EXPLAINED Wine and digestion
STORY MICHAEL APSTEIN, MD, ASSISTANT PROFESSOR OF MEDICINE, HARVARD MEDICAL SCHOOL & MEMBER OF THE DIVISION OF GASTROENTEROLOGY, BETH ISRAEL, BOSTON
In Timothy 5:23, Paul advises: ‘Drink no longer water, but use a little wine for thy stomach’s sake.’ Red wine, and even red wine that has had its alcohol removed, can inhibit the growth of bacteria in the test tube. Maybe Paul felt that a little wine would counteract the bacterial impurities found in water in Biblical times. But, is there something else at work here? As is usual with science, the answer is not clear and, worse, there’s good evidence that wine for many people worsens gastrointestinal problems.
INSIDE THE BODY
Let’s start with the intestinal microbiome, the billions of bacteria, viruses, fungi and other organisms that inhabit our intestinal tract. No doubt, the intestinal microbiome is important. It may be a marker of how healthy we are. Or changes to it may contribute to disease. Healthy people have a more diverse intestinal microbiome – more species of organism – than obese individuals or those with chronic inflammatory diseases.
It’s a fascinating observation, but the question remains, which is the cart and which is the horse? Does obesity or chronic disease, for example, cause the lack of diversity of the microbiome? Or is the lack of diversity the cause of obesity or chronic disease? If it’s the latter, changing the intestinal microbiome could be a crucial way to helping people lose weight or modify the disease process. If the former is true, altering the intestinal microbiome will make no difference.
WINE & THE BIOME
A recent study from King’s College, London suggested that drinking red wine – but not white wine, spirits, beer or cider – increases the diversity of the intestinal microbiome in humans, presumably because of its polyphenol content. The popular press embraced the findings as more evidence of the beneficial effect of red wine. It’s a tantalising prospect – altering our gut bacteria by drinking red wine could make us healthier. But, and this is key, until we can distinguish the cart from the horse, we won’t know whether that’s true.
Wine, both red and white, is a potent stimulus of gastric acid secretion. In contrast, a 12% solution of ethanol has no effect on gastric acid secretion. So, something other than alcohol – we don’t know what – is responsible for the bump in acid output. Unsurprisingly, many individuals report worse heartburn or gastroesophageal reflux after drinking wine. Excess acid washing back into the esophagus likely explains their discomfort. But distilled beverages, even those with a higher alcoholic content, such as whisky and Cognac, have no effect on acid secretion. Yet they still induce heartburn. As with the intestinal microbiome, the relationship between alcohol and heartburn is not straightforward.
Everyone ‘knows’ that drinking causes ulcers. Wine’s ability to induce hyperacidity would seem to fit that paradigm. But multiple studies show that wine drinking is associated with a lower, not higher, risk of peptic ulcer disease. Sometimes the conventional wisdom is incorrect.
Though the liver is the primary site of the metabolism of alcohol, the stomach plays a key role. The stomach lining contains an enzyme that also breaks down alcohol. That explains why eating while drinking results in lower blood alcohol levels. Food slows the rate at which contents leave the stomach. As a result, the alcohol spends more time in the stomach where it is broken down before it could be absorbed.
Conversely, drinking on an empty stomach allows more alcohol to escape breakdown there, be absorbed and result in a higher blood alcohol level. Women have less of this enzyme in their stomachs compared to men, which helps explain why they are more susceptible to alcohol’s effects.
So, if you take Paul’s advice, have a bite to eat with the wine.