Seasonal affective disorder or SAD, is a form of depression that tends to occur in late fall and winter months and tapers off in early spring. The cause of SAD is not known, but some experts believe it may be due to an imbalance in certain hormones that affect mood like serotonin and melatonin. Also the shorter days and reduced hours of sunlight associated with the colder seasons have been associated with increased symptoms of depression like sadness, lethargy, and sleep disturbances in those who struggle with SAD. Lack of sunlight is associated with low mood for many people. Vitamin D also appears to play a role. Estimates for the United States indicate that anywhere from 10% to 20% of Americans experience SAD to some degree. Studies exist linking SAD (and depression in general) with low levels of vitamin D. This makes perfect sense, considering SAD occurs during the darker winter months, when there is less sunlight available to help the human body synthesize vitamin D. Supplements may help. SAD and Vitamin D Levels A 2017 article published in the Journal of Global Diabetes & Clinical Metabolism emphasized the connection between low levels of vitamin D and symptoms of SAD. When vitamin D levels are low, levels of serotonin are also low, and this can lead to symptoms like loss of interest in activities, cravings for carbohydrates (in an attempt to raise serotonin levels), and feelings of guilt or irritability. What’s more, during shorter days, levels of melatonin increase, causing people to “wind down” and become tired after the sun sets. This can add to the feelings of depression experienced by those with SAD. Study: Vitamin D Can Improve Mood in People with SAD The good news is, you don’t have to have abundant sunshine to increase vitamin D levels, because it can also be obtained through foods or through supplements. When purchasing a vitamin D supplement, look for vitamin D3 vs D2, for vitamin D2 is less effective at raising blood levels, and in some cases, vitamin D2 can result in lower levels of vitamin D over the long term. Adults may be prescribed up to 6,000 IU of vitamin D3 daily during fall and winter months. I take 5,000 IU daily from October through April and recommend the same to my clients. I have seen my total serum 25(OH)D levels remain in optimal range each year as a result. In the summer months I reduce my daily dose to 2,500 i.u. daily. 
Supplements, as well as foods rich in vitamin D can help boost levels and make winter more palatable. Be sure to take your D3 supplements with food, and in particular, with foods that contain fat. Vitamin D is a fat-soluble vitamin (along with vitamins A, E, and K), and absorption is improved when consumed with a source of dietary fat. Great Food Sources of Vitamin D Some excellent food sources of vitamin D may already be in your kitchen, and if not, they’re easy to obtain. They include:
Other Ways to Ensure Sufficient Vitamin D Production Foods and supplements aren’t the only way to increase your levels. Even when the sun spends the days closer to the horizon, getting outside helps your body synthesize vitamin D, especially for people with lighter skin colors. Some people use a tanning bed during winter, though care must be taken to minimize the risk of UV damage to the skin. Full-spectrum light boxes that contain blue light, including light in the 280-330 nm wavelength range, can help with synthesis of vitamin D and help people cope better with symptoms of SAD. Vitamin D levels fall in the winter, but there are many things you can do to ensure you have enough of it to keep your bones and moods healthier. There are plenty of healthy foods that contain vitamin D, as well as readily available supplements. And the old fashioned “cure” of getting outside can be good for our souls as well as our bodies. If you have any questions about vitamin D levels, SAD, or diet and health in general, we encourage you to contact us at any time.
