In addition, it was noted that recent animal and clinical studies observed that the risk of life-long disorders in these offspring may increase, including conditions such as systemic inflammation, insulin resistance, abnormal gut microbiota, and disordered adipogenesis.
“This conclusion suggests that VD plays a significant role in energy metabolism, and therefore may serve as a potential treatment or prevention of obesity in very early life,” the researchers from the Chinese Academy of Medical Sciences stress.
“Thus, there is an urgent need to take active steps to address maternal VD deficiency to relieve the global burden of obesity,” they conclude.
VD is essential for the body due to its crucial roles in calcium and phosphate homeostasis, as well as in bone metabolism. Its deficiency has been linked to many diseases, such as cardiovascular disease (CVD), type 2 diabetes, cancer, and autoimmune diseases.
Deficiencies of the vitamin during pregnancy represents a widespread concern, with the Developmental Origins of Health and Disease (DOHaD) theory suggesting that the potential unfavourable outcomes for both mothers and infants may be long-term.
Specifically, studies have noted that its status may be inversely associated with body fat mass percentage, highlighting its potential relationship with obesity. The DOHaD draws parallels between maternal vitamin D deficiencies and epigenetic modifications that result in increased susceptibility to obesity for the child.
Obesity represents a worldwide epidemic, with more than 1.9 billion adults being overweight whilst 650 million were obese in 2016, vastly increasing those at risk of developing chronic non-communicable diseases.
To address this possible cause of increased societal burden, the researchers conducted a literature review to assess the current knowledge on the impact of maternal VD deficiency on offspring obesity and lipid metabolism.
It is specified that VD can only be obtained through UVB-mediated synthesis within the skin, or through supplementation. Following hydroxylation into its active form, it interacts with the vitamin D receptor (VDR) which is present on many organ cells, including the intestine and bone, as well as in tissue such as the heart, skin, brain, and immune system.
This highlights its importance in many biological pathways, such as lipid and glucose metabolism, cell proliferation, and the activation of the immune system.
“VD deficiency during pregnancy is related to many pregnancy complications and adverse outcomes, including preeclampsia, gestational diabetes mellitus (GDM), bacterial vaginosis, preterm birth, adverse neurodevelopmental outcomes, and underdeveloped fetuses, such as small for gestational age,” the researchers assert.
In addition, it was observed in previous studies using rat models that maternal VD deficiencies occurring before and during pregnancy resulted in the increased proliferation and differentiation of adipocytes, and thus, eventually lead to obesity in the offspring. “This may be related to the epigenetic alterations (changed methylation level of promoters and CpG islets) of certain genes,” the report hypothesises.
“These results indicate that the effect of VD deficiency during pregnancy on the development of adipose tissue in offspring may be potentially long-term and may eventually make offspring predisposed to obesity more easily,” they conclude.
“VD deficiency is defined as a cut-off level of 50 nmol/L (20 ng/mL) to avoid bone problems; and VD insufficiency is defined as a serum 25(OH)D of 52.5~72.5 nmol/L (21~29 ng/mL). However, currently, there is no consensus on an optimal level during pregnancy,” the researchers highlight.
With regards to associated deficiencies, they add that there is “consistent evidence suggesting an incidence of 51% to 100% in developing countries and a re-emergence in developed countries, especially those with high-risk factors.”
These collated factors include vegetarians, limited sunlight exposure, malnutrition, obesity, and ethnic groups with dark skin.
In addition, it is highlighted that there is a general lack of population-based surveys on VD deficiency prevalence in pregnant women, despite their high-risk status.
Paired with the collated literature highlighting the dangers of VD deficiency, there is a need for further research to ensure further understanding of the role of maternal VD status, to ensure clarity for future policy to prevent the observed health effects.
“The Role of Maternal Vitamin D Deficiency in Offspring Obesity: A Narrative Review”
by Yifan Wu, Yuan Zeng, Qian Zhang, and Xinhua Xiao.