Low and high carbohydrate intakes are tied to increase mortality.
There is much disagreement about how much carbohydrates are recommended. For years, American experts have recommended anywhere from 45-65% of your calorie intake from carbohydrates. Some experts argue for a lower number, and others suggest higher numbers. Who is right? The answer will no less surprise you.
Low carbohydrate diets and those which restrict carbohydrate in favor of increased protein and/or fat intake. They are a common and popular weight-loss strategy today for many Americans. However, the long-term effect of carbohydrate reductions on your healthy is widely unknown. The impact on mortality is controversial and could greatly depend on the source for remaining calories or even the source for carbohydrates that you decide to ingest.
In the 25 years of follow up, the researchers determined that those that consumed 50–55% energy from carbohydrate was associated with the lowest risk of mortality. Both low carbohydrate consumption (<40%) and high carbohydrate consumption (>70%) conferred greater mortality risk than did the more moderate intake. Results varied by the source of macronutrients: mortality increased when carbohydrates were exchanged for animal-derived fat or protein and mortality decreased when the substitutions were plant-based.
The bottom line: Both low and high carbohydrate diets were associated with a higher risk of mortality. That being said, the source for the replacement calories matters. Plant-based replacement calories reduce risk and animal-based fats increase risk. If you are going to eat a low-carb diet, I recommend a blend of lean meats with plant products. A high fiber whole food diet with 50-55% of your calories from carbohydrates appears to be the magic zone and is the key to health and weight loss success.