到底该不该补钙？---来自西方的争议

    食品伙伴网报道，据美国营养成分（nutraingredients-usa.com）消息，一个来自meta分析的数据表明，补钙会增加心血管疾病发作的风险。这份研究报告是来自英国医学杂志（BMJ），奥克兰大学的研究称，根据数据分析结果，补钙所引发的心血管疾病（如心脏病和中风）的人数，远远大于他们所预防骨折的人数。


    该网站同时也发布了各界对此研究结果的看法：补钙是最佳选择。对于建立和维护健康的骨骼、防止骨质疏松，摄入充足的钙质是至关重要的。大多数人没有从饮食中得到足够的钙，而这正是为什么对所有年龄的消费者来说补钙都是重要的。在那个meta分析的15个试验评价中有7个关于心血管的数据结果没有或不完整，15个研究中只有5个包括了几乎所有心血管疾病的研究结果，并且，该分析未对在补充钙的同时也补充维生素D的案例进行分析，而根据“妇女健康倡议”在补钙时添加维生素D可降低心脏病和中风的危险。


    Meta分析作为科学评价有用的工具，我们必须认识到其局限性，其结果是基于过去的研究，不同的实验设计、研究人群和剂量补充。这种分析不应该劝阻采取补钙的消费者，尤其是年轻妇女。

    食品伙伴网编者注：Meta分析是指用统计学方法对收集的多个研究资料进行分析和概括，以提供量化的平均效果来回答研究的问题。其优点是通过增大样本含量来增加结论的可信度、解决研究结果的不一致性。meta分析是对同一课题的多项独立研究的结果进行系统的、定量的综合性分析。它是文献的量化综述，是以同一课题的多项独立研究的结果为研究对象，在严格设计的基础上，运用适当的统计学方法对多个研究结果进行系统、客观、定量的综合分析。

本报道由食品伙伴网编译整理，仅供食品行业相关人士参考，详细内容以国外原文报道为准。

原文地址：
http://www.nutraingredients-usa.com/Research/Risks-outweigh-benefits-for-calcium-supplements-Meta-analysis
http://www.nutraingredients-usa.com/Research/Industry-Calcium-research-cherry-picked-results

原文报道： By Nathan Gray, 30-Jul-2010

New research suggests that regularly taking calcium supplements might increase the risk of heart attack.

The study, published in the British Medical Journal, indicates that calcium supplements cause more cardiovascular events (such as heart attacks and stroke) than the number of fractures they prevent.

Calcium supplements are commonly taken by older people as a measure to reduce the effects of osteoporosis. The widely used supplements have been shown to marginally reduce the risk of fracture for osteoporosis sufferers and improve bone density, but very little research has been compiled on the risks of calcium supplementation.

The new study, led by Professor Ian Reid at the University of Auckland, is a meta-analysis of fifteen randomized trials on calcium supplements conducted in the last twenty years, with the aim to investigate the links between calcium supplementation and cardiovascular events.

From analyzing the data on the 12,000 people involved in the 15 trials, the researchers found that calcium supplements increase the risk of heart attack by about 30 percent. Although this increase in heart attack risk is modest, the researchers suggest that the widespread use of calcium supplements means “even a small increase in incidence of cardiovascular disease could translate into a large burden of disease in the population.” The researchers wrote: “The likely adverse effect of calcium supplements on cardiovascular events, taken together with the possible adverse effect on incidence of hip fracture and its modest overall efficacy in reducing fracture (about 10% reduction in total fractures) suggest that a reassessment of the role of calcium supplements in the prevention and treatment of osteoporosis is warranted.”

The results observed in this study only saw an increased risk in people using supplementation, and do not affect people with high dietary intakes of calcium. Professor Reid explained that this could be related to higher blood calcium levels from supplementation compared to dietary calcium – higher blood calcium levels are believed to lead to hardening of the arteries, which can cause heart attacks.

Prof. Reid also told NutraIngredients.com that he believes the findings of the study indicate a need to review the use of calcium supplements in the general population, saying that the industry needed to “sit back and not just look at the benefits, but the clearly demonstrated risks”. Prof. Reid continued: “When you do the arithmetic, then it just doesn’t add up. The risks outweigh the benefits.”

Prof. Reid also believes that the study has broader implications for all nutritional supplements. He told NutraIngredients.com: “We have tended to focus on just the benefits of supplements without really looking at their safety. In the future I think we need to look at both the efficacy and the safety of supplements.

People assume that these supplements are natural. A high calcium meal is natural, but taking highly concentrated calcium tablets is not, and does not have the same effects” said Prof. Reid.

The Health Supplement Information Service responded to the research findings saying: “While the results of this meta-analysis are interesting and should encourage more research, the authors did not include the totality of the evidence on calcium supplementation and there were limitations to the analysis. For these reasons, it is not appropriate at this stage to change public health advice on the use of calcium supplements to maintain bone health."

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By Nathan Gray, 30-Jul-2010

Following publication of new research suggesting calcium supplements could increase the risk of heart attack, industry has been keen to give its response to NutraIngredients-USA.com
One of the main responses to the study’s findings is to point out that the adequate intake of calcium plays an important role in building and maintaining bone mass, and that the study published in the BMJ should not cause consumers to doubt the importance of calcium supplements in maintaining bone health.

“Adequate calcium intake is vital to building and maintaining healthy bones, and to preventing osteoporosis. Most people do not get enough calcium from diet alone, and this is where a calcium supplement can be important to consumers of all ages,” said Andrew Shao.

Both Shao, Ph.D, Senior Vice President of Scientific & Regulatory Affairs for the Council for Responsible Nutrition (CRN), and Daniel Fabricant Ph.D, vice president of scientific regulatory affairs for the Natural Products Association, have told NutraIngredients-USA.com that the results of the recent study go against years of research that show the benefits of calcium supplementation. Mr. Fabricant suggests that the authors of the research ‘cherry picked’ the fifteen studies from hundreds of available research studies in the area.

Reassessment

The authors of the BMJ meta-analysis called for a reassessment of the role of calcium supplements for osteoporosis, and suggested to NutraIngredients that the whole supplement market should test their products for safety and not just efficacy.

According to CRN, such conclusions are ‘dramatically overstated’. Shao said: “Seven of the 15 trials evaluated had no, or incomplete, data on cardiovascular outcomes, and only five of the 15 studies accounted for almost all of the cardiovascular outcomes. Further, the researchers chose to exclude any trials administering calcium plus vitamin D – including the Women’s Health Initiative which found calcium plus vitamin D had no effect on the risk of coronary heart disease or stroke.”

Professor Ian Reid, the lead researcher of the new research responded to these claims by telling NutraIngredients that they are currently conducting further research that will look at vitamin D with calcium supplements. Reid said that early indications show that the research, which should be published later this year, may have similar findings to the present study.

Fabricant pointed out that none of the original studies included in the meta-analysis were designed to evaluate cardiovascular events, and even if they had been “one meta-analysis on eight studies, will never prove to be conclusive evidence.”

“Meta-analysis can be a useful tool for scientific evaluation, but we have to recognize its limitations, and keep in mind that its findings are based on a collection of past studies that may have different designs, doses and study populations,” added Shao “This analysis should not dissuade consumers, particularly young women, from taking calcium supplements”.

Diet or supplements?

However, according to the National Osteoporosis Foundation (NOF), food will always be the best source of calcium: “People who get the recommended amount of calcium from foods do not need to take a calcium supplement. These individuals still may need to take a vitamin D supplement. Getting too much calcium from supplements may increase the risk of kidney stones and other health problems.”

But Shao drew attention to other health benefits that may be associated with calcium supplementation, such as reduction of colon cancer risk. “This is not even considered by the authors” he said.