study: the impact of calorie restriction on gut bacteria and alzheimer’s disease

Written by Monica Mischie 

Look, us mere mortals never really get to find out what is going on in the world of science. Well, not unless it’s (sometimes) sensationalised in the press. So, we wanted to bring you a snapshot of the latest science to whet your appetite to find out more if it’s something that piques your interest. Or, simply to keep you all in the “gut world” loop. Remember most of the studies are VERY new science, so keep your critical thinking cap on!

Our report is brought to you by our student research squad who have their ears to the lab floor ground to keep us all informed.

 

Background

Alzheimer’s disease (AD), characterised by memory impairments, personality changes or speech problems. It is a major health problem that mainly affects older people. With rates of AD expected to go up due to an ageing population, finding ways to reduce progression and treatment of AD is imperative.

Scientists observed that people with AD had different gut bacteria composition when compared to healthy people. In addition, previous studies have shown that people or animals on calorie restriction (reduction of daily caloric intake by 20-30% without malnourishment) are generally healthier even when older. There is, however, no information on the impact of calorie restriction on gut bacteria and AD.

This study was published in Nature on 29th November 2019. It looked at the impact of calorie restriction on AD progression in mice with AD.

 

Study Findings

Female mice with AD on caloric restriction presented significant changes in their gut bacteria composition, This led to a halt of AD progression. There were no improvements in AD symptoms in male models of AD.

Calorie restriction reduced the abundance of Bacteroides bacteria (usually associated with inflammation). Which in turn reduced amyloid-beta plaque deposition (a hallmark of AD progression) in female mice models.

 

Type of Study

This was a study conducted on 56 mice (male and female). Half of them had a genetic form of AD and the other half were healthy. Within each group, half of them could eat as much as they wanted whereas the other half were on a calorie-restricted diet. Their carbohydrate intake was reduced by 30%. The mice were on these diets for just over 1 year. Scientists analysed the mice’s stool and brain tissues to see how the two types of diets affected the brain and gut bacteria.

 

Study Limitations

Although these results are compelling, this study was conducted in mice and it is not known whether these findings could be applied to humans as well. In addition, the mice that were used had a genetic form of AD. Which generally has an earlier onset and worse symptoms than the more common forms of AD. The result from a combination of environmental and genetic factors.

 

Conclusion

This study on mice showed that changes in dietary patterns (calorie restriction) affect the gut bacteria composition. Through the chemicals that the altered gut bacteria produce. The progress of Alzheimer’s disease is slowed down in females only. A lot more research is needed but it is an interesting start.

 

About the Author

Monica Mischie obtained an Msci in Human Genetics from University College London in 2018. She is now doing a Ph.D. on the gut microbiome and dietary fibres at Imperial College London. She loves cooking, discovering new flavour combinations, and visiting farmers’ markets.