As the winter season draws in, it officially marks the start of trying to boost your immune system. Cold and flu are spread by coughs and sneezes, and is especially common in the winter months. But, adding these supplements to daily routine could support the immune system when one needs it the most, reports Express.co.uk. The body does its best to deal with these invaders with a complex process that relies on a number of factors. In addition to known immune boosters, such as getting enough physical activity and eating a healthy diet, there are only a few supplements on the shelves that may help boost immunity. According to a dietician, Vitamins A, B12, C, D, zinc and selenium could help to prevent cold and flu this winter. Vitamin D supplements during autumn and winter, as sunlight hours - the biggest natural source of the vitamin - gets reduced during the seasons. Vitamin A helps in strengthening cells on the outer layer of skin - the body's first defence against harmful bacteria and viruses, but it also helps cells in the linings of the body's hollow structures, including the nose, throat, stomach and gut. A vitamin D deficiency, meanwhile, increased the risk of auto-immune diseases. Zinc and selenium helped the body fight infection, and maintained the body's defence system, she added. As with most things that help reduce the risk of infection, chronic disease and early death, it's not one thing that provides the "miracle cure," it's a variety of good lifestyle choices that make the difference.