London - Dietary advice to reduce fat consumption was not based on solid scientific evidence and should not have been introduced, researchers have concluded.
A study found that guidelines issued as early as 1977 suggesting that fat should form no more than 30 percent of daily food intake to reduce the risk of heart disease were based on data from "a small number of unhealthy men" and were not justified by the research available at the time.
The study said: "It seems incomprehensible that dietary advice was introduced to 220 million Americans and 56 million UK citizens, given the contrary results from a small number of unhealthy men.
"The present review concludes that dietary advice not merely needs review; it should not have been introduced."
Experts said there was now ample evidence which showed a link between dietary fat and heart disease, but suggested the emphasis placed on saturated fat as the "main dietary villain" had distracted attention from other risk factors such as sugars and carbohydrates. Victoria Taylor, a dietitian at the British Heart Foundation, said: "We continue to recommend switching saturated fat for unsaturated fat."
The Daily Mail reports that the guidelines - the first of their kind - were introduced when as much as one-fifth of the average British diet was saturated fat such as butter, cream and fattier cuts of meat.
Britons were advised by an official dietary committee to cut their fat intake to 30 percent of total energy and saturated fat intake to 10 percent, while increasing the amount of carbohydrate they ate. This led food makers to create low-fat spreads, including cholesterol-lowering products, while consumers shunned cheese, milk and cream.
However, now some scientists say the advice is responsible - in part - for the obesity crisis because it encouraged an increase in carbohydrate in our diets.
Reacting to the new review, many public health and nutrition scientists criticised the conclusions in the online BMJ journal Open Heart, saying wider evidence at the time and since has justified the advice and heart deaths have fallen dramatically.
The researchers carried out a review of data from trials that would have been available to UK and US regulators at the time. These trials were regarded as the "gold standard" of medical testing.
Six relevant trials were found, spanning an average of five years, and involving 2,467 men - most of whom had survived a heart attack or similar event.
The trials looked at the relationship between dietary fat, cholesterol, and coronary heart disease. The review found no difference in heart deaths, regardless of whether people were on a high fat or lower fat diet.
Professor Iain Broom, of the Robert Gordon University in Aberdeen, said there was now mounting evidence against the introduction of low-fat diets to combat heart disease.
Yet governments in both the US and UK have "practically destroyed the dairy industry by suggesting that butter, cheese and full fat milk increased cardiovascular disease risk, when the contrary is true," he said.
Professor Broom also said advice to increase carbohydrate consumption to 50 percent of energy intake was blamed by some experts for an epidemic of obesity and type 2 diabetes.
He said: "It is now time for the UK Government to grasp the nettle and stop an uncontrolled experiment, which has gone global and may have had bad outcomes in terms of the obesity explosion and creating a more unhealthy nation with the current idea of 'healthy eating'.
The review was led by Zoe Harcombe, Institute of Clinical Exercise and Health Science, University of the West of Scotland, Hamilton, and Dr James DiNicolantonio, Saint Luke’s Mid America Heart Institute, Kansas City.
In 1983, the country was told to reduce its overall fat consumption to 30 percent. Official guidelines were changed in 1991 raising this to 35 percent, but saturated fats remained at 10 percent.
This advice has remained unchanged even though new studies have continued to suggest that there is no association between heart disease and those fats.
Last year a US research scientist called for a campaign telling people they had been taken down the "wrong dietary road for decades" in avoiding saturated fat while not being warned about eating too much carbohydrate and sugar.
It is not the first time experts have blamed faulty interpretation of studies for creating a "myth" around the role played by saturated fat in heart disease.
Researchers last year conducted a "meta-analysis" of data from 72 studies involving more than 600,000 participants from 18 countries. It is a statistically powerful technique to reveal trends that may be masked in individual small studies, but which become obvious when they are amalgamated.
A key finding was that total saturated fat, whether measured in the diet or the bloodstream, showed no association with heart disease.
But cardiologist Dr Rahul Bahl, of the Royal Berkshire NHS Foundation Trust, also writing in Open Heart, said: "There is certainly a strong argument that an over-reliance in public health on saturated fat as the main dietary villain for cardiovascular disease has distracted from the risks posed by other nutrients, such as carbohydrates.
"Yet replacing one caricature with another does not feel like a solution."
Professor Tom Sanders, of King’s College London, said in the 1970-80s the UK and other Western countries were facing an epidemic of coronary heart disease.
He said: "It was effectively a policy choice between sitting on the fence and doing nothing or opting to follow what the evidence suggested - that cutting total fat intake would help prevent obesity and reducing saturated fat would lower blood cholesterol. Anyway it seems to have turned out okay- between 1997 and 2007/8 cardiovascular disease mortality under the age of 75 years fell by 55 percent."
Cahal Milmo, the Independent and Jenny Hope, Daily Mail