The Red Herring of Cholesterol

Back in 1913 a Russian scientist, Dr Anitschkov, thought he had found the answer to heart disease: he found that it was induced by feeding cholesterol to rabbits. What he failed to realise was that rabbits, being vegetarians, have no means for dealing with this animal fat.

I’ve kept an eye on studies ever since and they all show the same thing. Eating cholesterol doesn’t raise blood cholesterol. For example, here’s a more recent study, published in the European Journal of Nutrition in 2008. The researchers fed two eggs per day to overweight but otherwise healthy volunteers for 12 weeks while they simultaneously followed a reduced calorie diet.

A control group followed the diet but cut out eggs altogether. Both groups lost between 3 to 4kg (7- 9lbs) in weight and saw a fall in the average level of blood cholesterol. Research leader Professor Bruce Griffin stated: “When blood cholesterol was measured at both six weeks and twelve weeks, both groups showed either no change or a reduction, particularly in their LDL (bad) cholesterol levels, despite the egg group increasing their dietary cholesterol intake to around four times that of the control.”

But what about if you have a high blood cholesterol level already?

A study in the Journal of the American College of Nutrition took 161 people with high cholesterol levels and fed them either two eggs a day or a cholesterol-free egg substitute. After 12 weeks those eating two eggs a day had a tiny non-significant increase in LDL cholesterol of 0.07mmol/l, and a significant increase in the ‘good’ HDL of 0.1mmol/l, and therefore no real change in the ratio of HDL to LDL cholesterol, which is the more important statistic. Having an LDL cholesterol below 1.8 is consistent with a low risk, while having a level above 3.4 is consistent with high risk. A tiny 0.07 increase is inconsequential. But what if there’s something special about eggs? Other foods rich in cholesterol include shrimps.

A more recent study from Rockefeller University, published in the American Journal of Clinical Nutrition, gave participants either three servings (300 grams) of shrimps or two large eggs a day, each providing 580mg of cholesterol. Researchers found that both groups had an increase in both the good HDL cholesterol and the less desirable LDL cholesterol, which they interpreted to mean that neither diet would be likely to make any significant difference to cardiovascular risk.

Does eating high cholesterol foods increase heart disease risk?
Surely eating lots of eggs or other high cholesterol and high fat foods must be bad news? Inuit people of North America (Eskimos) were always an enigma with regard to the cholesterol theory. Their traditional diet, high in seal meat, has among the highest cholesterol levels of any cultural diet, yet their rate of cardiovascular disease is among the lowest. However, we now know their diet of seal meat is exceptionally high in omega 3 fats, which confer protection. But what about people eating high cholesterol foods that aren’t high in omega 3 fats? In fact, as long ago as 1974, a British advisory panel set up by the government to look at ‘medical aspects of food policy on diet related to cardiovascular disease’ issued this statement: “Most of the dietary cholesterol in Western communities is derived from eggs, but we have found no evidence which relates the number of eggs consumed to heart disease.” The same still holds true today. Every study I’ve ever seen says the same thing. Study after study, such as in the journal Medical Science Monitor, has repeatedly failed to find any increased risk of heart disease from eating six eggs a week versus one.

One study, in the American Journal of Clinical Nutrition finds that seven eggs or more a week confers a very slight increased risk but this is not confirmed by other studies, while two studies find that risk is slightly higher in diabetics either eating lots of eggs or having a very high cholesterol intake in their diet. It is now evident that there is no clear relationship between intake of dietary cholesterol and cardiovascular disease. This said, however, a lot of high cholesterol foods also happen to be high in saturated fat and often fried. While this might not significantly raise cholesterol you might get more oxidized cholesterol, which is bad news.

It is therefore prudent not to go overboard on high cholesterol foods, while at the same time there is no need for cholesterol phobia. So, if you are not diabetic you can assume that it is certainly safe to have six eggs a week. If you are diabetic it may be wise to limit your total cholesterol by having no more than three eggs a week and less other cholesterol rich foods such as prawns, shrimps and shellfish. However, it is likely that if you overall diet is healthy, even this may be unnecessary.

Does a high fat diet increase heart disease risk?
But what about fat? We’ve all been told to eat low calorie low fat diets and supermarkets are full of low-fat foods often implied to reduce your risk of heart disease. There are a lot of inconsistencies here in that some countries with a high fat intake (for example Finland) have a high rate of heart disease while others (like Greece) have a very low rate of heart disease. Then, of course, we have the Inuit, and also Pacific and other islanders who eat loads of coconut produce, high in saturated fat, and have low risk of heart disease. In the July issue I explored the myths around fat and why it really isn’t the driver for heart disease. If you replace saturated fat with omega 3 rich fish you’ll benefit, but if you swap it for more carbohydrates, you’ll be worse off. This conclusion was reached in a meta-analysis (a study of studies) in the American Journal of Clinical Nutrition, which reports that “an independent association of saturated fat intake with cardiovascular disease risk has not been consistently shown in prospective epidemiologic studies”.

Replacement of saturated fat by polyunsaturated or monounsaturated fat lowers both LDL and HDL cholesterol. However, replacement with a higher carbohydrate intake, particularly refined carbohydrate, can exacerbate many risk factors for cardiovascular disease including the “atherogenicdyslipidemia associated with insulin resistance and obesity, increased triglycerides, small LDL particles, and reduced HDL cholesterol”. In other words, diets high in sugar and refined carbohydrates are not only converted into fat but also raise cholesterol, while slow-releasing carbs, high in soluble fibres, such as oats, reduce risk. So, even though I have shown you that dietary fat per se, and cholesterol in particular, don’t increase your risk for heart disease, switching from a high animal protein diet towards more fish and vegetable protein, especially soya, does have significant effects on both lowering blood cholesterol and fat levels, as well as reducing heart disease risk.

Cholesterol more a marker than a cause
While you’ve seen that eating cholesterol and fat don’t either raise blood cholesterol or heart disease risk, you’ll find that foods that tend to reduce cardiovascular risk do tend to lower cholesterol levels as well. So, your blood cholesterol statistics are not irrelevant, they are just not quite as important as we’ve been led to believe. According to Professor Meir Stampfer, from Harvard School of Public Health, “total cholesterol is not a great predictor of risk.” His research group finds that eating a low carb (low GL) diet is one of the best ways of both reducing risk and lowering cholesterol.

If you or your doctor rely only on cholesterol to predict risk without assessing other critical risk factors such as triglycerides, homocysteine, glycosylated haemoglobin and lipoprotein(a), you may still be at high risk despite a normal cholesterol. A massive US survey of 136,905 patients, published in the American Heart Journal, found that more than half of those hospitalised for a heart attack had perfectly normal cholesterol levels (LDL below 2.6mmol/l) according to National Institute of Clinical Excellence and Department of Health guidelines who recommend an LDL below 3mmol/l, and 17% had healthy cholesterol levels (LDL below 1.8mmol/l). A five year survey, in the British Medical Journal, of elderly people aged 85, found that cholesterol was also a very poor predictor of cardiovascular death several years later.

The best predictor by far is your homocysteine level. If a person’s homocysteine level was above 13, it predicted no less than two thirds of all deaths five years on. You certainly don’t want to put all your eggs in the cholesterol basket because you might miss other important indicators. If you do, however, have a high cholesterol level avoiding cholesterol foods isn’t going to make much difference. But there are other diet and lifestyle changes that will. The reason for this is that the body needs cholesterol, it makes what it needs. It is only when you are eating, or living, in such a way that stops the normal cycle of cholesterol production and clearance by HDL that you start to get a change in cholesterol statistics. For example, if you eat a lot of fried foods or smoke (high in oxidants) and eat very little vegetables (high in antioxidants) cholesterol can get damaged by oxidation. Then the immune system attacks, producing harmful foam cells.

Alternatively, if you eat a high sugar or high GL diet, you start making more insulin and both the high sugar and insulin damage cholesterol particles which start to accumulate. Also, the excess sugar is converted into fat and up goes your triglycerides (blood fats). Also, those soluble fibres in low GL foods help eliminate excess cholesterol. So, the wrong kind of diet means you have more garbage, and less efficient waste disposal, which is reflected by raised LDL and lowered HDL. But it’s not just about diet. Stress (and exercise) also plays a major part in raising heart disease risk, and cholesterol. It is not really the cholesterol per se that causes the damage that leads to arterial disease, but that a high LDL and low HDL cholesterol is a predictive marker, or an indicator, that you are eating the wrong kind of diet or living too stressful a life. If you take a statin drug that blocks the enzyme in the liver that makes cholesterol it is a no brainer that cholesterol levels come down. After all, the brain and body need cholesterol to stay healthy. So, in effect your liver and brain, when starved of cholesterol by taking these drugs, is going to suck every bit of available cholesterol out of the blood for use elsewhere.

While these drugs do slightly reduce risk in those who have heart disease it is highly likely that the mechanism by which they do this is more likely to be because they act as an anti-inflammatory, than because they lower cholesterol per se. Lowering cholesterol is more likely to be a side-effect, and a bad one at that.

Why low cholesterol is as bad for you as high cholesterol
However, some people never give up and there’s talk that we just need to lower cholesterol even more to get more benefit from these rather ineffectual drugs as if the lower your cholesterol the better. All the talk of aggressively lowering cholesterol tends to ignore just how vital it is to the smooth running of our bodies. For example, it helps repair damaged arteries, is the raw material for making sex hormones, is vital for laying down memories in the brain and for the proper working of neurotransmitters (click here for a detailed discussion of the complex role of cholesterol in the body and a critical analysis of the big trials usually used to support statin use, by biochemists and nutrition authors Sally Fallon and Mary Enig). So it’s hardly surprising that blocking the production of cholesterol in the liver, which is what statins do, causes all sorts of problems.

Many of these are simply the problems that happen when you have too low cholesterol, some are the consequence of statins knocking out the essential nutrient CoQ10. When you realize that cholesterol is a vital nutrient for the brain and body it makes no sense to lower it beyond healthy levels (between 4 and 6mmol/l, provided your HDLs are reasonably high). But could it be bad for you? Here’s a few facts you might want to know: Having too low a cholesterol increases risk of stroke.

Japan used to have a very low fat intake in the 1950s, and average cholesterol levels of 3.9mmol/l, it also had a very high number of people suffering haemorraghic strokes (that’s the worst kind). According to the Food and Agricultural Organisation, after following advice to increase fat intake, largely from animal protein, their cholesterol levels went up to an average of 4.9mmol/l by 1999, and their stroke risk went down. In the last 50 years stroke risk (both haemorraghic and ischeamic) has reduced by 600%. Having too low cholesterol increases risk of death. Once you are getting below 4mmol/l, risk of death actually increases.

The dangers of having too low cholesterol seems strongest in older people, say over age 60. This association is made clear in Dr Malcolm Kendrick’s book The Cholesterol Con, if you’d like to dig deeper. Having too low cholesterol is also associated with increased rates of depression and suicide. According to a study, published in Psychosomatic Medicine, of 121 healthy young women by Duke University psychologist Edward Suarez, low cholesterol is a potential predictor for depression and anxiety. An eight-year Finnish study of 29,000 men aged 50 to 69, published in the British Journal of Psychiatry, found that those reporting depression had significantly lower average blood cholesterol levels than those who did not, despite a similar diet. One possible reason is that vitamin D is made from cholesterol. Having too low cholesterol is associated with feeling more aggressive.

A study published in Psychiatry Research suggests this association is thought to be because not having enough cholesterol disrupts serotonin, a key brain neurotransmitter required for balancing your mood. Having a low HDL has the strongest association. None of this should be at all surprising if you recognize cholesterol for what it is: a vital nutrient, and a relatively poor marker for heart disease. Certainly not the principle cause.