I guess he was extrapolating and referring to the idea that carbohydrate consumption is the root cause of most, if not all, modern diseases. An idea held by many, including me.
Bad example, to be honest. In fact, liver cancer can be directly attributed to drinking.
A life expectancy of 70 years under such conditions is actually astonishing.
[0]: https://www.who.int/tobacco/media/en/Mongolia.pdf
[1]: https://www.npr.org/templates/story/story.php?storyId=112485...
What I meant by "modern diseases" in my comment is a group of non-communicable diseases or so-called "diseases of civilization".
"Diet-related" is rather ambiguous, so different lines might be drawn there. As an example, would you say Alzheimer's is a diet-related disease? What about melanoma and/or sunburn?