Vitamin d tablets help to support normal immune system function, which can help lower the risk of contracting a cold or flu. it also plays a vital role in the process of cell division. exposure to sunlight allows our bodies to naturally produce vitamin d, but when there is a lack of sun, especially during the winter months, these levels can drop, leaving your immune system weakened to attack from cold and flu. supplementing your diet with vitamin d can aid your immunity when you need it the most. these tablets could also be beneficial to those working indoors during the day or people who are housebound and unable to get into their garden.