Milk and Parkinson’s

As the population has been getting older, there has been increased attention paid to neurodegenerative diseases, such as Alzheimer’s and Parkinson’s. These are diseases that cause a progressive loss of mental function (dementia), or problems with movement, such as tremors. The causes of these diseases are still relatively unknown, so there is a lot of public interest in studies that look at this. This week a paper was published that suggests there may be a link between high consumption of low fat dairy (particularly milk), and Parkinson’s. This was picked up by numerous media outlets, with predictable headlines.

Do you eat ‘low-fat’ branded food? Parkinson’s disease could be triggered by THIS

The Express, 12/06/17

It has been known for a few years that there may be a link between dairy consumption and Parkinson’s. However, this link has always been weak and controversial, so the benefits of drinking milk have far outweighed the potential harm. This week’s study took this further by analysing this link in a huge number of patients, far more than have ever been studied before.

So what have they found? Well firstly, there’s no need to give up drinking milk. The study did NOT find that low fat milk causes Parkinson’s. That’s not to say the headlines were entirely wrong, but the study was not designed to find whether milk causes Parkinson’s. It was designed to see whether people who drank lots of low fat milk were more prone to the disease. This is a subtle distinction, but an important one. I have written about this in the past (correlation vs causation), but it is worth repeating. Just because two things are happening together, doesn’t mean that one is causing the other. On top of that, milk is full of nutrients, so cutting it out or the diet may have unintended consequences.

This study was a big one, including nearly 130,000 people. Of those 1,036 people developed Parkinson’s over the course of the study. When they looked at how much milk these people drank compared to the rest, they found that there was no difference. However, if they specifically looked at the consumption of low fat milk, they found that people who drank 3 or more glasses per day were more likely to develop Parkinson’s. The association wasn’t very strong, with the general population having a 0.8% chance of getting the disease, and those who drink lots of  low fat milk having a 1% chance. It’s a small difference, but with an aging population, this could mean significantly more people with the disease.

The authors of the paper are careful to emphasise that they are not showing that milk causes Parkinson’s. They make several alternative suggestions themselves, including the possibility that Parkinson’s itself affects dietary behaviour, causing people to drink more milk. However, it must be considered a possibility that low fat milk is increasing the rate of Parkinson’s.

So is it advisable to limit your milk consumption? At present, the answer to that is no. Milk contains nutrients we need, including calcium and potassium, and has significantly less sugar than other drinks. Per glass (240ml), it has 2.6 teaspoons of sugar, compared to 5.2 teaspoons in orange juice, and 6.4 in Coca-Cola. Additionally, those at risk drank 3 or more glasses per day, which is quite a lot.

In short, there is no need to start drinking black tea and putting water on your cereal. Paranoid people might want to limit their consumption to less than a litre a day, but I won’t be changing my habits on the back of this evidence!

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