Which Substances Promote Good Sleep?

Three Key Substances.

There are three substances that are key to understanding how nutrition can affect the brain chemistry that promotes good sleep:

Tryptophan,
Serotonin, and
Melatonin

What is tryptophan?

All protein foods are composed of amino acids and tryptophan is one of them. It is the rarest of the amino acids, and is found in foods like turkey, steak, chicken and pumpkinseeds, and to a lesser extent in peanuts, sunflower seeds, beans and milk. Tryptophan is important because when it reaches the brain, it converts to an important chemical called serotonin.

What is serotonin?

You may have heard of serotonin because of its connection to drugs such as Prozac, which are known as selective serotonin reuptake inhibitors (SSRIs). Serotonin is actually a chemical that carries messages between brain cells (neurones) and other cells. Decreased serotonin levels can lead to anxiety, depression, and increased cravings for carbohydrate foods. At night-time, serotonin undergoes two metabolic changes to become melatonin, the chemical that induces sleep.

What is melatonin?

Melatonin is a hormone that helps to regulate the body’s circadian rhythm and promotes restful sleep. It is produced from serotonin in the evening to help us sleep. The best way of ensuring optimal melatonin production is to sleep in as dark an environment as possible. As we have mentioned, even low amounts of ambient light will suppress the production of melatonin which will affect not only sleep but have other health consequences as well.

Eating Tryptophan-rich foods is not the entire answer

If you’re having difficulty sleeping, it’s important that you increase the level of tryptophan in your diet; however it’s not that straight forward.

Natural food source tryptophan does not exist in isolation. Tryptophan belongs to the family of amino acids all of which bind together to form proteins. Various proteins vary in how much tryptophan is present. Research by Dr Craig Hudson has determined that gourds seeds (pumpkin and marrow or squash seeds) contain one of the highest sources of tryptophan known. Eating more of these seeds, however, will not increase your brain tryptophan levels because of what is known as the ‘tryptophan paradox’ in that eating protein foods rich in tryptophan will decrease rather than increase your brain tryptophan levels.

The reason behind the Tryptophan Paradox is something called the Blood-Brain-Barrier (BBB), a shield that protects the sensitive brain from noxious substances that are in the blood whilst allowing certain nutrients into the brain. In the case of tryptophan, access to the brain happens across a transporter that recognizes the tryptophan molecule and then facilitates its absorption into the brain.

The problem with tryptophan is that it shares this transport site with other amino acids which are far more abundant and better able to “stick” to the transporter. The result is that a high protein food contains tryptophan but also contains many more of the other amino acids that will out-compete tryptophan for access to the brain transporter site. Consequently, when you eat protein foods your blood tryptophan levels go up but your brain levels go down. Competition between tryptophan and other amino acids at the BBB transport site is the reason behind the tryptophan paradox and this is the primary reason why high-protein diets cause you to become more anxious, irritable and experience difficulty sleeping.