To do it, they pored over web pages from six world regions and found recommendations for more than 2500 food items - ultimately looking not just for the healthiest but those least environmentally harmful to grow.

Top of the crop were cruciferous and leafy green vegetables such as broccoli; vitamin-C-rich fruits such as citrus and pineapple; other vegetables; nuts; onions and garlic; and lycopene-heavy fruit and vegies including tomatoes and red capsicum.

"Eating an extra serving of any food in these six most frequently recommended food groups each day will, on average, reduce the risk of chronic diseases and all-cause mortality," Queensland University of Technology dietician Professor Danielle Gallegos said.

"Of 23 overall recommended food groups, we found (those) with higher online recommendation frequencies had significantly lower relative health risks than food groups that were less recommended."

Better still, the research revealed the average environmental impact of the six top groups was also generally lower than those rarely recommended.

Using data from two global studies, Prof Gallegos and Queensland ecologists Ayesha Tulloch and Rachel Oh examined the agricultural production of 150 different foods in relation to greenhouse gas emissions, land use, scarcity-weighted freshwater use and two types of soil nutrient pollution.

"Our analysis showed eating a serving of a more frequently recommended food over a less recommended one would result in lower environmental impacts for greenhouse gas emissions and land use, and lower health risks," Dr Tulloch said.

While land environments fared better, the outcome wasn't universally positive.

"Highly recommended food groups tended to have higher impacts on aquatic environments, due to use of chemicals and freshwater during production," she said.

"The latter was especially so for dairy products, farmed seafood, nuts, some fruits and legumes."

Nutrient pollution of waterways also increased with frequently recommended plant foods such as nuts, berries and some vegetables.

Australian Associated Press