Evidence is mounting that there is a relationship between what we eat and dementia.
I trained as a cognitive scientist/neuroscientist originally because I wanted to know more about how people could lower their risks of developing dementia in general and Alzheimer’s disease (AD) in particular. My interest in fermentation comes from exposure to research indicating that gut bacteria is correlated to a range of physical and mental health conditions. That if you have too many or two few of certain types of microbes within your digestive tract, then you are more likely to experience better or worse health.
Imagine my interest then when I receive details of research that stated,
“All the results suggest that AD may begin in the gut.”
This conclusion from Hu, Wang and Jin appeared in their 2016 study Alzheimer’s disease and gut microbiota. Clearly if the results stand up and can be replicated this will change much of what we know about AD, and how it might be treated. There is a growing body of research that has linked AD to diet, it is widely discussed in the vegan and vegetarian communities. But Hu, Wang and Jin take the current thinking further; that AD is not just linked to what we eat per se’ but the prebiotic and probiotic effects of our diet. This research suggests that future treatments for AD are likely to come in the form of dietary or microbiotial interventions. The investigation covers a wide range of evidence, the scientists also draw attention to known links between gastrointestinal diseases and reduced cognitive function as well as Parkinson’s Disease and abnormal levels of gut microbes. If you’re puzzled as to how the gut influences the brain, look into the gut- brain axis.
As a general rule I’m cautious about the findings of academic studies dealing with complex areas of human health like AD. There are such a wide range of factors able to influence wellbeing that to isolate and demonstrate causality is not a simple matter. There is also evidence linking a number of other behaviours (meditation, mindfulness) to reduced risks of neurodegeneration. So that if there is a correlation between both meditation and gut bacteria with lower risks of developing AD, we need to think about how it might work.
Anyone who has been around the meditation community for a while may have noticed a few things about regular meditators. They tend to be relatively calm and their diet and lifestyle tends to be a little different from the mainstream. For example I’ve observed that meditators appear to smoke tobacco and drink alcohol less than the general population. Anecdotally I have found more vegans and vegetarians in the meditation community than my non-meditating friends. You can see from these speculative ideas that the relationship between gut bacteria and AD could hold up even given the evidence linking meditation to lower risks of neurodegeneration.
Whilst this study in isolation does not prove that AD begins in the gut, it signposts further areas of potential research. We now need to look for more specific evidence and ‘joined up’ explanations. It seems that there has never been a better time to think about the benefits of bringing fermented food into your diet and protecting your gut health as far as possible.
Your diet can play a significant role in your chances of becoming obese, suffering from asthma or a range of other illnesses.
Discovery, a general science programme from the BBC World Service, has put together a helpful three part guide to the human microbiome. It is made for the wider World Service audience so it presents the issues in an interesting but accessible way. The discussion of the subject matter is engaging, and important contributions are made by leading scientists in the field such as Prof Rob Knight, from the University of California and Prof Tim Spector from Kings.
The show provides a general outline broken down into three parts; Manipulating Our Hidden Half, Dirt and Development and Gateway to the Mind. The idea that humans (in common with other animals) have not one but two genomes is central to this mini series. Our human genome is the one handed down to us through our parents, set in stone at conception. The so called second genome is made up of a vast pool of genetic diversity present in the microbes found throughout and within our bodies. The Human Microbiome Project has begun the process of analyzing the large number of microbes present in us. Two key issues that have started to excite scientists in recent years are,
the extent to which microbes can influence human health and experience.
the ability of individuals to alter their own microbial profile.
For example, it is generally observed that increased diversity of different kinds of helpful bacteria in the gut, is correlated with improved wellness. Studies in obesity, allergies, asthma and auto immunity suggest that gut bacteria may have a crucial role in meditating our health. This opens up the prospect that lifestyles remedies such as changes to diet may offer us significant potential benefits. It also raises the question about the long term benefits of medication known to have a detrimental affect on gut bacteria such as antibiotics.
This then takes us back to the discussion of probiotic and prebiotic food and drinks. When you consume products rich in helpful bacteria (probiotics) or the soluble fibre known to support microbial diversity in the large intestine (prebiotics), you are likely to be improving your health in a number of ways. It cannot yet be said that there is a direct causal relationship between your diet and certain illnesses. However the scientists are starting to think of gut bacteria as increasing or decreasing the chances of suffering from particular health problems.
At the time of writing all three programmes were freely available online or to download here.
Kefir appears to offer significantly greater benefit than commercially produced probiotic drinks.
Dr Michael Mosley has been helping to run a study for the BBC looking at the relative benefits to gut health from a range of products. Volunteers and scientists collaborated to try to discover which of three probiotics/prebiotics had the biggest positive impact on gut bacteria.
The first product was a commercially available drink, branded as a probiotic and available in major supermarkets. The second item up for comparison was kefir, a traditional milk and yeast fermented substance, a little like yogurt. These first two foods were compared with vegetables high in natural prebiotic fibre called inulin. Inulin is found in range of foods including chicory (chicory root is a rich source) and scallions (onions, leeks and garlic).
The poorest preforming of the three in this trial was the probiotic drink. The participants in this group demonstrated a modest (statistically non significant) change in lachnospiraceae gut bacteria. Conversely significant changes in gut flora were seen in the group consuming prebiotic fibre. The people that consumer kefir enjoyed the most positive increase to gut bacteria.
It should be pointed out that any comparison between prebiotics and probiotics is not a like for like test. Prebiotics deliver the food that supports existing bacteria and create the conditions for further colonization. A probiotic is intended to introduce microorganisms directly into the body.
The BBC study concluded that traditionally produced fermented foods (or even home made versions) may offer the greatest benefits to consumers in terms of increased gut flora. A key problem with mass produced fermented foods and drinks is pasteurisation. Pasturised goods are regarded as safer, which also correlates to a longer shelf life. By comparison traditionally made kefir has to be consumed in a relatively short space of time. This is perhaps the choice we consumers face, if we want maximum health benefits from the food we make or buy we may have to sacrifice some of the convenience of long sell by dates.
A basic guide to gut health, key terms defined and explained.
Understanding gut health; 1 the basics
The scientific investigation of gut bacteria and its relationship to wellbeing is at a very early stage. There are discoveries every week that support, coexist with or contradict earlier findings. It’s a rapidly developing and dynamic area of human knowledge. The good news is, there are many resources available to anyone who wants to understand and take control of their own health through diet.
As a starting point there are a few concepts that are best understood at the outset. Not everyone uses these terms in the same way but try these definitions as a starting point.
Microorganism is widely used in talking about gut health, it is a general description for any organism that is too small to see with the naked eye. Some scientists prefer not to use the word but you are likely to come across it widely if you start reading about gut bacteria. Bacteria, viruses, archaea and fungi are all typically included in the term.
Microbiota is generally used to denote the population of microbes in any given community or system. Flora appears to have largely the same meaning as microbiota and appears interchangeably. For example gut flora means the same thing as gut microbiota.
The aggregate of all the genes of an entire population of microorganisms in any environment is described as a microbiome.
Typically scientists divide human microbiota into populations linked to their environment, such as skin, mouth, nose, digestive tract, and in females also the vagina. The largest population of microbes occur in the digestive tract, also known as the gut. Bacteria are the largest type of microbe in the human gut and bacteria reflects the dominant interest of scientific research. Gut bacteria are the main recipients of the benefits of prebiotics and probiotics, that is why the term gut bacteria and gut health is so prominent in media accounts of research findings. Technically speaking the plural of bacteria is bacterium but you will rarely see this outside of science journals, bacteria is typically used as the singular and plural form in most everyday situations.
A key point to make is that the gut has an important two way communication system with the human brain. That means to think of fermented food and drinks as only involved in what happens in the intestinal tract is a mistake. What we eat and drink has has the potential to exert a widespread influence across a number of systems.
People suffering from migraines tend to have particular profile of bacteria linked to nitrate processing.
I am keen not to overstate the potential of any individual scientific study. However this story highlights exciting news about a potential relationship between bacteria and migraines. In 2016 The Guardian featured a study that appeared to demonstrate a link between the efficient break down of nitrates in humans and the occurrence of migraines. As I understand the research, migraineurs (people that suffer from migraine) tend to have more nitrate reductase genes in both the mouth and in stool samples, than the wider population.
Nitrate reductase genes are responsible for processing nitrates in food and drinks, point being the greater their abundance the more efficient the nitrate processing. So getting more nitrates from food (compared to non migraineurs) may be linked to triggers for migraines. Obviously further research will be needed but the link between nitrates and headaches is not new. What this study is demonstrating is that the key might rest with the microorganisms in the mouth and gut.
Many migraine sufferers are aware of a relationship between certain foods and increased risks of attacks, through chocolate and wine for example. It is also known that certain drugs high in nitrates can provoke severe headaches. When broken down, nitrates lead to increased blood circulation in the cardio vascular system, this increase may be a key factor in migraines. The complexity of the human microbiome, particularly the gut-brain axis, makes demonstrating causality between food and health challenging. However this seems like a promising area of research. Controlling the intake of foods high in nitrates might be a short term solution. But given that fruit and vegetables are rich sources of nitrates, cutting down on them could present a range of risks and benefits. For more information visit the Migraine Action or Migraine Trust websites.
We always welcome your feedback, comments in the text box below. Thanks for Peter for suggesting the subject and as always please read our disclaimer.
There is growing evidence that gut bacteria is linked to obesity. Preliminary experiments with mice appear to be supported by human studies.
Ongoing research into the role of the microbiome (bacteria in the gut) in human wellbeing is at a very early stage. But the frequency of media headlines linking gut bacteria to health is growing. As with all areas of science, claims which have not been verified in clinical trials and subsequently replicated must be treated with caution. Nevertheless the evidence of a relationship between gut microbiome diversity and obesity has been repeatedly demonstrated in mice.
The microbiome is a term used to describe all of the genetic material of a microbiota, the entire range of microorganisms present in a particular context, in this case the human gut.
There have been a number of studies which show that obese mice tend to have fewer different types of gut bacteria than thin mice. The thinking is that a greater range of gut bacteria is likely to positively influence the way that the digestive system breaks down food. Having more (types of) bacteria is linked to efficient processing of what we eat, with the results of a tendency not to be obese. Recent research reported in The Independent looked at the weight gained by 1,632 female twins over nine years. The study calculated that only 41% of the weight increase could be explained by genetic factors.
On closer inspection it was estimated that becoming slimmer or maintaining the same weight was connected to the consumption of dietary fibre (typically found in whole grains, fruit and vegetables). The study also discovered that the women who had gained weight, had a lower diversity of gut bacteria. These findings were in line with similar studies with mice. Although not yet conclusive the overall evidence linking the shape of our body and the composition of our microbiome is growing.
Outstanding lecture from Prof Simon Carding, how gut bacteria mediates both physical and mental health
Emerging research is demonstrating a profound relationship between the bacteria in our gut and how well we are, our lived experience. In this outstanding lecture Prof. Simon Carding offers insights, new and old into ideas about our gut bacteria. Warning you may see the world a little differently after watching the video!