Calcium is an essential nutrient our body needs. It is very important for our bone health.
Many people take calcium supplement daily and it helps make their body stronger.
However, recent studies have found that calcium supplement can bring some health risks.
For example, one study from the University of North Carolina shows that taking calcium supplements may increase the risk of small growths in the bowel called polyps.
Specifically, the researchers focused on sessile serrated polyps.
The condition has only recently been recognized as important colon cancer precursors that give rise to 20-30% of sporadic colon cancer cases.
Sessile serrated polyps are an important target of colon cancer screening, but they are hard to detect because of their flat shape and subtle appearance.
In the study, the team analyzed findings from a large US trial involving over 2,000 patients aged between 45 and 75.
These people had had at least one serrated polyp detected and removed—and were due to have a follow-up colonoscopy in three to five years.
The team split the patients into groups to receive either daily calcium supplements, daily vitamin D supplements, both, or neither for three or five years (treatment phase) until their colonoscopsy.
They found that during the treatment phase, neither calcium nor vitamin D had any effect on cases of serrated polyps.
However, during the later observational phase (six to 10 years after treatment began), the researchers found increased risks of serrated polyps among patients taking calcium alone and among those taking a combination of calcium and vitamin D.
The link only existed in calcium supplements, not dietary calcium.
The researchers suggest that patients with a history of pre-cancerous serrated polyps, especially women and smokers, may avoid vitamin D and calcium supplementation.
The study is published in the journal Gut.
In another study, researchers from the University of Gothenburg in Sweden find that calcium supplements may be linked to a higher risk of dementia in older women with cerebrovascular disease.
Cerebrovascular disease is a group of disorders that affect blood flow in the brain.
These diseases, including stroke, are the fifth leading cause of death in the United States and increase the risk of developing dementia.
In older people, osteoporosis is a common problem. Because calcium deficiency contributes to osteoporosis, daily calcium intake of 1000 to 1200 mg is recommended.
But getting this recommended amount through diet alone can be difficult, so calcium supplements are widely used.
The study involved 700 dementia-free women who were followed for five years.
A total of 98 women were taking calcium supplements at the start of the study and 54 women had already experienced a stroke.
During the study, 54 more women had strokes, and 59 women developed dementia.
The researchers found that the women who were treated with calcium supplements were twice as likely to develop dementia than women who did not take supplements.
Further analysis showed that the increased risk was only among women with cerebrovascular disease.
Women with a history of stroke who took supplements had a nearly 7 times increased risk of dementia than women with a history of stroke who did not take calcium supplements.
The researchers suggest that more data are needed to confirm the results.
They also suggest that calcium from food affects the body differently than calcium from supplements and appears to be safe or even protective against vascular problems
The study is published in Neurology.
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