Managing the Winter Blues With a Healthier Gut

Anne Danahy, MS, RDN
Scottsdale, Arizona

Many people look forward to winter, or at least easily adapt to the weather and lifestyle changes that come with it. For an estimated 5% of the US population,1 however, the reduced levels of sunlight in the winter months lead to a type of mild depression known as the “winter blues,” or a more severe form of seasonal or cyclical major depression known as seasonal affective disorder (SAD). There are treatments that can help alleviate symptoms, but prevention may start in the gut.

Who Gets the Blues or SAD?

Seasonal depression affects more women than men.1 Those who live further from the equator are at greatest risk, as are those with a personal or family history of depression. SAD is a subtype of major depressive disorder. Symptoms include depression (most of the day, nearly every day), anxiety, lethargy, social isolation, sleep problems, and an increased craving for carbohydrate foods such as sweets or starches, which may result in weight gain.1,2

Traditional Treatments for SAD

It is believed that those who experience SAD have problems regulating the neurotransmitter serotonin and, possibly, the hormone melatonin. Researchers have noted increased levels of a serotonin transporter protein on brain scans of those with seasonal depression.3 Higher levels of serotonin transporter cause lower levels of serotonin activity, which leads to depressive symptoms. Healthy individuals appear to be able to downregulate serotonin transporter in response to less daylight.

Melatonin is produced by the pineal gland in response to darkness. It helps to manage circadian rhythms and causes sleepiness when it gets dark. Melatonin may increase the feelings of fatigue or lethargy in those with seasonal symptoms, especially when serotonin activity is reduced.4

Mild cases of the winter blues may not need treatment, but more severe cases of SAD are often treated with one or a combination of approaches.2,5 Antidepressant medications can help regulate serotonin levels but come with adverse effects. Light therapy has been shown to reduce serotonin transporter levels4 and is effective in improving symptoms without the adverse effects of medications. Vitamin D supplementation may also be helpful in alleviating symptoms. Insufficient levels of the vitamin are associated with depressive symptoms, and those living in northern latitudes may be more likely to have lower levels, especially during the winter months.6

The Gut Microbiome and Depression

In addition to the above treatments, RDs should be aware of the many ways the beneficial bacteria in our gut influence mood, and especially depression. Boosting these healthy bacteria may help to prevent or at least manage seasonal depression.

  • In animal studies, changing in the gut microbiome by administering Lactobacillus and Bifidobacteria probiotics affects brain behavior and various mood disorders, including anxiety and depression.7,8
  • Research on diet and mood disorders in humans has found that diets high in processed and fast foods are associated with less microbial diversity,9 as well as greater risk of depression,10 while diets rich in whole foods, fruits, and vegetables are associated with greater diversity and less depression.
  • The microbiome is thought to affect circadian rhythms and sleep cycle or sleep quality,11 which may in turn influence seasonal depression symptoms.
  • In vitro studies have demonstrated that certain bacterial strains can synthesize tryptophan, which is a precursor to serotonin, as well as serotonin itself.8

Those who experience mild to more severe seasonal depression may be more likely to crave refined carbohydrates or higher-fat foods. Especially as winter approaches, RDs should educate patients about the importance of probiotic supplements, prebiotic- and probiotic-rich foods, and replacing refined carbohydrates with healthy diet patterns such as the DASH or Mediterranean diets. These are beneficial not just for managing for winter weight, but also for feeding the gut and combatting the winter blues.


  1. Seasonal depression. Mental Health America. Accessed December 5, 2018.
  2. Seasonal affective disorder. National Institute of Mental Health. Updated March 2016. Accessed December 5, 2018.
  3. Mc Mahon B, Andersen SB, Madsen MK, et al. Seasonal difference in brain serotonin transporter binding predicts symptom severity in patients with seasonal affective disorder. Brain. 2016;139(5):1605-1614.
  4. Tyrer AE, Levitan RD, Houle S, et al. Serotonin transporter binding is reduced in seasonal affective disorder following light therapy. Acta Psychiatr Scand. 2016;134(5):410-419.
  5. Melrose S. Seasonal affective disorder: an overview of assessment and treatment approaches. Depress Res Treat. 2015;2015:178564. doi:10.1155/2015/178564.
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  11. Li Y, Hao Y, Zhang B, Fan F, Zhang B. The role of microbiome in insomnia, circadian disturbance and depression. Front Psychiatry. 2018;9:669.