Overuse of Vitamin D Supplementation: A Growing Concern in Cardiovascular and Geriatric Health

Dear Editor, Vitamin D deficiency is common in the general population, particularly among the elderly, leading to widespread supplementation. However, indiscriminate and prolonged use of high-dose Vitamin D, often combined with calcium, has raised concerns about vascular calcification and coronary artery disease (CAD). Emerging evidence indicates that excess calcium with or without Vitamin D may contribute to coronary artery calcium (CAC) deposition.[1,2] Multiple studies now highlight potential adverse effects associated with excessive Vitamin D intake, including a paradoxical increase in cardiovascular events due to vascular calcification.[3-5] Both low and high serum Vitamin D levels are linked to elevated cardiovascular risk[4-6] [Figure 1]. Furthermore, patients are often placed on long-term therapy without reassessment, increasing the risk of hypercalcemia and vascular calcification.[1,7] This indiscriminate use of supplements is especially concerning in individuals with pre-existing CAD or chronic kidney disease, where calcium–phosphate imbalance may already be present.[8]Figure 1: Hypothetical U-shaped curve illustrating cardiovascular risk relative to serum 25(OH)D levels. Both deficiency and excess are associated with increased coronary artery calcium depositionVitamin K2, particularly in its menaquinone-7 (MK7) form, plays an essential role in calcium homeostasis by carboxylating matrix Gla protein (MGP), a potent inhibitor of vascular calcification. It prevents calcium buildup in arteries, reducing the chances of vascular stiffening. Without adequate Vitamin K2, MGP remains inactive, allowing calcium to deposit in soft tissues, including coronary arteries.[2,9] Supplementation with K2-MK7 has been shown to reduce arterial stiffness and slow progression of CAC in some clinical studies.[10] K2 (menaquinone) form is produced only by bacteria and hence found only in fermented foods such as natto, sauerkraut, miso, and certain cheese – gouda and edam. These foods are not easily available in India. There is a striking geographical gradient in natto consumption across Japan, which serves as a natural experiment for the effects of Vitamin K2-MK7 on health. In Eastern Japan (e.g., Tokyo and the Tohoku region), natto is a traditional dietary staple consumed frequently. Conversely, in Western Japan (e.g. Osaka, Kyoto, and Hiroshima), consumption is historically much lower. This dietary divide has profound clinical implications. There is a lower incidence of hip fractures and higher bone mineral density in Eastern Japan, whereas Western Japan exhibits higher rates of osteoporosis and fractures.[11] Furthermore, large-scale prospective studies have demonstrated that higher natto intake in Eastern regions is linked to a significant reduction in cardiovascular disease mortality compared to Western regions with lower intake.[12] Calcium that is derived from a natural source, such as ragi, milk, curd, paneer, black sesame seeds, almonds, and amaranth, offers a plethora of benefits in terms of additional macro- and micronutrients that these foods provide.[13] A dose of D3 (1000–2000 IU/day) and K2-MK7 (90–180 μg/day) is sufficient for most people as maintenance, especially in the elderly population. Alternatively, K2-MK7 (90–120 μg/day) may be added and taken for a few weeks, after a dose of Vitamin D3 60,000 IU is taken.[14,15] In the elderly population, Vitamin D supplementation is particularly indicated in individuals with limited sun exposure, such as homebound or institutionalized individuals, as well as those with low dietary intake or malnutrition. Supplementation is also recommended in elderly patients with osteoporosis or a history of fragility fractures, malabsorption syndromes, or chronic liver and kidney disease. Elderly persons with documented low serum 25-hydroxyvitamin D levels, as well as those at increased risk of falls or muscle weakness, are also important candidates for supplementation.[16] Despite this critical role, most formulations of Vitamin D and calcium do not include Vitamin K2-MK7. Vitamin K2 lacks a similar level of large intervention trials as the calcium–Vitamin D combination. Hence, adding it complicates regulatory filings and may invite legal risks. Furthermore, Vitamin K2 is costlier and sensitive to humidity and oxidation. It may also interact with anticoagulants. The practice of unmonitored, long-term supplementation in elderly patients, especially those who have suffered a recent bone fracture, may be potentially harmful. The interplay between Vitamin D, calcium, and vascular health must be better appreciated, particularly the protective role of Vitamin K2-MK7 in preventing calcium misplacement. Rational supplementation must replace indiscriminate practices to prevent iatrogenic harm, especially in vulnerable elderly populations. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.