Coronary artery disease is the most common non-communicable disease in Malaysia and the No. 1 cause of death of patients admitted to public hospitals. For patients surviving admission, compliance to guideline-directed medical therapy is priority. At the same time, aggressive lifestyle modifications including dietary modifications, exercise and weight control become part and parcel of the addictive treatment.
Nutritional advice is perhaps among the most commonly-asked queries by patients with cardiovascular disease. In the same vein, primary care physicians and cardiologists often ask: “What diet should we order for our inpatient with atherosclerosis?” Clearly, the general public believes that we are what we eat. It is not surprising therefore, that in our society with its abundant supply of cheap, high-calorie food, this is a subject of consummate interest.
Saturated fat: a culprit?
There is little doubt that the westernisation of diet is closely related to the development of atherosclerosis. The mechanism leading to atherosclerosis, or hardening of the arteries, involves other factors such as diabetes mellitus, hypertension, smoking and elevated blood levels of cholesterol or fat, in part related to the quantity and quality of dietary fat. Large amounts of saturated fat combined with obesity predict elevated blood lipids levels and a high chance of developing atherosclerotic vascular disease, which leads to strokes and heart attacks.
Over the last decade, population studies and animal experiments have supported that a westernised diet rich in saturated lipids was a major risk factor leading to atherosclerosis, strokes and myocardial infarction. When the relationship between diet and atherosclerosis was first understood, concerted effort was focused on recommending a diet low in saturated fat and cholesterol in patients with elevated blood lipids and those with a family history of coronary heart disease. Later trials demonstrated that it was the degree of saturated fat more than the amount of cholesterol that led to atherosclerosis. The amount of dietary cholesterol was shown to play only a minor role in the development of atherosclerotic arterial disease.
Debate continues as to how much saturated fat should be restricted in the diet, with recommendations ranging from moderate (20-30% of total calories as saturated fat) to marked restrictions (5-10% of total calories). It is difficult to prove that lowering saturated fat reduces stroke and heart attacks because of the challenging nature of human trials involving restricted diets.
Nonetheless, trials performed in the last 30 years involving highly-effective lipid lowering agents, for example statins, fibrates and high doses of niacin have convinced physicians that lowering lipids levels in the blood is an effective strategy for reducing heart attacks and death from vascular disease.
Many trials have proven that lowering low-density cholesterol (‘bad cholesterol’) and/or elevating HDL (‘good cholesterol’) results in marked clinical benefits. Clinical hard endpoints like death, heart attack and stokes can be significantly reduced with these lipid-lowering agents.
Following strictly-designed dietary recommendations will promote a heart-healthy lifestyle that seeks to minimise atherosclerotic vascular diseases. Drug therapy combined with dietary guidelines such as a low intake of saturated fat will lower blood lipids levels. Controversies remain among experts, however, to how strict a diet for individuals with established vascular disease or those at risk of vascular disease should be.
The Mediterranean diet, which was used in the Lyon Diet Heart Disease trial, is one such recommendation. This trial grew out of an observation termed the French paradox. Citizens living in the southern part of France close to the Mediterranean Ocean appeared to have significantly lower incidences of coronary artery disease-related deaths compared to those living in northern France.
In the trial, two groups of matched patients with established atherosclerotic coronary artery disease were compared. One cohort consumed the standard northern French diet rich in saturated fat and the comparator ate a Mediterranean diet rich in fruits, seafood, vegetables and olive oil. Both groups drank alcoholic beverages, usually wine; however, the consumption of wine was higher in the Mediterranean group. Interestingly, the patients following the Mediterranean diet were found to have markedly fewer heart attacks compared with their northern French counterparts.
The Atkins Diet
The second diet recommendation is the so-called Atkins-weight reducing diet. This diet is low in carbohydrates and high in fat. Trials have repeatedly documented that eating food rich in simple carbohydrates like white flour, white rice, sugar, pasta, and potatoes lead to a sudden rapid rise in blood sugar, which results in vigorous insulin secretion from the pancreas into the blood stream. This endogenous insulin wave causes blood sugar levels to fall quickly, stimulating an individual’s appetite and resulting in increased food consumption.
Clinical data show that a diet low in carbohydrates and rich in fat produces a chemical state known as ketosis, which tends to suppress satiety in individuals following a low-carbohydrate and fat/protein-rich diet. This has resulted in some individuals losing an impressive amount of weight. On the contrary, other data show that the fat-rich Atkins diet can lead to increased blood lipids levels harmful to blood vessels. Eventually, individuals who lose weight on the Atkins diet will lower their blood lipids levels, too.
Cut back on saturated fat
A third diet often used by individuals with established atherosclerotic disease is the well-established AHA restricted saturated fat diet. The individual restricts the amount of fat, but continues to eat moderate amount of carbohydrates and other fats e.g. monounsaturated oils from olive oil and polyunsaturated fats from canola oil. This diet features seafood and vegetarian sources of protein, thus leading to calorie control. It also emphasises multiple portions of fruit and vegetables in daily food consumption.
What is the best diet for patients with coronary vascular disease? In my opinion, the major precepts of a heart-healthy diet are as follow:
- Markedly reduce simple carbohydrates such as white rice, white flour, pasta, sugar, breads and potatoes. If weight is not a problem, moderate amounts of simple carbohydrates are allowed.
- Encourage food rich in complex carbohydrates such as beans, whole-grain and nuts. These raise blood sugar slowly compared to simple carbohydrates and also slow the pace of insulin secreted from the pancreas and smoothen the fall of blood sugar levels.
- Eliminate or abstain from food rich in animal fat like beef, lamb and pork. Emphasise lean cuts if you must eat red meat, and choose broiling or baking rather than frying.
- Encourage moderate amounts of olive or peanut oil. These oils are monounsaturated and clinically seem to have beneficial effects on blood lipid levels. Other favourable oils such as oil-palm and canola oil are also encouraged. Trans-fatty acid, the so-called hydrogenated or partially hydrogenated fats, is strongly discouraged. They are commonly found in commercially-available baked goods and margarines.
- Encourage liberal amounts of fruit and vegetables. Take at least six to nine daily portions of fruits and/or vegetables as recommended by most nutritionists.
- Eat seafood as the main source of protein. Seafood is an excellent dietary choice and should be preferred over red or white meat. Care must be exercised when eating some shellfish, however, as they contain cholesterol-like substances. White meat from chicken and turkey is preferred over red meat from beef, lamb and pork.
- Bean curd products like tofu are highly recommended sources of protein and complex carbohydrates.
- Foods containing sugar or corn syrup should be avoided in large quantities. These can lead to a sudden, rapid rise in blood sugar resulting from vigorous insulin secretion in the pancreas when stimulating appetite.
- Try as much as possible to eat vegetarian food.
- I am a strong advocate of daily exercise, which improves cardiovascular health as well as diabetic and hypertension control. Individuals should exercise for 30 minutes or more daily. Walking, jogging, swimming, rowing and cycling are ideal, as is some form of weight training performed two to three times weekly for approximately 30 minutes. If you have yet to exercise habitually, it would be prudent to consult your physician or a trainer before initiating an exercise programme.
With these simple dietary and lifestyle modifications, you hopefully can enjoy a healthy life based on the knowledge available today.