Gut Health & Microbiome

Rebuild the microbiome and improve digestion the evidence-based way, from named experts, covering fiber, fermented foods, and IBS, not cleanses.

Every claim below carries an evidence grade. What do these grades mean?

EVIDENCE GUT HEALTH

Eating MSG does not raise the glutamate level in your brain

Moderate

A viral post warns that MSG floods your neurons with glutamate. A review of the physiology by a University of Pittsburgh neuroscientist concludes it does not: the blood-brain barrier restricts dietary glutamate, so eating MSG does not raise the glutamate level in your brain. This rests on a narrative review rather than a large trial. For most people the evidence gives no reason to avoid it; if one specific food reliably gives you headaches, track it and mention it to a clinician.

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MEGAN ROSSI, PHD, RD GUT HEALTH

Plant variety beats fibre grams for your gut

the expert's own view, educational, not medical advice, not endorsed by us

LimitedMegan Rossi's rule of thumb is roughly 30 different plant types a week, counting vegetables, fruit, wholegrains, nuts, seeds, herbs and spices, not 30 portions
LimitedThe 30 plants figure comes from large observational microbiome data rather than a randomised trial, so treat it as a useful target, not a proven dose
ModerateFermented foods such as yoghurt, kefir and kimchi modestly raised microbial diversity in controlled feeding trials

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WILL BULSIEWICZ GUT HEALTH

Feed your gut bacteria, don't starve them

the expert's own view, educational, not medical advice, not endorsed by us

StrongFiber that reaches the colon feeds bacteria that produce short chain fatty acids
ModerateMore plant varieties per week beats eating more of the same few foods
ModerateRamp fiber up gradually, a fast jump is the top reason people quit

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EVIDENCE SLEEP

More fibre by day, deeper sleep at night

Limited

Observational data links higher daytime fibre with more slow-wave sleep. Not causal yet, but a low-risk lever worth the plate.

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GUT HEALTH

Calm and reset your gut

1Pull out the common gut irritants (For 3 to 4 weeks cut gluten, dairy, soy and eggs, plus sugar, alcohol, caffeine and ultra-processed food; you reintroduce them later one at a time)
2Support digestion (A digestive enzyme blend with meals; if you have low stomach acid, betaine HCl can help (work with a clinician first))
3Take a broad-spectrum probiotic (A multi-strain probiotic with lactobacillus and bifidobacterium daily; start low and build up if you bloat or have SIBO)

What to buy

Prebiotic fiber ~$11

DGL ~$13

L-glutamine powder ~$20

Zinc carnosine ~$25

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Tim Spector

GUT HEALTH

Feed your gut the right foods

1Aim for 30 different plants a week (Count veg, fruit, nuts, seeds, herbs, spices, wholegrains)
2Eat the rainbow for polyphenols (Mix colours across the week)
3Eat fermented foods daily (Aim for ~3 a day: kefir, kimchi, sauerkraut, miso, yoghurt)

What to buy

Prebiotic fiber ~$11

Microbiome test and program

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Bryan Johnson

GUT HEALTH

Eat the Blueprint way

1Compress your eating window (All meals in ~a morning window; long overnight fast)
2Build a 'Nutty Pudding' style breakfast (Plant/collagen protein, berries, EVOO, cocoa, nuts)
3Eat a 'Super Veggie' fibre plate (Black lentils, cruciferous veg, garlic, ginger, fermented foods)

What to buy

Plant protein blend ~$28

Kasandrinos Extra Virgin Olive Oil ~$28

Thorne Creatine ~$40

Vital Proteins Collagen Peptides ~$45

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Casey Means

BLOOD SUGAR

Build a plate that steadies energy

1Build the plate from whole, unprocessed foods (Make most of every meal recognisable whole food; minimise ultra-processed products)
2Get fibre, protein and healthy fat together (Aim for protein, a high-fibre plant portion, and a healthy fat at each meal; non-starchy veg first)
3Push fibre much higher than average (Work toward 50 g per day from beans, vegetables, seeds, berries; ramp up slowly with water)

What to buy

NOW Foods Psyllium Husk ~$13

Metabolic panel / CGM

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Tim Spector

BLOOD SUGAR

Find the foods that spike you

1Accept that your responses are personal (The same meal spikes people differently; judge foods by how you feel and respond, not just generic rules)
2Eat fibre and protein before the carbs (Start with vegetables/protein/fat, finish with starches; the sequence blunts the glucose spike)
3Pair carbohydrates with fat, protein or fibre (Add olive oil, nuts, yoghurt or vegetables to carbs rather than eating them alone)

What to buy

NOW Foods Psyllium Husk ~$13

Continuous glucose monitor

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Tim Spector

GUT HEALTH

Cut Ultra-Processed Food

1Read the ingredient list (Red flags: long lists, ingredients you would not have in your kitchen, and additives like emulsifiers, sweeteners and flavourings)
2Be skeptical of 'healthy' labels (Treat 'low-fat', 'low-calorie' and 'high-protein' claims as a prompt to check the ingredients, not as proof it is healthy)
3Target the most harmful, most frequent UPF (Prioritise dropping ultra-processed salty snacks, processed meats and sugary drinks, especially ones you eat often)

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Mark Hyman

AUTOIMMUNE

Autoimmune Gut-Support Protocol (5R Framework)

1Eliminate common inflammatory triggers (gluten, dairy, ultra-processed food) for a defined trial, then reintroduce one at a time (Trial period)
2Add digestive enzyme support with meals if needed (With meals)
3Eat colorful polyphenol-rich plants plus a multi-strain probiotic and fermented foods (Daily)

What to buy

L-glutamine powder ~$20

Enzymedica Digest Gold ~$45

Broad-spectrum probiotic ~$50

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Anthony William (Medical Medium)Self-Described Medium & AuthorMedical Medium Anthony William (Medical Medium)

GUT HEALTH

Celery Juice Morning Protocol

1Juice a large bunch of celery (William recommends at least 16 oz (about one large bunch) of pure celery juice, nothing added)
2Drink it right away, on an empty stomach (Within minutes of juicing; if stored, he says no longer than 24 hours)
3Wait before eating or drinking anything else (At least 15 to 30 minutes before your next food or drink)

What to buy

Juicer or high-speed blender ~$300

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Anthony William (Medical Medium)Self-Described Medium & AuthorMedical Medium Anthony William (Medical Medium)

GUT HEALTH

3:6:9 Cleanse - Overview

1Remove foods William says burden the liver (He recommends cutting gluten, dairy, eggs, corn, soy, pork, most oils and other foods he flags as 'liver troublemakers')
2Lemon or lime water, then celery juice (Water with lemon or lime on waking, then at least 16 oz celery juice on an empty stomach after a wait, then breakfast after another wait)
3Shift to the nutrient-dense, mostly plant meals William specifies in the book (Exact recipes and quantities are in Cleanse to Heal; not reproduced here)

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Will BulsiewiczGastroenterologistZOE Will Bulsiewicz

IBS

Gradual Fiber for IBS & Gut Tolerance

1Get IBS diagnosed by a clinician (Rule out red-flag symptoms (unexplained weight loss, rectal bleeding, anemia, family history of GI cancer or IBD) with a physician before starting an elimination diet)
2Monash low-FODMAP elimination, then structured reintroduction (Eliminate high-FODMAP foods for a short defined period, then reintroduce them one FODMAP group at a time to identify personal triggers, ideally with a dietitian)
3Gradual fiber and FODMAP reintroduction to build tolerance (Instead of staying strictly low-FODMAP long-term, slowly and incrementally increase fiber and reintroduce FODMAP foods over weeks, watching symptom response as you go)

What to buy

NOW Foods Psyllium Husk Powder ~$10

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Simon Hill

HEART HEALTH

The 5 Supplements That Made My List

1Creatine monohydrate, dosed to your body weight (0.1 g per kg of body weight per day (about 5 g at 50 kg, 7 g at 70 kg, 9 g at 90 kg))
2Omega-3, counted as combined DHA plus EPA (At least 1 g per day of DHA plus EPA combined)
3A high-quality protein powder, as a backup to food (Enough to help reach at least 1.6 g of total protein per kg of body weight per day)

What to buy

Prebiotic fiber ~$11

Multivitamin ~$30

Nordic Naturals Ultimate Omega ~$32

Thorne Creatine ~$40

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Megan Rossi, PhD, RDResearch FellowKing's College London, Department of Nutritional… Megan Rossi, PhD, RD

IBS

IBS: The Fiber-Diversity and Low-FODMAP Framework

1Get IBS diagnosed by a clinician before starting an elimination diet, ruling out red-flag symptoms (n/a, one clinical visit)
2Eliminate high-FODMAP foods for a short, defined period, ideally with a dietitian (Short-term, structured, dietitian-supervised where possible; not indefinite)
3Reintroduce FODMAP groups one at a time to identify your personal triggers (Structured reintroduction phase, ideally dietitian-guided)

What to buy

Broad-spectrum probiotic ~$50

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Mark Pimentel, MDExecutive DirectorCedars-Sinai Medical Center Mark Pimentel, MD

IBS

SIBO: The Low-Fermentation Diet (What To Eat During and After Treatment)

1The primary SIBO treatment is a physician-prescribed antibiotic course (commonly rifaximin, sometimes with neomycin or metronidazole for methane-predominant SIBO) (n/a, physician-prescribed and monitored)
2Eat normally, without cutting carbohydrates, for the duration of your antibiotic course (n/a)
3Once antibiotic treatment ends, shift to a low-fermentation diet: more liberal than low-FODMAP, limiting the most fermentable foods without eliminating broad food categories (Ongoing, individualized with a dietitian if possible)

What to buy

Ginger root extract capsules ~$15

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If a cleanse or detox tea promised a quick fix and you are wondering what actually works, that is common, and the honest answer is almost nothing sold as a cleanse has real evidence behind it. Diversity and consistency beat restriction almost every time.

Strong evidence

Plant diversity Aiming for roughly 30 different plants a week tracks with a more varied, resilient microbiome.

Cut ultra-processed food UK Biobank and 2025 dose-response data link the highest UPF intake to roughly 15% higher risk of early death, beyond calories alone. Linked to, not proven to cause.

Skip cleanses and detox teas Your liver and kidneys already do that job for free; no cleanse product has been shown to add to it.

Promising, evidence evolving

Fermented foods A 10-week Stanford trial found fermented foods raised microbiome diversity and lowered 19 inflammatory markers, while a matched high-fiber arm did not in that short window. A fiber-fermentation-timing mismatch, not proof fiber does not matter.

Fiber for IBS Gradual fiber reintroduction versus the RCT-backed mainstream low-FODMAP protocol; present both, neither is settled as universally superior.

The gut-brain axis Diet and the microbiome may affect mood, brain function and dementia risk via inflammation and metabolite pathways. Still an evolving, largely observational area.

Emerging or expert-opinion, covered honestly

The 5R functional-gut-reset sequence Remove, replace, reinoculate, repair, rebalance: a clinical framework, useful as a structured approach but not itself an RCT-tested protocol.

Most gut-health advice sold online, cleanses, detox teas, restrictive elimination diets, has little to no evidence behind it. What actually moves the needle is diversity: more plant varieties, more fermented foods, and for IBS specifically, a structured approach to fiber rather than blanket restriction. Here is the honest map, ranked by evidence, so you always know your next move.

Mark Hyman

Functional Medicine Physician · The Doctor's Farmacy

Tim Spector

Professor of Genetic Epidemiology · King's College London · ZOE

Anthony William (Medical Medium)

Self-Described Medium & Author · Medical Medium

Will Bulsiewicz

Gastroenterologist · ZOE

Michael Greger

MD, FACLM · Founder, NutritionFacts.org

Megan Rossi, PhD, RD

Research Fellow, Gut Health (disclosed Bio&Me commercial interest) · King's College London, Department of Nutritional Sciences

Mark Pimentel, MD

Executive Director, MAST Program · Cedars-Sinai Medical Center

Compare experts on Gut Health & Microbiome

Bryan Johnson vs Casey Means Bryan Johnson vs Mark Hyman Bryan Johnson vs Mark Pimentel, MD Bryan Johnson vs Megan Rossi, PhD, RD Bryan Johnson vs Simon Hill Bryan Johnson vs Tim Spector Bryan Johnson vs Will Bulsiewicz Casey Means vs Mark Hyman Casey Means vs Mark Pimentel, MD Casey Means vs Megan Rossi, PhD, RD Casey Means vs Simon Hill Casey Means vs Tim Spector Casey Means vs Will Bulsiewicz Mark Hyman vs Mark Pimentel, MD Mark Hyman vs Megan Rossi, PhD, RD Mark Hyman vs Simon Hill Mark Hyman vs Tim Spector Mark Hyman vs Will Bulsiewicz Mark Pimentel, MD vs Megan Rossi, PhD, RD Mark Pimentel, MD vs Simon Hill Mark Pimentel, MD vs Tim Spector Mark Pimentel, MD vs Will Bulsiewicz Megan Rossi, PhD, RD vs Simon Hill Megan Rossi, PhD, RD vs Tim Spector Megan Rossi, PhD, RD vs Will Bulsiewicz Simon Hill vs Tim Spector Simon Hill vs Will Bulsiewicz Tim Spector vs Will Bulsiewicz

Do detox teas or cleanses actually remove toxins?▾

No, your liver and kidneys already filter continuously; no cleanse product has been shown to add to that.

Is low-FODMAP or gradual fiber better for IBS?▾

Low-FODMAP has the stronger RCT base as a first-line approach, but gradual fiber reintroduction is a reasonable alternative many people tolerate better long-term; neither is one-size-fits-all.

Do fermented foods really beat fiber for gut health?▾

One well-run trial found fermented foods raised diversity faster than fiber did over 10 weeks, but that does not mean fiber is useless; longer fiber interventions do show benefits.

Can gut health really affect my mood or brain?▾

There is a real and growing body of research on the gut-brain axis, but most of it is still observational, so treat any single-study claim with caution.

Experts behind Gut Health & Microbiome protocols

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