Sunshine-vitamin: a vital nutrient
You probably know the primary source of vitamin D comes from sunlight on your skin. Are you getting enough vitamin D? And why is this vitamin so important?
Read on: symptoms of low vitamin D, when to test, and how to supplement.
In the northern hemisphere above the 37th parallel (Toronto's at the 43rd parallel), we rely on the longer days of summer to absorb sufficient vitamin D. We hit a sweet spot of hot enough and long enough days (the longest being the summer solstice at the end of June) to bare our skin for only a couple months of the year and otherwise must find an alternative source of vitamin D to the sunshine.
Hoe to know if you're low in Vitamin D: Have you had your vitamin D levels checked? Low vitamin D has been linked to:
poor immune function (ie. getting sick frequently, or slow recovery),
poor calcium absorption / osteoporosis
When to test your Vitamin D levels: Sufficiency of vitamin D is considered at 75nmol/L, though perhaps 100nmol/L is closer to optimal. I like to consider sufficiency as a matter of whether you have enough for each season. If you're at 75 at the end of the summer, what will your levels be by the end of winter?
I find the two most useful times of year to test Vitamin D are around the spring and fall equinox:
1) September: your high point (after maximum sun exposure you should be well above the sufficiency minimum), and
2) March: your low point (you still want to be at or above 75nmol/L here).
If your levels are suboptimal at either point, consider adding dietary and supplementary vitamin D through the next 6 months.
Your sunshine prescription: spend 10 to 20 minutes daily with at least 20% of your skin exposed (weather permitting!) to direct sunlight before you put on your sunblock – please know your own tolerance and don’t get a sunburn! Your absorption of vitamin D from the sun depends on the amount of skin exposed and the duration of exposure. In winter, with minimal skin exposure (closer to 5%), you'd need to be outside over 6 hours a day to convert 1000 IU of Vitamin D. For most of us, that's not practical.
Are there dietary vitamin D sources? Yes! Dietary sources provide vitamin D2, which is converted by your liver to the active bioavailable form, D3. The highest dietary sources are:
Mushrooms: if exposed to sunlight for 20 minutes = 600 IU per 1 cup
Fish: salmon and rainbow trout = 1000 IU per 6-8 oz serving
How do I choose a vitamin D supplement? It's a fat-soluble vitamin, best absorbed with other fats, so take it with food for best absorption. Here's what I look for:
Liquid form - readily available, tasty, usually cost effective, and reduces the pill burden.
Few ingredients - all you need is a carrier oil - ideally coconut MCT or olive oil
Vitamin "D3" (cholecalciferol), the most bioavailable form,
or a D3-K2 combo (K2 is directive, and aids absorption of calcium into bone and prevents calcification of arteries - a key ingredient if you don't get it in your diet)
Where do I get vitamin K2? K2, or “menaquinone” comes from bacteria fermentation – fermented foods like natto (soy - or other legumes) provide the MK-7 form, while meat, dairy and eggs provide the MK-4 form. Research suggests the MK-7 form promotes bone building best. More is not always better. If supplementing, stay under 120mcg of K2 daily.
CAUTION: This post is not intended as medical advice. Supplementation recommendations are best made by a medical professional who can take into consideration your whole person. Do not supplement without the advice of your medical practitioner if you have kidney stones. Testing vitamin D levels is always recommended prior to initiating supplementation.