About 40 patients have signed up for the study so far.

A new study at the Moncton Hospital aims to help family doctors prescribe a more precise dose of vitamin D for patients.

Many people take the supplement for good bone and muscle health, but there are several factors that could affect the appropriate dose, says Dr. Louis-Jacques Cartier, a medical biochemist and director of laboratory services at the hospital.

He is looking for about 200 patients between the ages of 50 and 75 to test vitamin D levels over a two-year period.

Those selected for the study will be given 1,000 International Units of vitamin D during the first year, and 2,000 IUs the following year, said Cartier.

The patients' blood will be tested along the way, he said.

"So we hope this way to have enough data to look at variables like obesity, female, males and so on and give a clearer understanding of what in our population here at our latitude and with our level of overweight and obesity in our population, what's needed for our family doctors to give to their patients."

Many people don't get enough vitamin D,  the so-called sunshine vitamin, said Cartier.

"Living in Canada at this latitude here and basically we don't get any vitamin d from the sun for quite a good part of the year," he said.

And it's not always possible to get enough vitamin D through diet, he said.

But right now, doctors only have general guidelines when it comes to the best supplement dose, said Cartier.

"If you go into your family doctor and you're over 50 he says well OK so you need at least 800 to 1000 IU's but he doesn't really know exactly how much you need."

About 40 people have signed up for the study to date, said Cartier.