Gill South discovers you need to expose your skin to the the sun for at least a few minutes a day to keep your vitamin D levels up.

My vitamin D levels are low, my holistic doctor, Dr Kerry Lamb, tells me, after a recent blood test. This rather perplexes me because I'm one of those insufferable women striding along the streets of my neighbourhood doing my morning stroll most days. But, in a bid not to lose that so-called English complexion I pride myself on after years in Britain, I always slap on suntan lotion. "You need to be exposing skin somewhere," she tells me.

A friend tells me sun through the eyes is very important, and I wear prescription sunglasses. Kerry does disabuse me of this notion, but not before I have spent several days walking along blind as a bat with my sunglasses up on my head, hoping none of my friends walk past because I won't be able to see them until they are 2cm away from me.

I'm now taking calciferol weekly to boost my vitamin D levels, but also I vow to get a minimum of five to 10 minutes of sunshine per day without sunblock on the skin.

I decide it's a good excuse to make an appointment with a recommended personal trainer and go for an hour's walk. I throw caution to the winds and leave the SPF lotion off - and meet up with Prue Jamieson at Les Mills in Victoria St. Prue is lovely and very tall, with long blonde hair and a tanned, toned body. She is slightly older than me but you wouldn't know this as she strides up Franklin Rd with me trotting along beside her, trying to keep up and carry out a conversation while gasping for breath.

Back on the glorious flat of Ponsonby Rd, I'm talking away again, although walking a hell of a lot faster than usual.

Prue is big on "finding hills" - every hour walk should have at least three good hills in it, she tells me. We go straight ahead into St Mary's Rd, past Ponsonby Library and left down to Shelley Beach Rd and beneath the Harbour Bridge. Although I could see Prue gliding over the bridge with barely an intake of breath, we head right along Westhaven and along Fanshawe St. "Oh good, a hill," says Prue and we stride vigorously up Nelson St, down Victoria St towards Queen St and end up outside Smith & Caughey.

To my astonishment I'm sweating - this doesn't normally happen to me in winter, an indication of my slack walking regime.

So next time you see a woman walking along at a medium-slow pace, but with her sleeves up on a freezing cold day, you'll know that's me, trying to get my vitamin D intake.