Vitamin D deficiency is like the silent troublemaker in public health. It’s incredibly common and sneaks in to cause skeletal issues like rickets (weak, soft bones in children) and osteomalacia (fragile bones in adults). But it doesn’t stop there—there’s growing evidence that it might meddle with other parts of the body, adding more items to its list of offenses.

Our primary ally in this fight? Sunlight! Specifically, ultraviolet-B (UV-B) rays, which trigger the production of vitamin D from its precursor, 7-dehydrocholesterol, in the skin. Natural food sources like fish and mushrooms try to pitch in, but their contributions are more like background help than the main act. When sunlight exposure is limited—whether due to lifestyle, geography, or cultural practices—this leads to a big gap in vitamin D supply. Add to that the effects of obesity, where vitamin D gets trapped in fat stores, and poor dietary habits, and you’ve got a widespread deficiency problem on your hands.

Laboratory detection of vitamin D deficiency is based on the measurement of serum concentrations of 25-hydroxyvitamin D (25(OH)D), the vitamin D metabolite that best reflects the overall supply from all different vitamin D sources, and that is the accepted parameter of vitamin D status. Vitamin D itself is inert—it’s only activated after being converted by enzymes in the liver, making 25(OH)D the star player in monitoring and diagnosing deficiency.

So, the key to staying ahead? A healthy dose of sunlight, balanced nutrition, and regular monitoring to keep this quiet disruptor at bay!

Some Gyan about Vitamin – D!

Vitamin D, also known as calciferol, is a fat-soluble vitamin naturally found in a limited number of foods, fortified in some, and available as supplements. It is also synthesized in the skin when ultraviolet (UV) rays from sunlight trigger its production.

The vitamin D obtained from sunlight, diet, and supplements is biologically inactive and requires two hydroxylation steps in the body to become active. The first step occurs in the liver, converting vitamin D into 25-hydroxyvitamin D [25(OH)D], commonly referred to as calcidiol.

The second hydroxylation takes place primarily in the kidney, producing 1,25-dihydroxyvitamin D [1,25(OH)2D], also known as calcitriol.

Vitamin D is essential for calcium absorption in the intestine and helps maintain optimal levels of calcium and phosphate in the blood, which are necessary for normal bone formation and mineralization. This process also prevents hypocalcemic tetany, which involves involuntary muscle contractions leading to cramps or spasms. Adequate vitamin D is critical for bone growth and the bone remodeling activities of osteoblasts and osteoclasts.

Without enough vitamin D, bones may become weak, fragile, or deformed. Adequate levels prevent rickets in children and osteomalacia in adults. When combined with calcium, vitamin D helps older adults reduce the risk of osteoporosis.

Apart from its role in bone health, vitamin D contributes to reducing inflammation and regulating cell growth, neuromuscular function, immune response, and glucose metabolism. It also influences the activity of several genes that control cell proliferation, differentiation, and programmed cell death (apoptosis).

Signs Your Body is Craving Vitamin D 

The symptoms of a vitamin D deficiency in adults may include: 

• Tiredness, Aches, and Pains
• Severe bone or muscle pain or weakness
• Stress fractures, Especially in your legs, Pelvis, and Hips

Healthcare providers can determine vitamin D levels through a blood test, and if a deficiency is found, they may use X-rays to assess bone strength.

What food is highest in vitamin D?

Some foods contain vitamin D naturally, and others are fortified with it. You can find vitamin D in the following foods:

• Salmon
• Sardines
• Herring
• Canned tuna
• COD liver oil
• Beef liver
• Egg yolk
• Regular mushrooms and those treated with ultraviolet light
• Milk (fortified)
• Certain cereals and oatmeals (fortified)
• Yogurt (fortified)
• Orange juice (fortified)

It can be hard to get enough vitamin D each day through sun exposure and food alone, so taking vitamin D supplements could help.

Vitamin D Dosage: How Much Do You Need?

Blood serum levels considered adequate range from 50–100 nanomoles per liter (nmol/L). Depending on your blood level, you may need more vitamin D.

The Recommended Dietary Allowances for vitamin D are as follows:

• Infants (0–12 months): 10 micrograms (mcg) or 400 international units (IU)Trusted Source
• Children and teens: 15 mcg (600 IU)
• Adults ages 18–70: 15 mcg (600 IU)
• Adults over age 70: 20 mcg (800 IU)
• Pregnant people or those who are breastfeeding to chestfeeding: 15 mcg (600 IU)

Health Risks from Excessive Vitamin D

Excess amounts of vitamin D are toxic. Because vitamin D increases calcium absorption in the gastrointestinal tract, vitamin D toxicity results in marked hypercalcemia (total calcium greater than 11.1 mg/dL, beyond the normal range of 8.4 to 10.2 mg/dL), hypercalciuria, and high serum 25(OH)D levels (typically greater than 375 nmol/l [150 ng/mL]) . Hypercalcemia, in turn, can lead to nausea, vomiting, muscle weakness, neuropsychiatric disturbances, pain, loss of appetite, dehydration, polyuria, excessive thirst, and kidney stones.

In extreme cases, vitamin D toxicity causes renal failure, calcification of soft tissues throughout the body (including in coronary vessels and heart valves), cardiac arrhythmias, and even death. Vitamin D toxicity has been caused by consumption of dietary supplements that contained excessive vitamin D amounts because of manufacturing errors, that were taken inappropriately or in excessive amounts, or that were incorrectly prescribed by physicians.

Conclusion about vitamin D supplements and bone health

All adults are encouraged to meet the recommended intake of vitamin D and calcium through their diet or supplements when necessary. Older men and women should seek advice from their healthcare providers regarding their specific requirements for these nutrients as part of a comprehensive strategy to support bone health and manage or prevent osteoporosis.

Frequently Asked Questions (FAQ’s)

1. What are the symptoms of Vitamin D deficiency?

Symptoms: Vitamin D deficiency can lead to fatigue, muscle weakness, bone pain, and an increased risk of fractures. In severe cases, it may cause rickets in children or osteomalacia in adults, both of which result in weak or deformed bones.

2. What are the best Sources of Vitamin D?

• Natural Foods: Fatty fish (e.g., salmon, mackerel, trout), fish liver oils, egg yolks, and cheese.
• Fortified Foods: Milk, orange juice, breakfast cereals, and plant-based milk alternatives like soy or almond milk.
• Supplements: Vitamin D2 (ergocalciferol) or D3 (cholecalciferol).
• Sunlight: Sensible sun exposure can stimulate the skin to produce vitamin D.

3. Can Vitamin D Reverse Osteoporosis?

Vitamin D alone cannot reverse osteoporosis but plays a critical role in managing it. By improving calcium absorption and bone mineralization, vitamin D supports stronger bones and reduces fracture risk. Combined with adequate calcium intake, weight-bearing exercises, and osteoporosis medications prescribed by a doctor, vitamin D helps improve bone health over time.

4. Can lack of vitamin D cause bone pain?

Yes, a deficiency in vitamin D can lead to bone pain, especially in the lower back, pelvis, and legs. This occurs because insufficient vitamin D impairs calcium absorption, weakening bones and causing discomfort or tenderness.

5. What  is  the  role  of  vitamin  D  apart  from  bone  growth? 

Vitamin D supports immune function, reduces inflammation, and regulates cell growth. It is also involved in neuromuscular function and glucose metabolism. Additionally, vitamin D influences genes responsible for cell proliferation and apoptosis (programmed cell death).

Dr. Swathy N, BAMS

Dr. Swathy N Ravindran, BAMS, graduate from the prestigious Vaidyaratnam P.S. Varier Ayurveda College in Kottakkal