It's felt by 7% of us every year. It's the leading cause of disability for adults 15-45yrs old, and it saps $70 billion from Americans each year, for medical costs and lost work. It increases the risk of heart attack fourfold, can hasten disease progression in the elderly... and it often causes subtle to striking carbohydrate cravings.
Countless research studies have found a significant relationship between low mood or depression with cravings for sugary or carbohydrate-rich foods. Why the carb cravings?
First, when you're depressed or even just feeling blue, sugary foods bring comfort. They taste good. Seeking pleasure when you're down isn't a bad thing--it's a healthy adaptation for getting on with life by helping ourselves improve our mood. But when the pleasure of food becomes a habitual coping mechanism to feel better, you may be on a slippery slope of emotional eating, which can lead to health problems, added depression, and a new problem to work through on top of your mood troubles. So, while eating sugary foods can help you feel better because of the hedonic pleasure they bring, proceed slowly and with caution, knowing your responses to life trials and your actions meant to improve your mood may cause unhealthy habits and ultimately worsen your mood.
Second, in addition to the pleasure the taste of sweets bring, there is a more indirect mechanism that drives our carb cravings when we're sad and low; carbs indirectly increase brain serotonin. You've probably heard of serotonin, the chemical in our brain that promotes good mood and is deficient in major depression. Serotonin is the target of the most common anti-depressants; by increasing serotonin in depressed persons, depression can be significantly improved.
With all this talk about sweets, it may surprise you that serotonin is a product of the amino acid tryptophan. Since tryptophan is found in protein sources, you probably would expect to boost serotonin by eating more high-protein foods. And, while that does indeed increase the amount of tryptophan in the body, it doesn't mean the brain is getting more serotonin.
There is a magnificent protective blood-brain barrier that prohibits many different chemicals from entering the brain with all of its blood vessels. While tryptophan can enter into the brain's cells through a transporter, certain other large amino acids from dietary proteins compete for entry and can crowd out tryptophan at this transporter. There simply aren't enough transporters for them all to flood into the brain. So less tryptophan enters the brain, and less serotonin ("5-HT" in the diagram above) is produced.
When you eat carbohydrates, your body release insulin, which is needed to bring glucose into cells. However, insulin signaling also causes certain amino acids to enter cells--not tryptophan, but tryptophan's competitors for brain entry. With less competition because the other amino acids have entered other cells like those of muscles, fat, and the liver, more tryptophan is able to enter the brain, and more serotonin can be produced.
So what does this mean? Eat more carbs when you're feeling the blues?
While carbohydrates can cause a temporary improvement in mood through increased pleasure and serotonin, it is only a temporary effect. It doesn't last. Relying on carbs to feel good can have negative health effects. Eating a high carbohydrate diet, especially the simple sugars we usually crave when we crave carbs, can cause spikes and dips in blood sugar during the day, leaving you to feel tired, anxious, and irritable. Simple sugars also only briefly satisfy your hunger, whereas proteins, fats, and fiber leave you feeling satisfied longer; relying on carbs can lead to overeating and weight gain.
What is the best nutrition advice for depression?
1. Practice general healthy eating. Whole grains, fruits, vegetables, lean meats, fish and dairy--balance, variety, and moderation. Getting the nutrients and energy your body needs is important for maintaining physical health when you're not feeling as upbeat as usual.
2. Eat at regular intervals. A symptom of depression is a significant change in appetite--usually a significant loss of appetite. Plan to eat regular meals and stick with your plan, knowing you're going to feel better soon. Eating with others may help improve your appetite and engaging in social interaction may relieve your blues too.
3. Enjoy your food with all your senses. Guide your attention to the tastes of your food. Do you taste something savory? Salty? Sweet? Bitter? Does your food look desirable? What does it feel like in your mouth? Is it chewy, crunchy, smooth, velvety? What different aromas can you smell? By practicing mindfulness and engaging your senses in your meal, you can boost your pleasure in eating and through nutrition brighten your mood.