Amino acids, particularly branched-chain amino acids (BCAAs), are popular in fitness circles for their bodybuilding powers: They may be tapped as an alternative source of energy, thus boosting athletic performance, and they prevent muscle loss and aid in muscle recovery and repair. They may even help with weight loss by upping your body’s fat-burning capabilities. But it turns out the benefits of amino acids go beyond physical health and into the realm of mental health. Read on to find out what amino acids your body needs to help boost your mood.

What Are Amino Acids?

Before we dive into the specific amino acids that can alter your mood, some basics on amino acids: They are the building blocks of protein, which in turn are the building blocks of muscle. There are 20 amino acids in all, and nine of those are essential, meaning they’re not naturally produced by the body and thus have to be taken from outside sources (food and supplements): phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, and histidine. Valine, leucine, and isoleucine make up BCAAs.

Non-essential amino acids are those naturally produced by the body. All amino acids perform a specific function, ranging from muscle recovery and wound healing to helping in hormone production and improving sleep.

In order to get all essential amino acids, you have to consume complete proteins like meat, dairy, eggs, and poultry. Those on a plant-based diet need to the right combination of food as most plant sources are incomplete proteins, meaning they’re lacking some essential amino acids. (Soy is an exception as it is considered a complete protein.)

Protein supplements are especially helpful for those who are undergoing some form of recovery, whether from illness, injury, or an intense workout. This is the reason the buff guys at the gym walk around with a shaker—shakes made with whey protein provide amino acids that help with muscle recovery.

Mood-Boosting Amino Acids

Only a couple of decades ago, most people didn’t even see depression as an illness that can be addressed through medical means; it was just something one was expected to “snap out of.”

These days, we have a better understanding of and a growing concern for mental health. We now know the importance of neurotransmitters—those chemical messengers that carry and boost signals between cells in the body, having an effect on everything from heart rate to appetite to mood.

A neurotransmitter imbalance can lead to depression, anxiety, obsessions, and hormone dysfunction among a host of other illnesses. Where do amino acids come into play? Amino acids are the precursor to neurotransmitters, meaning they are necessary to produce neurotransmitters.

If you have a neurotransmitter imbalance, it may because your body isn’t producing enough non-essential amino acids. Supplementing with certain amino acids may help that:

Theanine. This non-essential amino acid can be found in tea leaves. It has been shown to boost levels of gama amino butyric acid (GABA), which keeps you calm and relaxed, as well as of serotonin (a.k.a. the happy hormone) and dopamine (associated with feelings of bliss and motivation).

According to an article in Psychology Today, theanine also enhances alpha brain waves, which are linked to a somewhat meditative state. Thus, getting enough theanine can help reduce anxiety and lower stress.

Tyrosine. Another non-essential amino acid, tyrosine is a precursor for epinephrine, norepinephrine, and dopamine, which seem to have antidepressant effects. One study published in the Annals of Neuroscience concluded that tyrosine may be an effective treatment for depression. Further studies need to be conducted.

Glutamine. Glutamine and stress are closely linked: In times of stress, glutamine levels may be deficient, and this deficiency may lead to even more stress an anxiety. Supplementing your glutamine can help produce GABA, help your relax, increase your concentration, and improve sleep quality. It may even help keep depression at bay.

Tryptophan. A study published in Acta Psychiatrica Scandanivica found some evidence that supplementing with tryptophan may be an effective treatment for depression as it increases serotonin production but more studies need to be conducted.

If you’re thinking of supplementing with amino acids to help boost your mood, it’s best to first consult with your physician. Don’t be afraid to seek help for any mental health issues that you suspect you might have.