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Insects have been touted as the future of food with the ability to feed the world's growing population with minimal environmental impact.

But now US scientists say that crickets are not yet all they're cracked up to be as an alternative source of protein to meat.

Researchers found that insects need to be fed on high quality food and waste to grow large enough to eat.

US scientists say that crickets are not all they're cracked up to be as an alternative source of protein to meat. Researchers led by Mark Lundy (pictured) found that insects need to be fed on high quality food and waste to grow large enough to be a good meal

Crickets are the most widely cultivated insects for the human diet across the world and are considered the 'gateway bug' for people who choose to eat insects.

They, along with other insects are touted as highly nutritious and much better for the planet - environmentally and financially - than traditional livestock, due to the comparatively efficient rate at which they convert feed into body mass.

But scientists at the University of California, Davis, say the issue of incorporating insects into mainstream human diets is more complex than previously thought.

'While there is potential for insect cultivation to augment the global supply of dietary protein, some of the sustainability claims on this topic have been overstated,' said Mark Lundy of the university.

Crickets (pictured) are the most widely cultivated insects for the human diet across the world and are considered the 'gateway bug' for people who choose to eat insects

'Our study demonstrates that the sustainability gains associated with cultivating crickets as an alternative source of protein will depend, in large part, on what the crickets are fed and which systems of livestock production they are compared to.'

'Insect cultivation is more likely to contribute to human nutrition at a scale of economic and ecological significance if it does not rely on a diet that competes with conventional livestock, but more innovation is needed for this to become a reality.'

He believes that the goal will be to design cost-effective processes to feed large populations of insects on organic waste.

Professor Michael Parrella, who was also involved in the study, said that it's widely assumed that crickets and other insects are more efficient than mammals such as cows in converting feed to protein.

But he explained that there's very little data to support this.

To find out, the researchers measured the biomass output of crickets that were reared on foods ranging from grain to cellulose.

They found that the amount of biomass - biological material derived from living, or recently living organisms - was strongly influenced by the quality of the diet.

But scientists at the University of California, Davis say the issue of incorporating insects into western diets is more complex than previously thought. A 'mince fly' including meal worms and locusts is pictured

They found crickets that were fed a poultry-feed diet showed little improvement in protein conversion efficiency, compared to the industrial-scale production of broiler chickens, which are foul reared for their meat.

Crickets fed on processed food waste grew to a harvestable size with conversion efficiency similar to the chickens.

But 99 per cent of crickets fed on food waste and diets composed largely of straw, died before reaching a harvestable size, proving that they can't simply be fed waste to create cheap food.

Bringing crickets into the global protein supply will depend on collecting and using relatively high-quality waste side-streams that are not currently being used for livestock production, the researchers said.

Dr Lundy said that he ate some of his experimental subjects after weighing them for the research.

He dusted them with cornmeal and Cajun seasoning and fried them in olive oil and also snacked on protein bars made with cricket flour.

'I'm all for exploring alternatives, and I am impressed by the amount of innovation that has sprung up around insect cultivation and cuisine in the last few years,' he said.

'However, I also think we need to be clear-eyed about what the sustainability gains are and aren't, and focus our innovative efforts and limited resources to where they will have the most lasting impact.'

Crickets are readily available in pet stores as food for frogs and other pets and are considered delicacies or snacks in many countries.