We know that there are good reasons to believe that insulin resistance may be one of the main causes of heart disease, and possibly the most important cause. Heart disease itself is the leading killer in the U.S. Higher blood sugar and insulin raise the odds of dying — and this is true even when these numbers are only a bit above normal.
Insulin is the hormone that helps to control blood glucose (sugar) by rising when carbohydrates are ingested and glucose increases, causing cells to take up glucose from the blood. Insulin resistance is the condition in which insulin becomes less effective, is characteristic of type 2 diabetes, and is often seen in obesity, sedentary people, and smokers.
The EPIC-Norfolk study looked at over 4600 men, age 45 to 79, who had glycated hemoglobin measured, and then were followed for an average of about four years.(1)
Glycated hemoglobin, often referred to as HbA1c, is a measure of long-term blood glucose levels. When blood glucose rises, some of the glucose attaches permanently to the hemoglobin in red blood cells, and this lasts for the lifetime of the red blood cell, which is about 4 months. An average blood glucose value can be calculated from the HbA1c.
So what happens when you measure HbA1c in a group of men and then see who died? See the following chart.
The chart is based on data from the EPIC-Norfolk study (source) and shows that each 1% increase in HbA1c is associated with a 28% increased risk of death in any given time period.
This is death from any cause, not just heart disease.
The first two bars in the graph represent normal HbA1c — depending on whom you ask. The next three bars represent pre-diabetes to diabetes, which is above 5.7.(Ref.)
Two points here, besides the obvious increase in death rates:
1. Death rates rose even below the level of pre-diabetes or diabetes. Therefore you could be at higher risk even if your doctor doesn’t think your blood glucose or HbA1c is too high.
2. The increase in death rates was continuous. Any increase in HbA1c means a higher death rate. This points to causation, not just association.
A number of other studies have looked at the association between blood glucose and death rates, the Helsinki Policemen Study being one of them.(2) In this study, the participants were given a 2-hour glucose tolerance test, in which the subject takes a glucose drink and has his blood drawn at 0, 1, and 2 hours. Glucose and insulin are measured.
This chart shows the incidence of coronary heart disease over follow-up of up to 25 years. The measurements are men grouped by quintiles (fifths) of insulin. Greater insulin resistance means more insulin is produced for a given glucose load.
The greater the insulin, the greater the incidence of coronary artery disease.
Ivor Cummins has a nice write-up of the Helsinki Policemen Study, and he suggests that the results minimized the relation between insulin and heart disease. That’s because the study measured insulin only once, at the beginning, and many of the policemen would have gone on to develop insulin resistance in the following years, for example by gaining weight. Hence if insulin had been measured more often, we might even less heart disease among men who kept their early insulin sensitivity.
There’s little doubt in my mind that insulin resistance is a powerful, perhaps the most powerful, predictor of heart disease. Cholesterol and lipoproteins are red herrings that have little if anything to do with heart disease.
Other than the first step, staying lean, not much else is even talked about in the mainstream, which is all about avoiding “high cholesterol” and saturated fat, and taking toxic statins.
So to avoid heart disease, you need to be independent and ignore much of what you hear elsewhere.