People who are out in the sun getting more vitamin D tend to live longer, a new study has found.

Researchers looked at the medical records of about 4300 adults aged over 60 and found those who had low levels of the vitamin had double the risk of dying early. Those who were frail tripled their risk.

"What this really means is that it is important to assess vitamin D levels in older adults and especially among those who are frail," said lead researcher Dr Ellen Smit of Oregon State University.

"As you age, there is an increased risk of melanoma, but older adults should try and get more activity in the sunshine," Dr Smit said.


"Our study suggests that there is an opportunity for intervention with those who are in the pre-frail group, but could live longer, more independent lives if they get proper nutrition and exercise."

When a person is frail they walk slowly, have weak muscles, lose a lot of weight unintentionally, are often exhausted and have low levels of physical activity, according to the university.

The design of the study means researchers can't be certain whether frail people become vitamin D deficient or whether low levels of the vitamin cause people to be frail.

"If you have both it may not really matter which came first because you are worse off and at greater risk of dying than older people who are frail and don't have low vitamin D," Dr Smit said.

About 30 per cent of New Zealanders don't get enough vitamin D.

You can increase your levels of the vitamin through safe sun exposure and by eating things like oily fish (think salmon, tuna, sardines, eel and warehou), milk and milk products and eggs.