Is cold weather good or bad for your health? It depends. Cold weather can be hard on your health in some ways, but it may also be good for it, reports the January 2010 issue of theHarvard Health Letter.

Most people spend the winter trying to stay warm, but a little bit of exposure to cold may not be such a bad thing, the report says. There are two types of fat in the human body: white fat and brown fat. Brown fat is the heat-producing, calorie-burning fat that babies need to regulate their body temperatures. Most of it disappears with age, but adults retain some brown fat. Dutch researchers reported findings last year that showed that moderately cool temperatures of 61°F activated brown fat in 23 of 24 study volunteers. This is a good thing because brown fat burns calories more efficiently than white fat, and so may help control weight. When we get chilled this winter, we may take some consolation that at least we’re firing up those brown fat cells.

In some countries, the use of cold temperatures for medical purposes is taken quite seriously. Several years ago, Finnish researchers reported the results of a study of 10 women who, for three months, took cold-water plunges (20 seconds in water just above freezing) and submitted to whole-body cryotherapy sessions. Blood tests showed a two- to threefold jump in norepinephrine levels minutes after cold exposure. Norepinephrine is a chemical in the nervous system that wears many hats, including a possible role in pain suppression.

Before heading north in search of a colder climate, it’s important to think about the toll that cold and winter can take, cautions theHarvard Health Letter. Last year, French researchers found that the increase in systolic blood pressure that occurs during the winter was especially pronounced in people ages 80 and older. Cold weather and respiratory disease, including flu, also go hand in hand.