Correlation vs causation
Aka how to decipher the world of wellbeing
I’ve often mentioned that I love to deep dive into a subject, exploring as many sides of an argument as I can, and then I come to my own conclusions. It’s this last bit that’s important. As you know, you can find a supporting view for almost any opinion on the internet — blueberries cure cancer to drinking olive oil helps you lose weight. Both bunkum. If all of the ‘pop health’ claims we read about were true, wouldn't we all be doing them already?
As such, I want to highlight two keys words that will help you when you’re trying to decipher ‘news’ for yourself, particularly in the world of wellbeing.
Correlation and Causation.
Correlation means that two variables move together in some way, but it does not prove that one causes the other. For example, ice cream sales and drowning incidents tend to peak at the same time—but this does not mean that eating ice cream causes drowning. Instead, a third factor (hot weather) influences both.
Causation on the other hand, means that one variable directly causes a change in another. For example, lack of sleep causes decreased cognitive performance. In this case, there’s a clear cause-and-effect relationship.
The phrase to remember is “Correlation does not imply causation.” Just because two things happen together doesn’t mean one causes the other. Let me give you FIVE commonly cited examples, and why they are misleading if taken at face value…
1. Drinking Red Wine Improves Heart Health
Some studies showed that moderate red wine drinkers had lower rates of heart disease, leading many to believe that red wine itself was protective.
Why It’s a Mistake of Correlation:
Further research found that other lifestyle factors, not just wine, played a big role—moderate wine drinkers were more likely to have Mediterranean diets (rich in healthy fats, vegetables, and fish), exercise regularly, and have strong social connections, all proven to support wellbeing.
Red wine contains polyphenols like resveratrol, which do indeed have antioxidant properties, but the amounts are too small to have a significant impact in normal consumption.
Excessive alcohol consumption increases risks of high blood pressure, liver disease, and certain cancers, meaning any supposed benefits would be outweighed by the harms of excessive drinking.
Better Alternatives for Heart Health: Many of the beneficial compounds in red wine are also found in grapes, berries, and dark chocolate—without the risks of alcohol.
2. Taking Vitamin Supplements Prevents Illness
Studies show that people who take vitamins tend to be healthier, but this doesn’t mean the supplements themselves are making them healthy.
Why It’s a Mistake of Correlation:
Many supplement users already practice other healthy behaviours, such as eating well, exercising, and avoiding smoking. Thus the people who take vitamins are often the ones who least need them because they already eat a nutrient-rich diet.
Research also shows that for most people, vitamin supplements offer little benefit if they already get adequate nutrients from their diet. If vitamin supplements truly prevented illness, studies would show consistent benefits across different populations—not just in those who were initially deficient.
Caveat: specific cases exist where supplementation is necessary, but the idea that taking vitamins automatically makes you healthier is misleading.
When Supplements Are Necessary: If a doctor confirms a deficiency through blood tests (e.g., low vitamin D, iron, B12), supplementation can be crucial for health. Specific groups benefit more from supplements: Vegans/vegetarians: May need B12. Pregnant women: Need folic acid to prevent birth defects. People in low-sunlight areas: May need vitamin D in winter. Older adults: Often require vitamin B12, D, and calcium for bone health.