The facts on vitamin D

Q: What does vitamin D help with?

A: It can prevent or help treat a remarkable number of ailments, from obesity to arthritis, from high blood pressure to back pain, diabetes, muscle cramps, upper-respiratory-tract infections, and cancers of the breast, colon, pancreas, prostate and ovaries.

It can help safeguard pregnancy, support ideal weight management, reduce abnormal cell growth, and stave off infections and chronic diseases. What all this really means is that vitamin D may be the most under-appreciated and misunderstood anti-ageing secret. It can also help with depression, Alzheimer’s, dementia, PMS and sleeping disorders.

Q: How do I know if i'm low in vitamin D?

A: Risk factors and signs that may point to deficiency are: being older than 60 or younger than 20; being overweight; feeling like you have less energy and muscle strength than you should; not taking a multivitamin and vitamin D supplement daily; and rarely going out in the sun.

Q: What do I do if I think i'm deficient?

A: Get your doctor to do a blood test called a 25-hydroxy vitamin D test. Deficiency is considered as having this 25-vitamin D level below 20 nanograms per millilitre. Ideally you should have 30 nanograms per millilitre.

I take about 2700 IU daily from supplements and milk, in addition to the vitamin D I get from sensible sun exposure, and my blood level remains at a healthy 50 nanograms per millilitre throughout the year.

Q: What are good sources of vitamin D?

A: The best source is sunlight, through sensible exposure two or three times a week. Sunlight is the fuel that enables your body to manufacture vitamin D. Most of us need only a few minutes a day of sun exposure during the summer months to maintain healthy levels throughout the year. Exposing your arms and legs for just a few minutes without SPF will often do the trick.

Vitamin D is also found in oily fish, in mushrooms and in fortified foods like milk, yoghurt, margarine, and some cheeses. But to eat a sufficient amount of vitamin D (1000 to 2000 IU), you’d have to consume three cans of sardines, drink ten to 20 glasses of fortified milk, gulp down ten to 20 bowls of cereal, snack on 50 to 100 egg yolks, or eat 200 grams of wild salmon for dinner every night.

Q: How can i build my vitamin D levels?

A: Protect your face with SPF and spend one quarter to one half the amount of time in the sun that it takes you to get pink. Doing this three times a week will provide you with a good weekly dose of vitamin D.

Michael Holick (PhD, MD) is Professor of Medicine at Boston University Medical Centre. He has spent more than 30 years studying vitamin D and is the author of Vitamin D Solution (Scribe, $35).