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The association between calcium supplementation and adverse cardiovascular events has recently become a topic of debate due to the publication of two epidemiological studies and one meta-analysis of randomized controlled clinical trials. The reports indicate that there is a significant increase in adverse cardiovascular events following supplementation with calcium; however, a number of experts have raised several issues with these reports such as inconsistencies in attempts to reproduce the findings in other populations and questions concerning the validity of the data due to low compliance, biases in case ascertainment, and/or a lack of adjustment. Additionally, the Auckland Calcium Study, the Women's Health Initiative, and many other studies included in the meta-analysis obtained data from calcium-replete subjects and it is not clear whether the same risk profile would be observed in populations with low calcium intakes. Dietary calcium intake varies widely throughout the world and it is especially low in East Asia, although the risk of cardiovascular events is less prominent in this region. Therefore, clarification is necessary regarding the occurrence of adverse cardiovascular events following calcium supplementation and whether this relationship can be generalized to populations with low calcium intakes. Additionally, the skeletal benefits from calcium supplementation are greater in subjects with low calcium intakes and, therefore, the risk-benefit ratio of calcium supplementation is likely to differ based on the dietary calcium intake and risks of osteoporosis and cardiovascular diseases of various populations. Further studies investigating the risk-benefit profiles of calcium supplementation in various populations are required to develop population-specific guidelines for individuals of different genders, ages, ethnicities, and risk profiles around the world.
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The majority of the vitamin D in our body is produced by cutaneous synthesis in response to sunlight. As more and more people live in cities and spend the bulk of their time indoors, it can be difficult to get sufficient sun exposure for adequate cutaneous production of vitamin D. Therefore, vitamin D insufficiency has become a very common health problem worldwide. The Korea National Health and Nutrition Examination Survey IV 2008 showed that the prevalence of vitamin D insufficiency, defined as a serum 25-hydroxyvitamin D [25(OH)D] level below 50 nmol/L, was 47.3% in males and 64.5% in females. Only 13.2% of males and 6.7% of females had a serum 25(OH)D level of greater than 75 nmol/L. In Korea, vitamin D insufficiency was more prevalent in young adults than in elderly people, likely due to the indoor lifestyle of younger people. Compared with the United States and Canada, Korea has a lower mean 25(OH)D level and a higher prevalence of vitamin D insufficiency. To improve the vitamin D status of the Korean population, more aggressive policies on food fortification and vitamin D supplementation are needed.
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