The Bloomberg Healthiest Country Index, which ranks 169 countries, moved Spain to the top spot to overtake Italy.
Great Britain placed 19th, while the US only made it to 35th – Australia was the only English-speaking country to make it into the top 10, ranking seventh.
Countries’ life expectancies, smoking rates and obesity were all taken into account by the rankings, as well as access to clean water.
Experts suggest the Mediterranean diet, which is known to be good for the heart and circulation, could play a role in Spaniards’ good health.
And Spain officially has the European Union’s longest life expectancy at birth, and ranks third globally – behind Japan and Switzerland, Bloomberg reported.
A study led by the University of Navarra, in Spain, said a ‘Mediterranean diet, supplemented with extra-virgin olive oil or nuts, had a lower rate of major cardiovascular events than those assigned to a reduced-fat diet’.
Italy slipped to the second spot. The rest of the top 10 was completed by Iceland, Japan, Switzerland, Sweden, Australia, Singapore, Norway and Israel.
The countries in the top 50 which made the biggest improvements on the previous index, in 2017, were South Korea – which rose from 24th to 17th – Estonia, which rose six places from 38th to 32nd, and Albania, which rose from 50th to 43rd.
Meanwhile, Macedonia was the biggest faller – dropping 12 places from 44th to 56th.
A separate ranking of healthy countries done last year, by educational charity the Legatum Institute, claimed Spain was the 22nd healthiest country.
Scientists regularly publish studies praising the health benefits of the Mediterranean diet, which contains a lot of vegetables, nuts, fish and oils.
It is known to improve heart health and also believed to be good for the brain and liver, and may improve sexual function in men.
Although the Legatum’s Institute ranking is at odds with Bloomberg’s assessment, there is crossover in the top 10 on both lists.
Singapore, Japan, Switzerland, Sweden and Norway all feature in the 10 healthiest countries on both Bloomberg’s and Legatum’s lists.
No African nations made it into the top 50 of today’s index, and only a handful of those in the Middle East did – Bahrain, Qatar, Lebanon, Brunei, the United Arab Emirates and Oman.
Countries in sub-Saharan Africa – where access to clean water and sanitation are lingering issues and deadly diseases are rife – made up 27 of 30 unhealthiest countries.
Haiti, Afghanistan and Yemen were all also among the worst performing.