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The Science of Gut Health (& Why It Matters)

2023-04-26 · Long video (solo, talking head or whiteboard) · Ali, Sophie Medlin · recording, 15:53 · watch on YouTube

Topic: Health, sleep and habits (also: Medicine and his doctor years) · mode: List of tips or lessons · tags: Evidence-based framing, His medical past, Sponsor segment present

Drawing on his Deep Dive interview with the dietitian Sophie Medlin, Ali explains that gut health, a balanced and diverse gut microbiome, affects mental and physical health, and gives five things to add to the diet (30 plants a week, variety, 30 grams of fibre a day, a probiotic, oily fish) and five to cut down (red meat, processed food, artificial sweeteners, diet fads and detoxes, calorie counting).

What is said

The parts of the video and what is said in each (★ — how much it matters to the video).

00:00:00 — Gut health affects digestion, immunity, mood and focus; Ali's interview with Sophie Medlin

  • ★★★ Ali says gut health affects not only digestion but also physical health, such as the immune system, and mental health, including concentration, focus and general productivity. — 00:00:00 · Mental health
  • ★ Ali says that as a doctor he learned a lot about the diseases and pathologies that can affect the gut, but medical school teaches much less about nutrition and everyday gut care. — 00:00:00
  • ★★ To learn about the link between the gut and the body, Ali interviewed Sophie Medlin, a consultant dietitian specialising in gut health, chair of the British Dietetic Association and a lecturer at King's College London. — 00:00:29

00:00:55 — What gut health is: the gut and its microbiome

  • ★★ Ali says a healthy gut means a well-balanced and diverse range of microorganisms, bacteria, viruses and others, in the digestive tract: a healthy gut microbiome. — 00:01:27
  • ★ Ali explains that the parts of plant fibre we cannot digest are fermented in the colon by bacteria, yeasts and other microorganisms, producing gas and metabolites that interact with the body. — 00:01:27
  • ★★ Ali says an imbalanced gut microbiome can lead to digestive problems such as bloating, constipation, diarrhoea and irritable bowel syndrome. — 00:01:56
  • ★★ Ali says that in the last 30 years scientists have found the effects of gut health go well beyond digestion. — 00:01:56

00:01:58 — Why gut health matters: digestive problems, the gut-brain axis and the immune system

  • ★★ Sophie Medlin says the gut is the chattiest organ between the brain and the gut, constantly sending the brain messages it has to deal with. — 00:02:55
  • ★★ Ali says three connections link the gut and the brain in the gut-brain axis: a chemical one, a hormonal one through the HPA axis and a physical one through the vagus nerve. — 00:02:55
  • ★★ Ali says the gut microbiome produces neurotransmitters such as serotonin and dopamine, and that 95% of the body's serotonin is produced in the gut. — 00:02:55
  • ★ Ali says studies have shown that the bacteria in the gut affect the stress response of the HPA (hypothalamus-pituitary-adrenal) axis. — 00:03:24
  • ★ Ali says the gut and the brain are physically connected through the vagus nerve, the main nerve of the parasympathetic nervous system. — 00:03:24
  • ★★ Ali says 70% of the body's immune cells live in the bowel, where gut bacteria constantly interact with them. — 00:03:53
  • ★ Ali says studies that change the gut bacteria of germ-free mice show a clear link between the gut microbiome and the ability to produce immune cells and antibodies. — 00:04:23

00:04:44 — Five things to add: 30 plants a week, variety over consistency, 30 grams of fibre a day, a probiotic

  • ★★ Ali says social media carries a lot of misleading and potentially harmful fake news on health and nutrition, especially on gut health, where people search for quick fixes and miracle cures. — 00:04:52
  • ★★★ Ali's first tip for gut health is to aim for 30 different plants per week. — 00:04:52
  • ★★★ Sophie Medlin says the important thing for gut health is eating 30 different plants a week, a wide variety of plant types. — 00:05:21
  • ★★ Ali says plants for this count are more than green leaves: all fruit and vegetables, legumes such as peas, lentils, tofu and beans, grains such as rice, corn, barley, oats and wheat, and plant milks. — 00:05:21
  • ★★ Ali passes on Sophie Medlin's tip for reaching 30 plants a week: break the number into days, about four or five different plants a day. — 00:05:50
  • ★★ For 30 plants a week, Ali suggests a breakfast of wholegrain cereal or oatmeal with seeds, nuts and dried fruit, fruit as a mid-morning snack and some vegetables with lunch or dinner. — 00:05:50
  • ★★ Ali's second tip for gut health is to aim for variety in the diet rather than the consistency much diet advice favours for losing weight or building muscle. — 00:06:19
  • ★★ Ali's third tip for gut health is to aim for 30 grams of fibre every day. — 00:06:19
  • ★★ Sophie Medlin says most people in England eat less than half of the fibre they need every day. — 00:06:46
  • ★ Ali says fibre reaches the colon undigested, where it acts as a prebiotic, food for the good bacteria. — 00:06:46
  • ★★ As a rough guide to enough fibre, Ali suggests five servings of fruit and vegetables a day, whole grains with two of the three meals, and seeds, nuts and dried fruit as snacks. — 00:06:46
  • ★ Ali suggests swapping foods for higher-fibre alternatives, such as wholegrain rice instead of white rice. — 00:07:15
  • ★★ Ali's fourth tip for gut health is to take a probiotic, though he calls the point a little controversial because the evidence is not wholly in its favour. (hedged) — 00:07:15
  • ★★ Sophie Medlin cites a study in which 55 healthy volunteers given a probiotic, against a placebo group, had significant reductions in psychological stress and in cortisol. — 00:07:44
  • ★ When buying a probiotic, Ali advises checking the manufacturer and the expiry date, since one that has sat on the shelf for ages may be less effective. — 00:08:13

00:08:30 — Sponsor read for the Heights Smart Probiotic

  • ★★ Ali's fifth tip for gut health is two portions of oily fish a week, since its long-chain omega-3 fatty acids help the good gut bacteria that control inflammation. — 00:09:12

00:09:20 — Five things to add: two portions of oily fish a week

  • ★★★ Sophie Medlin says we need two portions of oily fish a week for brain health; not eating it is like replacing 25 (as heard) of the bricks of your house with polystyrene. — 00:09:41

    “it's a bit like taking out 25 of the bricks of your house and replacing them with polystyrene”

  • ★★ Ali says salmon, mackerel and sardines count as oily fish but tuna, cod and sea bass do not; vegetarians can use flaxseed, flaxseed oil, canola oil or soybean oil for omega-3, or simply take an omega-3 supplement. — 00:09:41

  • ★★ Ali says it will be hard to cut the five gut-unfriendly foods out of the diet completely, so aiming to reduce them is probably more realistic and sustainable. (hedged) — 00:10:10

00:10:18 — Five things to avoid: red meat, processed food, artificial sweeteners, diet fads and detoxes, counting calories

  • ★ Jordan Peterson (quoted): Jordan Peterson says that on the all-meat carnivore diet his psoriasis and his gum disease have gone. — 00:10:39
  • ★★★ Ali's first thing to avoid is too much red meat: the evidence shows it is not good for gut health, as its metabolites are linked to a higher risk of cardiovascular disease and cancer. — 00:10:39
  • ★★ Sophie Medlin says the World Cancer Research Fund advises only three portions of red meat a week, 350 to 500 grams in total, as more puts us at higher risk of bowel cancer. — 00:10:39
  • ★★ Ali's second thing to avoid is processed food, basically anything that comes in a packet, such as sausages, bread or crisps. — 00:11:23
  • ★★ Ali says the preservatives that keep processed food from going off also stop the good bacteria from growing in the gut. — 00:11:23
  • ★★ Sophie Medlin says emulsifiers are thought to disrupt the bowel lining, opening the tight junctions between bowel-wall cells and letting too much inflammation into the body. (hedged) — 00:12:07
  • ★★ Ali says that for the many people relying on cheap processed foods in the cost-of-living crisis, meeting basic food needs comes first and refining nutritional value second. — 00:12:07
  • ★★★ Ali's third thing to avoid is artificial sweeteners: before talking with Sophie Medlin, Diet Coke was his go-to fizzy drink because he thought artificial sugar was good, but it is not good for gut health. — 00:12:36
  • ★★ Sophie Medlin says data suggest artificial sweeteners increase insulin production, making us hungrier, so ideally sweeteners go in the no-thank-you bucket. — 00:13:05
  • ★★ Ali's fourth thing to avoid is diet fads and detoxes: Sophie Medlin recommends being very wary of social media gut-health trends, which generally do not come from qualified medical professionals. — 00:13:35
  • ★★ Sophie Medlin says a juice cleanse deprives the body of many important nutrients, so it has to work much harder. — 00:13:35
  • ★★ Ali says a gluten-free diet matters for people with gluten intolerance or coeliac disease, but outside that 1% of the population cutting out gluten has few health benefits and is a bit of a fad. — 00:14:04
  • ★★ Ali's fifth thing to avoid is counting calories: according to Sophie Medlin it is not very effective for gut health, because calories do not reflect the nutritional value of food. — 00:14:04
  • ★ Ali says a medium portion of McDonald's chips has around 340 calories, about the same as meals of very different nutritional value. — 00:14:04 · McDonald's
  • ★★ Ali says food labels are allowed to be up to 20% wrong about calories, so a calorie-tracking app is probably at least 20% out. — 00:14:33
  • ★ Ali says the body does not absorb all the calories in nuts shown on the packet, as some are lost in digestion. — 00:15:02
  • ★★ Ali says he is choosing to somewhat ignore Sophie Medlin's tip against counting calories: he counts calories and macros to get hench, keeping in mind that calories are only one part of the story. — 00:15:02
  • ★★ Sophie Medlin says the best approach would be to move away from calories and think about whether we are physically hungry. — 00:15:02

00:15:31 — The full podcast episode with Sophie Medlin; sign-off

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Mentioned

Central: gut microbiome · Sophie Medlin

Also: People: Jordan Peterson

Projects: Deep Dive

Organizations: British Dietetic Association · Heights · King's College London · McDonald's · TikTok · World Cancer Research Fund

Concepts: brain health · cancer · cardiovascular disease · carnivore diet · gut-brain axis · Mental health · parasympathetic nervous system · probiotic

Places: England

Products: Diet Coke

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