Women with low vitamin D levels are more likely to have hypertension and metabolic syndrome, both important cardiovascular risk factors. (Photo/AI-generated)A 53-year-old woman came to me with dizziness, fatigue, fainting, shortness of breath and a chest squeeze now and then. And just when the usual tests seemed normal, an imaging test showed calcium deposits in her aorta, the largest artery in the body. The aorta is meant to be supple and elastic, expanding with every heartbeat and recoiling to propel blood smoothly to the rest of the body. Hers was beginning to harden. Why? She did not smoke. She had no history of heart disease, either, no co-morbidities.The answer lay not in what she lacked, but in what she had consumed in excess. Vitamin D. Months earlier, she had been diagnosed with severe vitamin D deficiency. Her level was just 6 ng/ml, when anything above 30 ng/ml is considered normal. She was prescribed a weekly vitamin D sachet for six weeks. Instead, she took it for six months. When she eventually returned for review, her calcium level had climbed to 11.5 mg/dL, above the normal upper limit of 10 mg/dL. Her kidneys too had begun to suffer, her creatinine rising to 2. But what caught my attention as a cardiologist was not the kidney injury. It was the calcium in her aorta. Because cardiologists spend their lives fighting the hardening of arteries.Vitamin D: A friend of the heartVitamin D has had a remarkable journey. For decades, we thought of it only as the vitamin that kept bones healthy. Then researchers discovered vitamin D receptors in blood vessels, heart muscle and many other tissues. Suddenly, vitamin D was no longer just about bones; it was being discussed in the context of heart disease, blood pressure and even stroke prevention.There was a good reason for the excitement. Adequate vitamin D levels appear to support endothelial function — the ability of blood vessels to dilate and constrict normally. It helps regulate inflammation and may influence blood pressure. Women with low vitamin D levels are more likely to have hypertension and metabolic syndrome, both important cardiovascular risk factors. Deficiency, therefore, should be corrected. But somewhere along the way, an important distinction was lost. Correcting a deficiency is not the same as taking unlimited supplements.The heart does not need excessMy patient, keen to correct her deficiency faster, continued taking in Vitamin D supplements without consulting a doctor. Large clinical trials have shown that while Vitamin D is essential for cardiovascular health, taking high doses does not confer extra protection against heart attacks or strokes. Once adequate levels are achieved, stop taking it.Excess vitamin D increases calcium absorption. And that is where trouble begins. Too much calcium in the bloodstream — hypercalcaemia — can settle in the heart vessels as plaque, damage kidneys and cause stones. This process, known as vascular calcification, stiffens blood vessels and robs them of their natural elasticity.The aorta, which should cushion the force of every heartbeat, becomes rigid. The heart must work harder against this increased stiffness. It is a silent process. You cannot feel your arteries hardening. You only discover it when the damage is already under way.Story continues below this adExtra calcium directly disrupts the electrical impulses that control the heart’s pumping cycle, causing dangerous arrhythmias or irregular heartbeats. This may cause the heart’s circuit to snap and trigger sudden cardiac arrest. Over time, the combination of rigid blood vessels and abnormal heart rhythms contributes to high blood pressure (hypertension), which can ultimately lead to congestive heart failure or increase the risk of a heart attack.Vitamin D is not harmless in excessVitamin D has become one of the most popular supplements of our times. Patients take it because they are tired. They take it because their neighbour takes it. They take it because somebody on social media called it a miracle vitamin. And because it is a vitamin, they assume it is harmless. But like any medicine, vitamin D has a dose, a duration and a purpose.As cardiologists, we want our patients to have healthy vitamin D levels. The goal is to keep calcium where nature intended it to be — in the bones, and out of the arteries. That, in the end, is what keeps the heart young.(Dr Shetty is lead cardiologist and medical director, Sparsh Hospital, Bengaluru)