Meat eaters who justify their eating habits feel less guilty and are more tolerant of social inequality say researchers.

An international team of researchers led by Dr Jared Piazza of Lancaster University examined the ways in which people defend eating meat.

They found that the vast majority of omnivores defend consuming animals by rationalizing their behavior using one of four rationalizations, which they call the 4Ns.

He said: "The relationships people have with animals are complicated. While most people enjoy the company of animals and billions of dollars are spent each year on pet care and maintenance, most people continue to eat animals as food. People employ a number of strategies to overcome this apparent contradiction in attitude and behavior.

"One important and prevalent strategy is to rationalise that meat consumption is Natural, Normal Necessary and Nice. "

This study asked students and adults in the United States why they find it OK to eat meat. The largest category used to justify their choice was that that it is "necessary" followed by the other three categories.

Typical comments used to justify eating meat include these 4Ns:

Natural "Humans are natural carnivores"

Necessary "Meat provides essential nutrients"

Normal "I was raised eating meat"

Nice "It's delicious"

Dr Piazza said: "Morally motivated vegetarians may serve as a source of implicit moral reproach for many omnivores, eliciting behaviors designed to defend against moral condemnation."

Men endorsed the 4Ns more than women while people who rejected these justifications showed a greater concern for animal welfare.

People who said meat eating is Natural, Necessary, Normal and Nice also share other characteristics; they attributed fewer mental capacities to cows and were more tolerant of social inequality.

Dr Piazza said: "The 4Ns are a powerful pervasive tool employed by individuals to diffuse the guilt one might otherwise experience when consuming animal products."

The research "Rationalising Meat Consumption. The 4Ns" is published in the journal Appetite.