Winter fatigue is a condition where people experience depression during the same season each year. There are many different opinions, but the general consensus is that winter fatigue is partly due to light sensitivity, biochemical reactions in the brain, and Vitamin D deficiency.
Symptoms of seasonal fatigue can mimic those of major depressive disorder and may include decreased energy, increased appetite, increased need or desire for sleep, loss of interest in usually enjoyable activities or performing activities, carbohydrate cravings, irritability, and weight gain.
Although seasonal disorders can occur during any season, for our geographical location, it is most common from late autumn to early spring, when the weather is characterized by shorter days, reduced sunlight, low temperatures, and spending more time indoors.
Vitamin D is known as the "sunshine hormone" because people produce it in response to skin exposure to the sun's ultraviolet light. With limited sunlight exposure, Vitamin D levels decrease, leading to a deficiency in the body.
How does Vitamin D deficiency lead to weight gain?
One explanation is evolution. For our ancient ancestors, sunlight exposure was the primary source of vitamin D. Its level was higher in summer when people spent more time outdoors hunting and gathering food, and lower during the cold winter months when food supply was limited, and they entered a state of pseudo-hibernation. Physiologically, low vitamin D levels may signal the body to shift into a winter metabolic pattern characterized by fat storage and weight gain, which was essential for the survival of our Paleolithic ancestors.
Another reason is brain biochemistry. Vitamin D increases serotonin, a substance in the brain responsible for bowel movements, mood, hunger, and sleep. When serotonin levels drop, our mood worsens, and our bodies often experience cravings as a means of increasing serotonin levels. Carbohydrates, as well as caffeine and nicotine, temporarily increase serotonin levels in the brain and lead to a temporary boost in our mood. Unfortunately, the body eventually gets used to the increased serotonin levels, and cravings intensify. In addition to abdominal fat accumulation, other signs of vitamin D deficiency include depression, chronic musculoskeletal pain, frequent respiratory infections, infectious diseases, and some autoimmune diseases.
How much Vitamin D do we need?
For proper functioning, the human body uses approximately 3000-5000 international units (IU) of Vitamin D daily. Based on this figure, a daily intake of at least 5000 IU of Vitamin D is recommended for healthy adults.
What can you do to combat seasonal depression? Check your body's Vitamin D level. This can be done through a blood test. The level of 25-hydroxy vitamin D is the most accurate way to measure the amount of circulating vitamin D in the body. For optimal health, 50 ng/mL is recommended.
It is very difficult to obtain adequate levels of Vitamin D through diet alone. For people with insufficient sunlight exposure, supplementing with Vitamin D3 is necessary. In case of Vitamin D deficiency, the recommended dose of dietary supplements is from 400 IU to 600 IU daily. B vitamins, as well as calcium and magnesium obtained through diet or supplements, are necessary cofactors for Vitamin D absorption and serotonin synthesis.
Limit your intake of caffeine and refined carbohydrates like bread, pasta, and desserts. They can temporarily boost your mood, but they can also reduce your body's sensitivity to serotonin and, over time, lead to cravings and weight gain.
