Now the bad news: red wine not great for health after all
NUTRITION research often loses sight of the wood for the trees by focusing on a single component of food.
The latest example of this comes from a study published in JAMA Internal Medicine on Tuesday that shows the much-hyped resveratrol may not be as super as previously touted.
Resveratrol is a naturally occurring plant chemical found in the skin of grapes, red wine, peanuts, cocoa powder, and certain berries and roots.
There's interest in the chemical because of its proposed antioxidant, anti-inflammatory, and potential anticancer effects.
Combine that with a possible role in extending lifespan (there's some evidence for this in yeast and flies), and you can see why this common substance has captured the imagination of medical researchers and the public alike.
But despite all this interest, there's little research linking resveratrol to favourable health outcomes when it's a normal part of the diet.
Sure, using high doses of the stuff in supplement form has shown mixed benefits on inflammation and markers of heart disease in short-term studies.
But there's need for caution; studies with supplements are far removed from normal diets - a person would need to drink a case of red wine each day to get similar doses of resveratrol.
This latest JAMA Internal Medicine paper has filled this gap by looking at real-world diets and resveratrol consumption.
What the study found
The study authors looked for a link between resveratrol and health and longevity in a group of 783 elderly adults from the Chianti region of Italy.
Rather than use dietary records to estimate how much each person was consuming from food, the researchers measured breakdown products of resveratrol metabolism in their urine.
So, with a more robust measure of resveratrol on hand, how had the health of this group of Italians fared when they were followed up nine years later?
The answer was as you would expect: rates of cardiovascular disease, cancer, and mortality had no link with amounts of resveratrol metabolites in participants' urine.
Throwing the spotlight on individual nutrients, such as resveratrol, as being a health saviour or unfairly demonising single foods, such as sugar or saturated fat, takes the focus off the whole diet.
Even blood markers of inflammation, which lie at the heart of metabolic disease risk, had no link with resveratrol levels.
Still, one research study can't prove or disprove a theory so it would be foolish to put too much weight on these results.
Besides, there are problems with the study too - the number of participants is relatively small, and urinary resveratrol metabolites were only measured at the beginning of the study.
It could be that higher amounts of dietary resveratrol are needed for a beneficial effect.
Still, as this was a group of people from Chianti following their traditional lifestyle, they were likely consuming ample wine and foods high in the chemical.
The authors did find that people with the highest levels of urinary resveratrol metabolites also drank the most alcohol, so wine was its most likely source.
Drilling too far down
Much of the interest in resveratrol comes from a theory that seeks to explain what's known as the "French paradox".
The paradox is that the French have relatively low heart disease rates despite high consumption of saturated fat.
The resveratrol in red wine is thought to be the reason for this. Correlation does not prove causality, but this theory about the French paradox has attained a life of its own.
In fact, the red wine and resveratrol theory is just one of dozens of plausible potential explanations for the link.
The French eat most of their meals at home, prepared from a wide variety of ingredients. Contrast that with diets containing similar amounts of saturated fat from mostly take-away or processed sources.
The fact is, saturated fat tells you little about the overall nutritional quality of a person's diet.
And this is the salient point here. Throwing the spotlight on individual nutrients, such as resveratrol, as being a health saviour or unfairly demonising single foods, such as sugar or saturated fat, takes the focus off the whole diet.
A dietary pattern of mostly unprocessed plant foods, which is also low in highly-processed foods and sugar, consistently comes out on top in offering the best long-term health.
Resveratrol is just one of hundreds of potential health-promoting components found in food, especially fruit and vegetables.
It may yet prove to be another over-hyped field of nutrition research where individual nutrients are trumped by the whole diet.
Still, enjoying an odd glass of red and eating plenty of plant-based foods that don't come in packages hedges your bets either way.
Tim Crowe is an associate professor in nutrition at Deakin University. This article first appeared on The Conversation website here.