How Does Alcohol Impact Your Gut Microbiome & Leaky Gut? | Dr. Andrew Huberman
00:00:00.000 | [Silence]
00:00:03.280 | For those of you that enjoy alcohol,
00:00:04.920 | I, again, I really like to say,
00:00:07.760 | I feel guilty about telling you this
00:00:09.440 | because I know how much some people enjoy a good drink
00:00:11.880 | every once in a while.
00:00:12.720 | And I say a good drink
00:00:13.540 | because some people do like the taste of alcohol.
00:00:16.080 | I suppose I lucked out
00:00:16.960 | and then I don't really like the taste of alcohol.
00:00:18.620 | And that just puts me to sleep,
00:00:19.960 | but I know that people do enjoy it.
00:00:21.560 | And I do want to point out that there is zero evidence
00:00:27.120 | that provided somebody is of drinking age,
00:00:30.960 | or certainly not in the stage of brain development,
00:00:34.200 | that having one drink or two drinks every now and again,
00:00:37.720 | meaning every three or four weeks or once a month,
00:00:40.780 | that is not going to cause major health concerns
00:00:44.380 | or major health issues for most people.
00:00:46.960 | I suppose if you have zero
00:00:49.140 | or very little alcohol dehydrogenase,
00:00:51.000 | it might make you feel sick,
00:00:51.840 | but then you're probably not the kind of person
00:00:53.200 | that's going to be drinking at all.
00:00:55.120 | So again, if you enjoy alcoholic drinks,
00:00:57.940 | I'm not trying to take them away from you by any means,
00:01:03.000 | but you should know what drinking does
00:01:05.240 | if you're consuming it in this kind of typical
00:01:07.640 | chronic pattern, as we can now refer to it,
00:01:09.520 | which is that one or two a night
00:01:11.760 | or a few stacked up on Friday
00:01:15.520 | and maybe three or four on Saturday,
00:01:17.200 | this kind of pattern of drinking, which is quite common.
00:01:20.240 | And one of the more serious effects
00:01:21.760 | that we should think about is the impact
00:01:23.920 | on the so-called gut brain axis,
00:01:25.360 | or for sake of today's discussion,
00:01:27.160 | the gut liver brain axis.
00:01:29.040 | I don't think the gut liver brain axis
00:01:30.600 | has ever been discussed on this podcast,
00:01:32.160 | maybe any podcast, although the moment I say that,
00:01:34.440 | I'm going to, you know, the gut liver brain axis,
00:01:37.680 | people are going to come after me with,
00:01:38.920 | I suppose, gut, liver, brain, and brains.
00:01:41.280 | In any event, you have a brain, you have a gut.
00:01:46.040 | That gut runs from your throat
00:01:48.160 | down to the end of your intestine.
00:01:52.880 | Your gut and your brain communicate
00:01:54.840 | by way of nerve cells, neurons, and nerve connections,
00:01:58.200 | the vagus nerve in particular,
00:02:00.080 | and by way of chemical signaling.
00:02:02.520 | Your gut also communicates by way of chemical signaling,
00:02:05.200 | and believe it or not, by way of neural signaling too,
00:02:07.960 | to your liver.
00:02:09.240 | And as we talked about earlier,
00:02:10.680 | the liver is the first site in which alcohol
00:02:13.640 | is broken down and metabolized into its component parts.
00:02:17.060 | The liver is also communicating with the brain
00:02:21.120 | through chemical signaling and neural signaling.
00:02:23.760 | So we have the gut liver brain axis.
00:02:27.080 | And what you find is that people who ingest alcohol
00:02:31.720 | at any amount are inducing a disruption
00:02:35.840 | in the so-called gut microbiome,
00:02:37.900 | the trillions of little micro bacteria
00:02:40.820 | that take resident in your gut
00:02:42.280 | and that live inside you all the time,
00:02:43.640 | and that help support your immune system,
00:02:45.120 | and that literally signal by way of electrical signals
00:02:48.760 | and chemical signals to your brain
00:02:50.780 | to increase the release of things like serotonin and dopamine
00:02:53.960 | and regulate your mood generally in positive ways.
00:02:56.440 | Well, alcohol really disrupts those bacteria.
00:02:58.840 | This should come as no surprise.
00:03:00.000 | I mean, earlier we talked about this,
00:03:01.320 | and it's well-known if you want to sterilize something,
00:03:04.120 | you want to kill the bacteria, you pour alcohol on it.
00:03:06.880 | And I can remember scraping myself or cutting myself.
00:03:10.680 | I was always injuring myself when I was a kid.
00:03:12.680 | And the moment they take out the peroxide,
00:03:15.320 | you're like, "Oh boy, here it comes."
00:03:16.440 | But if there's no peroxide around
00:03:18.200 | and you've got a wound there and you need to clean it out,
00:03:20.200 | yeah, they'll use alcohol,
00:03:21.780 | which I do not recommend, by the way,
00:03:23.260 | and that's one of the harshest ways to clean a wound.
00:03:25.440 | But for centuries, thousands of years, really,
00:03:27.860 | alcohol has been used in order to clean things
00:03:30.780 | and kill bacteria.
00:03:32.460 | So alcohol kills bacteria, and it is indiscriminate
00:03:36.540 | with respect to which bacteria it kills.
00:03:39.020 | So when we ingest alcohol and it goes into our gut,
00:03:41.260 | it kills a lot of the healthy gut microbiota.
00:03:44.680 | At the same time, the metabolism of alcohol in the liver,
00:03:47.820 | which you now understand that pathway
00:03:50.000 | involving NAD, acetyl aldehyde, and acetate,
00:03:54.360 | that pathway is pro-inflammatory.
00:03:57.640 | So it's increasing the release of inflammatory cytokines,
00:04:00.680 | things like IL-6, et cetera, tumor necrosis factor alpha.
00:04:04.640 | If you'd like to learn more about the immune system,
00:04:06.240 | we did an episode all about the immune system.
00:04:08.320 | You can find it hubermanlab.com.
00:04:09.800 | It'll teach you all the basics of what are cytokines,
00:04:12.240 | what are mast cells, et cetera.
00:04:14.340 | In any event, all these pro-inflammatory molecules,
00:04:17.640 | those are being released.
00:04:20.760 | You've now got disruption of the gut microbiota.
00:04:24.180 | As a consequence, the lining of the gut is disrupted,
00:04:27.360 | and you develop at least transiently leaky gut.
00:04:31.840 | That is, bacteria that exist in the gut,
00:04:34.260 | which are bad bacteria,
00:04:35.540 | can now pass out of the gut into the bloodstream.
00:04:37.640 | So you've got a two-hit kind of model here.
00:04:39.860 | In biology, we talk about two-hit models.
00:04:42.260 | That is kind of a one plus one equals four.
00:04:44.800 | And it's generally when you hear two-hit,
00:04:46.120 | it's not a good thing.
00:04:47.560 | So you've got bad bacteria
00:04:49.840 | from partially broken down food moving out of the gut.
00:04:53.100 | The good bacteria in the gut have been killed.
00:04:55.200 | You might say, why doesn't the alcohol
00:04:56.600 | kill the bad bacteria in the gut?
00:04:58.800 | Well, the bad bacteria that are from partially digested food
00:05:03.800 | oftentimes escape the gut
00:05:06.240 | before the alcohol can disrupt them.
00:05:09.240 | And so now you've got leaks in the gut wall.
00:05:12.200 | You've got the release of this bad bacteria.
00:05:14.020 | You've got inflammatory cytokines
00:05:16.100 | and other things being released from the liver.
00:05:18.060 | And they are able to get into the brain
00:05:20.620 | through what's called a neuroimmune signaling.
00:05:23.260 | And what's really bizarre in terms of the way
00:05:25.700 | that this manifests in the brain,
00:05:27.580 | I mean, it's not the way I would have done it,
00:05:29.680 | but then again, as I always say,
00:05:31.000 | I wasn't consulted at the design phase.
00:05:33.500 | And anyone who says they did,
00:05:34.520 | you should be very skeptical of them.
00:05:36.380 | The net effect of this is actually to disrupt
00:05:40.860 | the neural circuits that control regulation
00:05:43.240 | of alcohol intake.
00:05:44.560 | And the net effect of that is increased alcohol consumption.
00:05:49.180 | So this is just terrible, right?
00:05:50.600 | I mean, you're taking in something
00:05:52.840 | that disrupts two systems, the gut microbiota,
00:05:55.600 | and it disrupts in two ways.
00:05:56.680 | It's killing the good gut microbiota,
00:05:58.760 | and it's allowing the bad bacteria
00:06:02.660 | to move from the gut into the bloodstream.
00:06:04.320 | You've also got pro-inflammatory cytokines
00:06:06.520 | coming from the liver.
00:06:07.800 | And those converge or arrive in the brain
00:06:11.900 | and create a system in which the neural circuits
00:06:15.100 | cause more drinking.
00:06:16.940 | That's a bad situation.
00:06:18.300 | And this is why people who drink regularly,
00:06:20.840 | even if it's not a ton of alcohol,
00:06:23.600 | again, of the sorts of patterns of drinking
00:06:25.280 | I talked about before,
00:06:26.120 | and certainly for those that are chronic heavy drinkers,
00:06:29.400 | what you end up with is a situation
00:06:31.160 | in which you have inflammation
00:06:32.780 | in multiple places in the brain and body,
00:06:34.800 | and the desire to drink even more
00:06:37.160 | and to further exacerbate that inflammation
00:06:39.140 | and the gut leakiness.
00:06:40.920 | So this is basically a terrible scenario
00:06:43.080 | for the gut-liver-brain axis.
00:06:45.420 | And it's especially prevalent
00:06:46.720 | in so-called alcohol use disorder.
00:06:48.240 | Again, people that are ingesting
00:06:49.240 | somewhere between 12 and 24 drinks per week.
00:06:51.760 | For those of you that are interested in learning more
00:06:53.560 | about the gut-liver-brain axis
00:06:55.040 | and in particular alcohol use disorder,
00:06:56.920 | I'll provide a link in the show note captions.
00:06:59.100 | And there's a wonderful review on this that details that.
00:07:02.380 | But on the positive side,
00:07:04.280 | it points to the possibility that at least some,
00:07:06.880 | again, at least some of the negative effects
00:07:09.440 | of alcohol consumption,
00:07:10.480 | whether or not you're somebody
00:07:11.600 | who's currently ingesting alcohol
00:07:13.800 | or who used to ingest alcohol
00:07:15.120 | and is trying to so-called repair these systems
00:07:17.240 | of the brain and body,
00:07:18.360 | whether or not replenishing the gut microbiota
00:07:20.800 | is going to be beneficial.
00:07:21.680 | And we know that there are ways to do that.
00:07:23.840 | And we know that there's at least some promise
00:07:25.900 | for the ability for the system to repair itself.
00:07:28.640 | How does one do that?
00:07:29.920 | Well, I've talked before about this on the podcast,
00:07:32.040 | but studies done by colleagues of mine at Stanford,
00:07:34.520 | Justin Sonnenberg,
00:07:35.360 | who's been on this podcast as a guest,
00:07:36.880 | an amazing episode all about the gut microbiome
00:07:38.960 | and his collaborator, Chris Garner,
00:07:40.560 | also at Stanford School of Medicine,
00:07:42.680 | have explored not alcoholism,
00:07:45.640 | but what are ways to improve the gut microbiota
00:07:49.680 | in particular to reduce the production
00:07:53.440 | of inflammatory cytokines
00:07:55.320 | and to adjust what's called the inflammatome.
00:07:57.360 | You've heard of the genome and the proteome, et cetera.
00:07:59.920 | Well, the inflammatome is the total array
00:08:03.720 | or at least the near total array of genes and proteins
00:08:06.800 | that control inflammation.
00:08:08.160 | How can you reduce inflammation
00:08:09.600 | and make that inflammatome healthier?
00:08:12.000 | Well, they've shown that two to four servings
00:08:14.840 | of fermented foods per day,
00:08:16.480 | and here I'm not referring to fermented alcohol,
00:08:18.520 | I'm talking about low sugar fermented foods,
00:08:20.120 | so things like kimchi, sauerkraut, natto,
00:08:23.400 | for those of you that like Japanese food.
00:08:26.800 | There are others, I know things like kefir,
00:08:29.160 | things like yogurts that have a lot of active bacteria,
00:08:32.440 | again, low sugar varieties of all these things.
00:08:34.960 | Those are terrific at reducing inflammatory markers
00:08:39.920 | and at improving the gut microbiome.
00:08:42.640 | One could imagine that either inoculating oneself
00:08:45.840 | from some of the effects of alcohol,
00:08:47.520 | although I'd prefer that people
00:08:48.440 | just not drink alcohol chronically, frankly,
00:08:51.360 | or if somebody is trying to repair their gut microbiome
00:08:54.020 | because they ingested a lot of alcohol
00:08:56.360 | or because they had a lot of these inflammatory cytokines
00:08:58.480 | for many years or even a short period of time,
00:09:01.280 | regular ingestion of two to four servings
00:09:03.440 | of these fermented foods can be quite beneficial.
00:09:06.700 | I want to make it clear that has not been examined
00:09:10.040 | specifically in the context of alcohol use disorder,
00:09:14.000 | but because a huge component of the negative effects
00:09:17.480 | of alcohol use disorder are based
00:09:19.560 | in this gut-liver-brain axis and disruption
00:09:21.360 | of the gut microbiome and the inflammatory cytokines,
00:09:23.960 | it stands to reason that things that are well-established
00:09:27.080 | to improve inflammation status,
00:09:29.800 | in other words, reduce inflammation,
00:09:31.420 | such as ingesting two to four servings
00:09:33.040 | of low-sugar fermented foods per day,
00:09:35.020 | make sense in terms of trying to repair
00:09:38.320 | or replenish the system.
00:09:40.080 | One could also imagine taking probiotics or prebiotics.
00:09:42.640 | Certainly that would work as well,
00:09:44.640 | although I've sort of favored the discussion
00:09:46.640 | around fermented foods and replenishment
00:09:48.480 | of the gut microbiome, mostly because there are more studies
00:09:52.680 | that have examined that in humans
00:09:54.360 | and because of the direct relationship
00:09:56.340 | that's been established between doing that
00:09:57.980 | and reducing negative markers within the inflammatome.
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