There has been a lot of hype about the "sunshine vitamin" in the past decade due to its many important roles within the body. At my first meet and greet with a family physician in Calgary, he gave me a requisition to get my blood work done. After scrolling through the checked boxes on the sheet I asked if I could also get my vitamin D levels checked. To this question my physician answered “most Canadians are deficient in vitamin D so we don’t bother checking it”…….
I went on to tell him that I have been supplementing with 1000 IU/day and want to make sure it’s enough to keep me within the normal range. He reluctantly checked the box and off I went. [vitamin D is no longer tested in Alberta unless you display outward symptoms of deficiency]
So, why do I care? Why does this matter?
Vitamin D is necessary for the normal metabolic functioning of the body.
Unlike other vitamins, vitamin D can be produced in the body through a photosynthetic reaction that occurs when the skin is exposed to sunlight.
Vitamin D can also be categorized as a hormone based on the fact that it is produced by the body and controls and regulates the activity of certain organs and cells.
Vitamin D appears in several different forms in the body – a precursor form, a vitamin form, and a bioactive hormonal form. These transformations depend on a variety of different factors. There is potential for the precursor of vitamin D to never become either a vitamin or a hormone if there are disruptions in the pathway of precursor to hormone. These disruptions to a successful transformation may help to explain why some individuals have sufficient exposure to sunlight and still have low levels of active vitamin D in the bloodstream or why some people have adequate levels of active vitamin D according to their blood work, yet they have evidence of vitamin D deficiency as a result of inadequate transformation of vitamin D into the bioactive hormonal form.
A meta-analysis of eight prospective cohort studies from Europe and the United States showed that being in the lowest 20% of serum 25(OH)D (the active form of vitamin D) was associated with cardiovascular and all-cause mortality. The results were consistent across study populations, age groups, sexes, and seasons of blood drawn (Schottker, 2014).
Adequate levels of vitamin D (measured as serum 25(OH)D) are defined by the National Osteoporosis Society as above 50 nmol/L. Inadequate is defined as serum 25(OH)D levels of 30-50 nmol/L and deficient is less than 30 nmol/L.
3 of the top responsibilities of vitamin D in the body include:
1) Bone Health
The most critical effect of vitamin D and the one we hear about the most is the maintenance of bone health. Vitamin D has been linked to various skeletal disease including osteoporosis, fractures, and rickets/osteomalacia.
Vitamin D does not act directly on bone cells, rather it works to enhance absorption of calcium and phosphorus from the intestine and may increase reabsorption of calcium in the kidneys. Without adequate vitamin D levels, calcium can accumulate in the inner surface of the intestinal cells instead of being channeled into bone cells (Bikle, 2009).
2) Immune System Support
Vitamin D plays a basic role in regulating the immune system and as a result, vitamin D deficiency has been correlated with increased rates of infection (Gombart, 2009). The reason for this inverse relationship is likely due to vitamin D’s ability to improve the effectiveness of barriers to infection in the skin, gut, lungs and placenta by increasing production of cathlicidin, a bacteria-killing protein (Adams, 2010). In addition, when intracellular bacteria is detected by the immune system in our body, it responds by converting 25(OH)D (serum vitamin D) into 1,25(OH)2D (the hormonal form). It is now believed by some experts that low serum vitamin D is a consequence of uncontrolled bacterial infection and chronic inflammation (Mangin, 2014).
Prior to the discovery of antibiotics, cod liver oil, a rich source of vitamin D, sunlight and pharmacological doses of vitamin D were used to treat the infectious disease, tuberculosis.
A significant association was found between children and teenagers with several food and environmental allergies and low serum vitamin D levels (it was not noted in adults). This association did not suggest that low levels of vitamin D caused allergies, rather that the anti-inflammatory effect of vitamin D could be protective against developing these allergies (Sharief, 2011).
There is also a potential link between low vitamin D status and autoimmune conditions (multiple sclerosis, lupus, rheumatoid arthritis, type 1 diabetes, psoriasis, Crohn’s disease).
3) Cognitive Function
Higher serum vitamin D levels have been associated with better memory and cognitive function after adjusting for other risk factors (Lee, 2009; Llewellyn, 2010). The Cardiovascular Health Study, a study of older participants, found that very low levels of vitamin D (under 25 nmol/L) was associated with a 122% increased risk of dementia (Littlejohns, 2014).
A systemic review of the literature found that people with Alzheimer’s disease had lower concentrations of vitamin D than those without Alzheimer’s disease. Better cognitive test results were also lined to higher serum concentrations of vitamin D (Balion, 2012)
Lower levels of vitamin D were also associated with increase in depressive symptoms, PMS, seasonal affective disorder, and non-specified mood disorder (Murphy, 2008; Llewellyn, 2010).
Sometimes when we think a little is good, a lot is better. With vitamin D that is definitely not the case, as toxicity is definitely a possibility when a person is using supplements. Toxicity can only occur when using supplements due to the body’s ability to self regulate. Taking 50,000 IU per day over time has been known to cause vitamin D toxicity.
Buildup of calcium in the blood is one of the major consequences of vitamin D toxicity. This buildup can cause nausea, vomiting and poor appetite. Kidney problems and frequent urination can also occur. People dealing with liver or kidney conditions are at increased risk of developing negative effects of vitamin D toxicity.
As I’ve said before, in my practice I follow a food first policy. Below are some of the most nutrient dense foods rich in vitamin D. That being said, it can be extremely difficult to get enough vitamin D from food sources alone (particularly in the winter), so vitamin D is one of the vitamins that is a staple recommendation for most of my clients.
Recommended Daily Intake
Men and Women aged 19-50
Aim for: 600-3000 IU/day
*Note - supplementation/intake amount will vary based on your blood levels of vitamin D
Men and Women aged 51-70
Aim for: 600-3000 IU/day
Men and Women aged 71 and older
Aim for: 800-3000 IU/day
Meat and Alternatives Serving Size Vitamin D (IU)
Egg, yolk, cooked 2 large 57-88
Pork, various cuts, cooked 75 g (2 ½ oz) 6-60
Beef live, cooked 75 g (2 ½ oz) 36
Fish and Seafood
Salmon, sockeye/red, canned, cooked or raw 75 g (2 ½ oz) 530-699
Salmon, humpback/pink, canned, cooked or raw 75 g (2 ½ oz) 351-497
Salmon, coho, raw or cooked 75 g (2 ½ oz) 326-421
Snapper, cooked 75 g (2 ½ oz) 392
Salmon, chinook, raw or cooked 75 g (2 ½ oz) 319-387
Whitefish, lake, cooked 75 g (2 ½ oz) 369
Mackerel, Pacific, cooked 75 g (2 ½ oz) 342
Salmon, Atlantic, raw or cooked 75 g (2 ½ oz) 181-246
Salmon, chum/keta, raw or cooked 75 g (2 ½ oz) 203-221
Mackerel, canned 75 g (2 ½ oz) 219
Herring, Atlantic, pickled 75 g (2 ½ oz) 210
Trout, cooked 75 g (2 ½ oz) 150-210
Herring, Atlantic, cooked 75 g (2 ½ oz) 161
Roe, raw 30 g (1 oz) 145
Sardines, Pacific, canned 75 g (2 ½ oz) 144
Halibut, cooked 75 g (2 ½ oz) 144
Tuna, albacore, raw or cooked 75 g (2 ½ oz) 82-105
Mackerel, Atlantic, cooked 75 g (2 ½ oz) 78
Tuna, white, canned with water 75 g (2 ½ oz) 60
Fats and Oils
Cod liver oil 5 mL (1 tsp) 427
Milk and Alternatives
Goat’s milk, fortified with Vitamin D 250 mL (1 cup) 100
Rice, oat, almond beverage, fortified with Vitamin D 250 mL (1 cup) 88-90
Yogurt (plain), fortified with vitamin D 175 g (3/4 cup) 58-71
Milk (3.3 % homo, 2%, 1%, skim) 250 mL (1 cup) 103-105
Source: "Canadian Nutrient File 2010"
When a client is unable to consume the above foods on a regular basis (due to dislikes, allergies, sensitivities, etc.) I follow the National Osteoporosis Society recommendations of 1000 IU per day of vitamin D during the winter months (October – April here in Alberta). During the spring and summer months, in order to keep serum vitamin D levels adequate it is suggested that 15-20 minutes of sun exposure between 11 am – 2 pm with arms, shoulders and back uncovered (and not covered is sun screen) is necessary.
As always, please consult your personal care practitioner or pharmacist before starting a new supplement routine. Keep your eyes open for my next post on why I pair my vitamin D with a vitamin K2!
Hopefully this post answers some of your questions regarding vitamin D in the body. Please don’t hesitate to let me know if you have any questions or concerns.
Yours in health,
Adams JS, Hewison M. Update on vitamin D and hypertension: a casual association? Lancet Diabetes Endocrinol. 2014; 2:682-684.
Balion C, Griffity LE, Strifler L, et al. Vitamin D, cognition, and dementia: a systematic review and meta-analysis. Neurology. 2012;79(13):1397-1405.
Bikle D. Nonclassic actions of vitamin D. J Clin Endocrin Metab. 2009;94:26-34.
Gombart AF. The vitamin D-antimicrobial peptide pathway and its role in protection against infection. Future microbiology. 2009;4:1151-1165.
Lee DM, Tajar A, Ulubaev A, et al. EMAS Study Group. Association between 25-hydroxyvitamin D levels and cognitive performance in middle-aged and older European men. J Neurol Neurosurg Psychiatry. 2009;80:722-729.
Littlejohns TJ, Henley WE, Lang IA, et al. Vitamin D and the risk of dementia and Alzheimer disease. Neurology. 2014;83:920-928.
Llewellyn DJ, Lang IA, Langa KM, et al. Vitamin D and risk of cognitive decline in elderly persons. Arch Intern Med. 2010;170:1135-1141.
Magin M, Sinha R, Fincher K. Inflammation and vitamin D: the infection connection. Inflamm Res. 2014;63:803-819.
Murphy PK, Wagner CL. Vitamin D and mood disorders among women: an integrative review. J Midwifery Women’s Health. 2008;53(5):440-446.
Schottker B, Jorde R, Peasey A, et al. Vitamin D and Mortality: Meta-analysis of individual participant data from a large consortium of cohort studies from Europe and the United States. BMJ. 2014;348:g3656.
Sharief S, Jariwala S, Kumar J, Muntner P, Melamed ML. Vitamin D levels and food and environmental allergies in the United States: results from the National Health and Nutrition Examination Survey 2005-2006. J Allergy Clin Immunol. 2011;127:1195-1202.
Zeratsky K. What is vitamin D toxicity, and should I worry about it since I take supplements? Accessed on Nov 1, 2015 at http://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/expert-answers/vitamin-d-toxicity/faq-20058108