The amount of sun exposure required to produce Vitamin D is small – about a quarter of the time it would take before experiencing a sunburn, although this will vary age, skin type, season, time of day, and so on. Your body will store the Vitamin D it makes in your fatty tissues and release it during periods when your sun exposure is not sufficient to meet your Vitamin D needs.
In spite of this, Vitamin D deficiency is relatively common, especially for Canadians, because of reduced hours of sunlight, use of sunscreens and other sun-avoidance tactics. Older adults are even more at risk of Vitamin D deficiency because they have fewer skin receptors that convert sunlight to vitamin D, may not get vitamin D in their diet or have trouble absorbing it, or may have difficulty activating it because of reduced kidney function.
Supplementation may be appropriate for older people, people living in northern countries such as Canada, and for dark-skinned people who need longer periods of sun exposure to generate adequate amounts of Vitamin D.
Adults need 4,000 IU of Vitamin D per day; children need amounts that vary by age, ranging from 1,000 IU for newborns to 4,000 IU for pre-teens and adolescents.
Because Vitamin D is stored in body fat, it is possible to experience toxicity symptoms if large amounts are taken for extended periods of time. Symptoms include: weakness, fatigue, sleepiness, headache, loss of appetite, dry mouth, metallic taste, nausea, vomiting, among others.
People with kidney disease, atherosclerosis, sarcoidosis, histoplasmosis, hyperparathyroidism, and lymphoma should not take Vitamin D supplements without medical supervision.
Vitamin D can interact with other substances and medications such as:
- aluminum antacids
- Atorvastatin (Lipitor)
- Calcipotriene (Dovonex)
- Cimetidine (Tagamet)
- Digoxin (Lanoxin)
- Diltiazem (Cardizem, Dilacor, Tiazac)
- Heparin , Low molecular weight heparins (LMWHs), Lovenox, dalteparin (Fragmin), and tinzaparin (Innohep)
- lovastatin (Mevacor), clarithromycin (Biaxin), cyclosporine (Neoral, Sandimmune), diltiazem (Cardizem), estrogens, indinavir (Crixivan), triazolam (Halcion)
- Verapamil (Calan, Covera, Isoptin, Verelan)
- Thiazide diuretics including chlorothiazide (Diuril), hydrochlorothiazide (HydroDIURIL, Esidrix), indapamide (Lozol), metolazone (Zaroxolyn), and chlorthalidone (Hygroton)
If you are on any of these medications, consult your health care provider before taking Vitamin D.