expert reaction to study looking at flavonols and Alzheimer’s disease

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Research, published in the journal Neurology, reports that the antioxidant flavonol may be linked to lower risk of Alzheimer’s.

Dr Ada Garcia, Lecturer in Public Health Nutrition, University of Glasgow, said:

“This study shows that when elderly people, in particular females, self-reported to eat foods that contained about 15mg of favonols in their diet (for comparison a cup of black tea will provide that amount) then their risk for developing Alzheimer’s over a period of 6 years was reduced by about 44 percent. However, when the authors considered the effect of consuming other nutrients such as omega-3, vitamin E, folate and lutein, which have similar actions to flavonols, then the protective effect of flavonoids was no longer present. These types of studies are informative but need to be consider carefully before making public health recommendations. They rely on participants memory to report what foods were consumed over a period of time, this is in particular difficult in elderly participants because reduction in cognitive function is a normal process of ageing.

“Following a ‘healthful diet pattern’ which includes a variety of foods such fruits, vegetables, oily fish, seeds, nuts, legumes is known to be a good approach to chronic disease prevention rather than focusing on particular nutrients. This is important because the general public might interpret this study wrongly and think about the term “antioxidant” as a magic pill that will prevent the onset of dementia. It is important to remember that consuming isolated flavonols or extracts of flavonol rich foods, for example tea extracts, will not work on isolation to reduce risk of disease but high doses can also have negative effects on health.”

Prof Bart De Strooper, Director, UK Dementia Research Institute, said:

“The relationship between food and health always draws a lot of attention from the public. This new study suggests that specific components in fruit, vegetables and tea are protective against Alzheimer’s Dementia. For studies of this sort we must however not forget that it only describes an association which was observed in a small group of individuals. Association does not demonstrate that there is a real biological or causal link. To give confidence in this observation it must first be repeated in other groups. Many studies in the past have shown however that such observations do not replicate well. So, in general one should be careful not to overstate the importance of such findings.”

Dr Adrian Ivinson, Director, UK Dementia Research Institute, said:

“We’ve long known that there are links between what we eat and our health. This new study suggests tea could be added the equation and shows that the general health benefits may extend to brain health. However, it only describes an association, so further work is needed to see if there are true biological links. But Alzheimer’s disease is exceptionally complex. Whilst diet may help stack the odds in our favour, we need to do discovery research to understand the disease and from there develop ways of preventing or slowing it.”

Dr James Pickett, Head of Research, Alzheimer’s Society, said:

“Early-stage research in mice does show flavonols might reduce the build-up of toxic proteins in the brain we know are involved in Alzheimer’s. This new study in people isn’t definitive about whether flavonols can lower dementia risk, and it definitely doesn’t provide enough evidence to say that drinking tea, and eating food rich in flavonols, will ward off dementia. But the study results do suggest we should keep investigating the potential of flavonols.

“Our researchers are currently looking at a specific flavonol called Epicatchin to understand exactly which components are responsible for slowing the build-up of toxic proteins. This will help fill in the missing pieces of the puzzle as to whether flavonols have any protective effects against Alzheimer’s.

“In the meantime, we can say for sure that eating a balanced diet, with lots of fruit and vegetables, and getting enough exercise is a proven way to reduce your risk of dementia.”

Dr Ana Rodriguez-Mateos, Lecturer in Nutritional Sciences, Kings College London, said:

“This research reports an association between flavonols and lower risk of Alzheimer’s disease. To estimate flavonol intake in this population, researchers used a type of food questionnaire which is not the best tool to measure food intake, as it relies on what people remembered they ate over a year.

“The intake of flavonols in this study is very low, between 5 and 15 mg/day. A big limitation of this study is that they did not report associations with other flavonoids and phytochemicals present in the same foods as flavonols. This is particularly important because flavonols tend to be present in foods in much lower amounts than other phytochemicals. For example, tea is very abundant in other flavonoids and phytochemicals, such as thearubigins, theaflavins and flavanols, while red wine is very rich in other flavonoids such as anthocyanins and flavanols. Olive oil is very rich in phenolic compounds such as tyrosols. In comparison, the amount of flavonols in such foods are tiny.

“The estimated flavonoid intake in the UK for example is typically between 500-1000 mg of flavonoids/day, and existing meta-analysis of clinical studies investigating the efficacy of flavonols have used typically amounts of flavonols between 100 to 700 mg/day. It looks more feasible that the effects observed here are related to the consumption of foods containing flavonols and to other phytochemicals and bioactives present in such foods than to the flavonols themselves.”

Prof Tara Spires-Jones, UK Dementia Research Institute Programme Lead and Deputy Director, Centre for Discovery Brain Sciences, University of Edinburgh, said:

“This paper by Dr Holland and colleagues provides more evidence that a healthy diet rich in vegetables is associated with a reduced risk of Alzheimer’s disease. Scientists followed over 900 people for up to 12 years and found that people who reported they ate a diet rich in flavonols (found in vegetables including onions, kale, broccoli, and spinach) were less likely to develop Alzheimer’s disease than people who ate lower levels of these compounds. This study was well conducted and […]

Read more at www.sciencemediacentre.org

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