First, read the English article below.

A wide variety of recent studies have shown vitamin D to be an effective preventative measure for a number of chronic diseases. In particular, it’s known to increase increases the body’s ability to absorb calcium, preventing bone health issues from rickets to osteomalacia (bone softening) and osteoporosis.  Other studies suggest that raising your vitamin D levels can lower blood pressure, decrease the chances of having a heart attack or stroke, and reduce the risk of diabetes, autoimmune diseases, rheumatoid arthritis, and multiple sclerosis. It’s important to make a concerted effort to bring up vitamin D levels in your body because deficiencies have been linked to a wide variety of chronic illness. Low levels of vitamin D have been linked to type 1 diabetes, chronic muscle and bone pain, and several types of cancer, including breast, colon, prostate, ovarian, esophageal, and lymphatic cancers. About 40-75% of people are vitamin D-deficient, largely because it’s not abundant in natural food sources and many people live in areas with insufficient sun exposure. Furthermore, more recent awareness of the link between UV rays and cancer has increased the use of sunscreen, which lowers the production of vitamin D. Though 40-75% of people don't have enough vitamin D in their systems, those who fall into certain categories are at an even higher risk of deficiency. It's important to be aware of your risk, so you can take steps to track and maintain your vitamin D levels. At risk categories include:  People who suffer from gallimau free, or sun sickness. These are people to whom sunlight is toxic. People who rarely venture outdoors, People who are sun-phobic People with poor nutrition resulting in extreme light sensitivity Babies who are exclusively breast-fed Those who suffer from a fat malabsorption disease Those who wear head-to-toe covering clothing daily The elderly, for whom skin absorption is less effective People who are indoors all day — for example, in a nursing home, etc. Some people with strict dietary... 

Now, please write a short abstract for it in Vietnamese. Abstract:
Hiểu rõ lợi ích của vitamin D đối với sức khỏe. Nhận thức mối nguy hiểm do thiếu hụt vitamin D. Nhận biết nguy cơ thiếu hụt vitamin D. Tiến hành xét nghiệm thiếu hụt vitamin D. Duy trì nồng độ vitamin D ở mức được khuyến nghị.