Some of the foods in the popular Mediterranean diet help to keep people alive longer, according to a study published by the BMJ.

The diet promotes eating more vegetables, fruits, nuts and olive oil. It also means staying away from big portions of meat and excessive alcohol.

But the study says that the fish, seafood and cereals in the diet don't do much to encourage a long life.

Dimitrios Trichopoulos of the Harvard School of Public Health said in a news release that a team looked at surveys of 23,000 Greek men to see how closely their diets matched the Mediterranean diet.

The authors said that when high intake of vegetables, low intake of meat or moderate alcohol intake were excluded from the rating system, the benefits of following a Mediterranean diet were substantially reduced. They also note that there are clear benefits in combining several of the key components, for example high consumption of vegetables and olive oil.

Trichopoulous said that the main reasons the Mediterranean diet can lead to living longer are moderate consumption of alcohol -- especially from wine -- low consumption of meat and meat products, and high consumption of vegetables, fruits and nuts, olive oil and legumes.