Summary
Postmenopausal women are significantly more likely to suffer from vitamin D deficiency and obesity. It is common for postmenopausal women to have lower back pain (LBP), impaired muscle strength, and poor muscle function due to 25(OH)D deficiency. Obesity may also have a relationship with reduced muscle strength. On the basis of serum 25(OH)D concentration and body mass index (BMI), In an observational study, Chen et al. [1] studied 365 postmenopausal women with chronic LBP who were divided into four groups. Serum 25(OH)D concentrations in combination with BMI were assessed for their influence on paraspinal muscle (PSM) atrophy, fat infiltration, and severity of LBP. Results show that people with increased BMI and vitamin D inadequacy have less sun exposure time, decreased hand grip strength (HGS), decreased level of physical activity (lower Short Physical Performance Battery [SPPB] score), and PSM cross-sectional area than controls. However, this group’s fat infiltration degree of the PSMs and visual analogue scale (VAS) score was significantly increased. The authors conclude that high BMI and vitamin D insufficiency/deficiency have a significant positive additive interaction in terms of fat infiltration and impaired muscle strength of PSM.
Commentary
Vitamin D is fat-soluble, and its sources include synthesis in the skin after sunlight exposure and exogenous supplementation. Its active form, 1,25(OH)2D3, interacts with the vitamin D receptor to regulate bone growth and calcium and phosphorus metabolism. This receptor exists in a variety of tissues. Vitamin D can also regulate cell proliferation, differentiation, apoptosis, and immune response and reduce inflammation and oxidative stress [2]. At present, vitamin D-related research is a very hot topic. LBP is a common musculoskeletal disorder that can interfere with sufferers’ daily activities and work. Unlike Western women, whose most common menopausal symptoms are hot flushes and night sweats, Chinese women’s primary menopausal symptoms are muscle or joint pain [3]. A more significant percentage of Chinese postmenopausal women suffer from vitamin D deficiency than Caucasians [4]. Postmenopausal women suffer from vitamin D deficiency at a high rate due to reduced biosynthesis, absorption, and hydroxylation of vitamin D [5]. Studies have shown that the intensity of LBP increases as vitamin D levels decrease, and vitamin D supplementation can effectively relieve their pain when LBP patients are deficient of vitamin D [6]. Vitamin D may be involved in several inflammatory signalling pathways and reduces pain in vivo by reducing the release of pro-inflammatory cytokines and inhibiting prostaglandin E2 (PGE2) synthesis [7]. Decreased strength and function of PSM are often seen in patients with LBP. Vitamin D status regulates mitochondrial biosynthesis and energy production in muscle cells, further affecting the strength and function of skeletal muscle [8]. Vitamin D deficiency is correlated with decreased mitochondrial function, oxidative stress imbalance, and atrophy of the PSM in LBP patients [9]. A clinical study has shown that continuous supplementation of calcifediol (800 IU) for six months in postmenopausal women with vitamin D deficiency can significantly enhance muscle function and reduce the risk of falls [10]. Besides, vitamin D supplementation reduces the severity of stress incontinence in premenopausal women and improves adipokine profiles in postmenopausal women [11,12]. Vitamin D supplementation is generally safe, and there are few reports of poisoning caused by its supplementation at regular doses.
Estrogen levels drop dramatically due to ovarian failure in postmenopausal women, leading to increased visceral fat, reduced lean muscle mass, and increased BMI. Vitamin D deficiency is common in obese individuals, probably due to less sunlight exposure and volumetric dilution related to vitamin D sequestration in fat tissue [5]. In turn, vitamin D affects adipogenesis, lipolysis, and inflammation in adipose tissue [13]. In the pathogenesis of LBP, it is uncertain whether vitamin D deficiency and obesity are causal or co-causative. Individuals with an unhealthy lifestyle are more likely to be obese, leading to vitamin D deficiency; whereas, those who exercise more outdoors are sure to get more sunlight and are less likely to suffer from vitamin D deficiency.
Finally, it is recommended that middle-aged women take vitamin D supplements and appropriately increase outdoor activity.
Yang You, MD
Qi Yu, MD
Peking Union Medical College Hospital
Beijing, People’s Republic of China
References
- Chen H, Xu HW, Zhang SB, Yi YY, Wang SJ. Vitamin D inadequacy combined with high BMI affects paraspinal muscle atrophy and pain intensity in postmenopausal women. Climacteric. 2022;25(4):376-382.
https://pubmed.ncbi.nlm.nih.gov/34694955/ - Bhutia SK. Vitamin D in autophagy signaling for health and diseases: Insights on potential mechanisms and future perspectives. J Nutr Biochem. 2022;99:108841.
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https://pubmed.ncbi.nlm.nih.gov/28609386/ - Xie Z, Xia W, Zhang Z, et al. Prevalence of Vitamin D Inadequacy Among Chinese Postmenopausal Women: A Nationwide, Multicenter, Cross-Sectional Study. Front Endocrinol (Lausanne). 2019;9:782.
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https://pubmed.ncbi.nlm.nih.gov/32547536/ - Gendelman O, Itzhaki D, Makarov S, Bennun M, Amital H. A randomized double-blind placebo-controlled study adding high dose vitamin D to analgesic regimens in patients with musculoskeletal pain. Lupus. 2015;24(4-5):483-489.
https://pubmed.ncbi.nlm.nih.gov/25801891/ - Salles J, Chanet A, Guillet C, et al. Vitamin D status modulates mitochondrial oxidative capacities in skeletal muscle: role in sarcopenia. Commun Biol. 2022;5(1):1288.
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https://pubmed.ncbi.nlm.nih.gov/31281588/ - Iolascon G, Moretti A, de Sire A, Calafiore D, Gimigliano F. Effectiveness of Calcifediol in Improving Muscle Function in Post-Menopausal Women: A Prospective Cohort Study. Adv Ther. 2017;34(3):744-752.
https://pubmed.ncbi.nlm.nih.gov/28205055/ - Shahraki SK, Emadi SF, Salarfard M, Chenari Z, Tadayyonfar F, Alikamali M. Effect of vitamin D supplementation on the severity of stress urinary incontinence in premenopausal women with vitamin D insufficiency: a randomized controlled clinical trial. BMC Womens Health. 2022;22(1):431.
https://pubmed.ncbi.nlm.nih.gov/36333692/ - Schmitt EB, Orsatti CL, Cangussu L, et al. Isolated vitamin D supplementation improves the adipokine profile of postmenopausal women: a randomized clinical trial. Menopause. 2022;30(1):56-62.
https://pubmed.ncbi.nlm.nih.gov/36256949/ - Pramono A, Jocken JWE, Blaak EE. Vitamin D deficiency in the aetiology of obesity-related insulin resistance. Diabetes Metab Res Rev. 2019;35(5):e3146.
https://pubmed.ncbi.nlm.nih.gov/30801902/
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