Why vitamin D is vital in warding off sickness as you age

This is particularly true for seniors, who are more vulnerable to colds and flu and are often concerned about maintaining good immune health.

While many seniors have their own favoured remedies for warding off illness, from hot tea with lemon to daily exercise, it's important to understand what else can help contribute to a strong immune system, including vitamins like Vitamin D - also known as the 'sunshine vitamin'.

And yet while vitamin D is known to help boost the immune system, nearly a quarter of all Australian adults have a vitamin D deficiency, according to the Australian Bureau of Statistics.

Sydney-based GP Dr Michela Sorensen said the immune system evolves with age. "As people get older, they are exposed to an increased risk of infection and allergies.

"This means that it is important that people above 50 take an active interest in supporting immune health, especially ahead of the start of the flu season."

She said vitamin D plays a fundamental role in supporting immune health.

"It is an important micronutrient that helps to enhance immune system function. There is also emerging scientific evidence that supports the important role of vitamin D in the body's response in resolving and lowering the risk of acute respiratory tract infections."

Vitamin D is typically obtained through sunlight, diet and supplements but many people don't realise that they don't get enough and quickly enough.

Low levels of vitamin D are known to impact immune function and are associated with an increased risk of chronic disease and infection of the respiratory tract.

Most people with vitamin D deficiency don't experience symptoms but some may. Symptoms of low vitamin D may include fatigue, bone pain, muscle weakness, aches and cramps, and even mood changes.

"It is not always easy to know if you're getting enough. People who are more likely to have lower levels of vitamin D include people over 50, people who work long hours or night shifts, people who live in in-patient settings like aged care, pregnant women, people with fairer skin who might be very cautious about sun exposure and conversely, people with darker skin who cannot absorb vitamin D as easily," said Dr Sorensen.

She said another factor to consider how exposed we are when we are in the sun. "The things we need to do to protect our skin from the sun - like wearing sunscreen, long sleeves or staying in the shade - are all important but limit our vitamin D intake from the sun."

Dr Sorensen said a good start is getting exposure to the sun in the mornings and evenings every day, when there are lower levels of UV.

"For those who cannot do that, a vitamin D supplement is a good option," she said.

"There are lots of different types of Vitamin D supplements - some that are more effective than others - and this can be difficult to navigate.

"Some vitamin supplements containing D3 can take months to get absorbed into the system, whereas calcifediol, which is a natural form of vitamin D, is better absorbed into the body. It can raise vitamin D levels much faster, helping to support immune system function in days to weeks, not months."

Other things seniors can do to boost their immune health include keeping up with regular exercise, and staying connected with others socially to maintain good mental health.

"We know that stress and other mental health concerns can weaken the immune system," said Dr Sorensen.

"Also, try to eat a well-balanced, nutritious diet."

Recent research commissioned by Australian Eggs found 45 per cent of Australians don't understand the benefit of vitamin D for immunity.

The research also found most Aussies (96 per cent) wouldn't first turn to their diet in order to increase their intake of vitamin D.

But did you know an average serve of eggs contains over 80 per cent of the daily requirement of vitamin D?

Dietitian Dr Joanna McMillan said: "Eggs are easy to get into your diet, are much more cost effective than supplements, and deliver a whole bunch of other vitamins, minerals, carotenoids, protein and good fats, making them a highly nutritious whole food to include in your diet."

She said egg yolks are one of the highest natural food sources of vitamin D.

"An average serve of two eggs has 82% of the daily recommended vitamin D intake for adults making it the easiest way to top your body up," added Dr McMillan.

Other food sources of vitamin D are fatty fish like salmon, herring and mackerel. Some milk, soy drinks, breads and cereals may also be fortified with vitamin D.