The idea that cheese can make you sleepy is a common piece of folklore, often linked to the Thanksgiving turkey effect. Many people report feeling lethargy after eating cheese, especially later in the day. This widespread personal experience raises the question of whether cheese acts as a somnolent food or if other factors are at play. Understanding the composition of cheese and the body’s digestive processes helps determine if this dairy product truly induces drowsiness.
Examining the Tryptophan Connection
The popular theory connecting cheese to sleepiness centers on the amino acid L-tryptophan. Tryptophan is an essential amino acid, meaning the human body cannot produce it and must obtain it through diet. It serves as the precursor to the neurotransmitter serotonin, which regulates mood. Serotonin is then converted into melatonin, the hormone that governs the sleep-wake cycle and promotes sleep.
Cheese naturally contains tryptophan, with hard varieties like cheddar, Swiss, and cottage cheese often containing higher concentrations. The underlying logic suggests that consuming this tryptophan-rich food increases the brain’s supply of the precursor, thereby boosting melatonin production and causing drowsiness.
The Physiological Reality of Tryptophan Absorption
While cheese contains tryptophan, the physiological reality of how this amino acid reaches the brain makes it an inefficient sleep inducer. Tryptophan must cross the blood-brain barrier (BBB), a selective membrane that protects the brain. It uses a dedicated transport system, but this system is shared with several other large neutral amino acids (LNAAs), including leucine, isoleucine, and valine.
Since cheese is a high-protein food, it delivers a high concentration of all these competing LNAAs into the bloodstream simultaneously. This influx creates fierce competition for the shared transporters, limiting how much tryptophan can successfully cross the BBB and enter the brain. This competition lowers the crucial tryptophan-to-LNAA ratio. The dose of tryptophan in a typical serving of cheese is insufficient to overcome this competitive blockade, meaning very little is available for conversion into serotonin and melatonin.
Other Dietary Factors Contributing to Drowsiness
If tryptophan is largely ineffective, the feeling of tiredness after eating cheese is likely due to other aspects of the meal and digestion. Cheese is high in both fat and calories, which significantly impacts the digestive workload. Digesting a high-fat, high-calorie meal requires the body to expend a substantial amount of energy, a process known as diet-induced thermogenesis. This energy expenditure can lead to fatigue as the body redirects resources toward the gastrointestinal tract.
Studies show that diets high in fat may be directly linked to increased daytime drowsiness. This effect may involve the release of certain gut neuro-hormones that promote sleepiness.
Cheese is rarely eaten in isolation; it is often part of a larger meal that includes high amounts of carbohydrates. The consumption of a high-carbohydrate meal alongside cheese can indirectly facilitate tryptophan’s entry into the brain, but not because of the cheese itself. Carbohydrates trigger a strong insulin release, which promotes the uptake of many competing LNAAs into skeletal muscle tissue. This action effectively reduces the number of competing amino acids in the bloodstream, thereby improving the tryptophan-to-LNAA ratio. The resulting drowsiness is often more attributable to the overall meal size, the insulin spike, and the high fat content rather than the small amount of tryptophan in the cheese.