SECOND OPINION: Bad news for wine lovers - there's no right way to drink

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Bad week for wine lovers

Two separate studies this week threw cold water on the theory that moderate drinking improves heart health. And a third report triggered headlines warning that even a single drink per day could increase breast cancer risk.

Silvia Balbo, assistant professor at the University of Minnesota, who studies the metabolic effect of alcohol on human tissue, points to the mixed health messages that surround drinking alcohol.

There is a trend associating alcohol consumption with breast cancer, butthe precise mechanisms are still not understood, she said.

"It hasn't really been clarified if the problem is disruption of hormonal balance or the metabolism of alcohol that includes the formation of acetaldehyde,which is a known carcinogen which can interact with DNA and lead to mutations," she said. "Breast cancer is so complex with so many different types and variables. It's really complicated."

So far the only clearly defined mechanism between alcohol and cancer is in the liver "where heavy alcohol consumption leads to cirrhosis and inflammation and that induces liver cancer."

"For other sites in the body, such as head, neck and esophagus, we're still trying to understand the relationship between alcohol and cancer."

She says experts are also unclear about safe exposure levels.

"Most are based on self-assessment, where researchers ask patients how many drinks they had in the past week or month, and even the definition of a 'drink'can be difficult.

"And large numbers of people are exposed but don't develop cancer, so what is the difference between the two groups?"

In other words, researchers still aren't certain how much is too much.

"Clearly if I drink one glass each day of the week it's different than if I drank sevenglasses of wine all on Friday."

Balbo says she does drink alcohol, and points to the recent U.K. guidelines for direction. Those guidelines advise a low level of alcohol consumption with several drink-free days every week.

Crisis in health news?

There is a whiplash effect for readers when one week red wine is reported to prevent heart disease and the next week another study says it causes cancer.

"If you follow the arc of these stories over time, they go back and forth over the years and we rarely if ever get a definitive answer," sayshealth journalist KevinLomangino.

Lomanginoblames both the media and the scientific community.Researchers know they'll get attention if they look for health effects of popular food, he said, so there's a proliferation of research where people are surveyed about what they eat and then they sift through the data looking for some kind of health outcome.

This week featured headlines announcing that wine caused cancer, that chocolate offers protection from heart arrhythmia, that coffee reduces the risk of liver cancer, and a high fibre diet prevents arthritis in the knee.

"I can't remember a week that has featured so much useless reporting about studies that are meaningless to the average reader," he said.

"I'd call it nothing short of a crisis of crap health news," he wrote in a colourful commentary on the media website HealthNewsReview.

"It was just shocking to me," he said of the stories, one after the other proclaiming health effects of common foods.

"These are generally observational studies based on questionnaires where researchers go and ask people what they ate and then try to correlate it with a health outcome," he said, adding that while that kind of research can be useful, there are many limitations which are not shared with readers. "And the conclusions are never definitive."

A statistical "association" of a food with a health outcome is not the same asa cause, he warns. Just because two things seem related, it doesn't mean one caused the other. And there is simply no way to prove causationin observational, survey-based research.

One red flag for readers should bestories reporting the increase or decrease in risk without reporting the original risk. In other words, if someone has a 1:1,000 chance of getting a disease, then a doubling of the risk, to 2:1,000, or cutting it by 50 per centto .5:1,000 would probably not be reason enough to stop eating something or start eating something.

"I think these stories overall are giving people a misguided sense of how beneficial these practices are, or in some cases, how harmful they are."

History written in our teeth

A group of researchers at McMaster University in Hamilton discovered that vitamin D deficiency has been around in humans from the earliest times.

"The story of humanity's vital, and fragile relationship with the sun has been locked inside our teeth for hundreds of thousands of years," they said after studying teeth from the past.

"This is not a modern day problem,"says Professor MeganBrickley. And to understand what happened back then, Buckley and her team went looking for answers hidden in teeth.

Take the molar, of a 23-year old man from Quebec, born in the 1800s.

"Poor man,"Buckley says, after examining the preserved tooth. Besides having rickets as a child, he had four periods of vitamin D deficiency in his life.

The story of of his sun exposure was written into the imperfections in the dentin, the layer underneath the tooth's enamel.

When the dentin can't repair itself, it leaves behind clues that scientists can read, like rings of a tree.