What's the Best Diet for Seasonal Depression?
Updated: Oct 12
Fall is definitely my favorite time of year. But for some people, the waning daylight and shorter days can bring an increase in symptoms of depression.
Seasonal affective disorder (SAD), sometimes called seasonal depression, is a subtype of major depression corresponding with the change of seasons and affects two to three percent of the population. Whereas major depression can occur at any point of the year, SAD is associated with specific seasons and unlike in major depression, once the difficult season is over, patients have full remission of their symptoms. Most people are affected during the fall and winter months, but some people experience SAD during spring and summer. If you are female, have a history of depression, and/or live far away from the equator, you are at greatest risk for SAD. But, remember, even people without a clinical diagnosis may have depressive-type symptoms as summer turns to fall.
Symptoms of SAD include:
Low energy levels
Overeating (especially carbohydrates)
Retreating from your normal social activities
What causes SAD?
While the exact cause of SAD is unknown, it is believed that one root cause involves the dysregulation of serotonin. Many mental health conditions have serotonin dysregulation in common and the serotonin levels of healthy people are known to vary when the seasons change. In addition to serotonin alteration, some people with SAD have a higher than normal amount of melatonin (the hormone that helps prepare the body for sleep) and lower than normal vitamin D levels.
What's the treatment for SAD?
Bright light therapy can be very helpful for people with SAD, but nutrition-related changes to target the health of the gut and optimize vitamin D levels can be helpful too.
Serotonin and the gut
We've all probably heard about serotonin as a neurotransmitter and neuromodulator that regulates mood, emotions, appetite, and sleep. But serotonin also acts as a hormone that links your emotions and cognition with your gastrointestinal tract function. That's right, your gut and your brain are connected by the vagus nerve and this nerve allows the bacteria in your gut to actually talk to your brain!
90 percent of serotonin is made in the cells of the GI tract and your gut bacteria communicate with these cells by making short chain fatty acids and bile acids that in turn regulate serotonin. So, if your gastrointestinal tract is unhealthy and/or your gut bacteria aren't receiving their preferred fuel, your serotonin is likely being affected. In fact, people with symptoms of depression typically have higher levels of potentially harmful bacteria and lower levels of helpful bacteria. This gut dysfunction can be targeted with food - in essence, we remove foods that are known to damage the beneficial bacteria and then add back their preferred foods to help balance the gut and restore normal serotonin creation and function in the body.
Nutrition-related changes to improve SAD symptoms
I always personalize meal plans for my clients, but there are a few recommendations that are appropriate for everyone when it comes to preventing and managing SAD symptoms:
1. Avoid sugar: Sugar is known to affect glucose (blood sugar) in the brain causing inflammation (which can cause depressive symptoms), but it may also decrease bacterial diversity, increase intestinal permeability, and increase inflammation in the gut. Essentially, sugar damages the gut lining and is harmful to your helpful gut bacteria.
And before you switch to artificial sweeteners to get that sweet fix, the
research indicates that these calorie-free sweeteners are just as harmful to the gut
microbiome, plus they create an environment in the body that can lead to
metabolic diseases like diabetes.
2. Avoid inflammatory fats: Fat is crucial for healthy brain function, but the type of fat you eat definitely affects depression risk and your gut bacteria. People who eat a high amount of omega-6 fats like those found in vegetable oils, margarine, and hydrogenated vegetable oils are four times more likely to suffer from depression. But those consuming more omega-3 fats have a lower risk of depression. It's not that omega-6 fats are bad, in fact, it's the ratio of omega-6 to omega-3 fats that matters. The typical diet in the US is high in omega-6 fats and low in omega-3 fats. This imbalanced ratio (for most people it's, 15 to 1) changes how we regulate our emotions and can lead to depression. And, just like sugar, inflammatory fats can negatively affect the gut lining and increase gut inflammation.
3. Consider a modified Mediterranean diet: As a base meal plan, the modified Mediterranean diet has been shown to help improve symptoms of depression. This meal plan is high in vegetables, fruits, whole-grain cereals, oily fish, legumes, unsalted nuts and seeds, and extra virgin olive oil. In addition, it includes a low to moderate amount of reduced-fat dairy products and lean red meat.
4. Add healthy fats: Monounsaturated fats (MUFAs) tend to lower depression risk, so switching from inflammatory fats to MUFAs can be an easy way to decrease SAD symptoms. Good sources include olives, olive oil, avocado, avocado oil, almonds, cashews and nut butters. In addition, omega-3 fats specifically can lower brain inflammation and protect your nerve cells. Eating high-quality fatty fish such as salmon, mackerel, sardines, and anchovies twice per week can help keep your omega-6 to omega-3 ratio balanced. If you don't like to eat fish, high-quality fish oil supplements can be a substitute, but speak to your provider.
5. Add in fiber and resistant starch: Remember the preferred fuel we were talking about for your gut microbes? Fiber and resistant starch are two of the things our gut bacteria thrive on. Most people are not eating even half the recommended amount of dietary fiber each day. I recommend aiming for at least 25 grams of fiber per day for women and 38 grams per day for men. If you are following a Mediterranean-type diet, you will naturally increase fiber intake, but good food sources of fiber include ancient grains, legumes, beans, fruits, and vegetables.
We said earlier that the gut bacteria regulate serotonin by creating short-chain fatty acids. Resistant starch is one option for increasing production of these valuable acids and can be found in cooked, cooled and then reheated starches like potatoes and rice, but green bananas, uncooked oats (YAY overnight oats!!!), white beans, and lentils are also great sources.
Grab my favorite overnight oats recipe here.
5. Optimize vitamin D: We probably all know vitamin D is the sunshine vitamin, but as we move from summer into fall, temperatures drop and daylight hours shrink. You're likely to spend less time outside, but even if you do get outside in fall and winter, if you live in the northern hemisphere, the sun just isn't strong enough to create adequate amounts of vitamin D in the body. Vitamin D is important for serotonin regulation and suboptimal vitamin D levels are associated with depression. Vitamin D supplementation has been shown to improve SAD symptoms and it's important to know your vitamin D level. It's a simple blood test and once you know your level, you can work with your provider to create a plan to optimize your vitamin D level. There are some food sources of vitamin D like egg yolks, mushrooms, and fatty fish, however they are not adequate to maintain the vitamin D level even for those with a normal vitamin D.
Of course, every person is unique and a personalized approach is required. But, making nutrition-related changes and improving vitamin D levels can be powerful to prevent and/or improve SAD symptoms.
**This information is not meant to diagnose or treat any medical condition, but is for informational purposes only**
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