The Sunshine Vitamin’s Hidden Power

For decades, Vitamin D was synonymous with strong bones and calcium absorption. Today, experts understand it very differently. Far from being just another vitamin, it functions more like a hormone, influencing multiple organs and biological systems across the body. Its reach extends well beyond skeletal health. Emerging research links Vitamin D to immune function, muscle strength, cardiovascular health, metabolic wellness and healthy ageing. From fatigue and body aches to low mood and frequent infections, Vitamin D deficiency may be behind symptoms many people dismiss as stress or a busy lifestyle.

“Vitamin D functions more like a hormone than a vitamin,” says Dr Ravi Sankar Erukulapati, senior consultant endocrinologist, Apollo Hospitals. “Research shows it plays an important role in immune regulation, muscle function, cardiovascular health and healthy ageing.”

The deficiency we don’t see

One reason Vitamin D deficiency often slips under the radar is because its symptoms are easy to overlook, says Dr Ravi Sankar. Fatigue, muscle weakness, body aches, low mood and recurring infections rarely trigger alarm bells. Instead, they are often accepted as a consequence of ageing, poor sleep or a hectic schedule. The irony is hard to miss. Despite abundant sunshine, Vitamin D deficiency remains widespread in India. According to Dr Dr Ravi Sankar, indoor lifestyles, long working hours, air pollution, sunscreen use, darker skin pigmentation and limited consumption of Vitamin D-rich foods all contribute to the problem.

Weight connection

Vit D’s role in metabolic health is attracting growing attention. Low levels are frequently found among people with obesity, type 2 diabetes and metabolic syndrome. Researchers believe the nutrient influences both insulin secretion and insulin sensitivity, two critical factors in blood sugar regulation.

According to Dr Kesava Reddy Mannur, clinical director of metabolic and bariatric surgery, Continental Hospitals, the relationship between Vitamin D and body weight is particularly complex. “Vitamin D is genuinely tangled up in the weight-management story,” he says.

People with obesity consistently show lower circulating Vitamin D levels because the vitamin becomes stored in fat tissue rather than remaining readily available in the bloodstream. At the same time, low Vitamin D levels are associated with fatigue, insulin resistance and metabolic dysfunction—factors that can make weight management more challenging.

Yet Dr Mannur cautions against oversimplification.”Vitamin D is a supporting factor in metabolic health rather than a missing key to weight loss,” he says. “Correcting a deficiency can improve overall metabolic health, but it is not a weight-loss tool by itself.”

Sunshine, food and the right balance

While sunlight remains the body’s most efficient source of Vitamin D, nutrition plays a crucial supporting role. “Food alone may not provide sufficient Vitamin D for most people,” says Ms B. Santosha, MSc (Nutrition & Dietetics), Consultant Dietetics & Nutritionist, Kamineni Hospitals. “A combination of safe sun exposure, balanced nutrition and supplementation when required remains the most effective strategy.”

WHY ARE INDIANS DEFICIENT DESPITE ALL THE SUN?

· Indoor lifestyles

· Long work hours

· Limited direct sun exposure

· Air pollution

· Sunscreen use

· Darker skin pigmentation

· Covered clothing

· Poor dietary intake

Eat your Vit D

· Fatty fish such as salmon, mackerel, sardines and tuna

· UV-exposed mushrooms

· Fortified milk and yogurt

· Fortified breakfast cereals

· Fortified plant-based beverages

· Egg yolks

Common mistakes

· Taking supplements without testing

· Using incorrect dosages

· Stopping supplementation too early

· Missing follow-up blood tests

· Taking Vitamin D on an empty stomach

VIT D & THE HEART

Fatigue may not always be a heart problemMany heart patients and those recovering from cardiac surgery complain of persistent tiredness and reduced ability to walk or exercise. According to Dr A.R. Krishna Prasad, Director and Chief Consultant Cardiothoracic and Vascular Surgeon at Medicover Hospitals, low Vitamin D levels are often the hidden reason. “Many patients assume their fatigue is due to heart disease, but blood tests frequently reveal Vitamin D deficiency,” he says. While Vit D does not directly improve heart pumping or prevent heart disease, it plays an important supporting role. Low levels can cause fatigue, making people less active and reducing their ability to exercise — a key part of heart health and recovery. Dr Prasad also cautions, “Both very low and very high Vitamin D levels can be harmful. The goal is to maintain optimal levels.”