NHFT Libraries Health News: Saturated fat link with heart disease questioned

Thursday, 24 October 2013

Saturated fat link with heart disease questioned

Saturated fat link with heart disease questioned "The risk from saturated fat in foods such as butter, cakes and fatty meat is being overstated and demonised, according to a cardiologist," BBC News reports.

In an opinion piece, a doctor specialising in heart disease writes that warnings over saturated fats are misguided.

Writing in the British Medical Journal, Dr Aseem Malhotra argues that advice to avoid saturated fats over the last 40 years has paradoxically increased the risk of obesity and heart disease.

Dr Malhotra makes the case that while saturated fats have been removed from many products, they have been replaced with sugar to improve the taste. In his opinion, it is the consumption of sugars, rather than fats, that is chiefly responsible for the obesity "epidemic", as well as the increase in related diseases such as type 2 diabetes.

He also says that the "obsession" with cholesterol levels has led to the "overmedication" of millions of people who are prescribed the cholesterol-lowering drugs statins.

What's been said?

Dr Malhotra's article, which has been made available on an open access basis and is free to read, says that saturated fat – found in meat and dairy products such as butter and cheese – has been unfairly "demonised" for the last 40 years.

This was as a result of a very influential study from the 1970s, which found a link between the incidence of coronary heart disease and total cholesterol levels.

Dr Malhotra disputes the idea that this proves a direct cause and effect between cholesterol levels and heart disease: "correlation is not causation", he writes.

The article points out that saturated fat is believed to raise levels of low density lipoprotein (LDL) cholesterol (so-called "bad" cholesterol), which in turn raises cardiovascular risk.

Yet only one type of LDL cholesterol seems to be associated with saturated fat intake, the article says. This type of cholesterol is called large buoyant (type A) LDL particles.

The second type of LDL cholesterol – the small, dense (type B) particles associated with carbohydrate intake – is linked to cardiovascular disease.

Recent studies have found no significant association between saturated fat intake and cardiovascular risk, writes Dr Malhotra. Instead, saturated fat has been found to be protective of the heart.

He points out that dairy foods provide important dietary sources of nutrients that have beneficial effects on the cardiovascular system, such as vitamin D, calcium and phosphorus.

Dr Malhotra's article states that fat has been "notorious" for its higher energy content per gram in comparison with protein and carbohydrates.

However, he cites research from the 1950s that shows that people on diets of 90% fat lost more weight than those on carbohydrate and protein diets. This may be because the body breaks down these foods in different ways (known as "the calorie is not a calorie" theory).

He also says that in the United States, over the past 30 years the proportion of energy consumed from fat has fallen from 40% to 30%, although absolute fat consumption has remained the same. In spite of this, obesity levels have rocketed.

Is fat or sugar to blame for greater risk of cardiovascular diseases?

The paper says one reason for this rise in obesity is that food tastes worse without fat, so the food industry compensated by replacing saturated fat with added sugar.

Scientific evidence is now mounting that sugar is a possible independent risk factor for a condition called metabolic syndrome, a combination of diabetes, high blood pressure, obesity and high levels of "bad" fats, such as triglycerides and LDL cholesterol. Metabolic syndrome puts people at greater risk of heart disease, stroke and other conditions affecting the blood vessels.

Two-thirds of people admitted to hospital with a diagnosis of heart attack have metabolic syndrome, but 75% of these patients have completely normal total cholesterol concentrations, says the paper. "Maybe this is because total cholesterol isn't really the problem," the article suggests.

Since total cholesterol was "sanctified" as a risk factor for coronary artery disease, cholesterol-lowering drugs called statins have become a "multibillion dollar global industry", with eight million people taking them regularly in the UK alone – a figure up from five million a decade ago.

Statins, fat and death risk

Yet, says Dr Malhotra, the decline in smoking and the use of emergency treatments for heart attack patients (primary angioplasty) makes it difficult to know whether statins have had a significant additional effect on the decline in death rates from cardiovascular disease.

Despite the common belief that high cholesterol is a significant risk factor for coronary artery disease, several independent studies have shown that low total cholesterol is associated with a higher risk of death. This arguably indicates that high total cholesterol is not a risk factor in healthy people.

Moreover, says Dr Malhotra's article, "real world" research indicates that statins have "unacceptable" side effects, including muscle pain, gastrointestinal upset, sleep and memory disturbance, erectile dysfunction and loss of muscle function (myopathy) in 20% of participants.

If accurate, these findings massively contradict the figures published by the drug companies, which say that serious side effects such as myopathy only affect 1 in every 10,000 people.

The strongest evidence for the benefit of statins is in people who have already had a heart attack, where 83 people would need to take statins to prevent one cardiovascular death over five years.

But the fact that no other cholesterol-lowering drug has shown a benefit in terms of reducing risk of death suggests that the benefits of statins may be independent of their effects on cholesterol. Any benefit may actually be caused by their anti-inflammatory properties, Dr Malhotra writes.

Adopting a Mediterranean diet after a heart attack is almost three times as powerful in reducing mortality as taking a statin, says Dr Malhotra's paper, and is more effective than a low-fat diet.

"It is time to bust the myth of the role of saturated fat in heart disease and wind back the harms of dietary advice that has contributed to obesity," he concludes.

How accurate is the reporting?

Most of the coverage of this complex and controversial issue was fair, with several papers, including the Daily Express, reporting critical comments from independent experts.

However, many of the headlines were misleading. For example, the Daily Express' claim that "Doctors change their minds after 40 years" could give the impression that new dietary guidelines have been produced. This is not the case – this was an opinion article written by one doctor.

The Express' claim that a "diet packed with fat is the healthy way to prevent heart disease" does not fairly reflect the paper's arguments. Dr Malhotra says that the role of saturated fat in heart disease has been overplayed, not that we should now eat nothing but butter, cheese and cream.

Why do experts think saturated fats are bad?

As Dr Malhotra says, saturated fat intake has been found to be correlated with coronary heart disease and high cholesterol. This is because the liver turns saturated fats into cholesterol.

Most experts agree that high levels of "bad" LDL cholesterol increase the risk of diseases such as heart attack, stroke and narrowed arteries.

Saturated fat is the mostly solid type of fat found in foods such as butter and lard, pies, cakes and biscuits, fatty cuts of meat, sausages and bacon, cheese and cream, and palm and coconut oil.

What new evidence has come to light?

No new evidence has come to light to support these arguments. This article is one doctor's opinion based on his own knowledge, research and experience.

However, it is fair to say there is an ongoing debate about how far cholesterol is a risk factor for heart disease, especially in people who are otherwise healthy.

There is also a similar debate about the use of statins in people who have no evidence of cardiovascular disease. This is alongside ongoing research into the components of LDL and the different types of lipoproteins known to increase risk the most. None of this relevant new evidence is covered by the news reporting.

What should you eat?

There is no need to change current advice. As with many things in life, the adage of "everything in moderation" applies to your fat consumption.

The body needs small amounts of fat to help it work normally. But most of us eat too much saturated fat – about 20% more than the recommended maximum amount.

Current guidelines state that:

The average man should eat no more than 30g of saturated fat a day.
The average woman should eat no more than 20g of saturated fat a day.
You should avoid trans fats where possible. These fats are mainly produced by an industrial process called hydrogenation and are thought to increase the risk of cardiovascular disease through increasing inflammation. They are found in deep fried foods and biscuits, cakes and pastries.
Eat mono-unsaturated fats in small amounts. These fats are found in olive oil and rapeseed oil, as well as in some nuts and seeds. They are thought to help maintain healthy cholesterol levels.
Eat polyunsaturated fats in small amounts. These include soya, vegetable and safflower oils, as well as the omega-3 oils found in oily fish.

It is also important to moderate your sugar consumption. Sugars are added to a wide range of foods, such as sweets, cakes, biscuits, chocolate and some fizzy and juice drinks. These are the sugary foods that we should cut down on, as they can lead to obesity.

Finally, Dr Malhotra's suggestion that we should all eat a Mediterranean diet is sound advice. Mediterranean cuisine varies by region, but is largely based on vegetables, fruits, beans, whole grains, olive oil and fish. The Mediterranean diet has been associated with a better quality of life and good health, including a healthier heart, a longer lifespan and good weight management.

Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter.