In a recent study published in the journal FLOOR ONEresearchers examined the relationship between C-reactive protein (CRP) and vitamin D levels in older adults.
survey: Vitamin D status and associations with inflammation in older adults. Image credit: Rawpixel.com / Shutterstock.com
Vitamin D, a secosteroid hormone, is critical for musculoskeletal and bone health. The main source of vitamin D is synthesis in the skin upon exposure to ultraviolet B (UVB) light.
Vitamin D has been associated with chronic diseases such as cancer, cardiovascular disease (CVD) and diabetes in prospective and observational studies. Modulation of inflammation and maintenance of endothelial function through vitamin D effects on asymmetric dimethylarginine kinetics are proposed mechanisms for these relationships.
Ireland does not mandate fortification of foods with vitamin D, which contributes to inadequate dietary intake. The prevalence of vitamin D deficiency among middle-aged and elderly Irish people is currently estimated at one in eight, rising to around one in two for those over 85.
These high levels of deficiency warrant special attention given the links between immune function and vitamin D. In addition, previous studies have shown a link between vitamin D and inflammation. However, there remains a lack of data from studies involving older adults.
About the research
The researchers used frozen whole plasma samples without fasting to analyze blood biomarkers. CRP and 25-hydroxyvitamin D (25(OH)D) concentrations were measured in 5381 community-dwelling Irish participants aged 50 years or older from the Irish Longitudinal Study of Aging (TILDA).
Questionnaires, including computer-assisted personal interviews (CAPI), were used to assess lifestyle, demographic, and health variables. Categorical proportions of CRP were generated by age and vitamin D level. Additionally, the association between CRP and 25(OH)D status was assessed using multinomial logistic regression.
Written informed consent was obtained from all study volunteers. In addition, the study was approved by the Ethics Committee of the Faculty of Health Sciences at Trinity College Dublin. Experimental methods were conducted in accordance with the Declaration of Helsinki, and trained nurses performed all assessments.
Vitamin D deficiency increases the risk of inflammation
The average age of the study participants was 62.9 years, 53.5% of whom were female. The obesity rate in the study population was 33.9%, the mean body mass index (BMI) was 28.6 kg/m2, and 70.8% of participants reported being physically active.
Additionally, 13% of study participants were vitamin D deficient, with higher deficiency status observed among the less educated, the oldest, those with poor socioeconomic status, and smokers. Of note, 8.5% of participants were supplement users.
The mean CRP levels of all participants were 3.30 mg/dl. The prevalence of normal CRP levels, which is usually between 0-5 mg/dl, is 83.9%, an elevated state of 5-10 mg/dl is 11%, and a high state exceeding 10 mg/dl is 5, 1%.
Mean CRP concentrations were significantly lower in study participants who were male, younger, college educated, nonobese, nonsmokers, and had no more than three chronic diseases. Relatively higher rates of high CRP levels were observed among participants with three or more chronic diseases, those aged 75 years or older, primarily educated, physically inactive and obese compared to those with fewer than three chronic diseases, between 50 and 64 years old, with higher education, physically active and respectively without obesity.
The mean CRP level of 25(OH)D deficient subjects was 2.22, which was significantly different from the sufficient and deficient groups. Those with normal 25(OH)D status had lower mean CRP concentrations than patients with 25(OH)D deficiency.
Compared with participants with deficient 25(OH)D levels, those with sufficient or deficient 25(OH)D status were less likely to have high CRP status. Thus, CRP status decreases as vitamin D levels increase.
Logistic regression analysis showed that those over 80 years of age, 25(OH)D deficiency, smoking, obesity, female sex, chronic diseases, lack of physical activity, and high levels of glycated hemoglobin (HbA1c) and creatinine were negative correlates of elevated CRP status.
Older adults with vitamin D deficiency more often have higher levels of inflammation based on their CRP levels. However, adequate levels of vitamin D were associated with reduced CRP concentrations, even after accounting for conventional risk variables.
Thus, optimizing vitamin D levels above deficient levels may be an effective, inexpensive, and low-risk approach to controlling inflammation in community-dwelling older adults.
Previous studies have shown that vitamin D supplementation can reduce inflammation in certain diseases. Because inflammation is a significant pathological mediator of chronic diseases associated with aging, vitamin D therapy may be an effective treatment modality to mitigate the increased risk of morbidity in older adult populations.
- Laird, E., O’Halloran, AM, Molloy, AM, et al. (2023) Vitamin D status and associations with inflammation in the elderly. FLOOR ONE 18(6): e0287169. doi:10.1371/journal.pone.0287169