Where are we with research into nutrition and Parkinson’s?

Not a week goes by that there isn’t something in the news about what we should or shouldn’t be eating. But the general advice for people with Parkinson’s is still the same old ‘healthy, balanced diet’ — so why don’t we know more about diet and nutrition?

Nutrition is undoubtedly important in Parkinson’s — and research has shown that people with the condition are more likely to lose weight and suffer from malnutrition. And there is a growing body of evidence that suggests that improving nutritional status could improve quality of life. Read more about this in this recent review.

However, unlike with conditions like scurvy and anaemia, which can be solved by upping the intake of key nutrients, the solution to Parkinson’s isn’t as simple as eating more citrus fruits or iron-rich foods.

Parkinson’s is a complex condition that develops gradually over many years (if not decades), which may involve a myriad of genetic, lifestyle and environmental factors, combined with the natural process of ageing.

This makes teasing out aspects of diet that may play a part in this process messy and complicated. And, despite decades of research, we’ve struggled to find conclusive proof that any particular diet is beneficial for Parkinson’s.

Let’s take a look at some of the main types of studies that have been done and where the problems lie.

Studying big groups

So far, most research into diet has used the same basic approach. Take a big group of people (usually hundreds of thousands). Ask them about their diet regularly over a long period of time (usually decades). Then see whether any patterns linking particular dietary factors and their risk of developing a particular illness emerge.

This approach can be helpful in identifying things that affect the risk of developing illnesses. For example, eating lots of processed and red meat can increase the risk of bowel cancer.

But it comes with problems. One of the biggest is that the patterns you spot may actually be due to something else entirely. If a study were to find that people who eat lots of caviar and drink lots of champagne live longer, healthier lives you might wonder whether other factors (such as wealth) could be behind this result?

Although researchers do their best to take these other factors into account, it’s impossible to eliminate their influence.

Another challenge is that it can be difficult to interpret the results. For example, a number of studies have suggested that people who drink more milk are more likely to develop Parkinson’s. But as this article explores, it’s unclear how milk may be causing the increased risk — could it be pesticide contamination or milk’s ability to lower urate levels (known to be linked to Parkinson’s)? The authors suggest that it could in fact be explained by changes in eating behaviour that people experience in the early stages of the condition (before symptoms appear) and have urged people not to limit their consumption of dairy products.

In the lab

At the other end of the spectrum, researchers based in the lab are also investigating the effects of chemicals that can be found naturally in our diets.

In these studies, the researchers can test the effect of the chemical they’re interested in on cells in a dish, an animal model, or — as in research that hit the headlines recently which explored the effects of protein found in fish called parvalbumin — sometimes they will look at how their chemical interacts with alpha-synuclein (a protein that goes rogue in Parkinson’s) in a test tube.

The problem with this approach is that researchers will often use extremely high concentrations of the chemical in their experiment. And this may not be possible (or even safe) to achieve through diet or supplements.

So, while this research is very interesting scientifically and could provide a route to developing new treatments, it’s usually too far removed from people to be helpful as a source of nutritional advice.

What about clinical trials?

When new treatments are developed they must be tested in clinical trials to see whether they are safe and effective.

With a drug, designing a clinical trial is relatively straightforward. If you have 100 participants, 50 get the real drug and 50 a ‘placebo’ (an inactive or dummy version that looks exactly like the real one). Neither participants or the researchers will know who is receiving what. This helps ensure that the only difference between the two groups is the drug itself.

With a diet, things are considerably more complicated. If you are asking participants in a trial to follow a specialist diet, how do you create a placebo version? And how do you ‘blind’ the participants to whether they are on the ‘real’ diet or the placebo version?

In addition, making significant lifestyle changes — whether it’s eating more healthily, quitting smoking or doing more exercise — is difficult to maintain. So, getting participants in a trial to stick to a diet for a significant period of time can be challenging.

As a result, so far clinical trials have focused more on investigating the effects of particular dietary supplements. However, to date trials have failed to provide firm evidence of benefit.

Time for a new approach

So far research into nutrition and diet for Parkinson’s has not provided the clear results needed to provide helpful advice to those living with the condition. It’s time for something new.

A research study led by Dr Laurie Mischley at Bastyr University called CAM Care in PD is investigating the influence of diet and lifestyle factors in Parkinson’s using a very different approach.

The team is using an online survey to collect a broad range of data from people with Parkinson’s and related conditions from all over the world. Participants are surveyed every six months, answering questions about medications, diet, supplements, exercise, medication and an array of other factors. At the same time, they are asked to rate the severity and impact of their Parkinson’s symptoms.

The goal is to collect as much data as possible over a five-year period with the hope of finding dietary and lifestyle factors that are linked with a slower progression of the condition.

The first results from this innovative study (based on data collected from over 1000 people) were published in September 2017 and have already identified foods associated with slower and faster progression:

  • Foods associated with slower progression included: fresh vegetables, fresh fruit, nuts and seeds, non-fried fish, olive oil, wine, coconut oil, fresh herbs, and spices.
  • Foods associated with faster progression included: canned fruits and vegetables, diet and non-diet soda, fried foods, beef, ice cream, yogurt, and cheese.

The team also looked to see whether there were any patterns linking the use of nutritional supplements to faster or slower progression. Interestingly, of all the nutritional supplements investigated in the study (a very long list) only two — coenzyme Q10 and fish oil — were associated with slower progression. Although the association between coenzyme Q10 disappeared when the data was adjusted for income. Meanwhile, iron supplements were associated with faster progression.

These initial results are interesting, they add to previous research that Mediterranean style diets which include lots of fresh vegetables, fruit and fish may be protective. But they also throw up some new patterns such as the suggestion that fizzy drinks are linked to faster progression, which now need further investigation.

It’s important to take these findings with a pinch of salt (sorry, I couldn’t resist!). It’s still early days and as with other population-based studies, there may be more to these patterns than meets the eye. But it’s definitely a study worth keeping an eye on. And if you’d like to participate yourself, it’s not too late to get involved.

You can read the full open access report of the research here and a more thorough discussion of it on the Science of Parkinson’s blog, which is well worth a read.

This blog is not meant as health advice. You should always consult a qualified health professional or specialist before making any changes to your medications or lifestyle.

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