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.