Vitamin D’s role in the immune defense inhibits the ageing process

Most cells in the body have receptors for vitamin D, a nutrient that works as a steroid hormone. The different immune cells in the body are particularly dependent on vitamin D. Not only is this important for our ability to fight infections, but it also helps the body regulate inflammatory processes, which are the common thread in most chronic diseases and in ageing, according to a study that is published in Nutrients. The authors, Professor Carten Carlberg and Dr. Eunike Velleur, two of the world’s leading experts on vitamin D, explain why we need much more vitamin D than officially recommended when it comes fighting age.

Vitamin D is primarily known for its role in bone health. However, the vitamin’s key role in the human immune defense is thought to have developed evolutionarily much earlier around 550 million years ago.
The widespread lack of vitamin D that we are witnessing today is mainly a result of modern living, where we spend too much time indoors and don’t get enough sunshine, which is our primary vitamin D source. We need the UVB rays from the sun to convert a cholesterol precursor in our skin, and this is only possible if the sun sits sufficiently high in the sky. The cholesterol precursor is called 7-dehydrocholesterol and must first be converted into 25-hydroxyvitamin D3 – the form of vitamin D that is measured in the blood. This conversion takes place in the liver and is handled by two enzymes (CYP2R1 and CYP27A1). When vitamin D is needed in the different cells in the body, 25-hydroxyvitamin D3 is converted in the kidneys and in other tissues into the active steroid form called 1,25dihydroxyvitamin D. This process is handled by an enzyme called CYP27B1.
It appears that white blood cells such as monocytes, macrophages, and dendrite cells are able to suppress this enzyme, which enables these different immune cells to convert vitamin D into its active steroid form on their own.
The cells of the immune defense and most other cells in the body have vitamin D receptors (VDR) that control hundreds of different genes by way of different on-off switches. Active vitamin D is therefore an essential steroid hormone such as other steroid hormones like estrogen, testosterone, and cortisol. The sun, as mentioned earlier, is our primary source of vitamin D, but our ability to synthesize and activate the vitamin is also affected by things like genetic factors, skin color, BMI, chronic diseases like diabetes, and ageing.

The immune defense’s function and vitamin D’s role

Our immune system consists of our innate immune defense and our adaptive immune defense that is developed after birth when we get in contact with microorganisms and other foreign subjects. The innate immune defense consists of different types of white blood cells, including monocytes, that can eat and break down (phagocytosis) various pathogens and foreign particles. Monocytes can also develop into star-shaped dendrite cells that represent the first line of defense of our skin and our mucous membranes but are also found in lymph nodes and in the spleen. Monocytes are also able to develop into macrophages in the different tissues, where they gorge on microorganisms and foreign particles and break them down, while at the same time marshaling T and B cells as backup. These white blood cells that belong to the adaptive immune defense are like special troops that develop immunity in the form of programmed T cells and antibodies. Still, our innate immune defense can fight most germs on the spot without us noticing anything.
As part of its combat techqnique, the immune defense can launch an inflammatory attack, which is the body’s protective reaction to intruding microorganisms and damage to cells and tissues.
Here, it is primarily the monocytes that control the inflammatory processes, which also includes the production of dendrite cells and macrophages. Monocytes also regulate different reactions to stress.
In their review article, the researchers explain how vitamin D can directly affect the immune stem cells in the bone marrow and the programming of monocytes. The cells in the innate immune defense also appear to be extremely dependent on vitamin D in order to function optimally.

How chronic disease and ageing impair the immune defense

Ageing is a natural and inevitable process that includes accumulated damage to cells and molecules, which can result in dysfunctional cells, tissues, and organs. Ageing is characterized by dysbiosis, where potentially harmful microorganisms from our natural gut flora or from infection suddenly become dominant. Ageing is also associated with chronic low-grade inflammation and oxidative stress caused by too many free radicals that attack cells and tissues.
All this points to a weak and derailed immune defense as having a major role in the ageing process. There is even a new term called “inflammaging”, which is age-related inflammation. The article also mentions how a weak immune defense increases the risk of infections. If the inflammatory processes are too violent and turn into what is known as hyperinflammation it may result in sepsis, or virus infections like influenza and COVID-19 may become potentially life-threatening. Moreover, autoimmune diseases like sclerosis and rheumatism are linked to chronic inflammation that attacks specific tissues. Chronic low-grade inflammation is involved in cardiovascular diseases, diabetes, Alzheimer’s disease, cancer, and many other chronic diseases where older people are typically particularly vulnerable. Impaired function of the T cells increases the risk of virus infections and cancer, because we need T cells to destroy virus-infected cells and abnormal cells.

High-dosed vitamin D supplements inhibit ageing

Multiple studies point to a direct link between vitamin D deficiency and a host of diseases that are related to ageing and premature death. According to the current review article, the underlying mechanism is a weak and derailed immune defense. It is therefore vital to restore and regulate the immune defense by raising levels of vitamin D to make sure that all immune cells have enough of this nutrient.
The authors address the fact that it can be difficult to assess the individual need for vitamin D because it is affected by things like genes, skin color, BMI, and other factors. They recommend that everyone take a high-dosed supplement to be on the safe side. Specifically, they suggest taking one microgram for every kilo of body weight. So, a person weighing 80 kilos should ideally take 80 micrograms per day. This is far more than what the health authorities normally recommend. The normal guidelines for vitamin D call for a daily intake of 5-20 micrograms, but these are one-size-fits-all doses and fail to take into account that people have different needs. What is important, and the authors also mention this, is that the high levels they recommend are below the intake level that may cause adverse effects such as hypercalcemia (elevated blood levels of calcium). Their recommendations are also below the vitamin D level that most white-skinned people can reach on a sunny day. In any case, it is important to have an optimal level of vitamin D in the blood, which should lie in the range between 75-150 nmol/L.

References:

Carsten Carlberg and Eunike Velleur. Vitamin D and Aging: Central Role of Immunocompetence. Nutrients 2024

Lobachevsky University. Scientists have identified the role of chronic inflammation as the cause of accelerating aging. Medical Xpress. 2020