Member - Academy Of Nutrition & Dietetics. USA.
Nutrition for Cardiovascular Disease
Epidemiology
Your heart is where your life is. Alas!! Cardiovascular diseases (CVDs) are the primary cause of death globally. Around 17.5 million (31%) deaths happened in 2012 where an estimated 7.4 million were due to coronary heart disease and 6.7 million were due to stroke. The average age of death is around 80 in the developed world where death rates are declining and the average age of death is around 68 in developing countries where the death rates are increasing. For example, proportion of deaths reported in people in the age group of 35 to 64 years is 35% in India, 41% in South Africa while it is only 12% in United States and 9% in Portugal. Epidemiology evidence support dietary changes with low-nutrition foods high in fat, sugar and oil as responsible for increased CVD rates in developing countries.
Pathophysiology
Atherosclerosis
Atherosclerosis is the accumulation of fat and cholesterol in and on your artery walls (plaques), which can restrict blood flow. Plaques stay in the artery walls, can grow in a slow and controlled way into the path of blood flow or suddenly rupture clotting blood inside an artery. This causes stroke in the brain and heart attack in the heart. Plaque formation happens in the endothelium in the artery wall. Endothelium becomes dysfunctional before a plaque, but this is reversible with diet modifications and lifestyle changes. Elevated LDLs, decreased HDLs, obesity, cigarette smoking and diabetes contribute to the dysfunction. Atherosclerosis begins in childhood but symptoms show up only after narrowing restricts blood flow to various organs.
Clinical Evaluation
Electrocardiograms, treadmill tests, thallium scans, echocardiography and angiography are used to diagnose CHD. MRIs show very small lesions and are used in the follow up of atherosclerosis progression or regression following treatment.
Lipoproteins
Blood Lipids and Lipoproteins
Blood lipids are cholesterol, triglycerides and phospholipids which are transported in the blood combined with proteins. Lipoproteins are molecules made of proteins and fat. Particles with high proteins are denser and called HDLs while others are LDLs. Lipoproteins transport lipids to cells for energy and storage. Studies indicate that high serum cholesterol levels and specifically high LDL cholesterol is a leading cause of CHD, stroke and mortality.
Risk Factors and Prevention
Studies have proved that 62% of coronary events could have been avoided if healthy lifestyle and proper medication were followed.
Prevention of CHD and Stroke
CHD and stroke have common risk factors and altering these factors toward a healthy patient profile is the primary goal. Optimal lipid levels are required to prevent stroke. LDL cholesterol level of less than 70mg/dl is desirable for high-risk patients. Primary prevention of CHD should begin from childhood. Though dietary recommendations are quite liberal compared to adults, ideal body weight must be maintained in children too.
Assessing Risk
The most popular method to assess risk in asymptomatic persons is the Framingham study. You take in all the risk factors and use an algorithm to determine 10-year risk in this method. Based on the assessment, the patient is categorized under four types: very high risk, high risk, moderate risk and low risk. The other methods involve imaging tools, ankle-brachial index and coronary artery calcium score.
Markers in Blood
A normal lipoprotein profile is a total cholesterol level of less than 200mg/dl, LDL <130mg/dl, HDL>40mg/dl and triglycerides<150mg/dl. It is always safe to get a fasting lipoprotein profile done every 5 years once you reach 20 years of age.
Factors that trigger rise in LDL cholesterol include age, genetics, diet, diabetes, hypothyroidism, obesity and antihypertensive drugs. Triglyceride and HDL levels are inversely related. Diet, obesity, hypothyroidism, alcohol, diabetes and liver disease are few causes for increased triglyceride levels. Treatment for hypertriglyceridemia include: weight loss in obese patients, low fat-low cholesterol diet, decreased carb consumption, increased protein consumption, physical activity and finally quitting from smoking and restricting alcohol use. Drugs are usually prescribed for this disease when they coexist with CHD and when treatment is not effective with the above mentioned solutions.
HDL levels and CHD are inversely relation, meaning, high HDL levels are negative risk factors and low HDL levels are positive risk factors for CHD. Major contributors to increase HDL levels include exogenous estrogen, exercise, loss of excess fat and moderate consumption of alcohol. Obesity, inactivity, smoking, diet and genes lower HDL levels.
Inflammatory markers indicate the presence of atherosclerosis in patients. The outcome of diet restriction on these markers is still an issue to be resolved.
All subheadings under ‘Markers in Blood’ and third level subheading ‘Inflammatory Markers’ have been omitted.
Lifestyle Risk Factors
Cigarette smoking is the second leading factor for increased CVD risk, next to BP. Nearly 6 million people die from tobacco use or exposure to smoking, accounting for 6% of female and 12%male deaths every year. The magnitude of risk depends on the number of cigarettes smoked each day.
Physical inactivity increases risk of CHD as much as BP, smoking and hypertension. Though the importance of exercise has been stressed upon by doctors and public health services, people who follow it are minimal. Young obese children tend to lose weight when engaged in simple aerobic exercises.
Poor diet is the main environmental cause of coronary atherosclerosis. There has been a gradual increase in calorie consumption by individuals. This is due to increased portion sizes and decreased intake of fruits. Stress has also been reflected as one of the major causes of increased CVD risk.
Don’t be surprised to find that one or two glasses of alcohol is associated with reduced CHD risk. The French people experience low CVD risks in spite of their high-fat diet because of their magic potion-‘red wine’.
Related Diseases and Syndromes
Hypertension is a leading risk factor for stroke, CHD and heart failure. Treating this disease reduces the occurrence of the other mentioned diseases. Diabetes, like hypertension, is both a disease and a risk factor. People affected by diabetes have been on the rise globally, increasing the risk for CHD.
We, as humans, are getting fatter. There are 400 million obese adults and 17.6 million overweight children aged less than five years globally. The higher the BMI, greater is the risk of CHD. Ideal waist circumference is less than 35 inches for women and 40 inches for men.
Nonmodifiable Factors
Premenopausal women are at a reduced risk of CVD due to the presence of endogenous estrogen. During menopausal period total cholesterol, LDL cholesterol and triglyceride levels increase while HDL cholesterol level decreases. Age, along with gender, again is a nonmodifiable risk factor for CHD. Premature disease in men 35 to 44 years of age is thrice higher than that in women of the same age. Age 45 and above is considered a risk factor for men while women aged above 55, after menopause, are at a higher risk. Family history is another significant risk factor for CVD even when other risk factors are present.
Medical Nutrition Therapy
Medical Nutrition therapy which includes physical exercise is the best course of treatment for patients with elevated LDL cholesterol. When physicians direct a patient to visit the RD diet, exercise and weight reduction can be planned which would help the patient reach serum lipid goals. This diet and lifestyle change is possible to adapt in all people over the age of 2 years. Aim should be to increase physical activity and decrease energy intake over a time period of 3 to 6 months to achieve the required target. Increased intake of low-fat grains, legumes, fruits, vegetables and nonfat dairy food should be encouraged.
Saturated fatty acids (SFAs) should be consumed as minimal as possible because of their direct impact on LDL cholesterol. SFAs raise LDL cholesterol levels by decreasing LDL receptor synthesis and activity. Polyunsaturated fatty acids (PUFAs) and monounsaturated fatty acids (MUFAs) lower serum cholesterol levels, LDL cholesterol levels and triglyceride levels when compared to SFAs.
Research has confirmed that consuming fish rich in omega-3 fatty acids at least twice a week reduces the risk of CVD. Obesity is related to total fat consumed, which affects many risk factors for atherosclerosis. Dietary cholesterol increases total cholesterol and LDL cholesterol but to a lesser extent than SFAs.
Fiber consumption is said to lower lipid levels. But the lipid-lowering effect depends on the type of fiber food consumed. Fruits, vegetables and whole grains are highly recommended. Antioxidants like red wine, red grapes, tea, chocolate and olive oil reduce CVD risk and are recommended to be incorporated into the diet plan.
Drugs are also prescribed along with dietary treatment to get the desired effect. The big question of prescribing drugs depends on the risk category and the attainment of LDL cholesterol goal. Medical intervention in the form of surgeries is also advocated in few cases.