Taking two popular supplements after the menopause could raise women's risk of heart attack, according to major 20 year study

Taking supplements to stave off the effects of menopause could leave you more vulnerable to cardiovascular disease, according to a landmark study involving 36,000 women. 

Researchers from The US National Heart, Lung and Blood Institute looked at the health outcomes of roughly 18,000 women who took daily calcium and vitamin D pills for seven years - all of whom were between the ages of 50 and 79. 

They followed the women up 20 years later, and compared the incidence of heart disease and cancer to a group of a similar number who didn't take supplements in their later years. 

The results, published in the  journal Annals of Internal Medicine, showed that those who'd taken the pills - which are said to strengthen bones  - had a six percent higher risk of dying from cardiovascular disease, compared to the other group.

The so-called 'sunshine pill' has been touted as an effective preventative treatment for bone problems after the menopause, but a new study highlights potential harms

However, those in the supplement arm of the study were also seven percent less likely to die from cancer. 

Notably, the authors said the increased risk of cancer was only seen in those who had been taking supplements in their younger years, before the study launched.

This is the largest randomized trial of women using these supplements, according to the study's authors.

It was led by the Women's Health Initiative, which itself is funded by the Government's US National Heart, Lung, and Blood Institute. 

The initial study was launched to investigate whether vitamin D and calcium supplements would help prevent hip fracture in post-menopausal women. 

It is estimated that, on average, women lose up to 10 per cent of their bone mass in the first five years after menopause

 Estrogen is crucial for repairing and strenghtening bones. It declines when women stop menstruating, impacting bone density and increasing the risk of fractures and breakages.

Taking in more of the raw materials that strengthen bones, like calcium and vitamin D, can be beneficial for preventing injury.  Calcium provides the building blocks for new bone, while vitamin D helps the body to absorb the mineral.

A number of major health organizations, like Johns Hopkins Medicine, recommend increasing consumption of these vitamins after menopause, and some doctors recommend taking supplements.

The Women's Health Initative study found that the supplements resulted in a slightly decreased risk of hip fracture in the 14 years following the menopause.

The authors suggest that one potential reason these supplements could harm the cardiovascular system is due to the impact of excess calcium on the blood vessels.

The calcification of blood vessels can cause them to stiffen and plaque to build up, which can limit the flow of blood to the major organs and contribute to a heart attack down the line, according to the British Heart Foundation. 

The authors also offered potential explanations for why these supplements might decrease cancer risk. 

They referred to previous studies that show these nutrients may block the formation of blood vessels within tumors, support cancer killing genes, and help the immune system fight cancer.

Though the authors caution that these results might not be generalizable. They say that some of the results may be due to factors other than supplementation, as the women differed ' on several demographic and health behavior characteristics.'

However they say the findings warrant further study in order to explore 'benefits or harms of supplementation'.