Carbohydrates can affect levels of serotonin, but only indirectly. Eating carbohydrates together with protein-rich foods may boost the amount of tryptophan in your brain; tryptophan is then converted into serotonin. However, there are no guarantees that you will change levels of serotonin by simply adjusting your carb intake. Other nutritional variables, as well as factors unrelated to your diet, such as sleep and exercise, also influence serotonin production.

Serotonin Overview As a neurotransmitter, serotonin carries signals between nerves. In the brain, serotonin regulates mood, pain perception, hunger and sleep cycles. It’s also active in your gut, but carbohydrates only affect serotonin in your brain. A structure called the blood-brain barrier determines which substances in the bloodstream get through to your brain. Since the barrier blocks serotonin, it must be synthesized inside the brain from an amino acid called tryptophan.

Tryptophan's Role Tryptophan is an essential amino acid, so it must be obtained through your diet. After it’s consumed, tryptophan gains access to your brain through a transport system built into the blood-brain barrier. However, it competes with other amino acids to access the same transport structures. Tryptophan is outnumbered because foods contain a larger proportion of other amino acids, so its chances of getting into your brain are low. The best sources of tryptophan are poultry, fish, meat, milk and dairy products, eggs, soy products and nuts.

Impact of Carbohydrates When you consume sugars and starches, your pancreas releases insulin, which is responsible for transporting sugar from your bloodstream into cells. Insulin also lowers the amount of amino acids in your blood except for tryptophan, which avoids insulin's influence because it tends to bind with the protein albumin. As a result, the concentration of tryptophan increases and more transports across the blood-brain barrier.

Choosing Carbs While carbs increase the levels of tryptophan in your brain, and higher levels of tryptophan result in more serotonin, simply adding carbs does not guarantee you’ll increase serotonin levels. Some complex carbs, such as brown rice and beans, are also good sources of protein, and serotonin synthesis goes down when you consume large amounts of amino acids, according to the "Encyclopedia of Neuroscience." While simple carbs such as processed white bread and baked goods will trigger insulin without adding much protein, fresh fruits offer a healthier alternative.

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