- Inflammation is the mechanism by which the body responds to and fights infection.
- However, chronic, or long-term, inflammation is associated with many diseases, including diabetes, cardiovascular disease, arthritis, and dementia.
- Age, obesity, poor diet, and smoking increase the risk of chronic inflammation.
- A new study has added to growing evidence of a link between vitamin D deficiency and inflammation.
- The researchers suggest that, in older adults, vitamin D supplements may help reduce the risk of many inflammatory diseases.
Acute inflammationTrusted Source occurs in response to tissue damage, infection, or allergensTrusted Source, and is a necessary part of the body’s defenses. It occurs rapidly and generally lasts up to a few days.
Chronic inflammation, however, can last for months or even years. It can be caused by triggers includingTrusted Source:
Inflammation is linked to lifestyle factors, including obesityTrusted Source, a diet high in fried, processed, and sugary foods, and smoking tobaccoTrusted Source.
It also increases with age, so much so that the process has been termed “inflammagingTrusted Source.” Inflammaging has been linked to cardiovascular disease, chronic kidney disease, diabetes, cancer, depression, and dementia.
Several studiesTrusted Source have suggested a link between vitamin D deficiency and inflammation.
Now, a large-scale community study in Ireland has found that older adults with vitamin D deficiency have higher levels of inflammation markers than those with sufficient levels of the vitamin.
The authors suggest that vitamin D supplementation could decrease the risk of diseases linked to chronic inflammation.
The study is published in PLoS ONETrusted Source.
Lead author Dr. Eamon Laird, visiting research fellow at Trinity College, Dublin, told Medical News Today: “We did anticipate seeing these findings as previous research has indicated strong associations of vitamin D with inflammation across different groups in the population.”
“However, our work is nearly one of the largest population-based studies yet to look at this. We were surprised at the strength of the association and how it survived in the models even after adjusting for multiple factors,” he added.
Inflammation is characterized by a number of biomarkersTrusted Source, which may be detectedTrusted Source in blood, saliva, and urine. One such biomarker, C-reactive protein (CRP), is connected to a wide variety of inflammatory conditions.
There is growing evidence of a relationship between CRP and cytokines, which play a role in acute and chronic inflammation.
“Regulation of inflammation and cytokine expression is of crucial importance given the hypothesis of ‘inflammaging’ — with increased age the shift toward a more pro-inflammatory state can lead to chronic low level grade inflammation and a slow accumulation of damage, with subsequent progression to chronic disease.”
– Dr. Eamon Laird
In this study, researchers measured CRP and 25-hydroxyvitamin D (25(OH)D) concentrations in blood samples from 5,381 independent-living participants aged 50 years or older from the Irish Longitudinal Study on Ageing (TILDA).
They collected demographic data through computer-aided personal interviews. This included age, sex, education level, smoking status, and CAGE alcohol score.
Participants self-reported diagnoses of chronic diseases, including diabetes, stroke, heart disease, and transient ischemic attack.
The participants ranged in age from 50 to 98 years (mean age 62.9 years). Their mean body mass index (BMI) was 28.6 kilograms per square meter, 33.9% had obesity, and 70.8% were physically active based on the International Physical Activity QuestionnaireTrusted Source (IPAQ).
Although there is no clear standard value for CRPTrusted Source levels, the higher the CRP concentration, the greater the inflammation.
In this study, the researchers divided the participants into different inflammation groups based on CRP concentration, as follows:
- normal — 0–5 milligrams per deciliter (mg/dL)
- elevated 5–10 mg/dL
- high CRP — more than 10 mg/dL.
Dr. Michael Holick, a professor of medicine at the Boston University School of Medicine, not involved in this study, explained why vitamin D deficiency is such a widely studied phenomenon.
He told us:
“Vitamin D deficiency is probably the most common medical issue worldwide. It’s estimated that a billion people, maybe even half the world’s population, [are] vitamin D deficient or insufficient. And the reason is simple. Our major source of vitamin D is sunlight, and we are no longer out in the sun. We avoid the sun because of worries about skin cancer.”
In this study, 13% of participants were deficient in vitamin D. Most of those with deficiency were in the oldest group, had lower education, poorer socio-economic status, or were smokers.
The researchers found high CRP levels in those aged 75 years or over, with lower education, and higher rates of obesity. Those who were less physically active, or had three or more chronic conditions also had higher CRP.
After controlling for other risk factors for inflammation, Vitamin D deficiency was strongly associated with higher CRP, indicating higher levels of inflammation.
“There’s a lot of evidence that vitamin D plays a very important role in immunity,” Dr. Holick told MNT.
“We know that your immune cells, called T-cells, have vitamin D receptors, and that the macrophagesTrusted Source […] release active vitamin D,“ he noted.
“They make vitamin D, and then they send that off to the T-lymphocytes that increase production of cytokines that help to preserve health and reduce cytokines that cause cytokine storm like [it] was seen in COVID,” Dr. Horlick explained.
Dr. Laird told MNT that vitamin D supplements could benefit not only those with inflammatory conditions: “A number of countries and public health agencies recommend vitamin D supplements/intakes for older adults. In Ireland, for older adults this is 15 micrograms (mcg) [or] 600 international units (IU) a day. In the U.S., this is 15–20mcg [or] 600– 800 IU daily.”
“However, it is not just older adults. Recent research has shown younger adults (18–39 years) are most at risk and have the highest levels of deficiency which long term may contribute to the risk of chronic disease in later life,” he added.
Prof. Holick was emphatic that: “There’s essentially no vitamin D in your diet. Cod liver oil, oily fish, and mushrooms exposed to sunlight — that’s it! Everyone needs vitamin D supplements in my opinion, unless you work outdoors all day.”
However, the National Institutes of HealthTrusted Source caution that, while your skin will make only the vitamin D you need from sun exposure, it is possible to take too much vitamin D.
An average adult should take no more than 100 mcg (4000 IU) per day from diet and supplements to avoid the risk of side effects such as nausea, vomiting, and confusion.
And Dr. Laird cautioned that vitamin D alone is unlikely to be the answer to combating chronic inflammatory conditions:
“Vitamin D is not a magic bullet; it is the combination of the lifestyle medicine approach — physical activity, sleep, non-smoking, alcohol in moderation, healthy nutrition choices — with vitamin D which will give the biggest risk reductions for inflammation.”