Vitamin D Deficiency


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Previous evidence indicates that vitamin D deficiency and insufficiency are becoming global epidemics.22 It is estimated that 1 billion people worldwide have vitamin D deficiency.23 Multiple epidemiologic studies continue to highlight vitamin D deficiency as a marker of cardiovascular risk, promoting accelerated atherosclerosis and subsequent cardiovascular events.24-26 There are rising concerns regarding the level of vitamin D in South Asian populations. Nimitphong et al27 reported the existence of a high prevalence of vitamin D deficiency in South Asians. The vitamin D deficiency is predicted to be as high as 70% in this population, in comparison with citizens of Western countries, where studies indicate that vitamin D deficiency is present in only 20% to 25% of the total population.22,28-30 Poverty and lack of healthcare literacy regarding vitamin D deficiency remain underlying determinants that provoke vitamin D deficiency in South Asians.27,31 Failure to associate the deficiency with inadequate exposure to sunlight, skin pigmentation, and insufficient consumption of dietary vitamin D compound the issue. In addition, cultural practices may discourage skin exposure and variation of the traditional South Asian diet, which is typically low in vitamin D-containing foods.32

Environmental Factors

Due to rapid cultural modernization and transformation from a rural agrarian population to an urban sedentary population, and the propensity of genetic factors to take several years to display their effects, a greater emphasis has been placed on modifiable environmental ASCVD risk factors.11

Migration

The general health status of migrants, both within South Asian countries and internationally, is well studied. Well-settled migrants in high-income countries achieved rapid socioeconomic prosperity; however, rural-to-urban areas in low-income countries remained poor and became unhealthier.5 Rural-to-urban migration in South Asia is associated with decreased physical activity, higher intake of dietary fats, lower intake of fruits and vegetables, truncal obesity, hypertension, and other cardiometabolic abnormalities associated with increased cardiovascular risk.5 The general health status of migrant women has been demonstrated to be inferior to that of migrant men.5

Geographic location of South Asian people may be the strongest cardiovascular risk factor discovered and is multifactorial; it includes inadequate health care and infrastructure, high levels of poverty, and remote locations.33 Over the past 50 years, as South Asian countries have become rapidly industrialized, the prevalence of hypertension, obesity, hypercholesterolemia, and type 2 diabetes has increased significantly.

Physical Activity

Regular physical activity plays a significant role in lowering the risk of heart disease. Unfortunately, the prevalence of sedentary lifestyle remains high in South Asians.20 South Asian women are less likely to participate in physical activity than other populations.20 More than 90% of adults of South Asian ethnicity report no recreational exercise during leisure time.9 Increased aerobic physical activity has been demonstrated to reduce visceral adiposity and ASCVD risk independent of weight loss in white populations; however, until recently, this has not been studied in South Asian populations.20 Lesser et al20 found that South Asians did not have a consistent reduction in visceral adiposity with moderate-intensity exercise but did demonstrate a regular reduction with vigorous-intensity exercise. This may suggest an ethnic-specific response requiring a greater exercise stimulus to mobilize fat cells.

Active travel to and from work has been promoted within the South Asian population to decrease ASCVD risk. Gordon-Larsen et al34 found that active commuting was inversely related to obesity, elevated body mass index, blood pressure, and triglyceride and fasting insulin levels, and positively associated with elevated HDL cholesterol levels. Individuals who actively travel to and from work have higher overall physical activity levels and are less likely to be overweight or obese.35 Current World Health Organization guidelines recommend ≥150 minutes of moderate-intensity or 75 minutes of vigorous-intensity exercise per week; more than 50% of the population does not meet these recommendations.9 It is of paramount importance to encourage the inclusion of exercise in the daily routine and to build infrastructure to support these recommendations.

Diet

Important ethnic customs and cultural beliefs influence dietary intake, and the South Asian population is often exposed to high-fat, high-carbohydrate, and low-protein and low-fiber diets beginning in childhood. These negative dietary patterns are correlated with increased inflammatory markers and insulin resistance in the South Asian population.11 Specifically, an increase in white rice consumption, a staple of the South Asian diet, has been correlated with an increased risk of type 2 diabetes; the same correlation was made with increased consumption of refined grains.11 High-fat and high-carbohydrate diets also increase plasma endotoxin levels, which, by downstream effect, increases insulin resistance and inflammatory markers. South Asians consume large amounts of hydrogenated fat, ghee, butter, milk, ground nut oil, trans-fatty acids, and coconut oil, compounding these dietary risks.

Refined sugar was invented in India in approximately ad 350, and India is the largest consumer of refined sugar in the world. In South Asians, particularly Indians, consumption of a large amount of sweetened food and beverages is popular.36 The consumption of sugar-sweetened foods is important to many traditions within the Indian culture, and it is customary to “sweeten the mouth” after each meal.9 Although sugar is a significant source of calories and a fundamental aspect of the Indian culture, the consumption of refined sugar and carbohydrates poses a significant threat to the long-term health of an increasingly sedentary population with an innate predisposition to type 2 diabetes and metabolic syndrome. Recent socioeconomic changes and cultural beliefs within the South Asian population have contributed to the amplification of these negative dietary habits and predisposed an entire population to increased prevalence of ASCVD.

Dietary fiber and protein intake was negatively associated with insulin resistance, inflammatory markers, and improvement in ASVCD risk in South Asians; similarly, dietary intake of fruits and vegetables was negatively associated with insulin resistance and inflammatory markers in the same population. A low-protein diet was positively associated with islet cell dysfunction in South Asians.11

Regardless of how much the South Asian diet contributes to ASCVD, the diet is of central importance to cultural identity.8 Dietary suggestions often challenge the core principles of the South Asian diet, and it is thought that adhering to these suggestions makes someone less South Asian and more American.