单选题
New Zealand researchers say guidelines advising seniors to consume at least 1,000 to 1,200 milligrams of calcium a day are misplaced.
No proof was found that boosting calcium intake beyond normal dietary levels strengthens older bones or prevents fractures, said researcher Dr Mark Bolland, a professor at the University of Auckland. "We"ve gathered all the clinical studies of calcium supplements and dietary calcium intake for both bone density and fractures," said Bolland. "Taken together, we think this is the strongest possible evidence that taking calcium supplements will not be beneficial unless there are, clear medical reasons that a calcium supplement is needed," he said.
Moreover, excess calcium supplementation can be harmful, he and other experts said. "The findings probably will surprise clinicians and patients", Bolland said," because they have received very strong messages for many years about the importance of calcium for bone health in guidelines for osteoporosis (骨质疏松症) management and by osteoporosis advocacy groups."
"Clinical trials have shown that calcium supplements often cause minor gastrointestinal (胃肠的) side effects such as constipation (便秘)", Bolland said. "They also cause a small increased risk of kidney stones, heart attacks, high calcium levels and hospitalization with acute gastrointestinal symptoms." He also said. "The small risk of these important adverse effects, together with the moderate risk of minor side effects such as constipation, outweighs any benefits of calcium supplements on fracture."
However, Dr Duffy MacKay, president for the Council for Responsible Nutrition, disagreed with Bolland"s conclusions, and countered that scientific evidence does show that calcium reduces fracture risk. "The degree of benefit varies from study to study," he said. "However, the largest benefit is generally found in those who take their calcium supplements throughout the entirety of a study. Other important factors that influence the benefit of calcium supplementation include giving calcium supplements with other important bone nutrients including vitamin D and vitamin K."

单选题 Dr Bolland says that calcium intake beyond normal dietary levels has ______.

单选题 The clinical studies have been gathered to investigate ______.

单选题 The findings about the excess calcium intake are surprising because they are ______.

单选题 The adverse effects from the calcium supplements include the following EXCEPT ______.

单选题 According to Dr MacKay, the most important factor affecting the result of the study is ______.