The Blood-Brain Barrier Bus Showed Up…

Let me point out one person that you should absolutely not take medical advice from… me! I mean, seriously, I know enough to be dangerous and nothing more. As a retired aviator, now photographer, writer, and traveler, I have zero authority with any of this stuff other than being a fellow Parkinson’s combatant myself and maybe a bit more physically ambitious than most. With that in mind, I’m going to point out something that I learned about recently that may be a factor for some of us who are taking levodopa and eating a lot of protein.

Even when I was in the Army I was wisely advised to “fly like you have a little lawyer on your shoulder”, so here’s a disclaimer:

Disclaimer: I am not a physician, nor do I intend to offer advice like one. The following dispatch is simply an ultra-simplified overview of my recent learning process when it comes to understanding the competition of protein and levodopa in getting past the blood/brain barrier. Which isn’t a problem for all Parkinson’s patients, just a subset of us. Talk to your neurologist or movement disorder specialist if you suspect this applies to you individually. And for the love of all things holy, righteous, and good, don’t take anything I say as having the same intellectual or scientific rigor as a well peer-reviewed research study. ‘Nuff said!

Levodopa/protein competition is something that I had absolutely no awareness of until just recently, as there have been a few other social media outlets and forums that have brought this forward as of late. Doing my homework on a neurologist-prescribed medication changeover from carbidopa/levodopa (Sinemet) to benserazide/levodopa (Madopar), I stumbled onto the concept of offsetting your protein intake at different times from your levodopa dosage. (I had to change medications due to availability issues with Sinemet in the country I’m in.)

Why is this important? In layman’s terms… because for a subset (keyword: subset) of us who aggressively work out and consume relatively large amounts of protein at different times of the day… and who are dependent on levodopa dosages throughout the day… it MIGHT be that the protein you’re eating (for all the right reasons) is competing with your levodopa dosage and causing less levodopa to transport past your blood/brain barrier and to your brain where it belongs.[1]

Bottom line up front though: this likely isn’t a factor for you, as it has only been an issue with a certain subset of Parkinson’s patients[2]. There is that word subset again. Let’s get started on this with some word-pictures, shall we?

In the process of earning my degree and attending flight school, I had the pleasure of learning about the intricate and remarkable transport of oxygen through our alveoli sacks in our lungs and how it went to our brain. It was something like Aviation Physiology 101. It was in this environment that I learned the school bus analogy for the first time. One of the reasons we pilots need to be aware of our oxygen processing capability (or transport, for this discussion) is to recognize different situations where our oxygen transport is compromised… since getting a continual flow of fresh oxygen is an acutely critical bodily process.

The general term for compromising your oxygen distribution is hypoxia, and without getting into great detail, it shows up in four different ways. I’m about to grossly oversimplify (on purpose) … but hypemic hypoxia, one of the four variants of hypoxia, happens when the blood transport mechanism is working fine but something interrupts the oxygen from being carried. In other words, the bus gets to the bus stop, the students try to get on, but they can’t, and the bus moves on without the oxygen students and they don’t end up getting delivered to the school (brain, or other organs) where they are needed. There are plenty of students, and there is plenty of capacity at school, they just can’t get onto the bus.

The classic culprit in an aviation context for keeping the students from boarding the bus is carbon monoxide poisoning, as carbon monoxide “hitches a ride much more quickly”. The carbon monoxide bullies effectively shove the oxygen students out of the way and fill up the bus before the oxygen students can get on.

So, let’s talk about protein and levodopa, like cats and dogs… living together! The school bus analogy, from what I have come to learn, is also somewhat similar and useful to explain what could potentially be happening with some of us Parkinson’s combatants when it comes to describing the competition between protein and levodopa in getting across the blood-brain barrier.

You see, along comes the blood-brain membrane transporter, the bus… and standing at the bus stop is a crowd of both protein and levodopa, in numbers greater than what the bus can handle! They are all there at the same time. There isn’t the same level of aggression that the carbon monoxide molecules display toward the oxygen molecules in the prior example. By and large, both types of students get on the bus. The only problem is that not all the levodopa students get on and some of them never make it to school! There are just too many students!

We Parkinson’s combatants typically need to get all of our levodopa students to school.

Let me firmly reinforce that according to the recent literature, this isn’t a factor for most of us, and if you don’t present more noticeable “off” times after you have had a large amount of protein coupled with your routine dose of levodopa, don’t go changing anything! The most noticeable subgroups according to one study “… suggests that clinically significant protein interaction with levodopa may occur mostly in a subset of Parkinson’s disease patients with earlier disease onset and those with familial disease.”[2]

Of course, there are plenty of variables associated with this type of study, perhaps most notably the variability of our diets in general. Such a thing is extremely difficult to nail down when it comes to getting clinically accurate data unless you actually physically control everything your study participants eat, which has thus far been outside the scope of what most of these studies have done.

This may only really be useful for a few of us, and I seriously wondered if this was something I should even include in a dispatch, but knowledge is power despite my admitted over-simplicity here. I, for one, would have appreciated knowing this sooner rather than later. This information hasn’t caused me to change my routines or dosage times, but I am a bit more judicious of when I chow down a large protein serving or have a protein shake. I’m simply aware… not reinventing anything.

Slow travel and living in a place that you are non-native to is full of surprises, challenges, and full-stop roadblocks, especially for us combatants. Medication changes, like I recently had, make holding back the leviathan more variable… less predictable. Regardless, if you think this may apply to you and your situation, talk to your neurologist!!!

The is the Nomadic Parkinson’s Dispatch.

[1] Rusch, C., et al. (2023). To restrict or not to restrict? Practical considerations for optimizing dietary protein interactions on levodopa absorption in Parkinson’s disease. npj Parkinson’s Disease, 9, Article 98.

[2] Virmani, T., Tazan, S., Mazzoni, P., Ford, B., & Greene, P. E. (2016). Motor fluctuations due to interaction between dietary protein and levodopa in Parkinson’s disease. Journal of Clinical Movement Disorders, 3, 8.

Shuler, M. S., Prasad, A., Flanagan, R., Dayal, V., & Lithander, F. E. (2026). Nutrition in Parkinson’s disease: What neurologists need to know. Practical Neurology. Advance online publication.

Anwar, L., Ahmad, E., Imtiaz, M., Ahmad, M., Aziz, M. F., & Ibad, T. (2024). The impact of diet on Parkinson’s disease: A systematic review. Cureus, 16(9), e70337.