Every month or two, we’re bombarded with news about how certain foods are good or bad for our health. Red meat is bad, chili peppers are good. Broccoli is both life-saving and life-destroying. If you want to live longer, eat blueberries. But wait a minute. Them blueberry.
The latest of these stories, the one about olive oil, has been all over the place. Apparently, olive oil is the key to preventing death from dementia in later life: Consuming an extra half tablespoon of this premium oil per day could lower the risk of death from dementia by a whopping 28 percent.
Unfortunately for salad lovers (and bread dippers) the world over, the truth isn’t quite so simple: While it’s possible that olive oil is good for you, it’s very likely just another interesting association that’s not all that important in your life.
The study that has everyone excited about olive oil is a new nutritional epidemiology paper that looked at two large cohorts recruited and followed in the U.S.: the Nurses’ Health Study and the Health Professionals Follow-up Study. Published in the journal Nutrition, Obesity, and Exercise, the authors looked at the diets these people reported and compared the risk of dying from dementia over a 28-year period between those who reported consuming a lot of olive oil (11 grams, or about one tablespoon, per day) and those who reported consuming less olive oil.
At the end of the study, the researchers found that people who reported a higher olive oil intake were less likely to die from dementia. “The results suggest that olive oil intake is a potential strategy to reduce the risk of mortality from dementia,” the researchers wrote.
For a nutritional epidemiology study, this was not a bad one. The authors controlled for a variety of factors in their analysis, such as whether participants smoked or had other health conditions. In addition, they controlled for other components of participants’ self-reported dietary intake. The researchers also performed various sensitivity analyses to try to rule out other factors that may have contributed to the results.
Still, I wouldn’t advise anyone to go buy a gallon of olive oil. This kind of study is, by definition, complicated. Ultimately, despite the authors’ hard work, it’s very hard to know whether olive oil reduces the risk of death from dementia or if it’s just an association.
Even if we take the results at face value, olive oil is not a special substance. The paper also included an analysis of the effects of substituting olive oil for other fats, and this cohort of people benefited when they substituted olive oil for mayonnaise. But the study also found that canola oil and sunflower oil had the same protective effect as olive oil.
Moreover, somewhat oddly, the authors found that olive oil just Reduces the risk of death from dementia. Also reduces the risk of death in general. Why don’t they advertise these results? Why does olive oil Plausible It contains compounds that may reduce inflammation in the brain, which may reduce the risk of death from dementia. (I’m still skeptical, but it’s at least a possibility!) It’s much harder to know how it relates to breast cancer or suicide risk, which seems to be why the findings are taken with a pinch of salt. The simplest explanation is that there’s something else going on in people who choose olive oil, and it’s not because olive oil is some kind of health elixir.
And indeed, in these kinds of studies, you only have so much control. For example, the authors didn’t actually have data on the wealth of their study participants; that data wasn’t collected in the ’70s and ’80s, when the two cohorts were set up. To control for socioeconomics, the authors instead used a neighborhood-level measure that calculates an average score for the neighborhoods people lived in, which is a statistic that can be very misleading when it comes to individuals. Someone’s neighborhood can mean a lot to you. Speculation It’s the same amount as your bank account balance, but not more.
In addition, people Very bad It’s hard to know how much of anything specific you ate. The dietary questionnaires that these kinds of studies rely on are notoriously problematic; they ask participants to recall what they’ve eaten from all kinds of food groups over the past few months. That means the measurements of olive oil intake cited by the authors may not accurately reflect how much study subjects actually consumed. Unless you cook all your food and carefully measure and record every time you add olive oil, it will be very hard to give researchers an accurate picture.
The magnitude of the effect claimed here must also be considered: on average, over decades of follow-up in these cohorts, about 24 people per 10,000 died of dementia each year in the group that did not consume olive oil at all. a lot Olive oil consumption reduced the mortality rate to 16 per 10,000 people — less than 0.1 percentage points, not a significant reduction in risk.
Finally, and perhaps most interesting, the benefit of olive oil was only seen in women. The Nurses’ Health Study, which was all female because of the decade it was in, found a relative benefit of 33 percent from olive oil consumption (although this relative benefit amounts to a small reduction in mortality for several thousand women). The Health Professionals Follow-Up Study, which recruited men, found no benefit for those with high olive oil intake.
It is certainly possible that olive oil is healthy. Of course, if you believe the research, this only applies to women, and you can use other vegetable oils instead.
Olive oil is simply Related Health is generally good. These studies control for what we know and can measure, but they can’t control for what we don’t know and can’t do. These studies don’t involve locking people in a lab for 28 years. Humans are complex beings, and it’s essentially impossible to ask them about every aspect of their lives and have them write it down accurately.
If you like olive oil, there’s no reason to stop eating it, but there’s also not much evidence that eating more olive oil will improve your health. life.
