Recently a daily glass of apple juice has been added to the proven list.
It isn't the same as 'an apple a day' as like tinned tomatoes there is something gained in the processing which aids the metabolism.
We've had all the lifestyle advice. Now the purely medical approaches. Keep up to date with any immunisations and boosters that might be necessary to protect at home, work or holiday eg tetanus, hepatitis, influenza, yellow fever, smallpox etc etc.