ARE SOUTH ASIANS PREDISPOSED TO HEART DISEASE, HEART ATTACKS AND DIABETES?

Those of South Asian descent originate from what is broadly referred to as the Indian subcontinent, which is home to the countries of India, Bhutan, Nepal, Bangladesh, Pakistan, Sri Lanka, Afghanistan and the Maldives.^[1]

Research since the late 90s has revealed that the South Asian population appears to be at a much higher risk for cardiovascular disease (CVD), heart attacks and diabetes. Several factors are thought to underpin why, including diet, lifestyle and genetics.

The following article attempts to explore why South Asians are more susceptible to cardiometabolic diseases through exploring by factors and more. The global prevalence of these conditions amongst South Asians, risk factors and differences in metabolism are discussed below.

Global South Asian Prevalence of Cardiovascular Disease, Heart Attack and Diabetes

CVD and Heart Attacks. Death due to heart attack and cardiovascular disease ranks as the leading cause of mortality in South Asia, independently of urbanization. Coronary heart disease (CHD) and coronary artery disease (CAD) are the leading CVDs affecting South Asians, both known to increase the risk of Heart attack. Onset of these conditions typically affects South Asians earlier than other ethnic groups, with the diagnosis often taking place before individuals hit their 40s.

Amongst South Asian expats, the same trend has been shown throughout previous studies in the 90s and early 2000s. The rates for cardiovascular disease amongst South Asians were also found to be up to 3-5 times more than for other ethnicities living abroad.

Diabetes. The elevated risk for CVD and the higher CVD mortality rate correlate with the increased prevalence of diabetes seen across this population. Both CVD and diabetes are independent risk factors for one another and share many metabolic commonalities, including deficits in fat metabolism. South Asians have a unique fat metabolism compared to other ethnic groups, which likely increases the risk of contracting any of these conditions.

Cardiometabolic Disease Risk Factors

Cardiovascular disease, diabetes and other diseases listed below are common progressions of metabolic syndrome, which South Asians are predisposed to acquiring. The following points denote the risks pertaining to the South Asian population for each of these conditions as well as heart attacks, many of which share significant overlap.

Dyslipidemia. South Asians appear to be genetically prone to inheriting a specific form of dyslipidemia which raises triglycerides, reduces HDL cholesterol and promotes stored abdominal fat. Dyslipidemia is known to be a significant risk factor for all the metabolic diseases noted to be of higher prevalence in South Asian populations. Furthermore, most of these diseases induce dyslipidemia. South Asian genes pertaining to dyslipidemia are discussed in more depth in the following section.

Cardiovascular disease is a risk factor for most of the below diseases across all populations. In South Asians, young onset cardiovascular disease is associated with dyslipidemia, hyperglycemia, regional obesity and hypertension, most often manifesting as coronary heart disease or coronary artery disease. If insulin resistance is present, it may increase the risk of blood clotting and thrombosis^[2], which raises the risk for premature heart attack, CVD and stroke^[3].

Diabetes is one of the leading risks associated with early onset CVD, heart attack and mortality in South Asians. Risk factors attributed to the development of diabetes in this population are strongly linked with:

• Poverty
• Sedentary living
• Body fat mass
• Age
• Family history
• Genetics

The incidence of diabetes has been shown to be higher in immigrants living abroad, suggesting that living a more Western lifestyle could be a stronger risk factor than the ones highlighted above. Furthermore, south Asians tend to have higher fasting insulin levels coupled with unusual triglyceride elevations in response, which correlates with the higher incidence of diabetes.

Heart Attack Risk. Despite sharing commonality, researchers also acknowledge that compared to other ethnic groups, South Asians are less affected by conventional cardiovascular disease risk factors. In a large scale study that surveyed over 15000 patients (of all ethnicities) across 52 countries, there were 9 risk factors identified for heart attack onset. Of these, South Asians tended to display more risk with:

• Cholesterol
• Diabetes
• Psychosocial stress or depression
• Sedentary living
• Lower consumption of fruits and vegetables

Other risk factors that contributed less toward South Asian heart attack onset in the study included alcohol consumption and hypertension. High body fat mass and smoking were nearly equitable risk factors compared to other ethnic groups. Despite these findings, they are still important considerations for preventing heart attacks and CVD.

Obesity. While obesity is certainly a risk factor for CVD, heart attacks and diabetes in people of all ethnicities, conventional obesity is not as common in South Asians compared to other ethnic groups. In this population, body fat is distributed differently, with a trend for increased abdominal obesity, a smaller waist circumference and lower BMI. Studies looking at gender show that women tend to have higher total body fat than men. In contrast, men tend to have more internal fat, particularly liver fat. The extra abdominal fat in South Asians is linked to the trend for heightened fasting insulin and low HDL levels.^[4] Some studies suggest that nutritional deficiencies or surpluses during pregnancy increase the risk for obesity in South Asian offspring.

Liver Disease. South Asians are known to be at a higher risk for contracting non-alcoholic fatty liver disease (NAFLD). NAFLD is considered a liver-related manifestation of metabolic syndrome and is associated with diabetes, heart disease, and obesity. The risk factors for liver disease are similar to the cardiometabolic diseases listed above. The occurrence of liver disease in patients with metabolic disorders ranges from 35 to 75%.^[5] Part of the susceptibility of South Asian folk is because their livers tend to store more fat than other ethnicities, irrespective of obesity.

How Are South Asians at an Increased Risk for Cardiometabolic Diseases?

Many South Asians have unique genetics that predispose them to cardiometabolic diseases. Westernization, irregular routines and poor diagnostics conspire with these underlying genetic characteristics to increase the risk.

South Asian Genetics

Genetic differences in South Asian fat and glucose metabolism are connected to their increased susceptibility to cardiometabolic diseases and heart attacks, as discussed below.

Fat Metabolism

Dyslipidemia. Many South Asians are prone to acquiring a specific type of dyslipidemia (dysfunctional fat metabolism), with some data reporting the risk in South Asians to be 49.2% higher than in other ethnicities.

Faulty fat metabolism in South Asians is characteristic of the following cholesterol markers^[6]:

• HDL cholesterol levels are found to be lower on average than in other ethnicities, as well as being smaller, faulty and proatherogenic^[7]. This is attributed to genetic differences in South Asian HDL metabolism, as discussed in the below section.
• Triglyceride levels are increased by comparison, which further alludes to the increased storage of abdominal fat, the tendency to store more fat as an energy reserve (see below) and the larger size of fat cells as compared to other populations.
• LDL cholesterol levels are typically seen to be higher or equitable to that of other ethnicities.
• ApoB Lipoprotein levels are also higher in South Asians with dyslipidemia. ApoB is a structural component of fatty membranes that help to transport cholesterol and triglycerides. It is also a known requirement for crossing the cell membrane and depositing cholesterol into cells. ^[8]

South Asian SNPs Lower ApoA-1. Three gene deviations (SNPs) coding for ApoA-1 lipoproteins were found to be related to South Asian dyslipidemia, namely C655T, C756T, and C1001T. These are correlated with decreased production of ApoA-1 in South Asians^[9] and appear to be a common ancestral trend. While data about these SNPs is scarce, C655T (also known as T13254C^[10]) codes for blood platelet receptors and is associated with an increased risk of premature heart attack.^[11]

Less ApoA-1 Promotes Dyslipidemia. These findings could explain the low levels of HDL seen in many South Asians, as ApoA-1 is required for producing HDL cholesterol. South Asian ApoA-1 SNPs may also be responsible for the higher presence of faulty HDL particles seen in those with dyslipidemia. Low ApoA-1 and high ApoB levels have been associated with delayed chylomicron clearance^[12], which correlates with higher triglyceride levels and an increased tendency to store abdominal fat.

Raised ApoB Ups Cardiometabolic Risk. ApoA-1 and ApoB form a ratio together that serves to regulate cholesterol production and transport. As a result of having lower ApoA-1 levels, ApoB levels are seen to be too high in South Asians. Increased ApoB promotes the deposition of cholesterol and triglycerides into blood vessel walls and is associated with atherosclerosis risk^[13], insulin resistance^[14] and diabetes.^[15] In this way, South Asians are more vulnerable towards contracting CHD, CAD, premature heart attacks and metabolic syndrome.

Other Genetic Differences. While the above SNPs are some of the most common found to affect fat metabolism in South Asians, several other genetic differences serve to increase the risk for cardiometabolic diseases. These other gene switches may allude to the course of disease in members of this population. For example, a few changes to genes governing fat mass, obesity and homocysteine were shown to reflect in some South Asians, serving to increase dietary intake and predisposing them to obesity. Most of these genes were shown to be regulated through dietary and lifestyle changes.^[16]

MicroRNAs. MicroRNAs are single stranded genetic fragments produced by DNA that affect cellular functions through regulating gene transcription and translation^[17]. While very little is known about them, a few microRNAs have been associated with the South Asian profile of dyslipidemia and diabetes^[18]. These are likely expressed as a result of the gene switches described above. However, more research is required to clarify their role in fat metabolism and whether they ought to be targeted or not for disease prevention.

Genetic Differences in Glucose Metabolism

Several genetic variants have been found to be common to South Asians which predispose them to diabetes. The effects of many of these SNPs are unknown, despite their association with diabetes in South Asians. A few of them pertain to faulty fat metabolism, a known risk for diabetes development^[19]. Of these, there were two SNPs found to interfere with glucose metabolism^[20]:

SNPs Coding Lower Beta Cell Function. Several changes in genes that regulate liver growth and function were shown to reduce pancreatic beta cell function in South Asians. Lower beta cell functionality reduces insulin secretion, which promotes hyperglycemia. This is associated with an increased risk for adolescent diabetes and diabetes type 1. Not all South Asians are prone to this genetic switch as hyperinsulinemia is another common trend in this population.

Vitamin D Receptor SNPs. Some studies show a weak association between genes coding for the vitamin D receptor in South Asians and diabetes. Alterations in these genes lead to reduced vitamin D metabolism, lower pancreatic function and heightened insulin resistance. These SNPs appear to be less common than the others listed above, found more often in women, those who are vitamin D3 deficient^[21] and those who live abroad in countries receiving less light per day (e.g. UK)^[22]. Those who are deficient tend to avoid sunlight or cover up completely when in the sun.

Supplementation was partially shown to help regulate these SNPs and reduce the risk for diabetes development.^[23] Spending more time in the sun is required to regulate the lower vitamin D metabolism seen in South Asians, who possess enough skin melanin to counteract UV radiation and achieve optimal vitamin D status.

Ancestral Adaptation May Be Responsible

There are several genetic hypotheses revolving around the above changes in energy homeostasis seen in South Asians.^[24] The two most relevant ones are listed below:

• Thrifty Genotype Hypothesis. Those born with the thrifty genotype possess genetic changes that increase the tendency to store abdominal fat, leading to a specific body type common among South Asian people. It is thought to be an adaptive response towards ancestral periods of food shortage or starvation. The fat reserve can be used quickly as an energy source during periods of starvation.
• Mitochondrial Efficiency Hypothesis. Mitochondrial energy distribution in many South Asian people has adapted towards expending less energy on generating body heat. As a result, they have more available ATP (or energy) and are more resilient to ambient heat. The positive energy balance is thought to promote extra fat production, if not balanced with enough physical activity.

It should be noted that the above theories pertain to ancestral adaptations from South Asia and that this population is one of the largest to have migrated all over the world. In several more generations, it is very likely that South Asian metabolism will take on a new form in line with different environments and lifestyle habits.

Dietary Practices and Westernization

Across population studies, it is evident that South Asians living abroad in Western countries tend to suffer from diabetes, CVD and heart attacks more on average than those living in South Asia. This has been attributed to some ethnic dietary trends, westernization and reduced levels of physical activity.

• Processed Foods. A handful of studies show that South Asians living abroad tend to consume more processed food (e.g. cakes, candies, sugar-sweetened beverages, etc) than those remaining in their country of origin. This could be due to increased availability, better earnings or more psychosocial stress. These foods are usually very high in calories and low in nutrients and fiber, all of which can promote metabolic syndrome and related diseases.
• Dietary Fat Intake. One study shows how South Asians consume a lot more omega-6 fats, trans fats and saturated fats, as well as less omega-3 fats and monosaturated fats than Caucasian people in the UK^[25]. The ratio of these fats is well known to promote an unbalanced cholesterol profile and CVD.
• Unbalanced Carb Consumption. South Asians were shown to consume a diet very high in carbohydrates (60-67%), low in fiber and lacking in nutrients^[26]. This combination can significantly add to a positive energy balance and promote common South Asian cardiometabolic conditions like diabetes, obesity and CVD. Carbohydrates that are low in fiber and nutrients are typically high on the glycemic index, highly refined and rich in starch (e.g. white potato, rice, wheat, corn and other cereal grains). If had in large quantities, these carbs are known to spike blood sugar levels excessively in the hours post consumption and fall into a similar category to refined carbs that are high in sugar.
• Alcohol Abuse affects South Asians worse than other ethnicities. Yet, drinking has been shown to be less common throughout this population^[27]. Studies reveal that South Asian expats in the UK constitute a higher percentage of alcohol-related liver cirrhosis patients and succumb to a higher alcohol-related death rate than the UK national average. In South Asians that do drink, other risk factors pertaining to heart attacks and diabetes are increased, such as increased stress in the home environment (e.g. domestic violence) and financial problems.^[28]

Irregular timing of meals

A few reviews mention irregular meal times amongst South Asian individuals and how this could contribute to the onset of cardiometabolic diseases^[29]. A few general trends have been observed:

• Eating at irregular times
• Spreading ingested calories over 15-20hours of the day^[30]
• Cramming the majority of food in the later part of the day and evening
• Eating dinner 2-3 hours later than European counterparts (i.e. closer to bed time)^[31]

These trends can theoretically interfere with both metabolism and circadian rhythm, having the propensity to disrupt sleep and the timing of metabolic processes (e.g. insulin release, energy production, etc).

Regulating meal times can help to keep the metabolism stable and improve sleep. However, it is difficult to say whether erratic metabolic signaling induces irregular eating patterns or vice versa. Nutritionally balancing one’s meals can help to regulate the timing of meals by satisfying potential underlying deficits in energy metabolism. This reduces spontaneous cravings and keeps energy levels consistent throughout the day, as does regular physical activity and sunlight exposure.

Under-Diagnosis

Globally, diagnostic measures for cardiovascular disease and metabolic syndrome have been largely focused on Caucasian populations. By comparison to these populations, South Asians with an identical BMI are often smaller in size with higher levels of abdominal body fat. Thus, diagnosis may fall short for members of the South Asian population. In this respect, while cardiovascular disease and metabolic syndrome rates are still higher in this population, they are likely to be detected too late and underestimated.

3 Big Tips for South Asians Looking to Prevent Cardiometabolic Disease

The following tips can help you to optimize your metabolism and better prevent cardiometabolic problems:

1. Eat for your metabolism

Reducing ApoB alone can serve to improve ApoA-1 levels and potentially help regulate cholesterol metabolism. Yet, due to the genetic differences in South Asians, it’s important to focus on boosting HDL and ApoA-1 production too.

Eat a Nutritionally Balanced Diet. The Mediterranean diet was associated with one of the lowest ApoB counts compared to other nutritionally balanced diets. Other comparable diets include the DASH diet, vegetarian diet, paleo and Nordic diets.^[32] These diets made use of macronutrients in the following ratios: 34-50% carbs, 27-39% fats and 18-24% protein, as well as placing an emphasis on fiber and micronutrients. This was shown to lower heightened ApoB levels and promote weight loss in overweight participants.

Emphasize Plant Food. When looking at the ancestral trends of South Asia, vegetarian diets are a large part of the culture and history, having shaped the metabolism of the population for many centuries. It is important to take this into account when acknowledging the negative aspects of westernization, i.e., increased animal product intake, refined food consumption and less physical activity. Plant-based diets are known to be more nutritious, complementary to South Asian metabolism and protective against the majority of cardiometabolic diseases.

Enhance Bile Acid Production. Increased bile acid secretion can theoretically serve to lower ApoB in the gut and improve overall fat metabolism^[33]. Bitter foods with their unique flavonoids are known to enhance bile acid production and reduce ApoB levels^[34]. Specific flavonoids that have been studied for these properties include naringenin, resveratrol, quercetin and puerarin^[35]. Foods rich in these bitter flavonoids include citrus fruits, herbs, dark green leafy vegetables, coffee and herbal teas. Many other fruits and vegetables contain these nutrients in variable quantities too.

Eat the Right Fats. HDL cholesterol production can be encouraged by consuming healthy fats in the correct ratios:

• Mono- and poly- unsaturated fats derived from vegetables are the best for enhancing HDL. Olive oil, coconut oil, avocado oil, grapeseed oil, sesame oil and many nut oils (excl. ground nut oil) being some of the healthier varieties. These also contain helpful fatty nutrients such as Vitamin E which support cardiovascular health. Vegetable oils farmed with a high degree of chemical pesticides are not recommended, as these can interfere with overall liver metabolism.
• Omega-3 fats are also important to consider for regulating not only HDL but for overall fat and glucose metabolism as well. These can be found in fish, seafood and some nuts and seeds, such as chia seeds, flaxseeds and walnuts.

The Microbiome in Fat Metabolism. For where the human genome falls short, the body often farms out genes from the microbial library in the gut, which outnumbers our human genes by 10 to 1. Studies show that maintaining a healthy gut microbiome can effectively lower ApoB and increase both ApoA-1 and HDL production in the liver of mice and in human liver cells. While preliminary, these studies add to a large body of evidence that highlights how the microbiome is intricately involved in regulating fat and cholesterol metabolism through producing helpful metabolites and signals.^[36]

Maintain Gut Health. Eating a balanced diet abundant in a variety of unrefined plant-based foods already goes a long way towards regulating the microbiome for optimal metabolism. These foods feed the right bacteria with plenty of fiber and nutrients; while additives, chemicals, antibiotics, and diets low in fiber typically serve to kill them off. Small amounts of probiotic foods daily are useful for maintaining a healthy gut ecology. These include vinegar, yoghurt, lacto-fermented vegetable condiments and fermented beverages such as kombucha.

2. Use Your Extra Energy

As explained previously, lifestyle, dietary and genetic factors predispose many South Asians towards having extra available energy at their disposal. If not put to good use, it can promote the progression of metabolic conditions. It’s best to make use of the energy through exercising!

South Asian Exercise Requirements. It is largely recommended in the US and elsewhere that “everyone” needs at least 150mins per week of moderate intensity exercise to remain healthy. Some research indicates that this may not be enough for South Asians who have a higher net energy balance (often stored in abdominal fat). After adjusting for the extra energy, it seems more appropriate for South Asian individuals to engage in at least 266mins of moderate intensity exercise per week.^[37]

Focus on Protein. Following on from consuming a balanced plant-based diet, some studies suggest that South Asians can benefit from increasing protein intake for weight loss^[38]. When sufficient protein is coupled with adequate physical activity, fat can be transformed into muscle and serve to balance the equation. Plant-based proteins are easier to digest and are far more compatible with South Asian ancestral trends.

3. Set Your Rhythm

Our cells follow a set rhythm every day, known as our circadian rhythm. Just like a busy work schedule, this biological clock governs all cellular processes, ensuring that everything runs smoothly without any clashes.^[39]

At various times of the day and night, specific hormones and other factors are produced in response to light, metabolic processes and our activities. When our rhythm is disrupted, our cells battle to know what and when to perform, which often leads to metabolic congestion and the misfiring of cellular signals.

There are a few very important factors that help to regulate circadian rhythm:

• Daily Routine. Maintaining a consistent daily routine gives your body a structure to work from. Once set, your cells will be adapted to performing in accordance with your routine, which extends to your energy requirements for being able to carry out your day. This can help balance one’s metabolism, especially if a balanced diet and exercise regimen is part of your daily schedule.
• Day Time Eating. Due to the connection between eating, replenishing energy stores and metabolism, when we eat weighs substantially on our metabolic clock. As a species active during the day, we ought to consume our food to sustain energy levels during the day, when it’s most needed. Studies confirm that night-time eating increases the risk for metabolic diseases and conditions due to its impact on the metabolism during a time that should be reserved for rest.
• Consistent Eating Patterns. Consistent daily meal times are important for optimizing metabolism and streamlining energy production and use. Food that covers our nutritional (and energy) requirements is also better for coordinating our bio clock and maintaining a stable metabolism.
• Light Exposure. Light is one of the key regulators of the circadian clock. It instructs the body to wake up at the beginning of the day, remain active during the day and wind down towards the end of the day when it gets dark. If we don’t get enough natural light during the day, it can cause us to feel more tired and interfere with our ability to get proper sleep. Likewise, having too much artificial light at night can interfere with the body’s ability to tone down the metabolism and prepare for sleep. Make sure to get at least some natural light every day, especially in the morning and late afternoon, if not throughout the day.
• Sleep Hygiene. Following on from light exposure, sleep hygiene is about ensuring that you optimize your routine for a good night of rest. This means consuming little food in the 2-3 hours before sleeping, avoiding stimulants (including very bright lights), relaxing in the hour before sleep and adjusting to a dimmer light environment. Sleeping at the same or similar time every night is also helpful in stabilizing your rhythm. All these things tend to promote better sleep in the absence of a sleep disorder.
• Stress Management. Stress is one factor that can disrupt our rhythm at any given time. When we stress, it causes the metabolism to undergo a major shift that uses a lot of energy to sustain. This typically lends itself to disrupted eating patterns, avoiding people and light, poor sleep quality, and turning one’s routine upside down. If one is facing major stress on a daily basis, it’s vital to incorporate wholesome techniques to manage it that do not detract from one’s health. Make time for hobbies that you find relaxing during your day, and don’t forget to take breaks and breathe! It also helps to develop a positive mindset about stress, as sometimes relief is just one thought away.

When It’s Best to See a Doctor

The prevalence of heart disease, heart attacks and diabetes among South Asians is rising, especially in younger individuals. At the same time, diagnostics are tailored towards Caucasian populations and may interfere with early detection, especially in South Asians living abroad. In light of this, it can be difficult to know when to see a doctor about cardiometabolic concerns as a South Asian individual.

If you carry excess fat, it need not be a cause for concern. We recommend learning about the signs and symptoms of diabetes and CAD, as well as following the tips in this article to optimize your metabolism. Nutritionists, lifestyle coaching and a personal trainer may all come in handy if you battle in any of these areas.

If you lead a healthy lifestyle and can still recognize symptoms, then it’s a good idea to have them checked out by a doctor. At Mya Care, finding a world-class physician is as simple as making a profile and doing a quick search!

Conclusion

Premature heart attack, diabetes and heart disease rates are on the rise in the South Asian population. A closer look at the data reveals that South Asians are not as affected by most of the usual risk factors, tending rather to have an underlying genetic vulnerability. Genetic differences in metabolism are now known to affect fat metabolism in South Asians, with the prevalence of ancestral dyslipidemia being one of the most common starting points for South Asian metabolic diseases. This is thought to have arisen from historical periods of starvation or an adaptation to increase heat tolerance.

South Asians with this metabolic profile can work with their genetic vulnerability by leading a healthy, physically active lifestyle. Consuming a balanced plant-based diet that emphasizes protein and engaging in at least 266mins of moderate exercise per week, is likely sufficient for maintaining optimal health in this population. However, if symptoms persist, it is important to seek a doctor familiar with the South Asian body type.

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