Previously I have written about the benefits of light therapy in treating seasonal affective disorder. Light therapy is a popular choice with those looking for a drug-free approach to dealing with SAD or the ‘winter blues’. An equally important consideration is how diet affects mood and symptoms in those with SAD – and in particular the importance of the macronutrients carbohydrate, protein and fat in the management of this condition.
Hormones and SAD
SAD is characterised by symptoms such as low mood, carbohydrate cravings, weight gain and fatigue (1, 2). These symptoms are linked to hormones that control our mood and energy levels.
Our body’s natural anti-depressant hormone, serotonin, is stimulated by light. The more light we have during the daytime, the more serotonin we produce. In the darker months of autumn and winter, serotonin levels can drop, resulting in feelings such as low mood, lack of energy and food cravings.
Likewise, darkness stimulates the hormone melatonin, which lowers body temperature and causes tiredness and feelings of fatigue.
How can diet help?
Those with SAD are thought to crave sugary and starchy foods because these types of carbohydrate temporarily boost levels of the body’s natural anti-depressant serotonin. These types of foods also boost energy levels and raise body temperature, countering the effects of melatonin.
Eating this type of diet can only be a temporary ‘fix’ however. In fact, a carbohydrate-rich diet based around sugary and starchy foods, leads to unstable blood sugar levels. This in turn can create a variety of symptoms that we might link to the ‘winter blues’ – moodiness, fatigue, foggy thinking and food cravings.
The solution is to eat a diet based around ‘low glycemic index’ carbohydrates that help to keep blood sugar levels stable. Whole grains such as brown rice and oats, as well as fresh fruits and vegetables are the wisest choices of carbohydrate.
Including a source of lean protein (such as chicken, turkey, eggs, beans or lentils) with each main meal is also a good idea. This helps the body in two ways. Firstly, including protein with each meal helps to control blood sugar levels, fighting off energy dips and cravings. Secondly, protein provides a source of the amino acid tryptophan, which the body can convert to serotonin. Including foods high in tryptophan – such as chicken, tuna, tofu, eggs, nuts, seeds and milk – in your daily diet can help to support your body in making serotonin.
Finally, healthy fats have been extensively studied in relation to depression and mood. Omega-3 fats also have a role in the production and utilisation of serotonin. Inflammatory chemicals in the body can cause serotonin deficiency in the brain. Omega-3 oils can reduce levels of these inflammatory chemicals, therefore helping to boost the brain’s serotonin levels.
The importance of omega-3 in dealing with SAD might explain the low incidence of SAD in Icelanders who have a diet high in oily fish (3). Ensuring a good level of omega-3 in your diet is essential. Including oily fish such as sardines, mackerel, herring or salmon in your diet can help to boost levels of omega-3, as can eating flaxseed oil, walnuts and omega-3 eggs.
Formal research in this area is limited, with many studies simply looking at the impact of a single meal on symptoms of SAD. This is an inadequate assessment of the role of diet. One study that looked at the longer term impact of diet on SAD showed promising results (4). I have certainly found in clinical practice that patients need to be consistent in their dietary choices in order to see an improvement in symptoms over time.
A well-managed diet, along with light therapy (such as a sunrise alarm clock or SAD light box), appears to be a safe approach to managing SAD. Of course carbohydrates, protein and fats are not the only nutrients of importance to those with the winter blues. Part 3 will examine the evidence behind other nutrients and dietary supplements in the support of SAD.
Written by Nadia Mason
1. Sher L. Genetic studies of seasonal affective disorder and seasonality. Comprehensive Psychiatry, 2001, Vol. 42, No. 2, pp. 105-110.
2. Magnusson A, Boivin D. Seasonal affective disorder: an overview. Chronobiology Int. 2003. 20(2):189-207.
3. Cott J, Hibbeln JR. Lack of seasonal mood change in Icelanders. American Journal of Psychiatry. 2001.
4. Wells, A, et al. (1998) Alterations in mood after changing to a low-fat diet. British Journal of Nutrition 79(1):23-30.
5. Image courtesy of Marcuso.