How Vitamin D Affects Our Lives

Vitamin D is an essential fat-soluble Vitamin for humans and an important regulatory factor in the body. It can be stored in adipose tissue and participates in blood circulation. Vitamin D is widely recognized to have multiple effects on the human body, not only involving calcium and phosphorus metabolism but also influencing muscles, cardiovascular health, metabolism, immunity, tumorigenesis, pregnancy, fetal development and so on. Recent studies have found that Vitamin D plays a significant role in diseases such as hypertension, cardiovascular diseases, diabetes, and tumors.

Why Vitamin D Matters?

Vitamin D deficiency can lead to various diseases. In children, it primarily manifests as rickets, while in adults it may cause osteoporosis or osteomalacia, depending on the severity of deficiency, and is also a common cause of secondary hyperparathyroidism. Particularly in elderly individuals, 25-hydroxyvitamin D levels showed significant correlation with decreased bone mineral density. Beyond skeletal disorders, research has identified potential associations between Vitamin D deficiency and multiple other conditions, including certain malignancies (such as colorectal and breast cancer), cardiovascular diseases (hypertension, atherosclerosis), metabolic disorders (type 2 diabetes), chronic kidney disease, and autoimmune diseases (multiple sclerosis, rheumatoid arthritis.

How To Get Vitamin D？

The human body obtains Vitamin D through two primary pathways: sunlight exposure and dietary intake. When skin is exposed to ultraviolet B radiation in the sunlight, 7-dehydrocholesterol in the epidermis is converted to Vitamin D₃ (cholecalciferol), which serves as the major source of Vitamin D for humans. The synthesis efficiency is influenced by factors such as geographic location, season, skin pigmentation, and sunscreen use. Dietary sources include animal-based foods (such as fatty fish, like salmon and sardines, egg yolks, animal liver, and cod liver oil), fortified foods (like milk and cereals enriched with Vitamin D), and UV-exposed mushrooms (which provide Vitamin D₂). It's noteworthy that Vitamin D₃ has superior bioavailability compared to Vitamin D₂.

How Our Body Makes Vitamin D？

25-OH-VD₃ is the primary circulating form of Vitamin D in the body. When 7-dehydrocholesterol in human epidermal cells is exposed to sunlight (UVB), it is converted to pre-vitamin D₃, which then thermally isomerizes into Vitamin D₃ (cholecalciferol). Vitamin D₃ binds to the Vitamin D-binding protein (DBP) and is transported to the liver, where it is hydroxylated by CYP2R1 (25-hydroxylase) to form 25-OH-VD₃. With a half-life of approximately two weeks, 25-OH-VD₃ serves as the clinical gold standard for assessing Vitamin D status. It is then transported to the kidneys and further hydroxylated by CYP27B1 (1α-hydroxylase) to produce the active form, 1,25-(OH)₂D₃ (calcitriol).

Who Should Get Tested？

Individuals with Bone Health Issues: Osteoporosis, Osteomalacia, history of fractures, or children with rickets.

Patients with Chronic Diseases: Hypertension, cardiovascular diseases, diabetes, autoimmune disorders, chronic kidney or liver disease.

Cancer Patients and High-Risk Groups: Especially those with breast cancer, colorectal cancer, prostate cancer, or other malignancies.

People with Limited Sun Exposure: Indoor workers, long-term bedridden individuals, excessive sunscreen users, and residents of high-latitude regions.

Obese Individuals: Vitamin D tends to be sequestered in adipose tissue, leading to lower circulating levels.

Pregnant and Lactating Women: Deficiency may impair fetal skeletal development and maternal health.

Elderly: Age-related decline in cutaneous Vitamin D synthesis, often compounded by osteoporosis.

Patients on Medications Affecting Vitamin D Metabolism: Antiepileptics, glucocorticoids, antifungals.

Malabsorption Syndromes: Inflammatory bowel disease (Crohn’s disease, ulcerative colitis), celiac disease, post-gastrectomy.

Testing & Interpreting Results

25-OH-VD is internationally recognized as the gold standard indicator for assessing Vitamin D nutritional status. The main detection methods currently include chemiluminescence immunoassay (CLIA), enzyme-linked immunosorbent assay (ELISA), and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Among these, CLIA has become the most commonly used method in clinical laboratories due to its advantages of high automation, large testing throughput, good sensitivity, and strong specificity.

Getein's CLIA Platform