Seasonal affective disorder is commonly referred to as ‘winter depression’ and directly relates to the time period after the clocks go back and the winter months present. The changing seasons affect many people, causing symptoms such as persistent low mood, loss of interest in normal activity, irritability, low self-esteem and increased stress.Vitamin D is thought to be involved in the body’s level of serotonin, the neurotransmitter responsible for mood. Low levels of Vitamin D, due to lack of sunlight during winter months, may play a key role in the rates of SAD.The feelings experienced when suffering from SAD result in loss of interest in exercising, healthy eating and overall wellbeing. Common dietary issues that occur are increased appetite, specifically cravings geared towards carbohydrates, which often result in excess calorie consumption and weight gain.Rather than accepting this as common behaviour during winter, there are some things we can all do to fight SAD and maintain a healthy lifestyle throughout winter.Nutrition is key to develop and maintain a healthy lifestyle throughout the year, and this could not be more valuable during winter.It is recommended we have a daily intake of 600 IU of Vitamin D. There are certain food sources that contain high levels of Vitamin D, ideal for fighting the symptoms of SAD.1. SalmonWithin an 85-gram portion of pink salmon, you can receive 447 IU. Salmon, which is rich in omega-3, is a very versatile ingredient to cook with. You can serve it over a bed of vegetables, flaked through a stir fry or salad.2. Skimmed milkA common household ingredient, cows’ milk is fortified with Vitamin D, providing you with 100 IU per cup.However, don’t worry if you don’t consume dairy, plant-based options such as almond, soy and coconut milk also function as good sources of Vitamin D.3. EggsLove a boiled egg or scrambled egg on toast for breakfast? Fantastic.One egg contains 40 IU Vitamin D. This is a perfect way to start your day and ensure your mood is lifted all day.Additionally, eggs are a good source of lecithin which acts as a mood stabilizer, further helping combat the signs of SAD.4. MushroomsNaturally containing small levels of Vitamin D, mushrooms are a great addition to any meal. Slice them up and throw them into Bolognese sauce, stir fry’s or pasta dishes.5. Orange JuiceDo you start your day with a freshly squeezed glass of orange juice? Perfect, you are on your way to a great day. One cup of orange juice can pack almost a third of your daily Vitamin D requirements, not to forget the high levels of Vitamin C in orange juice, helping ward off the winter colds and flu’s.