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High cholesterol is a leading risk factor for heart disease. During winter, the condition can become more prevalent. A cardiologist explains why it happens, encouraging more frequent cholesterol screenings.

Cold weather can impact your circulatory system in various ways. "The chill factor causes blood vessels to constrict (vasoconstriction) in order to conserve heat, thereby increasing blood pressure," shares Dr Hasija.

During winter, when your body feels cold, the blood vessels in the skin tend to narrow down, also called vasoconstriction, to conserve body heat. However, in doing so, it makes your heart work harder to pump blood, causing the blood pressure to rise.

High blood pressure, or hypertension, can damage artery walls and cause tears where excess cholesterol can collect and build up, explains the WebMD.

According to a study published in the , cholesterol levels tend to rise during the winter months, more significantly in women, with their total cholesterol peaking in January. Researchers noted that men saw a smaller increase peaking in December.

On average, total cholesterol levels were 222 mg/dL for men and 213 mg/dL for women.

Several factors contribute to higher cholesterol levels during winter. As per the study, the amount of fluid in your blood changes with the seasons, and this affects how concentrated things like cholesterol appear in blood tests. During the winter, people tend to be less active and are exposed to colder temperatures. This leads to a decrease in plasma volume, a condition known as hemoconcentration. And when the blood has less fluid, the concentration of cholesterol appears higher, even if the actual amount of cholesterol in the body hasn't changed drastically.

Dr Hasija also adds that lifestyle factors, such as high-calorie food and hot beverage intake, generate more heat in the body, which, combined with physical inactivity, add to weight gain.

According to the doctor, these factors potentiate two important risk factors for heart disease: an increase in blood pressure and an increase in cholesterol, more so the bad cholesterol (LDL).

“Another metabolic factor that gets altered during winter is reduction in vitamin D level due to restricted sun exposure and outdoor activities,” says Dr Hasija.

Vitamin D is a fat-soluble vitamin that helps your body maintain strong muscles, teeth, and bones.

According to the doctor, although vitamin D does not have any direct relationship with cholesterol levels, he notes that some evidence suggests that the sunshine vitamin could promote healthy cholesterol levels.

For instance, a study published in the journal Menopause found that calcium and vitamin D (CaD) supplementation improved lipid profiles in postmenopausal women.

However, according to the National Institutes of Health (NIH), research on the impact of vitamin D supplements on cholesterol levels shows inconsistent and mixed results. One analysis of 41 clinical trials, involving over 3,400 participants with an average age of 55, examined the effects of daily vitamin D supplementation. The analysis found that vitamin D supplementation led to reductions in total cholesterol, LDL ("bad") cholesterol, and triglycerides but did not significantly affect HDL ("good") cholesterol levels.

Although the findings are inconclusive, it is important to maintain your vitamin D levels and keep a check on your cholesterol levels as well.

Managing your cholesterol levels starts with healthy lifestyle choices. Some of the strategies include:

• Vitamin D-rich food intake
• Physical exercises
• Stress management

Dr Hasija says, “There is no doubt that healthy habits promote healthy living. Mindful eating and indoor exercises during the winter months will counter the ill effects of heightened risk of atherosclerotic heart disease and acute coronary events that usually peak during the winter months.”

Additionally, frequent monitoring of cholesterol levels—once in a six-week interval—during winter can help keep a closer watch on your heart health while still enjoying the joys of winter, the doctor concludes.