Vit­a­min D boosts immu­nity and mood; helps with blood sugar and bone health; pre­vents can­cer)
(defi­cient in between 75 and 90% of people)

We can get vit­a­min D through sun­light expo­sure as well through the diet, but very few foods nat­u­rally con­tain vit­a­min D and between long work hours that are pri­mar­ily indoors and the use of sun­screens many peo­ple don’t get ade­quate UV expo­sure to cre­ate suf­fi­cient vit­a­min D lev­els in sum­mer. In win­ter vit­a­min D lev­els plum­met in most people.  

Foods that are a good source of vit­a­min D include fatty fish, fish liver oil, and eggs. Most dietary vit­a­min D comes from for­ti­fied foods, such as milk, juices, yogurt, bread and break­fast cere­als. Vit­a­min D can also be obtained through supplementation.

Unfor­tu­nately most peo­ple do not get ade­quate vit­a­min D from these sources and as a result, vit­a­min D insuf­fi­ciency is lit­er­ally an epi­demic. Sta­tis­tics extracted from the National Health and Nutri­tion Exam­i­na­tion Sur­vey (NHANES) found that more than 90% of the pop­u­la­tion with pig­mented skin, and 75% of the white pop­u­la­tion, have insuf­fi­cient lev­els of vit­a­min D.

Vit­a­min D defi­ciency has been shown to lower immu­nity, increas­ing the chances of devel­op­ing res­pi­ra­tory ail­ments like coughs and colds.  Sea­sonal Affec­tive Dis­or­der (SAD) which is basi­cally win­ter depres­sion also seems to be largely due to Vit­a­min D defi­ciency and so are some cases of osteo­poro­sis.  Other effects of Vit­a­min D defi­ciency can also be insulin resis­tance which can lead to poor blood sugar con­trol and increased chances of devel­op­ing some can­cers.  

Mech­a­nisms by which vit­a­min D may mod­ify can­cer risk are not fully under­stood, but lab­o­ra­tory stud­ies have shown that vit­a­min D pro­motes cel­lu­lar dif­fer­en­ti­a­tion, decreases can­cer cell growth, hin­ders angio­gen­e­sis (new ves­sel for­ma­tion with­out which tumours can­not grow), and stim­u­lates apop­to­sis (death of unhealthy cells like can­cer cells).  Vit­a­min D sup­ple­men­ta­tion has been shown to reduce the risk and sever­ity of breast, prostate, ovar­ian and col­orec­tal can­cer to name but a few.

The cur­rent rec­om­mended daily allowance of vit­a­min D in the United States is 400 IU for chil­dren 0–12 months, 600 IU for chil­dren greater than 12 months old as well as adults up to age 70 and 800 IU for those >70 years old. How­ever, the emerg­ing evi­dence on the non-skeletal ben­e­fits of vit­a­min D has made these rec­om­men­da­tions obso­lete. Doses as high as 10,000 IU/day have been shown to be safely tolerated.

Peo­ple are more likely to not get enough vit­a­min D than to get too much. How­ever, exces­sive intake of any nutri­ent, includ­ing vit­a­min D, can cause toxic effects such as hyper­cal­cemia, hyper­cal­ci­uria, hyper­ten­sion, con­sti­pa­tion, fatigue and more. Exces­sive sun expo­sure does not cause vit­a­min D tox­i­c­ity, how­ever with sup­ple­men­ta­tion mon­i­tor­ing ther­apy is impor­tant to ensure ade­quate, but not exces­sive, dosage.

By Dr Jana Mostert (M Tech Hom)

Resources

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3. Holick MF. “Vit­a­min D defi­ciency.” N Engl J Med. 2007;357:266–281.
4. Holt PR, Arber N, Hal­mos B, et al. “Colonic epithe­lial cell pro­lif­er­a­tion decreases with increas­ing lev­els of serum 25­hydroxy vit­a­min D.” Can­cer Epi­demi­ol­ogy, Bio­mark­ers, and Pre­ven­tion 2002; 11(1):113–119.)
5. Jenab M, et al. “Asso­ci­a­tion between pre-diagnostic cir­cu­lat­ing vit­a­min D con­cen­tra­tion and risk of col­orec­tal can­cer in Euro­pean pop­u­la­tions: a nested case-control study.” BMJ 2010 Jan21;340:b5500.
6. Lenz, Thomas PharmD, MA, PAPHS. “Vit­a­min D Sup­ple­men­ta­tion and Can­cer Pre­ven­tion.” Am J Lifestyle Med. 2009;3(5):365–368.
7. Moreno J, Krish­nan AV, Feld­man D. “Mol­e­c­u­lar mech­a­nisms medi­at­ing the anti-proliferative effects of vit­a­min D in prostate can­cer.” Jour­nal of Steroid Bio­chem­istry and Mol­e­c­u­lar Biol­ogy 2005; 97(1–2):31–36
8. “Vit­a­min D and pre­ven­tion of breast can­cer: pooled analy­sis.” J Steroid Biochem Mol Biol. 2007 Mar;102(35):708–11.
9. www.cancer.gov. National Can­cer Institute.