From the BBC, an interesting short read about 1940's infectious disease advice, with an interesting comment I've highlighted about exposure to sunlight.
https://www.bbc.co.uk/news/stories-52152993
"but for streptococcal infections (such as scarlet fever or the most common form of pneumonia) "the liberal use of soap, water and exposure to sunlight will be effective."
Sunlight is main natural source of vitamin D, but it is accepted it doesn't provide enough for the body's daily requirement.
The value/effectiveness of Vitamin supplements is not fully proven, but further/continued research in this area may prove fruitful ?
"Vitamin D is necessary for the proper functioning of your immune system, which is your body’s first line of defense against infection and disease.
This vitamin plays a critical role in promoting immune response. It has both anti-inflammatory and immunoregulatory properties and is crucial for the activation of immune system defenses.
Vitamin D is known to enhance the function of immune cells, including T-cells and macrophages, that protect your body against pathogens.
In fact, the vitamin is so important for immune function that low levels of vitamin D have been associated with an increased susceptibility to infection, disease, and immune-related disorders.
For example, low vitamin D levels are associated with an increased risk of respiratory diseases, including tuberculosis, asthma, and chronic obstructive pulmonary disease (COPD), as well as viral and bacterial respiratory infections.
What’s more, vitamin D deficiency has been linked to decreased lung function, which may affect your body’s ability to fight respiratory infections".
Originally Posted by: llamedos