Does Alzheimer’s Start in the Gut? Part 2
Maintaining a healthy and diverse microbiota may help prevent the development of Alzheimer's.
“The baby boomers are getting older, and will stay older for longer. And they will run right into the dementia firing range. How will a society cope? Especially a society that can't so readily rely on those stable family relationships that traditionally provided the backbone of care?” —Terry Pratchett
Last week we discussed an experiment that transferred symptoms of Alzheimer’s to rats via gut microbes. This bizarre finding implies that we may actually be able to stave off dementia by keeping our microbes healthier.
An Alzheimer’s Epidemic?
The odds of dementia increase with age. So, as our life expectancy increases, the rates of Alzheimer’s naturally go up. But there may be another contributor to the current high rates of Alzheimer’s: diet.
Over the last 75 years, the consumption of ultra-processed foods has gone from essentially zero to 60 percent of our diet today. Today’s foods are more manufactured than grown.
Fiber can make food coarser and brown, so the first step in most food processing is to eliminate it. In the mid-1900s, fiber seemed like superfluous indigestible roughage.While we may not be able to digest fiber, our gut microbes can—and they love it. Eliminating fiber also has a side effect of concentrating the fats and carbs, which may favor pathogenic microbes.
Fiber supports beneficial bacteria like species of Clostridia and Coprococcus that create butyrate, a substance that both heals and nourishes the gut lining. The UCC study found that levels of these bacteria, as well as butyrate, were lower in the rats who got the Alzheimer’s microbiota.
The amino acid taurine was also decreased in the Alzheimer’s rats, and it may play an important role as well. Both butyrate and taurine can easily cross the blood-brain barrier, where they can encourage the growth of new nerve cells in the hippocampus.
The Alzheimer’s microbiotas had high levels of disease-associated bacteria like Desulfovibrio and Dialister that can secrete toxins when unbalanced. Low levels of butyrate could lead to a “leaky gut," allowing those toxins and other bacterial secretions to breach the gut lining and enter the bloodstream. Over time, that bitter cocktail can damage tissue and cause inflammation.
In a separate experiment, the UCC study found exactly that: Serum from Alzheimer’s patients was able to halt the growth of nerve cells.
What to do
The implication is that reintroducing fiber to our diets may protect us from Alzheimer’s. That’s as easy as rediscovering the veggie department in your local store.
A diverse gut microbiota is healthiest. To support it, you need variety in your diet. So aim for a couple of dozen different veggies a week. Broccoli, Brussels sprouts, cabbage, asparagus, and cauliflower are easy and familiar. But give Jerusalem artichokes, escarole, celeriac, ramps, dragon fruit, and kohlrabi a chance. Fermented foods like yogurt, kimchi, and sauerkraut include both probiotics and prebiotics and promote a healthy microbiota. A recent study found a protective effect of fish, coffee, cocoa, and red wine. That’s a Mediterranean-style diet, and it is not a hardship.
If you can’t manage to include these healthy foods in your diet, a probiotic or prebiotic supplement may help. Just make sure they have a good blend of ingredients to promote diversity.
And don’t forget to exercise! Exercise has tons of benefits, and it helps your gut microbes as well.
You may be set in your ways but give this lifestyle a try. If it lowers your odds of getting Alzheimer’s, a little novelty in your life is a small price to pay.
References
Grabrucker, Stefanie, Moira Marizzoni, Edina Silajdžić, Nicola Lopizzo, Elisa Mombelli, Sarah Nicolas, Sebastian Dohm-Hansen, et al. “Microbiota from Alzheimer’s Patients Induce Deficits in Cognition and Hippocampal Neurogenesis.” Brain, October 18, 2023, awad303.
Connell, Emily, Gwenaelle Le Gall, Matthew G. Pontifex, Saber Sami, John F. Cryan, Gerard Clarke, Michael Müller, and David Vauzour. “Microbial-Derived Metabolites as a Risk Factor of Age-Related Cognitive Decline and Dementia.” Molecular Neurodegeneration 17, no. 1 (June 17, 2022): 43.
Du Preez, Andrea, Sophie Lefèvre-Arbogast, Vikki Houghton, Chiara de Lucia, Dorrain Y. Low, Catherine Helmer, Catherine Féart, et al. “The Serum Metabolome Mediates the Concert of Diet, Exercise, and Neurogenesis, Determining the Risk for Cognitive Decline and Dementia.” Alzheimer’s & Dementia 18, no. 4 (2022): 654–75.