Eating an egg every day in winter can help keep your vitamin D levels up, new research has found. As many as one in three Australian adults may have vitamin D deficiency. It can lead to fatigue, aches, muscle weakness, mood changes and an increased risk of contracting respiratory infections. "Vitamin D deficiency can have a negative impact on bone health as the key function of vitamin D is to promote calcium absorption," says research lead, Professor Robin Daly. "Vitamin D deficiency may also increase the risk of other non-skeletal diseases such as type 2 diabetes, hypertension, depression and Alzheimer's...