Some thoughts on the role of the potato in healthy diets, and on frying them.
In 1962 British working class diets had more starch from potato than from bread.
Much of this, as today, came from chip shops.
https://www.cambridge.org/core/services/aop-cambridge-core/content/view/E6E6E78498D19B48CAF2E63957516EA2/S0029665164000295a.pdf/changes_in_the_pattern_of_carbohydrates_consumption_in_britain.pdf

This cheap, convenient energy food was made by making fairly thick chips of potato which were fried in beef tallow (probably beef and lamb in NZ) with some added MUFA.
These might be eaten undercooked or overcooked, but the surface area per calorie was lower than today. 2/n

A modern chip is thinly sliced, precooked twice to speed up service, and covered in flavor enhancers of uncertain provenance.
It's then fried again in PUFA oil (or high oleic if lucky) to enhance flavor across its large surface area.
Relatively little is left of its interior. 3/n

The Carnegie or Boyd Orr Cohort study measured the family diet of British, mostly working-class children in 1937-1939, a time when children ate very much what their parents ate - if they were lucky.
The outcomes for heart disease, cancer etc were described in follow studies. 4/n

This is the longest running dietary epidemiology study in history, n= after attrition ~4800.
The main sources of saturated fat were whole milk and chips from the chippie. More SFA correlates with more potato (as it did in my childhood). So what were the outcomes? 5/n

Saturated fat and total fat in 1937-39 were not associated with later cardiovascular mortality. (Remember the first paper, and that these populations did not radically change their diets for many decades). 6/n
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1768996/

In 60 years of follow up the saturated fat consumed in fried chips and whole milk is not associated with CVD mortality.
In a population with far lower rates of childhood and adult type 2 diabetes and obesity than today. 7/n