A recent study published in Nutrients explored the impact of vitamin D on breast cancer (BC).
Study: The Impact of Vitamin D and Its Dietary Supplementation in Breast Cancer Prevention: An Integrative Review. Image Credit: Johan Larson/Shutterstock.com
Background
Vitamin D is ubiquitous in almost all human cells and tissues. Research on vitamin D has been driven by its relationship with numerous diseases, including cancer.
Pre-vitamin D3 is synthesized from 7-dehydrocholesterol through exposure to ultraviolet rays from the Sun; subsequently, thermal isomerization leads to vitamin D3 formation.
Besides, vitamin D can be obtained from diets and supplements. Regardless of the origin, enzymatic hydroxylation in the liver produces 25-hydroxy vitamin D [25(OH)D], followed by conversion to form calcitriol [1,25(OH)2D] in the kidneys.
Calcitriol is critical in regulating phosphorous and calcium metabolism and has anti-cancer effects. BC is the most prevalent cancer in females worldwide.
The pathogenesis of BC is poorly defined, and research on the underlying mechanisms is critical for formulating prevention strategies. Some risk factors for BC are non-modifiable, but others, like lifestyle and obesity, offer intervention opportunities.
Vitamin D has a role in BC prevention and treatment by influencing cellular differentiation, inflammation, and hormone regulation.
The study and findings
The present study examined the relationship between BC and vitamin D supplementation. The researchers searched for relevant studies in PubMed, Scopus, and Web of Science databases.
Eligible studies examined vitamin D supplementation in adult females, provided serum levels of vitamin D, and assessed the effect of risk factors on the relationship between BC and vitamin D.
Database searches identified over 700 records; 16 studies were included after deduplication, screening, and exclusions.
First, five studies were analyzed for the relationship between serum vitamin D levels and the risk of BC development; the optimal levels required for decreasing the risk were also evaluated. The team determined that vitamin D could exert its protective effects against BC at 40.26 ng/ml, on average.
One meta-analysis highlighted that the average serum levels were 26.88 ng/ml and 31.41 ng/ml in BC patients and controls, respectively; vitamin D insufficiency could be related to BC development or progression. A case-control study reported an inverse association between vitamin D levels and the risk of BC development.
Further, one study observed that females with 60 ng/ml or higher vitamin D concentrations had an 80% reduced risk of BC compared to those with 20 ng/ml.
Another meta-analysis indicated that vitamin D deficiency was associated with BC onset, underscoring the significance of increased sunlight exposure and vitamin D supplementation for BC prevention.
Notwithstanding, other studies have not found associations between vitamin D levels and BC risk. Vitamin D receptor (VDR) is a critical factor in the relationship between vitamin D and BC risk.
VDR is characterized by its link to BC due to several polymorphisms that alter the main functions of the receptor. Besides, multiple genes are positively or negatively regulated through VDR activation.
Furthermore, evidence links VDR polymorphisms and vitamin D deficiency to BC risk. For example, one study identified that the rs2228570 polymorphism was associated with a higher BC risk.
This was corroborated by another study, which additionally indicated rs7041 to be associated with an increased risk. Nevertheless, there are studies with contradictory results.
Lifestyle has a crucial role in disease prevention. Diet is one lifestyle aspect that can be significantly modified, and healthy dietary patterns have been associated with considerably lower risks of BC.
One study suggested that consuming foods with high glycemic index and meat might be linked to a greater BC risk. By contrast, increased intake of vegetables and nutrients like vitamin D and calcium is inversely associated with disease risk.
Moreover, it has been reported that the Mediterranean diet, exercise, and sufficient vitamin D levels could improve the life of BC survivors. Given the increasing prevalence of vitamin D deficiency, food fortification is an important strategy to enhance the nutritional status.
While the positive effects of vitamin D-fortified foods have been established, studies are needed to validate their role in BC.
A case-control study suggested that maintaining adequate levels of vitamin D, calcium, and iron might be protective against BC in postmenopausal females.
As such, one study examined vitamin D and calcium intake in the context of BC over a 10-year follow-up and found that premenopausal females with a higher intake of both nutrients might have a lower BC risk.
Concluding remarks
Taken together, vitamin D deficiency is closely linked to BC development. The team determined that serum vitamin D levels of 40.6 ng/ml or higher could be considered protective against the risk of BC.
Various biological mechanisms may be involved in this relationship, including the VDR axis. Other genes are also implicated in this relationship.
Nevertheless, further studies are required to highlight the significance of vitamin D deficiency in BC risk and associated mechanisms and risk factors.
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