Posted on: September 29, 2025
With the winter approaching, it’s time to think about vitamin D once again.
There is a lot of research evidence showing the usefulness of vitamin D in cold and flu prevention. Naturopaths in Mississauga have also been touting its benefits for curbing joint inflammation, autoimmune disease (reducing the risk of Multiple Sclerosis by up to 54% for example), and seasonal affective disorder for years.
There are significant anticancer impacts as well: An optimal level of vitamin D can reduce the incidence of breast cancer by 83%, colon cancer by 60%, and Non-Hodgkins Lympoma by 18% or more. More detailed description of the impacts of vitamin D is covered in my blog from November 2013.
There are some new studies on vitamin D published in 2014 that are worth highlighting here as well. A study published in August 2014 in the research journal Neurology reported that elderly patients who had vitamin D deficiency had a 53% risk of cognitive decline over 5.6 years. Those who were severely deficient had a 125% increased risk of dementia. Fascinatingly, another study published in the same journal in November 2014 by another group of researchers showed 36% increased risk of dementia over 4.4 years in those who are vitamin D deficient.
Another study links vitamin D deficiency with infertility. Patients receiving egg donation treatment were assessed for vitamin D levels prior to treatment, and were monitored for success – as measured by pregnancy at 7-8 weeks. The pregnancy rates of those who were sufficient in vitamin D3 were 78% percent while the women low in vitamin D3 had a pregnancy rate of 37%. The live birth rates were 59% among vitamin D sufficient vs 31% in vitamin D deficient mothers. This is a fascinating study showing that vitamin D deficiency is associated with a 50% reduction in pregnancy (study abstract also included below). At our naturopathic clinic we have been recommending optimization of vitamin D levels for patients coming to us for help with increasing fertility, we will consider vitamin D testing for these patients as well.
Unfortunately there is no set recommendation for vitamin D intake, as the amount you need depends on weight, sun exposure, body metabolism, etc. There is however a blood test that can easily be taken at our office to determine your current level, and should be performed again after a month or two of vitamin D supplementation. Please contact our naturopathic doctor at the Mississauga clinic for further information.
Neurology. 2014 Sep 2;83(10):920-8. doi: 10.1212/WNL.0000000000000755. Epub 2014 Aug 6.
Vitamin D and the risk of dementia and Alzheimer disease.
Littlejohns TJ1, Henley WE1, Lang IA1, Annweiler C1, Beauchet O1, Chaves PH1, Fried L1, Kestenbaum BR1, Kuller LH1, Langa KM1, Lopez OL1, Kos K1,Soni M1, Llewellyn DJ2.
OBJECTIVE:
To determine whether low vitamin D concentrations are associated with an increased risk of incident all-cause dementia and Alzheimer disease.
METHODS:
One thousand six hundred fifty-eight elderly ambulatory adults free from dementia, cardiovascular disease, and stroke who participated in the US population-based Cardiovascular Health Study between 1992-1993 and 1999 were included. Serum 25-hydroxyvitamin D (25(OH)D) concentrations were determined by liquid chromatography-tandem mass spectrometry from blood samples collected in 1992-1993. Incident all-cause dementia and Alzheimer disease status were assessed during follow-up using National Institute of Neurological and Communicative Disorders and Stroke/Alzheimer’s Disease and Related Disorders Association criteria.
RESULTS:
During a mean follow-up of 5.6 years, 171 participants developed all-cause dementia, including 102 cases of Alzheimer disease. Using Cox proportional hazards models, the multivariate adjusted hazard ratios (95% confidence interval [CI]) for incident all-cause dementia in participants who were severely 25(OH)D deficient (<25 nmol/L) and deficient (≥25 to <50 nmol/L) were 2.25 (95% CI: 1.23-4.13) and 1.53 (95% CI: 1.06-2.21) compared to participants with sufficient concentrations (≥50 nmol/L). The multivariate adjusted hazard ratios for incident Alzheimer disease in participants who were severely 25(OH)D deficient and deficient compared to participants with sufficient concentrations were 2.22 (95% CI: 1.02-4.83) and 1.69 (95% CI: 1.06-2.69). In multivariate adjusted penalized smoothing spline plots, the risk of all-causedementia and Alzheimer disease markedly increased below a threshold of 50 nmol/L.
CONCLUSION:
Our results confirm that vitamin D deficiency is associated with a substantially increased risk of all-cause dementia and Alzheimer disease. This adds to the ongoing debate about the role of vitamin D in nonskeletal conditions.
Neurology. 2014 Nov 5. pii: 10.1212/WNL.0000000000001080.
Vitamin D deficiency predicts cognitive decline in older men and women: The Pro.V.A. Study.
Toffanello ED1, Coin A2, Perissinotto E2, Zambon S2, Sarti S2, Veronese N2, De Rui M2, Bolzetta F2, Corti MC2, Crepaldi G2, Manzato E2, Sergi G2.
OBJECTIVE:
To test the hypothesis that hypovitaminosis D is associated with a higher risk of cognitive decline over a 4.4-year follow-up in a large sample of older adults.
METHODS:
This research was part of the Progetto Veneto Anziani (Pro.V.A.), an Italian population-based cohort study of 1,927 elderly subjects. Serum 25-hydroxyvitamin D (25OHD) levels were measured at the baseline. Global cognitive function was measured with the Mini-Mental State Examination (MMSE); scores lower than 24 were indicative of cognitive dysfunction, and a decline of 3 or more points on the MMSE over the follow-up was considered as clinically significant. Analyses were adjusted for relevant confounders, including health and performance status.
RESULTS:
Participants with 25OHD deficiency (<50 nmol/L) or insufficiency (50-75 nmol/L) were more likely to have declining MMSE scores during the follow-up than those who were 25OHD sufficient (≥75 nmol/L). Among participants cognitively intact (baseline MMSE scores ≥24 and without diagnosis of dementia), the multivariate adjusted relative risk (95% confidence interval [CI]) of the onset of cognitive dysfunction was 1.36 (95% CI: 1.04-1.80; p = 0.02) for those with vitamin D deficiency and 1.29 (95% CI: 1.00-1.76; p = 0.05) for those with vitamin Dinsufficiency by comparison with individuals with normal 25OHD levels.
CONCLUSION:
The results of our study support an independent association between low 25OHD levels and cognitive decline in elderly individuals. In cognitively intact elderly subjects, 25OHD levels below 75 nmol/L are already predictive of global cognitive dysfunction at 4.4 years.
Fertil Steril. 2014 Feb;101(2):447-52. doi: 10.1016/j.fertnstert.2013.10.008. Epub 2013 Nov 5.
Influence of vitamin D levels on in vitro fertilization outcomes in donor-recipient cycles.
Rudick BJ1, Ingles SA2, Chung K3, Stanczyk FZ3, Paulson RJ3, Bendikson KA3.
OBJECTIVE:
To elucidate the role of vitamin D in reproduction by examining the relationship between recipient vitamin D levels and pregnancy rates in donor-recipient IVF cycles.
RESULT(S):
In a diverse population of 99 recipients (53% Caucasian, 20% Asian, 16% Hispanic, 7% African American), adjusted clinical pregnancy rates were lower among vitamin D-deficient recipients than among vitamin D-replete recipients (37% vs. 78%). Live-birth rates were 31% among vitamin D-deficient recipients, compared with 59% among vitamin D-replete recipients. There were no differences in adjusted clinical pregnancy and live-birth rates among recipients who were vitamin D deficient [25(OH)D<20 ng/mL] vs. among those who were vitamin Dinsufficient [20 ng/mL ≤ 25(OH)D<30 ng/mL].
CONCLUSION(S):
Nonreplete vitamin D status [25(OH)D<30 ng/mL] was associated with lower pregnancy rates in recipients of egg donation. Since the oocyte donor-recipient model is able to separate the impact of vitamin D on oocyte vs. endometrium, these data suggest that the effects of vitamin D may be mediated through the endometrium.