (osteoporosis) due to decreased mineralization of bones. This increases the risks of fractures. Increased calcium intake along with Vitamin D is recommended for this group. The current population-based study included a large number of women followed up on for many years. The findings of this study suggest that low dietary intake of calcium is definitely associated with risks of fractures. But a higher dose of calcium and vitamin D does not offer additional prevention from sustaining fractures.

Introduction
Increased lifespan has resulted in a proportionate increase in the aging population. This population is exposed to many health hazards including osteoporosis and fractures. Treating such fractures puts a severe strain on resources. Prevention of fractures due to osteoporosis is a very important public health concern. Calcium and vitamin D supplements have been advocated for the prevention of osteoporotic fractures. But past studies were based on a small number of patients treated clinically or in a population based group. Hence, it is difficult to recommend the exact amount of calcium intake on the basis of these reports. The current research used data from a large number of people included in a registry and followed them up for several years.

Methodology
* 90,303 women born between 1914 and 1948, and living in two Swedish counties, were invited between 1987 and 1990 for a routine mammography screening. Seventy-four percent of these responded to a questionnaire covering lifestyle and diet.
* In 1997, a second expanded questionnaire was sent to those still residing in the study area. Seventy percent responded to this second questionnaire.
* Since all Swedish permanent residents have a unique identity number, it was easy to find the data about fractures in these groups by using the Swedish National Patient Registry.
* Between November 2003 and October 2009, X-ray studies to determine the extent of osteoporosis were carried out in randomly selected members of the group living in the city of Uppsala.
* The participants could be divided into five groups on the basis of increasing daily calcium intake. The first group consumed less than 751 mg of calcium, the second group consumed between 751 to 882 mg of calcium, the third group consumed between 882 to 996mg of calcium, the fourth between 996 to 1137 mg and the fifth consumed greater than 1,137 mg of calcium.

Results
* As calcium increased for each group, both their incidence of fracture and osteoporosis decreased
* The number of first event fractures was 3,243 in the first group, 2,941 in the second group, 2,841 in the third group, 2,872 in the fourth group and 2,841 in the last group.
* The number of hip fractures was 956 in first group, 751 in the second group, 680 in the third group, 730 in the fourth group and 754 in the last group.
* Percentage of women with osteoporosis was 23.7 percent in the first group, 22.2 percent in the second group, 19.8 percent in the third group, 18.5 percent in the fourth group and 19.7 percent in the last group.

Next steps/shortcomings
The study used questionnaires for dietary assessment. The total calcium intake calculated from such questionnaires might be inaccurate. Vitamin D increases absorption of calcium from the intestine and increases conservation by kidneys. This study found that the optimal level for calcium intake for the prevention of osteoporotic fracture is higher when dietary vitamin D intake is low. This finding needs further elaboration by research.

Conclusion
This study showed a link between a low dietary calcium intake and an increased risk of fractures and of osteoporosis in women. However, increased daily calcium intake did not further reduce the incidence of fractures. This indicates that rather than recommending higher calcium and Vitamin D doses to all old people, only those with less calcium intake in diet should be identified and targeted. This would improve optimal utilization of public health resources. The study was based on a large population and considered factors such as alcohol, smoking and fertility that are linked to risks of osteoporosis. However, further studies are needed to determine for the right quantum of calcium intake as high levels of calcium interfere with bone remodeling and might delay bone repair.

For More Information:
Dietary Calcium Intake and Risk of Fracture and Osteoporosis: Prospective Longitudinal Cohort Study
Publication Journal: British Medical Journal, 2011
By Eva Warensjo; Liisa Byberg; Uppsala University, Uppsala, Sweden

*FYI Living Lab Reports Are Summaries of the Original Research.



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