Serotonin has become a key phrase letaley in the fitness and mental health world. Serotonin is a neurotransmitter that stabilizes your mood, helps you sleep, controls bowel function, reduces appetite, helps to form blood clots, high levels of serotonin can impact osteoporosis risks, and low levels of serotonin can increase your libido.
In 2016, an estimated 6.7% of all Americans 18 years and older had had at least one major depressive episode lasting at least 2 weeks.
Currently, the belief is that there is an association between low levels of serotonin in the brain and depression. This is why most health professionals use Selective Serotonin Reuptake Inhibitors (SSRIs) as a treatment for depression.
New research is coming out which is attempting to link the foods that we eat and depression. Inflammation is said to be the cause of depression and an anti-inflammatory diet is said to help relieve some symptoms. I am not sure how true this is, as I cannot find concrete evidence to back this theory up.
Inflammatory foods are things like sugar and high fructose corn syrup, artificial trans fats, vegetable oils and seeds, refined carbohydrates, excessive alcohol, processed meats, dairy, meats (due to high antibiotic usage), etc. etc… I could go on forever with the items that people are calling inflammatory.
The research is still in its infancy, and no definitive relationships have been found. There have been correlations, but as we all know, correlation is not causation. Also, many factors may go into the cause of depression in a person.
Increase Serotonin with Food?
Another way people are using food to relieve some symptoms of depression is by eating foods that can lead to increased production of serotonin. Serotonin is created in two places in the body. 95% is created in the gut, which goes to bodily function such as organ function. The other 5% is created in the brain. This 5% is what affects our mood. Serotonin that is made in the gut cannot cross the blood brain barrier to improve our mood.
This is where tryptophan comes in.
Tryptophan is an amino acid that the body cannot produce on it’s own and must be ingested. But it can make it through the blood brain barrier. Tryptophan is commonly found in eggs, cheese, poultry, salmon, nuts and seeds, spinach, and tofu. Below is a more complete list of the tryptophan levels in food. Keep in mind that being an amino acid, tryptophan has to compete with other amino acids that you have ingested to get into the brain.
One “cheat” that has been found to help improve the chances of tryptophan making it through the blood brain barrier is to eat higher carb, high fat foods. Now you don’t need the entire plate of alfredo, you only need about 25-30 of carbohydrates or 1 ounce to increase your insulin levels to help transport the tryptophan. Only approximately 3% of ingested tryptophan can get converted into serotonin.
Once tryptophan is in the brain, about 1% will get converted into serotonin. This sounds like a low amount, but it is enough to have some impact on brain serotonin levels.
Table 1 Tryptophan Levels Found in Food*
|L-tryptophan*(mg)||Sum of CAAs** (mg)||Ratio|
|Turkey, Skinless, Boneless, Light Meat (per pound, raw)||410||9,525||0.043|
|Chicken, Skinless, Boneless, Light Meat (per pound, raw)||238||5,122||0.046|
|Turkey, Skinless, Boneless, Dark Meat (per pound, raw)||303||7,036||0.043|
|Chicken, Skinless, Boneless, Dark Meat (per pound, raw)||256||5,492||0.047|
|Whole Milk (per quart)||732||8,989||0.081|
|2% Milk (per quart)||551||12,516||0.044|
|Wheat Bread (per slice)||19||317||0.060|
|White Bread (per slice)||22||439||0.050|
|Semisweet Chocolate (per ounce)||18||294||0.061|
|Sweet Chocolate (per ounce)||16||270||0.059|
|Canned Tuna (per ounce)||472||10,591||0.045|
|Cheddar Cheese (per ounce)||91||2,298||0.040|
|Peanuts (per ounce)||65||1,574||0.041|
|Oats for Oatmeal (per cup)||147||2,617||0.056|
|Dried Prune (one)||2||27||0.074|
|Banana (one medium)||11||237||0.046|
|Apple (one medium)||2||70||0.029|
**CAAs = Isoleucine, Leucine, Phenylalanine, Tyrosine, and Valine, the five large neutral amino acids typically included in the tryptophan/CAA ratio.
*Table from L-Tryptophan: Basic Metabolic Functions, Behavioral Research and Therapeutic Indications
Although there is more research on the connection between tryptophan and brain serotonin levels, there has never been concrete evidence that low serotonin levels is the cause of depressed states. This makes it even more confusing because we are trying to find solutions to the cause of a problem, and we’re not even sure if it is the cause….
Please note that I am not a doctor, nor am I saying that you can/should cure your depression or mood disorders with food. This is a rabbit hole that I fell into and felt I should share this information with you so that things are more clear because they were all sorts of muddy for me.
Please consult your doctor before you change your diet or alter any of your current medications.
Substance Abuse and Mental Health Services Administration. (2017). Key substance use and mental health indicators in the United States: Results from the 2016 National Survey on Drug Use and Health (HHS Publication No. SMA 17-5044, NSDUH Series H-52). Rockville, MD: Center for Behavioral Health Statistics and Quality, Substance Abuse and Mental Health Services Administration. Retrieved from https://www.samhsa.gov/data/
Richard, Dawn M et al. “L-Tryptophan: Basic Metabolic Functions, Behavioral Research and Therapeutic Indications” International journal of tryptophan research : IJTR vol. 2 (2009): 45-60.
Judith Wurtman and Richard Wurtman, “The Trajectory from Mood to Obesity,” Current Obesity Reports, December 7, 2017, doi:10.1007/s13679-017-0291-6