NUTRISPEAK by Vesanto Melina and Brenda Davis
• Around the year 1900 in the northeastern US, 80 to 90 percent of the children had the symptoms of rickets – bowed legs and seizures. The situation was eventually linked with a lack of vitamin D and sunlight. Glance out the window now. Is it grey? Well, our grey winter skies last until April and we need sunlight.
We Canadians first remedied this situation with cod liver oil, then by fortifying cow’s milk (and now non-dairy milks) with vitamin D and allowing the addition of vitamin D to margarine, cereals, a few other foods and vitamin D supplements.
Yet in a recent Canadian study, pediatricians reported 52 confirmed cases of rickets per year among youngsters with an average age of 1.4 years. While most had been breast-fed, they had not received the recommended vitamin D supplementation (400 IU/day). (Though breast is best, infant formula does contain vitamin D.) Many (89%) had intermediate or darker skin.
On clear days during warm weather, through exposing our face and forearms to the sun – without sunscreen – we may make sufficient vitamin D with approximately 15 minutes of exposure if we are light-skinned and 30 minutes or more if we are dark-skinned. The melanin pigment protects against sunburn for people close to the equator, but means longer sun exposure is needed for vitamin D production.
For those above 33° N latitude (at the Louisiana-Arkansas border or in Phoenix), there is little or no vitamin D production over winter months, even on sunny days. And as we go north, there are even longer “Vitamin D winters.” Don’t expect to make much vitamin D from about October to April. And recent studies show that in smoggy southern cities such as Los Angeles or San Diego, vitamin D production is also limited, despite sunshine above the smog.
Older people take longer to produce vitamin D with the same exposure to the ultraviolet radiation that stimulates our manufacture of this substance. One study showed adults aged 62 to 80 had one-third the vitamin D production of those aged 20 to 30. A few years ago, I spent three October weeks in Italy and two December weeks in Hawaii and I was still low in vitamin D in February. Now, I top up my intake with supplements.
To check one’s status, serum vitamin D can be tested through one’s physician (one option is to pay for the test) or a test kit (search online). Though vitamin D is present in a few fortified beverages and foods, it’s a challenge to reach optimal intakes this way. The official adult recommendation is 15 mcg (600 IU) until age 70 and 20 mcg (800 IU) after age 70. Yet these early recommendations were based solely on research related to bone health. We now realize vitamin D has many more functions (supporting our immune system, reducing risk of cancer, diabetes, depression). It seems that double or triple these amounts are safe for adults and may be advisable.
Wacker M et al. Sunlight and vitamin D: A global perspective for health. (Dermatoendocrinol 2013 Jan 1;5(1):51-108).
Ward et al. Vitamin D – deficiency rickets among children in Canada. (Canadian Medical Association Journal. 2007)
Vesanto Melina: 604-882-6782, www.nutrispeak.com and www.becomingvegan.ca Her award winning nutrition books e.g. Becoming Vegan: Comprehensive Edition andBecoming Vegan: Express Edition (Davis and Melina, Book Publishing Co) are available online, through bookstores and at libraries.