For years society has worked under the premise that a diet high in fat -- specifically saturated fats-- leads to a higher risk of cardiovascular disease. Within the last 20 years low fat foods have been considered the commonly accepted 'healthy choice'. How did we ever reach this conclusion and why has it been so engrained in our eating heritage?
History lesson time!
Ancel Keys compares cholesterol levels and fat content in diet between two populations in Italy: wealthy people with a diet of rich, fatty foods and the "working" class with a diet lower in fat. His findings showed that the wealthy population had higher cholesterol and higher frequency of cardiovascular disease.
Keys and his colleagues kick off a study that would eventually become "the Seven Countries Study" -- if you're looking for something to put you to sleep, here you go -- 12,000 men, 18 regions, seven countries. They compared the relative amounts of fat in the participants diets, cholesterol levels and death due to heart disease. They found that regions having diets higher in fat (America and Finland) were more likely to have high cholesterol levels and heart attack mortality rates were elevated.
A four page American Heart Association (AHA) report from a committee which included Keys concludes "the best scientific evidence of the time" strongly suggest that Americans would lower their cardiovascular disease risk by reducing fat in their diets and replacing saturated fats with polyunsaturated fats.
"Lowering Blood Cholesterol to Prevent Heart Disease" is issued by the National Institute of Consensus Health Development Conference. The article prescribes the virtues of a diet low in fat for overall heart health.
Time magazine puts cholesterol on the cover it's magazine. Opening headline reads, Sorry, It's True. Cholesterol Really Is A Killer. This, along with numerous other articles help kick off the 'low fat diet craze'
The American Heart Association introduces it's 'Heart Healthy' label to raise awareness of foods high in saturated fats. Labels are only applied to packaged foods, unintentionally implying to some that processed and packaged goods with the 'Heart Healthy' seal are better for you than their fresh food brethren.
In 1981 the National Institute of Health funded several studies that attempted to make similar correlations between blood cholesterol and heart disease. Rather than measure total cholesterol which studies had been doing to date, they used a new technique to measure both LDL (bad cholesterol) and HDL (good cholesterol) levels. What they found was that saturated fats do raise your cholesterol levels but they raise your good cholesterol, HDL. Replacing fats with carbs had the impact of lowering cholesterol, but it was lowering the GOOD cholesterol, not getting rid of the bad. Further, this study found that high levels of HDL, which saturated fats contribute too, was positively correlated to lower instance of heart disease.
So, with all of this conflicting evidence why did 'low-fat' win the battle of the proverbial bulge? There is a lot of interesting history behind this and if you ever have a spare hour you should watch Dr. Peter Attia's video on "the limits of scientific evidence and the ethics of dietary guidelines - 60 years of ambiguity". He takes a very complete look at the history of the science behind our understanding of fat and makes some very poignant observations on the limits of observational epidemiology (observation based studies). Coles notes: Ancel Keys came up with the hypothesis first, people (and the media) bought in and it became hard to fight against an assumed axiom of truth.
In recent years we have seen more and more studies coming out that confirm that fats and specifically saturated fats are not the 'Killer' that Time magazine claimed in 1984. Most recently the American Journal of Clinical Nutrition published an article that followed nearly 350,000 subjects over 5-23 years looking for a relationship between saturated fat and coronary heart disease. Their conclusion? "...there is no significant evidence for concluding that dietary saturated fat is associated with an increased risk of CHD (coronary heart disease) or CVD (cardiovascular disease)."
At the end of the day, keep in mind that you want to be choosing the most natural sources of fat you possibly can, organic eggs and dairy, grass fed meat, fresh fish, avocados, nuts. For cooking fats try to find an oil that has a high smoke point, a good Omega 3:6 ratio and one loaded up with antioxidants and minerals. Some of my favorites are Coconut oil, Avocado oil and good ol' fashioned butter. If you choose to fill your diet with these fat sources, keeping in mind healthy caloric intake for your nutrition goals, you will be taking steps towards a healthier and happier 'you'. Now, would someone please pass the bacon?
Live Your Best Life!