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Diet and Parkinson's disease

18 Sep 2020 15:00 - 16:00

Please note that all session and slide content are the views of the Speakers, not the Parkinson’s Academy. The content of the recording is the speaker’s personal opinion at the time of recording. Due to the everchanging situation, advice given at the time of recording is subject to change.

Reproduced with the kind permission of Professional Nutrition and Dietetic Review

Professional Nutrition and Dietetic Review

Presentation slides

Richelle's slides


Diet is a “missing piece of the puzzle” in the management of people with Parkinson’s disease (PD), said Richelle Flanagan.

Richelle first noticed the signs of PD when she was 47 and pregnant with her second child – just six years after she was diagnosed with celiac disease. She said she found it very frustrating when the non-motor symptoms of PD were underrecognised.

“I was dismissed when I said I had swallow problems and hip problems. You feel like a hypochondriac,” she said.


“We know that constipation is a prodromal symptom, and many people with Parkinson’s will complain that they had bowel issues, particularly constipation, for many years before they were diagnosed.”

It is often under reported, but Richelle believes that up to 70% of people with PD experience constipation. It’s worth noting that wholegrain fibre, she added, was associated with a higher level of levodopa availability.

“So, if you are constipated one of the key drugs for helping Parkinson’ treatment is not absorbed as well. This is really a key issue that that has to be sorted but is not being addressed,” she said.

For a healthy gut, people should be consuming 25-30g of a mixture of soluble and insoluble fibre a day, as well as plenty of fluids.


People with PD tend not to drink enough, and this may be due to the loss of the automatic processes that prompt thirs, or the possible dehydrating effect of levodopa. As well as contributing to constipation, dehydration can also affect blood pressure, Richelle explained.

Recommended daily fluid intakes, she said, were 35ml per kilogram of weight for under 65s, and 30ml per kilogram for over 65s.

She went on to say that people with PD shouldn’t be told to avoid caffeine. Moderate amounts of coffee – which she described as one cup of strong coffee, or three cups of instant a day – was a “great way for people to get some fluids in, because it is majority water”.

“Caffeine can help increase alertness and enhance performance, and we know that fatigue and low energy are problems in Parkinson’s,” said Richelle.

However, healthcare professionals should advise people not to drink too much coffee, particularly if they have high blood pressure, and to avoid caffeine in the four hours before going to bed.


Gastroparesis is common in PD, and one study has shown that gut rigidity increases by 5% every two years in these patients. The authors also found that the prophylactic use of laxatives can reduce the rate of decline. (ref)

As well as tying into the high prevalence of constipation, this finding also shows that there is “something else going on”, she said, possibly associated with dysbiosis in the microbiome.

“This spoke to me about the importance of the Parkinson’s diet, and how we are missing a trick by not improving that at baseline to see how much we could improve quality of life,” said Richelle.

Vitamin D

Lots of people with PD are deficient in vitamin D, which plays a major role in bone health – important for those at risk of falls – and may be neuroprotective.

The “general rule of thumb” for adequate levels is 50ug a day, Richelle explained, adding that it can be difficult to get enough of the vitamin from the sun during the winter months.


Protein foods interfere with the abortion of levodopa at the gut level and at the blood-brain barrier. Therefore, people should take their medicine either 30 minutes before eating a meal containing protein, or an hour afterwards.

Richelle said there was “quite a bit of evidence” to support the protein redistribution diet (PRD), which advocates only eating protein towards the end of the day. This enables the patient to have fewer symptoms throughout the daytime.

“The PRD should be done in correlation with a properly qualified dietitian to make sure they don’t lose body weight, and because we want to make sure people who have Parkinson’s do not lose muscle,” she said.


(28.25) Can diet or specific foods increase dopamine levels?

“There’s no evidence that your dopamine production goes up if you eat more beans or eggs, and, if you’re on levodopa medication, you can run into all sorts of problems with levodopa absorption,” said Professor Bas Bloem.

He went on to warn against the use of mucuna pruriens, a food supplement that comes from an Ayurvedic bean containing the same leaf adobo found in dopaminergic medications.

Unlike the medications, however, mucuna is not combined with a carboxylase inhibitor, and therefore, does not cross the blood-brain barrier. It means that the majority of the leaf abodo that is converted into dopamine will remain in the blood and never reach the brain.

(32.46) Bas also spoke about medications and bowel and bladder function. Entacapone, he said, can turn urine orange and discolour the underwear of people with urinary incontinence.

He added that almost all patients experienced at least some degree of constipation. “My own preference is to avoid long-acting drugs on people with slow bowel movements and delayed gastric emptying… my favourite drug for constipated patients is dispersible Madopar. It works quicker, but not shorter,” he explained.

(37.57) What can we do to avoid weight loss if people exercise a lot?

There is a lot of evidence to suggest that people with PD are at risk of losing weight, and that rapid weight loss is a poor prognostic sign. It can signal the presence of atypical Parkinson’s or be a predictor of early-onset dementia, early admission to a nursing home, and early death, said Bas.

“Whether mitigating weight loss avoids that risk is not known – that intervention study has not been done – but my interpretation is that we should really aggressively help and support people who have a lot of weight loss,” he said.

Dietary and vitamin advice could be useful for patients in this position, he said, adding that weight loss could be a result of nutritional deficiencies.

'The things you can't get from the books'

Parkinson's Academy, our original and longest running Academy, houses 20 years of inspirational projects, resources, and evidence for improving outcomes for people with Parkinson's. Led by co-founder and educational director Dr Peter Fletcher, the Academy has a truly collegiate feel and prides itself on delivering 'the things you can't get from books' - a practical learning model which inspires all Neurology Academy courses.