Vitamin D is good for bone density and heart health. Plus, it has anti-cancer properties and boosts immune function. After summer holidays, modern lifestyles naturally keep us out of the sun -- the body's main source of the vitamin. Here are three ways to top up vitamin D levels in time for winter to help keep seasonal viruses at bay.

Get out in the sun for five to 15 minutes

Doctors and naturopaths recommend getting outside when the sun is high in the sky. That means between 11am and 4pm, times that are usually not recommended when it comes to safe sun exposure. Here, the aim is to expose skin to sunlight, without sunscreen, in short but frequent spells. Try to expose the largest area of skin possible (dress in shorts, skirts and short-sleeved tops). Depending on the UV index and your tolerance level, a period of five to 15 minutes can be sufficient. Those with very fair skin may want to stick to around five minutes' exposure at a time. Between now and October, you can soak up some sun whenever the weather permits. Try heading out between 12pm and 1pm on your lunch break, for example.

Ten great foods for boosting vitamin D

Although diet plays a marginal role in vitamin D intake (20%), certain foods can help boost the body's levels of the vitamin. Load up on cod liver oil, salmon, trout, herring, egg yolks, milk, calf's liver, soy-based drinks, canned tuna and cooked mushrooms.

Supplement with vitamin D3 drops

Doctors often prescribe vitamin D supplements as vials to take every six months. The healthy range for vitamin D levels is considered to be between 40 to 45 ng/ml (100 to 112.5 nmol/l). To be more effective, vitamin D should be taken continuously. Vitamin D3 drops, for example, can be taken every day, especially in winter. Plenty of supplements of this kind are available to buy.