HEALTH WATCH
There was a time when vitamin D was hardly discussed outside medical textbooks. Today, it seems to be everywhere. A routine health check reveals a “low” vitamin D level, a friend recommends a weekly sachet, social media suggests a higher dose, and suddenly vitamin D becomes the explanation for fatigue, body aches, hair fall, poor immunity and even depression.
The popularity of vitamin D is not entirely misplaced. It is an important hormone-like nutrient with a central role in calcium absorption, bone health and muscle function. Severe deficiency can cause significant disease, particularly in children and adults with prolonged deficiency.
But somewhere along the way, the conversation has become unnecessarily simplistic.
We have moved from ignoring vitamin D to testing it excessively, treating borderline results aggressively and sometimes assuming that higher levels must automatically mean better health.
So, are we really facing a vitamin D deficiency epidemic—or are we simply testing more people than ever before?
The answer is somewhere in between.
The “sunshine vitamin”
Vitamin D is unusual compared with most vitamins because our bodies can produce it. When ultraviolet B radiation from sunlight reaches the skin, it initiates the production of vitamin D, which is subsequently converted into its active forms through processes involving the liver and kidneys.
Vitamin D then helps regulate calcium and phosphate metabolism, allowing the body to maintain healthy bones and teeth.
Its importance is particularly obvious in severe deficiency. In children, profound deficiency can lead to rickets, resulting in abnormal bone development. In adults, severe deficiency can cause osteomalacia, a condition in which bones become inadequately mineralised and may result in bone pain and muscle weakness.
Vitamin D also has roles in muscle function and the immune system. However, this is where the subject becomes complicated. Laboratory and observational studies have linked low vitamin D levels with a wide range of diseases, but an association does not necessarily mean that vitamin D deficiency caused the disease—or that taking extra vitamin D will prevent it.
That distinction is often lost in popular health discussions.
Why can deficiency occur despite abundant sunlight?
This is one of the most common questions.
India receives considerable sunlight, yet low vitamin D levels are frequently reported. The apparent contradiction has several explanations.
Modern lifestyles have changed dramatically. Many people spend most of their day indoors—at work, in schools, hospitals, offices or at home. Children who once spent hours outdoors may now spend much of their leisure time indoors.
Clothing also matters. When most of the body is covered, relatively little skin is available for vitamin D production.
Skin pigmentation is another factor. Melanin reduces the skin’s response to ultraviolet B radiation, meaning people with darker skin generally require more UVB exposure to produce the same amount of vitamin D as people with lighter skin.
Age is also relevant. The skin becomes less efficient at producing vitamin D as we grow older.
Obesity can be associated with lower circulating vitamin D levels as well, partly because vitamin D is fat-soluble and becomes distributed into a larger volume of body fat.
Certain gastrointestinal, liver and kidney disorders can interfere with vitamin D metabolism or absorption. Some medications can also affect vitamin D levels.
Therefore, simply saying “we live in a sunny country, so nobody should be deficient” is incorrect.
But the opposite statement—“everyone living in India is vitamin D deficient”—is equally misleading.
Should everyone get a vitamin D test?
This is perhaps the most important question.
The answer is no—not everyone needs routine vitamin D testing.
The blood test commonly used to assess vitamin D status is serum 25-hydroxyvitamin D. It is an appropriate test in people where there is a clinical reason to assess vitamin D status.
For example, testing may be considered in individuals with conditions affecting bone health, malabsorption, certain kidney or liver disorders, particular medications, or other recognised risk factors.
However, ordering the test indiscriminately as part of every health package creates another problem.
A laboratory report produces a number, and numbers have a psychological effect. Once someone sees that their vitamin D is below the laboratory’s reference range, they may automatically assume they are sick and require treatment.
But laboratory values must be interpreted in clinical context.
Different organisations and laboratories have not always used identical definitions for “deficiency” and “insufficiency.” The exact threshold that should trigger treatment depends on the clinical circumstances and the purpose for which the test was performed.
This is why treating the report rather than the patient can lead to unnecessary supplementation.
The problem with “more is better”
One of the most persistent myths surrounding vitamins is that because they are essential, taking more must provide additional health benefits.
This is particularly problematic with vitamin D.
Vitamin D is fat-soluble. Unlike water-soluble vitamins that are more readily excreted when consumed in excess, fat-soluble vitamins can accumulate.
Excessive vitamin D intake can cause toxicity, usually through excessive calcium absorption. This can result in hypercalcaemia.
Symptoms may include nausea, vomiting, weakness, confusion, excessive thirst, frequent urination and kidney problems. In severe cases, vitamin D toxicity can result in significant kidney injury and other complications.
This does not mean vitamin D supplements are dangerous when used appropriately. They are an important and effective treatment for people who genuinely require them.
The message is simply that the dose matters.
A medically appropriate replacement regimen for a person with deficiency should not be confused with indefinite high-dose supplementation taken without supervision.
Why do doctors sometimes prescribe high doses?
This is another source of confusion.
People often see someone taking a large weekly dose of vitamin D and assume that such a dose is appropriate for everyone.
It isn’t.
High-dose vitamin D regimens may be used for a limited period in people with clinically significant deficiency. Once the deficiency is corrected, the strategy may change to a maintenance dose, depending on the person’s circumstances.
Treatment is therefore not necessarily “one dose forever.”
The appropriate amount depends on factors such as the severity of deficiency, age, body weight, underlying medical conditions, medications and the reason for treatment.
Self-prescribing a high dose simply because it worked for a relative or friend is therefore not advisable.
Can vitamin D cure fatigue?
Fatigue is probably one of the most common reasons people blame vitamin D.
Someone feels tired, undergoes testing, finds a low vitamin D level and concludes that vitamin D deficiency is the explanation.
Sometimes it may be.
But fatigue is one of the least specific symptoms in medicine.
Poor sleep, long working hours, stress, depression, anaemia, thyroid disease, inadequate nutrition, infections, medication effects and several other medical conditions can cause fatigue. Even among people with low vitamin D levels, correcting the level may not necessarily eliminate fatigue if another underlying problem is responsible.
The same applies to body aches.
Vitamin D deficiency can cause musculoskeletal pain and weakness, particularly when deficiency is significant. But generalised body pain has numerous possible causes.
A vitamin D report should therefore be interpreted as one piece of the clinical puzzle, not as the automatic answer.
What about immunity?
Vitamin D and the immune system have an interesting relationship.
Vitamin D receptors are present on many immune cells, and laboratory research has demonstrated several ways in which vitamin D can influence immune responses.
This has generated considerable interest in whether vitamin D supplementation can prevent infections.
However, the public interpretation has often gone far beyond the evidence.
Vitamin D should not be regarded as a universal immunity booster or as protection against every infection.
Some studies have suggested benefits in particular groups, but clinical trials have not consistently shown that giving high doses of vitamin D to everyone prevents infections.
This is an important principle in modern medicine: biological plausibility is not the same as proven clinical benefit.
What about depression and mental health?
The same issue applies here.
Low vitamin D levels have been associated in observational studies with depression and other mental health conditions. But people who are unwell may also spend less time outdoors, have poorer diets and engage in less physical activity—all of which can influence vitamin D levels.
Therefore, low vitamin D may sometimes be a marker of poor overall health rather than the sole cause of a person’s symptoms.
Vitamin D replacement may be appropriate when deficiency exists, but it should never replace proper assessment and treatment of depression or other mental health conditions.
Sunlight: How much is enough?
This is probably the most misunderstood aspect of vitamin D.
There is no universal rule saying that every person needs exactly 10, 15 or 30 minutes of sunlight every day.
Vitamin D production depends on skin colour, age, season, latitude, time of day, clothing, exposed skin area, atmospheric conditions and other factors.
The amount of ultraviolet exposure required also varies considerably between individuals.
At the same time, deliberately seeking prolonged ultraviolet exposure is not a sensible health strategy because excessive UV exposure damages the skin and increases the risk of skin cancer.
The goal should not be to “burn” or excessively expose oneself to sunlight in the hope of maximising vitamin D.
Regular outdoor activity, sensible sun exposure and appropriate sun protection when exposure is prolonged are a much more reasonable approach.
Can food provide enough vitamin D?
Diet can contribute to vitamin D intake, although naturally occurring dietary sources are relatively limited.
Fatty fish are among the better sources. Egg yolks contain smaller amounts, while some foods such as milk, cereals and other products may be fortified with vitamin D depending on the country and product.
For some individuals, particularly those with limited dietary sources or increased requirements, supplementation may therefore be useful.
But supplements should complement—not replace—a nutritious diet.
Vitamin D and bone health: The part we should take seriously
While the evidence surrounding some of the broader claims about vitamin D remains mixed, its importance for skeletal health is well established.
Vitamin D helps the intestine absorb calcium. Without adequate vitamin D, maintaining normal calcium balance becomes more difficult.
Children require adequate vitamin D and calcium for normal bone development. Adults need them to maintain bone health throughout life.
Older adults are particularly important because falls and fractures can have serious consequences.
However, bone health is never just about vitamin D.
Adequate calcium intake, resistance and weight-bearing exercise, maintaining muscle strength, avoiding smoking, limiting excessive alcohol consumption and addressing osteoporosis risk factors are all important.
A person cannot compensate for a sedentary lifestyle simply by taking vitamin D.
The vitamin D industry and the health-check culture
There is another issue worth discussing: the commercialisation of health.
Modern consumers are increasingly encouraged to undergo large panels of blood tests, sometimes without a clear clinical indication.
Once an abnormal or borderline result appears, another product is often recommended.
This creates a cycle: Test → abnormal number → supplement → repeat test → more anxiety.
Medicine should instead follow a different principle: Clinical question → appropriate test → interpretation → appropriate treatment.
Testing is valuable when it answers a meaningful clinical question.
More testing does not automatically mean better healthcare.
Five common myths about vitamin D
Myth 1: Everyone needs a vitamin D test every year.
Not necessarily. Testing should be based on clinical circumstances and risk factors rather than simply being added to every routine health check.
Myth 2: If vitamin D is good, more is even better.
No. Vitamin D has an optimal physiological role, and excessive supplementation can be harmful.
Myth 3: Vitamin D prevents every infection.
There is insufficient evidence to treat vitamin D as a universal protection against infections.
Myth 4: Every episode of fatigue is due to vitamin D deficiency.
Fatigue has many possible causes. Vitamin D deficiency is only one possibility.
Myth 5: The more sunlight you get, the healthier you are.
Sunlight is useful for vitamin D production, but excessive ultraviolet exposure damages skin. More is not always better.
So, what should the average person do?
For most people, the answer is surprisingly straightforward.
Spend some time outdoors and maintain regular physical activity. Eat a balanced diet containing sources of calcium and vitamin D. Maintain a healthy body weight. Avoid smoking and excessive alcohol. Pay particular attention to bone health as you age.
If you have risk factors for vitamin D deficiency, symptoms suggestive of deficiency, a condition affecting bone health or another medical reason for testing, discuss it with your doctor.
If a vitamin D test is performed, don’t panic over the number. Discuss what the result means in your particular clinical situation.
And if supplementation is recommended, follow the prescribed dose and duration rather than assuming that a higher dose will produce a better result.
The bottom line
Vitamin D is neither the miracle vitamin that social media sometimes portrays it as, nor an insignificant nutrient that can be ignored.
True deficiency matters. Severe deficiency can cause significant disease and should be appropriately treated.
But we should also move away from the idea that every ache, every episode of tiredness and every health problem is caused by vitamin D deficiency—and that everyone needs high-dose supplementation.
Perhaps the most important lesson is that healthcare should be guided by evidence rather than anxiety about laboratory numbers.
A vitamin D test can be useful when there is a reason to perform it. A supplement can be extremely beneficial when someone genuinely needs it. But neither testing nor supplementation should become a ritual.
The sunshine vitamin deserves neither neglect nor hype. It deserves something much more useful: a balanced, evidence-based approach.
(The author is a registered medical practitioner and RK Health columnist. He can be reached at: [email protected])
