High Glycemic Index Carbohydrates are carbohydrates that generate insulin in a more rapid time-frame than others. Limited amounts of high glycemic index carbohydrates are a normal part of any healthy diet and allow natural source tryptophan access to the BBB transport sites which, in turn, increase brain serotonin levels and in low-light situations, melatonin. It is important to find the right balance between natural source tryptophan and high glycemic index carbohydrates. Taking too much protein without carbohydrates can suppress brain tryptophan.

Melatonin is made from serotonin when there is an absence of light. It is secreted by the pineal gland, a pea-size structure at the center of the brain, as our eyes register the fall of darkness. At night, melatonin is produced to help our bodies regulate our sleep-wake cycles. The amount of melatonin released at night varies among individuals, but can be related to age. Children, on average, secrete more melatonin than adults; melatonin levels may decrease with age. However, research has shown that older people with sleep problems do not always have lower melatonin levels than people who experience normal sleep.

Serotonin is a chemical in the body that is made from tryptophan and helps cells communicate with each other. In the brain, increased serotonin levels are associated with an elevated sense of calm, happiness and confidence. Lower levels of serotonin are associated with anxiety, depression, pain and risk of various addictions.

Tryptophan is the rarest of the protein building blocks known as "amino acids". Not only is it the rarest amino acid, tryptophan is also the weakest at competing for access to the transport sites across the BBB. It is an essential amino acid, meaning that the body cannot produce it and must ingest it.