Protein and Parkinson's Medications

Dietary Protein and Parkinson's Medication Interaction

red meat on a platter
How can protein sometimes reduce the affect of levodopa in Parkinson's disease?. MSEN/HAAP Media

If you or a loved one have Parkinson's disease, you may have heard that you should reduce the amount of protein in your diet or only eat protein at certain times of the day. Is this true? What is the reason? What other options are there?

How Might Protein Affect Parkinson's Disease Medications?

A problem that emerges in middle stages of Parkinson's disease (and sometimes even in early stages) is in the absorption of levodopa medication.

If you eat a diet high in protein, the protein can sometimes compete with levodopa or prevent an adequate amount of levodopa from gaining entrance into the brain. The reduction in the benefit of levodopa in response to dietary protein was first noted many years ago.

Several studies have now looked at methods of counteracting this decreased absorption, from limiting the total amount of protein consumed, to changing the time of day at which protein is eaten. What have we learned?

Does Restricting Protein Make a Difference?

Studies have found that protein intake can have an affect on the motor fluctuations with Parkinson's disease, but this is not true for everybody.

People who are more likely to report an interaction between protein intake and their Parkinson's disease symptoms are those in the earlier stages of the disease and those who have a family history of Parkinson's disease. A fairly large study found that around 6 percent of people with Parkinson's disease on levodopa and 12.4 percent of those who have motor fluctuations on levodopa noted changes in their response to the medication depending on the timing of protein intake.

Other studies have found that people with Parkinson's disease who consume more vegetable proteins and carbohydrates have more severe symptoms on levodopa.

In yet another study, close to 80 percent of people on levodopa for Parkinson's had a decrease in effectiveness or earlier wearing off of a dose after protein intake, raising the question of how much protein has to do with the "on-off phenomenon" with levodopa.

Reducing Dietary Protein With Levodopa—What Effect Does It Have?

Both reducing the amount of protein in the diet (low protein diets) and redistributing daily protein intake so that most dietary protein is consumed with dinner, have been studied as to their effects on motor symptoms. The ability of people to follow these diets, however, has been variable, which has hampered interpretation at times. Both reducing protein intake and restricting protein intake to one meal daily have been found helpful for some people

How Much Does Protein Influence Levodopa Response?

In order to better quantify the influence of dietary protein on levodopa, researchers evaluated the effect of dose in relation to protein intake. An increase in protein intake by 10 grams per day (over the physiological requirements of 0.8 grams/kg/day) corresponded to an average increase in levodopa of 0.7 mg/kg/day. The increased dosage of levodopa to compensate for protein intake was associated with an increase in constipation.

How and Why Does Protein Intake Affect Levodopa?

Serum levels do not show a correlation with protein intake, suggesting that levodopa is initially absorbed through the intestines during digestion. So why then would levodopa be less active?

It's thought that the passage of levodopa through the blood brain barrier, an area of tightly joined endothelial cells which restricts the passage of toxins (and sometimes medications) into the brain is the problem. Studies have found that some amino acids (such as phenylalanine, tyrosine, and tryptophan) found in protein meals may compete with levodopa with regard to passage through the blood brain barrier and absorption into the brain.

Reducing Protein Intake - Practical Advice

It might seem easy to suggest that people with Parkinson's disease should simply decrease their protein intake. Adequate protein, however, is needed for good health, and we can't simply eliminate protein from our diets.

Many people with Parkinson's disease are already at risk from a nutritional standpoint.

A protein redistribution diet is one way of ensuring adequate protein intake while interfering less with the absorption of levodopa. With this diet, daily protein intake is confined to one meal per day, usually dinner. Unfortunately, a protein redistribution diet in which people eat most of their dietary protein in the evening does not completely remove the effect of dietary protein on levodopa efficacy.

If you experience dyskinesias, these protein redistribution requirements may not apply. You may need to speak to your doctor about your diet because slowing absorption of your meds may actually be helpful. That is why continuous release forms of levodopa are sometimes given.

Bottom Line on Protein Intake for People with Parkinson's Disease on Levodopa

Protein intake and its distribution throughout the day can influence the effect of levodopa for those living with Parkinson's disease. Studies to date have found improvement in Parkinson's disease symptoms in those on a low protein or protein redistribution diet but the effects seem to be limited to a small subset of people. It appears to play a larger role for those in the earlier stages of the disease as well as for those who have familial Parkinson's disease.

Nutrition is extremely important for people living with Parkinson's disease and should be carefully addressed. In addition to the necessity of a healthy diet while living with Parkinson's disease, new research is finding that the gut microflora—bacteria which live in our intestines and are strongly influenced by our diet—may play a role in the severity of Parkinson's disease symptoms.

In many ways it appears that nearly anyone living with Parkinson's disease could benefit from talking with a nutritionist who is very familiar with the condition who can make sure you are not only get the calories and protein required for health, but the large number of other nutrients which make a difference in wellness. You may wish to take a moment to learn some of these healthy dietary tips for anyone living with Parkinson's disease.

Being aware of the effect of protein on levodopa is also a good reminder to make sure you get the greatest benefit possible from all of your medications. Check out these tips on getting the most out of your Parkinson's disease medications.


Barichella, M., Cereda, E., Cassani, E. et al. Dietary Habits and Neurological Features of Parkinson’s Disease Patients: Implications for Practice. Clinical Nutrition. 2017. 36(4):1054-1061.

Cereda, E., Barichella, M., Pedrolli, C., and G. Pezzoli. Low-Protein and Protein-Redistribution Diets for Parkinson’s Disease Patients With Motor Fluctuations: A Systematic Review. Movement Disorders. 2010. 25(13):2012-34.

Mulak, A., and B. Bonaz. Brain-Gut-Microbiota Axis in Parkinson’s Disease. World Journal of Gastroenterology. 2015. 21(137):10609-20.

Virmani, T., Tazan, S., Mazzoni, P., Ford, B., and P. Greene. Motor Flucuations Due to Interaction Between Dietary Protein and Levodopa in Parkinson’s Disease. Journal of Clinical Movement Disorders. 2016. 3:8.

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