Back in the summer of 2018, the ketogenic diet was (and still is) growing in popularity. As with anything trending, there were individuals on both sides of the spectrum — fans and critics. Among the critics were Sara Seidelmann and her team who published the paper Dietary carbohydrate intake and mortality: a prospective cohort study and meta-analysis in The Lancet. This meta-analysis observed the dietary habits of over 15,000 individuals and concluded that individuals who consumed higher amounts of carbohydrates were more likely to live longer than individuals who consumed lower amounts of carbohydrates.
This new research study took the media by storm and acted as ammunition for critics of keto. Online magazines and news sources began to buzz with headlines like “This Study on Nearly Half a million People Has Bad News For The Keto Diet”, “Huge Global Studies Find Low-Carb or Keto Diets Could Lead to Shorter Lifespan”, and “New study finds low-carb diets increase mortality”. Well, as shocking as it may be to believe, news headlines are often misleading, and research is often misinterpreted. So, let’s take a step back and look at this study and break down the conclusions.
What Did the Study Look At?
Study Participants: 15,400 individuals – Ages: 45 to 64
Time Span: 25 years
Methods: Participants filled out a 66-item semi-quantitative food frequency questionnaire approximately every six years.
Conclusions: Based on the frequency of food item consumption, total daily carbohydrate consumption percentages were calculated and correlated with lifespan.
Where Did the Study Go Wrong?
This was not a controlled study. Other factors that influence lifespan like physical activity, stress levels, and smoking habits were recorded, but not adjusted for. The “low-carb” group also consisted of the highest amount of smokers and the lowest amount of total physical activity conducted.
The data collection process left plenty of room for errors. In order to collect the data on total carbohydrate consumption, participants were given a questionnaire (FFQ) where they indicated how often they ate specific foods on a list over the past several years. Most individuals would not be able to accurately recall total food consumption over such a long period of time and were likely filled with errors.
Consuming under 44% of total daily calories from carbohydrates was considered low carb. To put this into perspective, if the average person consumes 2,000 calories a day, that is 220 grams of carbohydrates. This is nowhere near low-carb or keto territory.
This study is purely correlational, and correlation does not equal causation. Think of it like this: If a new study was published showing individuals who wear purple socks were more likely to get into a car crash than individuals wearing red socks, would you assume that purple socks cause car accidents? You probably wouldn’t and the same principle applies to this study.
The Science Behind the Ketogenic Diet and Longevity
When news of this study first hit the headlines in 2018, Dr. Ryan Lowery wrote an in-depth article debunking the idea that following a ketogenic diet would shorten your lifespan. In fact, research has shown that it may actually promote longevity.
It should be obvious, but you shouldn’t always believe what you read online. News headlines are often hyperbolic in order to attract attention and gain as many clicks as possible. New research studies are often boiled down to one key fact to create trending and shocking articles. We recommend that you always try to read the original paper yourself or reach out to us so that we can help break down the information for you.
Seidelmann, S., Claggett, B., Cheng, S., Henglin, M., Shah, A., & Steffen, L. Dietary carbohydrate intake and mortality: a prospective cohort study and meta-analysis. The Lancet. 2018, (9):419-428.
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