Eating too much red meat is not only bad for your health -- it is also bad for the planet, according to scientists.

Worldwide, agricultural activity accounts for about a fifth of total greenhouse-gas emissions and livestock production has a particularly big impact because of the large amount of methane emitted from belching cattle.

Tony McMichael of the Australian National University in Canberra and John Powles of Britain's University of Cambridge, writing in the Lancet journal, said worldwide average meat consumption could be realistically reduced by 10 percent.

This would help in the battle against global warming and also reduce health risks associated with excessive consumption of red meat, they said.

Global average meat consumption is currently 100 grams per person a day but there is a tenfold variation between high-consuming and low-consuming populations.

They point out that 22 percent of the planet's total emissions of greenhouse gases come from agriculture, a tally similar to that of industry and more than that of transport.

Livestock production, including transport of livestock and feed, account for nearly 80 percent of agricultural emissions, mainly in the form of methane, a potent heat-trapping gas.

At present, the global average meat consumption is 100 grammes (3.5 ounces) per person per day, which varies from 200-250 gm (seven to 8.8 ounces) in rich countries to 20-25g (0.71-0.88 ounces) in poor countries.

The global average should be cut to 90gm (3.17 ounces) per day by 2050, with rich nations working to progressively scale down their meat consumption to that level while poor nations would do more to boost their consumption, the authors propose.

Not more than 50g (1.75 ounces) per day should come from red meat provided by cattle, sheep, goats and other ruminants.

"A substantial contract in meat consumption in high-income countries should benefit health, mainly by reducing the risk of ...heart disease... obesity, colorectal cancer and, perhaps some other cancers. An increase in the consumption of animal products in low-intake populations, towards the proposed global mean figure, should also benefit health."