Hi everyone!

My name is Marisa and I am excited for my first reddit session today at 4-5pm BST!

Update: Wow, my fingers are hot from typing. It was really great to have so much interest in my first IAmA and it was a great experience trying to answer all your great questions. I am very sorry if I didn't get to answer your questions or if I didn't manage to answer it fully. This is a really interesting field of research with lots of new data coming through every day - we (this is including me!) still have much to learn and soon we'll hopefully know more about our diet is linked with our gut microbiota and how this is all linked to our health. If you want to learn more about this topic, I can recommend two books for in-depth reading (which will be much better at answering your questions):

"Gut" by Giulia Enders

"Missing Microbes: How the Overuse of Antibiotics Is Fueling Our Modern Plagues " by Martin Blaser


I am originally from Austria, but moved to the Linterman lab at the Babraham Institute in the UK three years ago to start my PhD, studying the cross-talk between the many bacteria living in your gut (= the gut microbiota) and the gut immune system which is in constant cross-talk with the gut microbiota and is crucial to protect your body from intestinal infections.

Because we can't easily study the gut immune system in humans, we used two-year-old mice to understand how the cross-talk between the gut microbiota and the gut immune system changes in old age. Previous studies have shown that the gut immune system deteriorates with age, and that many ageing-related symptoms are linked with age-associated changes in the composition of the gut microbiota.

In my experiments, I observed a reduction of certain gut immune cells in aged mice. The cool thing is that by transferring gut bacteria from adult into aged mice (by just cohousing them in the same cages or performing "faecal microbiota transplantation" - yes, that's about as glamorous as it sounds) we were able to revert these changes in the gut immune system - rejuvenating the gut immune system in a way.

Ask me anything you ever wanted to know about how the bacteria living inside you might influence how you age or about what a PhD in science is like! And if you want to find out more about my research, please check out my first scientific publication which came out on Tuesday (exciting!): https://www.nature.com/articles/s41467-019-10430-7

Good bye! It was a pleasure.

Comments: 1186 • Responses: 16  • Date: 

TheOneAndDudely606 karma

What foods contribute the most positive bacteria that anyone can afford? Also, how long does it take to repair/replace the gut mircobiota in an adult male? Thank you for doing this! What you’re studying is fascinating.

Immunity-and-beyond350 karma

Unfortunately I am not aware of the one "superfood" that will take care of it all for you, even though I know that there is a lot of research at the moment going into which diet might be most beneficial for your gut microbiome and health. I would stick to my mum's advice - trying to have a varied diet is definitely a good start. In terms of how long it takes for the gut microbiota to "heal" itself - this will obvioulsy depent on how disbalanced ("dysbiotic") the gut microbiota is. There is exciting research showing that changing the diet (e.g. from eating a lot of meat to a vegetarian diet), can have long-lasting effects on the composition of your gut microbiota within just weeks. So it's never to late to give it a go!

Jackandahalfass453 karma

These probiotics you see, the tablets and yogurts bragging about it. Are they actually of real benefit?

Immunity-and-beyond376 karma

Hi! Thanks for your question - this is a tricky one. I have seen a lot of data at scientific conferences showing that probiotics can indeed have beneficial effects on health and also in disease, but whether they work for you or not will depend a lot on your existing gut microbiota. And literally each of us harbours a different mix of millionds of bacteria in their gut - something sometimes referred to as "poo-print", similar to a fingerprint which is unique for every person. This makes choosing the right probiotics (=bacteria supplements) (and also prebiotics=nutrients design to feed bacteria in your good, to promote the growth of beneficial bacteria) for each person very difficult. What is more, most probiotics or prebiotics sold in stores were never actually tested in clinical studies. So we just don't know if they are actually beneficial or not. I am not a medical doctor, so I really can't make any informed recommendations - I would probably suggest to talk to your doctor about this, or just give them a go and pay close attention to whether they make you feel better (or maybe even worse).

mallenstreak180 karma

Hi Marisa! Thank you for doing this. What are your opinions on faecal transplants?

Immunity-and-beyond177 karma

They work amazingly well in patients suffering from C. difficile infections and faecal transplants are already used routinely to treat this in patients. In other settings, the effect of faecal transplants has not been fully elucidated yet. This is a really new (and exciting) field of research and I would first wait for more scientific data to be collected about this before trying any of it on myself.

velcrorex176 karma

Can gut bacteria influence which foods a person craves?

Immunity-and-beyond121 karma

Good questions - this is not my area of expertise, but from what I remember the gut bacteria can actually influence your cravings (especially as there is a strong connection between the gut microbiome and the brain - giving the phrase "gut feeling" a completely new meaning). Unfortunately, I do not know how exactly this works or which bacteria are involved in this. Same for the effect of artificial sweeteners on cravings, sorry!

YouSmeel174 karma

What are the best ways of cultivating a healthy gut biome?

Immunity-and-beyond99 karma

Hi! That's a really interesting question and exactly the question science is trying to address at the moment. Unfortunately, we don't have any definite answers yet. And as I said above - everyone's microbiota is different, so it is hard to find a solution which will fit all. There is a lot of data supporting a beneficial effect of a high fiber diet on health, however, so this might be one way to go - but again, your personal microbiota will impact how you respond to fibres - so please stop taking them if it makes you feel worse and better go talk to a doctor!

___ah133 karma

How does the gut microbiota affects one's brain ?

Immunity-and-beyond152 karma

There is more and more data showing that the gut microbiota can affect hormon levels and also the brain, giving the prase "gut feelings" a new meaning. Unfortunately I am really no expert in this field, so I am afraid I won't be able to give you any more details on this, sorry.

Syndicofberyl126 karma

Have you found any correlation between gut biome and the removal of the appendix?

Immunity-and-beyond55 karma

These are all very interesting questions, and I wish I knew the answer! I know that the composition of your gut microbiota is very different in every part of your intestine, so removing one part will definitely have an effect. But I also know that the gut microbiota can be very resilient, so I think in most cases the bacteria will find a way to just adapt to the new environment.

Xhenc70 karma

Does crohns disease affect it as well?

Immunity-and-beyond49 karma

Just to make sure - is the question how Crohn's disease (or UC) affects the microbiome? This is also a tricky question, thanks for reaching out to me. Crohn's disease and UC patients have definitely been found to have a different microbiota compared to healthy individuals, but we don't know whether the disease is cause by this or whether changes in the gut microbiota are driven by the gut inflammation in these patients. There is a lot of research at the moment into trying to find out whether these conditions could be treated by changing the microbiota (using probiotics and faecal transplants). Hopefully in a few years we will know more and will be able to better treat these conditions!

AnonLions57 karma

Hi Marisa! Firstly, why is it that this can’t be easily studied in humans? Secondly, what sort of tests would you need to be able to do - or is there any scope to expand on the methods used on mice so it is adaptable to humans instead? Thank you!

Immunity-and-beyond55 karma

The really beneficial thing about using mice for our research is that we can carefully control the environment they’re in. Even though the mice are sharing the same environment, eating the same food and drinking only water, we still see differences in the gut microbiome between individuals. Theoretically, we could use humans in the same way but it would be much harder to control the environment they live in and what they eat in order to allow us to make comparisons between them. Also, to study the local response of the gut immune system to faecal transplantation, we would need to surgically remove tissue samples from donors, which is something we want to avoid if we can.

Studentdoctor2956 karma

Hey Marisa,

This field is so fascinating, I definitely think it is the new frontier in medicine and deserves all the attention we can give it. Soon to be physician here, I'm wondering if we have any evidence to actually recommend specific diets to improve our non-metabolic health (not talking about triglycerides and cholesterol levels), such as anxiety, depression, energy etc. It is my understanding that the enteric immune system and nervous system are integrated with our CNS. Anything exciting you can think of?

Immunity-and-beyond17 karma

Hi, I am really happy to hear that you are as excited about the potential prospects of this research field as I am! Unfortunately I don't have any suggestions about specific diets - I think as a soon-to-be physician you probably know more about these things than me, a biologist doing most of her research in mice. I really hope further research into the gut microbiota will give us more clues about how we might be able to target the microbiome to treat or maybe alleviate mental disease in the future.

ndnman3350 karma

Does Hashimoto’s have anything linked with gut flora? Specifically how could I improve my diet in regards to Hashimoto’s?

Immunity-and-beyond16 karma

I have not heard of a link between the two so far, sorry, but am happy to be corrected!

brockmontana36 karma

How might the bacteria living inside me influence how I age?

Immunity-and-beyond43 karma

Ageing is a really complex process, and we still don’t know why we age. The focus of the research where I work is to try and discover the biology behind ageing, and what changes as we grow older. Previous research (as well as my results) indicate that it’s likely there’s a link between the decline in function of our gut microbiota and age-associated things such as frailty. Older people are more prone to stomach infections for example. Based on this, we think that maintaining a healthy gut microbiota might enhance healthy ageing, but more research needs to go into determining how exactly we can maintain this healthy gut microbiota (and what actually defines a "healthy" microbiota) and how exactly this affects ageing. Interesting times ahead!

crisukisu14 karma

Hey Marisa! Is there anything in the UK PhD system that makes life unnecessary hard for students? Or something that could be changed to reduce the level of mental health problems in PhD students? Thanks and stay strong! ;)

Immunity-and-beyond11 karma

Hi! That's a very good question. A PhD is a stressful time - partly because a lot of us choose to do a PhD, because they want to push the boundaries of science and challenge themselves. I think, in the end, your PhD experience will depend a lot on how supportive your environment is - and the problem with a PhD is that it is not easy to move labs when you are stuck in a less supportive environment. I was lucky enough to have a very supportive supervisor and institute as well as great lab members which helped me through the tougher days. I think it would help if funders/universities/scientific community would make it easier for PhD students to move labs/supervisors/projects if they are unhappy, but it will be hard to change the system from one day to another.

usx-tv13 karma

Hey Marisa. Thanks for the AMA.

What should I do to “cleanse” my gut bacteria after 10 years of eating shitty food?

Immunity-and-beyond12 karma

Hi! Just best to try and choose a healthy diet :) In terms of how long it takes for the gut microbiota to "heal" itself - this will obvioulsy depent on how disbalanced ("dysbiotic") the gut microbiota is. There is exciting research showing that changing the diet (e.g. from eating a lot of meat to a vegetarian diet), can have long-lasting effects on the composition of your gut microbiota within just weeks. So it's never to late to give it a go!

TheMassDisaster10 karma

Hey, I have wondered for an extremely long time, but how do people know that that you'd get the same results in mice and human beings?

Immunity-and-beyond6 karma

We often actually don't know whether the results from mice will be the same for humans. For example, mouse lifespan is only 2-3% of ours, some gene regulation differs and its brain is far simpler. Every model system has limitations. We use mice in cases, where working with humans would be too complicated or time-consuming. What we can do with laboratory mice, but not when working with humans, is shield them from many of the stresses we experience every day such as temperature fluctuations, viruses or pollutants. However, mice have the same organs, the same types of cells and nearly all the same genes as we do, which is what makes them a really useful model system. When planning and interpreting data from experiments on mice, researchers should always be considering what is likely to be similar in humans and what is likely to be different.