With the pandemic, there has been a lot of talk, and rightly so, about the importance of vitamin D in reducing the severe complications of Covid-19. Several studies have indeed shown that vitamin D insufficiency is associated with an increased risk of developing severe forms of COVID-19. And die of the disease. For example, a recent study reports that patients with COVID-19 who present with hypo-vitaminosis D upon admission to hospital are 4 times more likely to die.
Vitamin D anti-cancer and anti-recurrence protection
These spectacular figures clearly underline the importance that vitamin D exerts on health. Particularly with regard to cancer-associated mortality. Multiple studies have shown that vitamin D has a wide variety of direct (inhibition of cell growth) or indirect (immunomodulatory, anti-inflammatory, anti-angiogenic) anti-cancer actions. Collectively these effects can slow the progression of cancer and prevent the onset of advanced and invasive forms of the disease, including metastases. This protective effect has obvious clinical benefits. For example, a study has shown that women affected by breast cancer and who have insufficient vitamin D levels (< 50 nmol/L) have almost twice the risk of recurrence following treatment and of dying from the disease. .
Fewer serious cancers and metastases
The recently published results of a clinical study allow us to better appreciate this link between vitamin D and the risk of developing cancer. In this double-blind study, 12,938 men and women aged 50 and over were randomly separated into 2 groups. Consider a placebo group and an intervention group which received 2000 IU/day of a vitamin D3 supplement. For a period of five years. The researchers subsequently listed the occurrence of cancer in the participants of both groups.
Overall, the researchers did not observe a significant difference in the incidence of total cancers between the two groups. On the other hand, and this is where the results are interesting, they noted a significant decrease (17%) in the number of advanced and metastatic cancers among participants in the vitamin D group. This decrease in the incidence of advanced cancers is even more significant (38%) in thin people (BMI<25). But becomes insignificant (11%) in overweight people (BMI 25-29) and disappears completely in obese people (BMI ≥ 30).
Obesity plays against the protective effect of vitamin D
Vitamin D is fat soluble. It is therefore likely that the presence of excess fat in overweight people creates a reservoir that sequesters the vitamin. Thus decreasing its concentration in the blood. Another possibility is that the immune system is often deregulated in obese people (the cells specialized in the elimination of cancer cells, in particular). These changes decrease the immunomodulatory effect of vitamin D.
Long-lasting maintenance of vitamin D3
Be that as it may, this lack of protection observed in obese people illustrates once again how overweight is an abnormal physiological condition. It can contribute to the development of conditions as serious as metastatic cancers. Whether it is to prevent the complications of Covid-19 or reduce the risk of fatal cancers, taking a vitamin D3 supplement (1000 IU and more) therefore represents a simple and inexpensive intervention. In this winter period, this gesture makes it possible to compensate for the drop in our blood levels of vitamin D caused by the reduction in the hours of sunshine during the winter season.
De Smet D et al. Serum 25(OH)D level on hospital admission associated with COVID-19 stage and mortality. Am. J. Clin. Pathol. November 2020.
Keum N et al. Vitamin D supplementation and total cancer incidence and mortality: a meta-analysis of randomized controlled trials. Ann Oncol. 2019; 30: 733–743.
Feldman D et al. The role of vitamin D in reducing cancer risk and progression. Nat.Rev.Cancer.2014;14:342-357.
Goodwin et al. Prognostic effects of 25-hydroxyvitamin D levels in early breast cancer. J. Clin. Oncol. 2009; 27: 3757-3763.
Chandler PD et al. Effect of vitamin D3 supplements on development of advanced cancer: a secondary analysis of the VITAL randomized clinical trial. JAMA Netw Open. 2020; 3: e2025850.