Proteins are the building blocks of life -- and a chain of amino acids form the basic structure of protein. Tyrosine is a nonessential amino acid, meaning that the body makes it from other amino acids; however, during times of stress or illness, your body might not make all the tyrosine it needs -- and you would have to obtain it from dietary sources. A banana contains a high level of tyrosine in addition to healthy nutrients such as potassium, magnesium and the B vitamins. Other food sources of tyrosine include eggs, dairy products, fish, poultry, grains, nuts, seeds and legumes.
Why the Body Needs Tyrosine
The body needs tyrosine to produce the neurotransmitters dopamine, epinephrine and norepinephrine -- all brain chemicals that influence mood. Neurotransmitters are chemical messengers through with your brain cells communicate. In other words, they control how we think and feel. Tyrosine is the precursor to the class of neurotransmitters, which speed up brain activity. Dopamine plays a role in regulating energy, alertness and mental concentration. Epinephrine and norepinephrine are stress hormones that also affect different body functions.
Energy and Mental Alertness
Low levels of norepinephrine may be associated with decreased alertness, concentration, motivation and energy -- symptoms common in depression. While the neurotransmitter dopamine contributes to healthy immune and autonomic nervous system function, stress and lack of sleep can deplete the body’s stores. However, once the amino acid tyrosine crosses the blood-brain barrier, a person’s energy level and alertness increase. Tyrosine also helps regulate hormones produced by the thyroid, adrenal and pituitary glands. These glands produce the hormones responsible for regulating energy.
Although it's uncommon for individuals to be deficient in this nonessential amino acid, a low level of tyrosine in the blood can cause symptoms such as low pressure and a low body temperature. Tyrosine deficiency may also be a sign of an underactive thyroid. Common symptoms of an underactive thyroid include fatigue, lack of energy and slowed cognition. While bananas have a reputation for being a high-energy food, the fruit -- particularly a ripe banana -- has a high glycemic index, which means that it releases glucose into the bloodstream rapidly. The result is a fast rise in your blood sugar level, giving you a quick burst of energy instead of long-lasting endurance.
Additional Nutrients in Bananas
Besides being a source of the amino acid tyrosine, bananas are high in dietary fiber, potassium and other essential nutrients. The banana is a complex carbohydrate that offers additional nutritional value. Dietary fiber in the banana slows digestion and helps regulate the production of serotonin -- the “feel good” hormone. The mineral magnesium found in bananas helps the body produce energy and elevates mood. The B vitamins also play a role in energy metabolism. In addition to being a natural source of tyrosine, a banana is a source of tryptophan, an amino acid that the body needs to make serotonin, a chemical which has a calming effect on the brain.