A new study from the University of Cambridge found that there is insufficient evidence backing dietary guidelines that restrict saturated fat consumption and encourage intake of polyunsaturated fats.

Saturated fats - the kind of fat that goes into pizzas and cheese- increase LDL levels in the body and raise a person's chances of heart disease and stroke. Ideally, only ten percent of a person's daily energy must come from saturated fats in the diet, according toMedline Plus.

Health experts have been asking people to lower their levels of saturated fats to reduce heart disease risk. Additionally, doctors advocate polyunsaturated fats intake - found in fish and safflower oil- to boost heart health.

But, will replacing butter with "healthier" vegetable oils lower heart disease risk?

The study was based on data from 72 unique studies with over 600,000 participants from 18 nations. Their analyses showed that the link between saturated fats and heart disease is still unclear.

The study team also looked at specific subtypes within the omega-3 fatty acids and found that each subtype has a different effect on human health.

"These are interesting results that potentially stimulate new lines of scientific inquiry and encourage careful reappraisal of our current nutritional guidelines," Dr Rajiv Chowdhury, the lead author of the research at the University of Cambridge.

"Cardiovascular disease, in which the principal manifestation is coronary heart disease, remains the single leading cause of death and disability worldwide. In 2008, more than 17 million people died from a cardiovascular cause globally. With so many affected by this illness, it is critical to have appropriate prevention guidelines which are informed by the best available scientific evidence," Chowdhury said in a news release.

Their study showed that the presence of saturated fatty acids in the body wasn't associated with coronary heart disease. Also, researchers found no link between long-chain omega-3 and omega-6 polyunsaturated fatty acids and heart health.

The saturated fatty acid family also showed similar differences. Palmitic (palm oil) and stearic acids (animal fat) were weakly associated with a rise in cardiovascular disease risk. However, dairy fats (margaric acid) were linked with lower heart disease risk.

Efficacy of omega-3 fatty acids was also tested in clinical trials. Researchers didn't find any significant benefits of using these supplements.

Previous research published in the journal bmj.com, too, had raised questions about dietary guidelines that limit use of saturated fats.

Of course, the study doesn't provide an excuse for people to eat pizzas, cakes and cookies. Junk food still has lots of carbohydrate, salt and simple sugars- all of which are bad for health.

"Alongside taking any necessary medication, the best way to stay heart healthy is to stop smoking, stay active, and ensure our whole diet is healthy - and this means considering not only the fats in our diet but also our intake of salt, sugar and fruit and vegetables," Jeremy Pearson, Associate Medical Director at the British Heart Foundation

The study is published in the journal Annals of Internal Medicine.