Rediscovered study from 60s Minnesota shows up ‘heart healthy diet’ myth

By Benedict Jephcote
25th April 2016
In Depth
 
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A major clinical trial that started in the late 1960s showed vegetable oil to be linked with higher death rates. But it was left unfinished, shelved and only recently discovered in a basement.

US National Institutes of Health medical investigator Christopher E. Ramsden helped track down the study and, with the help of researchers, completed the analysis and published the study.

The findings, which have taken decades to come to light, ask serious questions about current dietary advice and cholesterol targets.

Minnesota Coronary Experiment

The Minnesota Coronary Experiment was run by researcher Dr. Ivan Frantz Jr. between 1968 and 1973 to test the following hypothesis:

  • Replacement of saturated fat with vegetable oils rich linoleic acid > leads to lower serum cholesterol > which leads to reduce incidence of coronary heart disease events and deaths

The researchers got half of this right; the other half, they didn’t.

The study included 9,423 people from six state mental hospitals and one nursing home in Minnesota.

The participants were divided into two groups:

One group had a standard diet for the times, which was high in saturated fat. The saturated fat included animal fats, common margarines and shortenings.

The other group had a diet in which the saturated fat was replaced with corn oil and corn oil margarines. Corn oil is a strong source of linoleic acid.

2,355 of the participants followed the study diets for at least a year. The researchers also had access to 149 completed autopsy files.

Low cholesterol warning

The results showed that the original researchers’ hypothesis was half right: substituting corn oil in place of saturated was indeed effective at lowering cholesterol levels. However, when it came to mortality rates, the opposite effect to the hypothesis occurred: lower cholesterol correlated with increased mortality. Put plainly, lower cholesterol levels were associated with greater rates of death.

The results become even clearer when you delve deeper into the data. The researchers divided the participants into different groups: one group consisted of those under 65, and the other contained people aged 65 or older.

Within the under-65 group, the mortality rates were closely matched between the two diets, with the saturated fat diet displaying marginally higher mortality rates. However, in over 65 year olds, mortality rates became significantly higher in the participants on the corn oil intervention diet two years after starting the intervention.

So what was it about the corn oil diet that plunged the elderly towards higher death rates?

Ramsden’s analysis of the figures shows that each 0.78 mmol/L reduction in cholesterol was associated with a 35% higher risk of death in the elderly (65 years old or more).

The finding now takes its place amongst many other research studies that have shown low cholesterol levels to be correlated with high death rates within the elderly.

To cite just one of a number of such studies, a study published in 2008 by researchers at Columbia University in New York stated:

“Whites and African-Americans in the lowest quartiles of total cholesterol, non-HDL cholesterol and low-density lipoprotein cholesterol (LDL cholesterol) were approximately twice as likely to die as those in the highest quartile”

What this means is that the group with the lowest cholesterol were around twice as likely to die as the group with the highest cholesterol.

Why is the NHS driving down cholesterol?

This asks the very important question: why do NICE guidelines place so much emphasis on reducing cholesterol levels when the link between low cholesterol and higher risk of death in the elderly is so well established?

In 2014, we reported that the UK National Diabetes Audit 2011-2012 showed that mortality rates were twice as high in people with the lowest cholesterol than in the group with the highest cholesterol levels.

The NICE clinical guideline (CG181) for ‘Cardiovascular disease: risk assessment and reduction, including lipid modification’ encourages lowering of cholesterol in the elderly and yet reserves no mention at all of the dangers of lowering cholesterol too far.

 

An admonishment for saturated fat?

In addition to showing that lowering cholesterol levels can be dangerous, the study also points to the fact that saturated fat may not be the enemy that the NHS and NICE paints it as.

Sure, cheese and chips, burgers and even biscuits should be off the menu and kept for rare occasions but you can’t fairly label these foods as fatty foods. They’re actually a mixture of carbs and not just saturated fat but unsaturated fats too. In fact, in the case of fries, most of the fat is unsaturated fat.

Saturated fat is far more than a bit part in fast food, it plays a much healthier role in diets such as the Mediterranean diet. Whilst oily fish, avocado, nuts and olive oil are held up as examples of foods high in polyunsaturated fat, the truth is that all of these foods contain significant levels of saturated fat too.

If there’s one thing that we should learn from the Minnesota Coronary Experiment, it is perhaps to trust nature to get the balance of saturated to unsaturated fat right and work with nature rather than against it.

Forget the idea of having processed foods filled with highly processed vegetable oils and ensure your diet comes from foods that derived straight from nature without being messed with in factories.

Goodbye fortified breakfast cereals, goodbye ready meals, goodbye fat free produce. Hello real food, hello good health.

What do you think?