Seniors who take calcium supplements along with vitamin D may lengthen their lives, a new analysis suggests. However, only the combination of the two appears to be effective; vitamin D by itself had no benefit, the researchers noted.
"Our study provides evidence of a cause-effect relationship--that calcium and vitamin D causes beneficial effects to general health," said study author Dr. Lars Rejnmark, an assistant professor at Aarhus University Hospital in Denmark. "Calcium with vitamin D has now been proven to reduce risk of osteoporotic fractures and death in the elderly."
The report will be published in the August issue of the Journal of Clinical Endocrinology and Metabolism.
For the study, Rejnmark's team collected data on more than 70,000 people who were around 70 years old and had taken part in one of eight trials that pitted vitamin D or vitamin D plus calcium against an inactive placebo by randomly assigning participants to one of the treatments.
The investigators found that, over three years, vitamin D alone did not reduce the risk of death (mortality), but when taken with calcium mortality was reduced 9 percent.
It is known that the combination of vitamin D and calcium can reduce bone fractures in older people.
However, Rejnmark's group noted that the reduction in mortality seen in this analysis was not due to fewer fractures, but an effect of these supplements that went beyond bone health.
Recently there has been data tying calcium supplements to an increased risk of heart attack.
A study in the May edition of Heart found that calcium supplementation increased the risk of heart attack by 86 percent. But the risk was not increased with calcium from foods.
On Tuesday, the U.S. Preventive Services Task Force proposed that postmenopausal women not take low-dose calcium and vitamin D supplements daily to ward off bone fractures, because the effect is negligible.
Dr. Michael Holick, a professor of medicine, physiology and biophysics at Boston University School of Medicine, said that "other studies have shown that if you have adequate vitamin D, [it] can reduce the risk of mortality by about 7 percent."
Although the exact mechanism of why these supplements prolong life isn't known, Holick believes that both improve cell function and cardiovascular health, he said.
Holick also believes the task force misunderstood the data on the benefit of vitamin D and calcium. He said the amount of these supplements taken in the studies they looked at were too low to have any beneficial effect.
Knowing what to do about supplements can be confusing, Holick said. He recommends adults take 1,500 to 2,000 international units of vitamin D daily with 1,000 to 1,200 milligrams of calcium from both diet and supplements in combination.
"By doing so, you will preserve your bone health, you will improve muscle strength and you may have additional health benefits including [lowering the] risk of cardiovascular disease, certain cancers, type 2 diabetes and infectious diseases," Holick said. "There is no downside to increasing your vitamin D intake."