At the New Zealand melanoma summit in Wellington tomorrow, Dr Reeder, who is director of the social and behavioural research in cancer unit at the Dunedin School of Medicine, will speak about research showing a decline in the number of severe and blistering sunburns since 1994.
The findings indicated that some small gains had been made in improving people's sun protection behaviour.
However, their worries about low vitamin D could counter the gains, Dr Reeder said.
Sun protection had never been a very popular message, and some people were keen to find an excuse not to follow the "slip, slop, slap, and wrap" advice.
Low vitamin D levels had been linked to increased risk of colorectal cancer, of which New Zealand had a high rate; but Dr Reeder said more research was needed.
The University of Otago, in conjunction with Auckland University and Niwa, was conducting research into the association between sun exposure and vitamin D.
The two-year study, involving 500 adults aged up to 80 in Otago and Auckland, was measuring participants' vitamin D levels at the beginning and after eight to 10 weeks outside in summer time.
Ultraviolet radiation was being measured by a dosimeter worn by participants, Dr Reeder said.
A smaller number of people were also participating in a study looking at the effect of sunbed exposure on vitamin D levels.
Levels of radiation for this were overseen by the National Radiation Laboratory to ensure they were safe, and people who had skin considered at high risk, or people taking medication which made their skin sun-sensitive, were excluded, Dr Reeder said.
Although the research had another year to run, such was the interest in the topic that preliminary findings could be released next year, he said.
Earlier this year, Dr Reeder reported on a study analysing the incidence of the most dangerous thick melanomas between 1994 and 2004 which showed they had not declined.
Dr Reeder said it could be that it was too early to see the impact of early detection, or that ways of detecting melanomas needed improvement.
New clinical guidelines for the management of melanoma in Australia and New Zealand were to be released this week, just before the summit.
The summit, which was expected to be attended by about 200 health professionals, including some speakers from Australia and Canada, would launch a New Zealand melanoma network linking all those working in melanoma.
Dr Reeder said he hoped improving co-ordination would help draw attention to the issues surrounding melanoma.
It was also important that researchers in the field collaborated with those working in related areas.
The vitamin D research was an example of that.
Dr Reeder would be one of eight speakers at a symposium on the evolving status of vitamin D in Auckland later this month.
This would look at the vitamin's role in immunity, bone health, diabetes and cardiovascular disease as well as explore the question of how much vitamin D was enough and how to measure that.
