If your team is looking a bit peaky at the moment, or you can't shift that lingering cold, there might be an easy way to restore health, scientists have found: Vitamin D supplements.
A new study, published in the British Medical Journal, has suggested taking daily or weekly Vitamin D supplements could be more effective than the flu vaccine (although it's worth pointing out that to prevent one case of flu, 40 people need to be vaccinated).
The study, of 11,321 people, found the vitamin helped to prevent acute respiratory tract infection. So effective could it be, the paper argues food should be fortified with Vitamin D to help the wellbeing of the general population.
"We show that people who are very deficient in vitamin D and those receiving daily or weekly supplementation... experienced particular benefit," it explained.
"Our results add to the body of evidence supporting the introduction of public health measures such as food fortification to improve vitamin D status, particularly in settings where profound vitamin D deficiency is common."
Vitamin D is already known to help the body absorb calcium and phosphate, strengthening bones, teeth and muscles. Deficiency in the vitamin can lead to rickets in children, and osteomalacia in adults.
NHS guidelines state that from March to the end of September, the majority of people in the UK get the amount of Vitamin D they need from sunlight - but between those times, people should either rely on food like fatty fish, orange juice and cheese, or take supplements to boost the amount of the vitamin in their system.