In a recent study published in the journal PLoS ONE, researchers explore the relationship between C-reactive protein (CRP) and vitamin D levels in older adults.
Study: Vitamin D status & associations with inflammation in older adults. Image Credit: Rawpixel.com / Shutterstock.com
Vitamin D, a secosteroid hormone, is crucial for musculoskeletal and bone health. The principal source of vitamin D is skin synthesis upon ultraviolet B (UVB) light exposure.
Vitamin D has been linked to chronic diseases like cancer, cardiovascular disease (CVD), and diabetes in prospective and observational studies. The inflammation modulation and maintenance of endothelial function through the effects of vitamin D on asymmetric dimethylarginine kinetics are proposed mechanisms for these relationships.
Ireland does not mandate the fortification of foods with vitamin D, which contributes to inadequate dietary intake. Currently, the prevalence of vitamin D deficiency among middle-aged Irish individuals and the elderly is estimated to be one in eight, rising to about one in two for those older than 85.
These high deficiency rates warrant special attention, given the connections between immune function and vitamin D. Furthermore, previous studies have indicated an association between vitamin D and inflammation. Nevertheless, there remains a lack of data from trials including older adults.
About the study
The researchers utilized frozen non-fasting whole plasma samples to analyze blood biomarkers. CRP and 25-hydroxyvitamin D (25(OH)D) concentrations of 5,381 community-dwelling Irish participants aged 50 years or older from the Irish Longitudinal Study on Ageing (TILDA) were measured.
Questionnaires, including computer-aided personal interviews (CAPI), were used to assess lifestyle, demographic, and health variables. Categorical CRP proportions were generated by age and vitamin D level. Furthermore, the relationship between CRP and 25(OH)D status was assessed using multi-nominal logistic regression.
Written informed consent was obtained from all study volunteers. In addition, the research was approved by the Ethics Committee of the Faculty of Health Sciences Research at Trinity College Dublin. The experimental methods were conducted in compliance with the Declaration of Helsinki, and trained research nurses performed all evaluations.
Vitamin D deficiency increases risk of inflammation
The mean age of the participants in the study was 62.9 years, 53.5% of whom were female. The obesity rate of the study population was 33.9%, the mean body mass index (BMI) was 28.6 kg/m2, and 70.8% of subjects reported being physically active.
Moreover, 13% of the study participants were vitamin D deficient, with higher deficiency status observed among the lower educated, oldest, poor socioeconomic status, and smokers. Notably, 8.5% of the subjects were supplement users.
Mean CRP levels of all participants was 3.30 mg/dl. The prevalence of normal CRP levels, which is typically between 0-5 mg/dl, was 83.9%, elevated status of 5-10 mg/dL was 11%, and high status exceeding 10 mg/dl was 5.1%.
Mean CRP concentrations were significantly lower in study participants who were male, younger, had tertiary education, were non-obese, non-smokers, and did not have more than three chronic conditions. Comparatively, higher rates of high CRP levels were observed among participants with three or more chronic illnesses, those aged 75 years or older, primarily educated, physically inactive, and obese relative to those with less than three chronic illnesses, between 50 and 64 years, tertiary educated, physically active, and non-obese, respectively.
The mean CRP level of 25(OH)D insufficient subjects was 2.22, which significantly differed from sufficient and deficient groups. Those with a normal 25(OH)D status had lower mean CRP concentrations than 25(OH)D deficient subjects.
Relative to participants with deficient 25(OH)D levels, those with sufficient or insufficient 25(OH)D status were less likely to have a high CRP status. Thus, CRP status declined as vitamin D levels rose.
The logistic regression analysis indicated that those aged 80 years or older, 25(OH)D deficiency, smoking, obesity, female sex, chronic conditions, physical inactivity, and high glycated hemoglobin (HbA1c) and creatinine levels were negative correlates for elevated CRP status.
Older people with vitamin D deficiency more frequently had higher inflammation levels based on their CRP levels. However, sufficient vitamin D levels were linked to reduced CRP concentrations, even after accounting for conventional risk variables.
Thus, optimizing vitamin D levels above deficient levels may be an efficient, low-cost, and low-risk approach to control inflammation in community-dwelling older people.
Previous studies indicate that vitamin D supplementation may decrease inflammation in certain disease settings. Since inflammation is a significant pathological mediator of chronic illnesses associated with aging, vitamin D therapy may be an effective treatment method for mitigating the increased risk of morbidity in older adult populations.
- Laird, E., O’Halloran, A. M., Molloy, A. M., et al. (2023) Vitamin D status & associations with inflammation in older adults. PLoS ONE 18(6): e0287169. doi:10.1371/journal.pone.0287169