Protein and Medications

The system that transports carbidopa/levodopa from the small intestine to the brain is the same system that transports amino acids. Both carbidopa/levodopa and amino acids must enter the bloodstream through the intestinal wall and then cross the blood-brain barrier to enter the brain. If too many amino acids are present along with carbidopa/levodopa, the medicine competes with the amino acids for absorption, and it won't enter the carrier system quickly. Similarly, some amino acids compete with carbidopa/levodopa for absorption in their brain. Their presence at the time when carbidopa/levodopa makes its way to the blood-brain barrier will delay the time it takes for the brain to transform the medication to dopamine and, therefore decrease the medication's efficacy. This, too, can lead to delayed or only partial ON times.

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In your stomach, protein is broken down into amino acids, which then travel to your small intestine. For your carbidopa/levodopa to work most effectively, it should enter your small intestine when few amino acids are present; this gives it easy access to the carrier system and fewer obstacles to crossing the blood-brain barrier. To maximize your ON times, avoid protein when you take your carbidopa/levodopa and talk to your physician about how dietary changes can help you get the most from your medications.