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Nutritional Strategies for Seasonal Depression

What is seasonal affective disorder (SAD)?

If you haven’t heard of the term seasonal affective disorder (SAD), you may think it is simply a case of the “winter blues.” As the season transitions into winter and the days become shorter, it is common that people may experience some changes in mood. For those with SAD, the mood changes may be much more significant. 

Seasonal affective disorder is a type of depression in which symptoms occur seasonally, for about 4 to 5 months per year. The most common is winter-pattern SAD, which occurs in the late fall and winter months, but there is also summer-pattern SAD, occurring in the spring and summer. Since SAD is a depressive disorder, the signs and symptoms that may occur are the same as major depressive disorders. 

If you or someone you know may have SAD, take the step to speak with a healthcare provider or a mental health specialist, and be aware of some of the important resources available: SAMSHA’s National Helpline 1-800-662-HELP (4357) and the National Suicide Prevention Lifeline toll-free at 1-800-273-TALK (8255).

Who is at highest risk for SAD?

Those at highest risk for SAD are those with a major depressive disorder, as well as those with mental disorders. This form of depression is more commonly seen in women, those who have family members who have a depressive disorder, and those living further north of the equator. The higher the latitude, the less sunlight seen in the winter time. This decrease in sunlight seems to trigger winter-pattern SAD.

How is vitamin D linked to SAD?

Depression is a complex disease, in which many chemicals, genes, medical conditions, neurotransmitters, stressful life experiences and more may contribute to the development. One common treatment for SAD and depression are selective serotonin reuptake inhibitors (SSRIs) which help make serotonin more available. 

Serotonin is a neurotransmitter that acts in regulation of mood, as well as other functions within the body such as sleep, pain and appetite. It has been found that some people with depression have reduced activity of serotonin. Vitamin D has been linked to SAD, and depression overall, due to its involvement in serotonin activity. 

Results from a meta-analysis demonstrated that blood levels of vitamin D (in the form of serum 25-hydroxyvitamin D) had an inverse association with depression risk in an older adult population. This means that those with adequate vitamin D levels were found to have less risk for depression. Research shows that vitamin D impacts serotonin levels by its action as a hormone, promoting the production of enzymes and transporters required for serotonin metabolism. Although this connection can be made with vitamin D and serotonin, studies have had mixed findings whether vitamin D can effectively treat SAD symptoms. 

What other changes in the diet prevent or manage SAD?

Vitamin D

Are you consuming enough vitamin D to support healthy serotonin levels? 

It’s challenging to get adequate amounts of vitamin D from food. Because of this, most people in the U.S. consume less than the Recommended Dietary Allowance (RDA) for vitamin D, which is 600 IU or 15mcg for adults. Individual needs may be higher than the RDA depending on genetic variation affecting vitamin D metabolism. 

The GenoPalate Analysis will help you identify any genetic variants that may warrant a higher intake. Those at additional risk for vitamin D deficiency include those with limited sun exposure, older adults, darker skinned individuals, and people with a BMI >30. Before jumping to supplementation, consider incorporating the following foods rich in vitamin D in your diet: 

-Oily fish (trout, salmon, herring, sardines) 

-Fortified cow’s milk and plant-based milks 

-Eggs (don’t skip the yolk!)

-Mushrooms (treated with UV light) 

If you don’t think you can get sufficient amounts of vitamin D through the diet, you may consider a supplement. Research shows that vitamin D3 is more efficacious than vitamin D2 at raising serum levels. Be careful of supplements that are higher than the upper limit which is 4,000 IU or 100 mcg for adults. These “mega” doses are intended for those with severe deficiencies and should only be taken under guidance from a healthcare professional. 

Omega-3 Fatty Acids

Other nutrients that support brain health are omega-3 fatty acids. These healthy fats are usually recognized for their role in heart health; however, they also play an important role in healthy functioning of the brain and central nervous system. Studies have shown that individuals with depression may benefit from a diet high in omega-3 fatty acids. Some good sources of omega-3 fatty acids include: 

-Nuts and seeds (walnuts, flaxseeds, chia seeds) 

-Plant oils (flaxseed, soybean, canola) 

-Fish (salmon, herring, sardines) 

Fish oil supplements are another popular way of consuming omega-3 fatty acids. Although this may be more convenient, studies show that individuals who consume fish 1-4x per week have better health outcomes than those who consume fish oil supplements. So try incorporating those food sources of omega-3 fatty acids before resorting to supplements for maximum health benefits! 

How else can you modify your lifestyle to help boost mood?

One of the most promising interventions to prevent or treat SAD is light therapy. Those experiencing winter-pattern SAD have decreased sunlight exposure, causing shifts in circadian rhythms which alters serotonin metabolism. Exposure to artificial white light can mimic the sun and act as a “signal” for the circadian clock. 

But, don’t just use any light or lamp in your home. It’s best to use a bright white light with a UV filter to protect your eyes and skin. The standard treatment is 10,000 lux for 30 minutes in the morning, ideally before 8:00 AM. To further help reset your circadian rhythm, plan a sleep schedule where you go to bed and wake up at similar times each day. 

It is likely not surprising that exercise can improve SAD. In fact, to get the mood boosting effects from exercise, it’s most important to focus on frequency of exercise rather than duration or intensity. You can also choose any type of exercise you like! Both aerobic exercise such as jogging and anaerobic exercise such as weight training may be effective at improving depression. 

Since it is best to exercise frequently, incorporate physical activity into your daily life that you enjoy doing. Be creative and think of ways to move your body that might not look like traditional exercise. Try turning on music and dancing to an upbeat song, or play an active game like Twister with your family. Whatever way you choose to move your body, do it often! 

What’s Next?

As with other medical conditions, understanding your risk and how to minimize them is important. Just as important is knowing where to start when making changes to your diet and lifestyle. Meeting with a nutrition professional may help provide additional guidance. Additionally, we now know that certain vitamin and mineral needs can be influenced by our genetics. 

Gaining a better understanding of how your body may respond to certain nutrients or eating patterns to further customize your diet and optimize your health can be a great first step. Learn more about how DNA testing and personalized nutrition can help you eat right for your genes. 


1. Helander, E. E., Wansink, B., & Chieh, A. (2016). Weight gain over the holidays in three countries. New England Journal of Medicine, 375(12), 1200-1202.

2. Yanovski, J. A., Yanovski, S. Z., Sovik, K. N., Nguyen, T. T., O'Neil, P. M., & Sebring, N. G. (2000). A prospective study of holiday weight gain. N Engl J Med, 342, 861-867.

3. Mason, F., Farley, A., Pallan, M., Sitch, A., Easter, C., & Daley, A. J. (2018). Effectiveness of a brief behavioural intervention to prevent weight gain over the Christmas holiday period: randomised controlled trial. bmj, 363.


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