Why is red wine healthy one day then unhealthy the next? Because nutrition science is really, really complicated

On Monday red wine is good for you, on Tuesday it’s best avoided, and by Wednesday it’s back to being good for you again.

Lately it seems like every nutrition study contradicts the last, and trying to be healthy has never felt more complicated.

It’s not just #fakenews and teenage bloggers muddying the health news waters. The problem, you see, is that nutrition science is really, really complicated. Here’s why.

Controlled, long-term human studies are almost impossible

One of the reasons there’s so much we don’t know about human nutrition science is that it’s extremely difficult to carry out foolproof studies on people long-term.

“Long-term clinical trials for diabetes, heart disease or cancer are difficult because those types of studies would require decades of follow-up, which would be expensive and logistically difficult,” Vasanti Malik, a research scientist at the Department of Nutrition at the Harvard T.H. Chan School of Public Health, told Coach.

“It would be very challenging for participants to adhere to a specified trial regimen for such a long duration of time, so long-term compliance would be a concern.”

Scientists are somewhat able to overcome this challenge by doing short-term clinical trials and combining the results with larger observational studies, Malik says.

“In nutrition, clinical trials are valuable for looking at intermediate biomarkers of disease such as blood lipids, glucose and insulin and markers of inflammation

“These types of studies can lend support to cohort studies that follow groups of people over time for occurrence of disease with many years of follow-up.”

“Short-term clinical trials can also be useful in understanding biological mechanisms linking diet to risk of diseases.”

Study findings are often misinterpreted

Despite scientists’ efforts to present research findings in a balanced way, results are often misinterpreted and exaggerated by various parties: media outlets being sloppy, brands twisting the results to sell a product, or uneducated pseudo-scientists.

Studies often note there’s an association between two factors, but it’s interpreted as a cause.

“Findings are sometimes taken out of context or misinterpreted leading to shocking reports that can confuse or mislead the public,” Malik agrees.

“Inaccurate information is sometimes disseminated by pseudo-scientists on the internet and social media which is not substantiated by scientific evidence.”

An example of research being wildly misconstrued was a spate of recent articles that claimed drinking wine before bed can help you lose weight, because an ingredient in red wine called reservatrol turns normal fat into “brown fat” which is easier to burn off.

It’s no surprise the study went viral – it’s something we’d all love to be true.

But read the study and you’ll find the researchers say reservatrol – found in fruits including berries and grapes – is filtered out in the wine-making process.

Some articles about the research also made the point that drinking two glasses of red wine at night could help you lose weight if it replaces snacking.

But really, you’re just adding about 250 calories to your daily diet from alcohol — and what if the wine weakens your self-control and you scoff a bag of M&M’s you wouldn’t normally?

Most nutritionists wouldn’t recommend drinking as an effective strategy for weight loss – Susie Burrell recommends taking a month off booze to speed up the process.

Oh, and the study was done on bees, not humans. Bees are not people.

Correlation does not imply causation

Science isn’t perfect, and sometimes it’s scientists themselves who misinterpret research results in their search for answers.

The most common way this happens is “reverse causation”, when an apparent cause-and-effect are mistakenly linked.

“For example, [in one study] we initially found a positive association between intake of diet soda and risk of diabetes” Malik explains.

“But [it was later realised] people who are overweight or at risk for diabetes may consume diet soda for weight management or health reasons, which results in a spurious positive association between diet soda and diabetes.

“When we adjusted for BMI in the analysis, the association was weakened.”

Another example was a body of research several years ago that found a positive association between moderately drinking alcohol and longevity, leading to claims that drinking extended lifespan, or healthspan – the part of our lives we’re healthiest.

But a meta-analysis published last year came to the conclusion that the reason for the correlation was because sick people may not want to or cannot drink alcohol, and that moderate drinkers tend to be well-educated and more affluent.

They’re living longer for other reasons and are more likely to drink alcohol for financial and social reasons – the alcohol itself isn’t prolonging their lives.

Say it with me now: correlation does not imply causation.

It’s for this reason that nutrition science and medical research is more important than ever – while it can seem confusing, it’s vital to continue to challenge assumptions and results to get to the truth.

“Nutrition science will continue to evolve and new findings will continue to inform dietary recommendations and nutrition policies to improve health,” Malik says.

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