An apple a day could help protect against Parkin-son's disease-the progressive neurological condition that famously affects actor Michael J. Fox and former champion boxer Muhammad Ali.
New research by Harvard University in the US and the University of East Anglia in the UK found that men who ate foods rich in plant compounds called 'flavonoids'-such as apples and berry fruits-had a significantly lower risk of developing the disease.
The study, published in the medical journal Neurology, involved around 130,000 men and women who had been tracked for 20 years. None of them had Parkinson's to start with but, by the end of the study, more than 800 had been diagnosed with the disease.
After performing a detailed analysis of their diets, and adjusting for age and lifestyle factors, the researchers discovered that the men who consumed the most flavonoids had a 40-per-cent lower risk of Parkinson's compared with those who consumed the least flavonoids-the main sources of which were apples, blueberries, strawberries, tea, red wine, oranges and orange juice. No significant link was found between flavonoid intake and Parkinson's in women, however.
Apples and berries appeared to be particularly protective for men. Those eating five or more servings of apples per week were roughly half as likely to develop Parkinson's compared with those eating less than one serving a month. Similarly, men eating two to four servings per week of straw-berries and blueberries had around a 25-per-cent reduced risk of having the disease. Berries were the only type of flavonoid-rich food associated with a reduced Parkinson's risk in women. Those consuming the biggest amounts of straw-berries and blueberries had a 20-per-cent lower risk of the disease compared with those eating the least amounts.
The researchers believe that flavonoids, especially a sub-class of flavonoids called 'anthocyanins', may have protective effects on the brain. In fact, at least in animal studies, anthocyanin-rich foods such as strawberries and blueberries have been found to increase the release of dopamine-a brain chemical that's known to be in short supply in people suffering from Parkinson's.
Anthocyanins also appear to reduce oxidative stress, sup-press inflammation and trigger detoxifying enzymes-all of which appear to play a role in the disease (Neurology, 2012; 78: 1138-45).
However, although the study leaves a lot of questions un-answered-for example, why flavonoid intakes in women are not associated with a reduced risk of Parkinson's-it has raised the intriguing possibility that the disease might be prevented to some extent through diet.
In fact, several other recent studies have suggested the same thing: that what we eat may have a big impact on whether we suffer from Parkinson's or not. According to the evidence, some foods could slash the risk, while others could dramatically increase it.
Cutting your risk
- A Mediterranean diet- one that includes lots of fresh fruits and vegetables, fish and olive oil-was negatively linked to Parkinson's disease in a recent Columbia University study. The researchers looked at the diets of around 450 people with and without Parkinson's disease, and found that those who tended to follow a Mediterranean-style diet were less likely to have Parkinson's. What's more, the participants with eating habits that least resembled the Mediterranean diet were more likely to be diagnosed with Parkinson's at an earlier age (Mov Disord, 2012 Feb 7; doi: 10.1002/mds. 24918; Epub ahead of print).
- Antioxidant-rich foods, such as those high in vitamin E and beta-carotene, may be protective against Parkinson's (Eur J Neurol, 2011; 18: 106-13). These foods include spinach, broccoli, kale, almonds, sunflower seeds, sweet potatoes, carrots and mangoes. Antioxidants can counter the effects of damaging molecules in the body called 'free radicals', which are reactive oxygen molecules thought to play a role in the development of Parkinson's (Ann Pharmacother, 2006; 40: 935-8).
- Foods high in vitamin B6, such as tuna, chicken, turkey, bell peppers, cashew nuts and chickpeas, may also be helpful for Parkinson's prevention. Indeed, researchers from a large consortium of neurologists in Japan-the Fukuoka Kinki Parkinson's Disease Study Group-discovered that people with the highest intakes of vitamin B6 from their diet were significantly less likely to suffer from Parkinson's than those with lower intakes. This could be because vitamin B6 plays a role in maintaining normal levels of the aminoacid homocysteine in the blood, the researchers said, and high homocysteine levels are thought to be involved in Parkinson's (Br J Nutr, 2010; 104: 757-64).
- Minerals in the diet could also be protective, according to another study by the Fukuoka Kinki Parkinson's Disease Study Group. Higher intakes of iron, magnesium and zinc were associated with a reduced risk of Parkinson's in their study of around 600 people (J Neurol Sci, 2011; 306: 98-102). Foods rich in these minerals include Brazil nuts, spinach, brown rice, raisins, avocado, adzuki beans, sesame seeds, oats, chickpeas and lentils.
Upping your risk
- Dairy foods could boost your chances of getting Parkinson's if you eat lots of them, it seems. Harvard School of Public Health researchers found that high intakes of dairy foods nearly doubled the risk of Parkinson's in men (Ann Neurol, 2002; 52: 793-801). There appears to be a slightly increased risk for women who are dairy fans, too (Am J Epidemiol, 2007; 165: 998-1006). However, rather than dairy products per se causing Parkinson's, it could be that these foods are contam-inated with toxic chemicals such as pesticides, which are known to have damaging effects on the brain (see box, page 26).
- Arachidonic acid, an omega-6 polyunsaturated fatty acid, has been linked to Parkinson's. Those who ate the most arachidonic acid-found mostly in lamb's liver, meat and eggs-were twice as likely to have Parkinson's compared with those who ate the least amounts of this fatty acid (J Neurol Sci, 2010; 288: 117-22). In general, the fattier the meat, the more arachidonic acid it has.
- Fruit consumption, oddly enough, has also been linked to an increased risk of Parkinson's. Researchers at the University of Hawaii found a connection between high intakes of fruit/fruit juice and Parkinson's in middle-aged men. As with the dairy research, however, it's may not be the fruit or juice itself that's the problem, but the pesticides that are often present in them (Presentation at the American Academy of Neurology 55th Annual Meeting in Honolulu, HI, 29 March-5 April 2003). For this reason, it's a good idea to stick to organic produce whenever possible.
An environmental disease
These findings all add to the growing body of evidence suggesting that Parkinson's may have less to do with genes and ageing, and more to do with environmental factors-such as what we eat and the chemical toxins we're regularly exposed to (see box, page 26).
Indeed, the experts now reckon that genes alone are responsible for less than 10 per cent of all Parkinson's cases-and, even then, the environ-ment may still play a part (Environ Health Perspect, 2009; 117: 117-21).
Not only does this latest information contribute to our understanding of the disease and offer up potential ways to prevent it, but it also paves the way for new ways to treat the disease by focusing on diet and lifestyle rather than just on drugs.
Factfile: Other ways to prevent Parkinson's
- Limit pesticide exposure. Numerous studies have linked pesticides to Parkinson's. People living within 500 metres of land sprayed with pesticides have a 75-per-cent greater chance of developing the disease. Those exposed to agricultural pesticides as a child or young adult have an even higher risk (Am J Epidemiol, 2009; 169: 919-26). Household pesticide use is also associated with Parkinson's. US researchers reported that using insecticides and herbicides in the home or garden can double your risk of having the disease (Lancet, 2000; 355: 1701). So, to reduce your risk, use non-toxic alternative pest-prevention methods or pesticides whenever possible. See WDDTY vol 19 no 2, pages 20-21, for some useful tips.
- Watch out for other toxins, too. Polychlorinated biphenyls (PCBs), man-made organic compounds known to contaminate high-fat meats and fish, might increase the risk of Parkinson's. Even low levels of PCB exposure might disrupt normal dopamine functioning in the brain and eventually lead to development of the disease (Toxicol Sci, 2006; 92: 490-9). Exposure to heavy metals such as lead, found in some paints and lipsticks, might also raise the risk (Environ Health Perspect, 2006; 114: 1872-6).
- Get enough vitamin D. The 'sunshine vitamin' has recently been linked to Parkinson's. A Finnish study found that people with higher levels of vitamin D in their blood had a significantly reduced risk of Parkinson's compared with those who had lower levels (Arch Neurol, 2010; 67: 808-11). If you don't get much sun, the natural source of vitamin D, supplementing with 600-1000 IU of vitamin D3 may be a good idea.
- Get moving. A large US study reported that high levels of moderate-to-vigorous physical activity-such as jogging, cycling or aerobics-can slash the risk of Parkinson's. This may be because exercise has beneficial effect on the brain as well as the body (Mov Disord, 2008; 23: 69-74).