Supplements for Reactive Dogs: Tryptophan and 5-HTP

This is part of an ongoing series on supplements recommended on the internet for reactive dogs. I am not a vet, nor have I personally tried most of these supplements with my dog, which means that I cannot tell you if you should or shouldn’t use them with your own. I’m also a lazy researcher, and used Wikipedia for my starting point. Google filled in the rest, and while I think I’m pretty good at separating the good sites from the propaganda, I cannot verify the accuracy of their claims. If you want to use a supplement with your dog, do your own research, and consult with your vet.

In other words: Use this information at your own risk.

Tryptophan, sold as Nutricalm
What is it? How does it work?
Tryptophan is an essential amino acid, which means that the body cannot make it on its own. It must be ingested. In the body, it is converted into 5-HTP, then into serotonin, (which can be converted into melatonin), and as such, is typically used as a sleep aid, or to treat seasonal affective disorder or depression.

In animals, it is used to decrease aggression and impulsivity, to stabilize moods and as an adjunct to treating compulsive disorders.

What are the risks of using it?
Tryptophan was banned in the US for many years after it was linked to eosinophilia-myalgia syndrome (EMS) in 1989, which resulted in 37 deaths and caused 1,500 people to be permanently disabled. It is commonly believed this was the result of an impure batch, but some people believe that the tryptophan caused the production of metabolites which resulted in excess histamine levels in the body.

More typical side effects include vomiting and diarrhea, but may interact with certain drugs, so check with your veterinarian before use.

Availability and dosing considerations.
Tryptophan is naturally occurring in many foods, especially proteins. It is especially plentiful in red meats, dairy products, certain seeds, eggs, and oddly enough, oats. It can also be purchased as L-tryptophan in health food stores. It is marketed for animals under the brand name Nutricalm, with capsules of 75mg and 150mg readily available.

Are there any scientific studies supporting its use in canines?
Tufts University did a study which found that 10mgs per kilo, given twice a day, significantly reduced “territorial and dominance aggression.”

To learn more about tryptophan, read any of the above links, as well as this article.

5-HTP
What is it? How does it work?
5-HTP, short for 5-hydroxytryptophan, is a metabolite of tryptophan, and is ultimately converted into serotonin by the liver. Like tryptophan, it is used to treat canine aggression, and compulsive disorders, reduce impulsivity, and to stabilize moods.

What are the risks of using it?
The most common side effect is diarrhea.

Since 5-HTP is converted into serotonin by the liver, it results in a high blood serotonin level, which has been implicated in heart valve disease. Although it is similar to tryptophan, it does not get diverted into other processes (excess tryptophan can be converted into niacin, too). This means that excess 5-HTP may result in serotonin syndrome, which can be deadly. Apparently, this is more common in dogs than in humans.

Availability and dosing considerations.
Although it is not found in food, 5-HTP can be made by the body if it has sufficient tryptophan. It can purchased in capsules of 50mg or 100mg.

Are there any scientific studies supporting its use in canines?
The Tufts studies found that 1 mg per pound, twice a day, resulted in a reduction in canine aggression.

Edit February 2015: Why I Chose Medication Instead of Supplements