Beer

What it is

Beer is a fermented drink made from malted barley, hops and yeast [1]. Its alcohol content typically ranges from about 3.5% to 10%, and alcohol-free versions have most or all of the alcohol removed [1]. Beer supplies polyphenols (plant compounds), and because hops are used almost only in brewing, beer is the main dietary source of the hop compound isoxanthohumol [1]. Filtration removes some polyphenols and live yeast, so unfiltered beers may retain more of them [1].

How it might work

Beer polyphenols reach the colon, where gut bacteria can use them, and the randomised trial's effect on gut bacteria did not depend on alcohol [1]. Some beers also contain live fermentation yeasts; researchers suggest unfiltered beers with more polyphenols and yeast could have a bigger effect on the gut microbiome [1].

What the research says

In a 2022 double-blind randomised trial, 22 healthy men drank 330 mL of beer daily for 4 weeks — half 0.0% alcohol, half 5.2%. Gut bacterial diversity rose in both groups (Shannon index 2.7 to 2.9 and 2.8 to 3.0), and a marker of gut barrier function tended to rise; weight, body fat and blood markers were unchanged [1].

An earlier 30-day study found both alcohol-free and regular beer shifted the gut bacteria towards Bacteroidetes; alcohol-free beer lowered fasting glucose and increased a marker of beta-cell function, while regular beer raised fasting glucose and lowered that marker — all within normal range [2].

Observational data point the same way: among 78 adults, moderate beer drinkers (200–600 mL a day) had more Blautia and Pseudobutyrivibrio and higher faecal butyric acid, a short-chain fatty acid linked to gut health, than abstainers, though such studies cannot show cause and effect [3].

Beer style matters: in a 2025 randomised trial, 44 healthy young men drank 660 mL a day of pilsener, mixed or wheat alcohol-free beer, or water, for 4 weeks. Mixed beer raised fasting glucose and triglycerides, wheat beer raised insulin, C-peptide and triglycerides, while pilsener lowered cholesterol and LDL; the authors attributed these differences to sugar and calories rather than polyphenols [4].

For heart-risk markers, a 2020 meta-analysis of 26 controlled trials found beer raised HDL cholesterol by 3.63 mg/dL and apolipoprotein A1 by 0.16 mg/dL versus controls, while total cholesterol rose by 3.52 mg/dL and LDL and triglycerides did not change; flow-mediated dilation improved by 0.65% after a single drink [5]. These are surrogate markers, not heart attacks [5].

Bone studies disagree: in the Framingham Offspring cohort, men drinking 1–2 drinks a day of beer or total alcohol had 3.4–4.5% higher hip bone density than non-drinkers, and the association disappeared after adjusting for silicon intake [6]. A 2023 study of 693 men found no association between usual alcohol intake and whole-body bone density, and low-strength beer was linked to slightly lower spinal density [7].

In active people, a review of 16 small studies found low-alcohol beer (under 4%) can be used for rehydration after exercise, while stronger beer adds to fluid losses unless paired with a non-alcoholic drink [8]. A 2025 meta-analysis found moderate beer drinkers' overall diet quality was similar to abstainers' [9]. A small crossover trial in 36 overweight adults found both regular and alcohol-free beer mildly changed the fat composition of red blood cell membranes, without changing membrane fluidity [10]. A pilot study in 14 people with type 2 diabetes found a specially modified alcohol-free beer lowered glucose and insulin-resistance markers — evidence about that product, not regular beer [11]. Reviews comparing beverage types find broadly similar disease associations for wine, beer and spirits at low-to-moderate intake [12].

Doses used in studies

Gut microbiome trials: 330 mL a day for 4 weeks (0.0% or 5.2% beer) [1]; 355 mL a day for 30 days [2]. Observational comparison: 200–600 mL a day of 5% beer [3]. Alcohol-free beer metabolic trial: 660 mL a day for 4 weeks [4]. The cardiovascular meta-analysis pooled 26 controlled trials of varying doses, durations and beer types [5].

Safety and interactions

Alcohol is a known carcinogen. A meta-analysis of 139 cohort studies linked even light drinking to higher risks of oesophageal, colorectal and breast cancers, and concluded there is no safe level of alcohol for cancer risk [13]. A Global Burden of Disease analysis found the intake minimising overall health harm is zero standard drinks a week and that, among people aged 15–49, alcohol was the leading risk factor for death in 2016 [14]. Dietary guidelines cited by the beer trial define moderation as up to 1 drink a day for women and 2 for men [1]. The short beer trials reviewed here did not measure common side effects such as hangovers.

Beer and cider are the alcoholic drinks most strongly linked to gout: each extra pint per day was associated with about 60% higher gout risk in a UK Biobank cohort, and more than 1–2 drinks in the previous 24 hours raised the odds of an attack by 36–51% in people with gout [15][16]. Beer carried a 49% higher gout risk per daily serving in a US cohort, ahead of spirits, while wine was not associated [17]. People with gout are advised to limit alcohol of all types [16].

Drinking at or above about 1 drink a day for women or 2 for men was linked to about 40% higher risk of liver cancer in a meta-analysis of cohort studies [18].

Alcohol in pregnancy is linked to a higher risk of miscarriage — about 19% higher overall, and about 6% higher for each additional drink per week up to five — so alcohol-free beer is the safer choice during pregnancy [19].

Alcohol interacts with medicines: placebo-controlled trials found it raised blood levels of diazepam, opioids, cannabis and methylphenidate, and the authors advise people taking those medicines to avoid alcohol [20].

Strong beer can worsen fluid balance after exercise unless it is paired with a non-alcoholic drink [8]. We found no studies of beer in people with kidney disease for this review.

Caveats and open questions

The gut-bacteria evidence is thin: the main trials included roughly 20–44 people, lasted 4–30 days and enrolled mostly healthy men, so effects in women, older adults and people with gut conditions are unknown [1][2][4]. The trials disagree on whether alcohol matters for the gut effect: the 2022 trial found the same diversity rise with and without it, while an earlier study found alcohol-free beer more favourable [1][2]. Bacterial diversity and butyric acid are markers, and no study has yet measured real outcomes such as infections or disease risk [1][3]. The 2025 alcohol-free beer trial was small, and one author is a company founder and an inventor on patents related to the work [4]. Bone findings come from two observational studies that point in different directions [6][7]. The main gut-microbiome trial (NCT03513432) is complete, and no newer trial of beer and gut bacteria is registered.