Category Archives: Diet and Heart Disease

Eggs and Heart Disease

The Wonderful Egg and Your Heart

photoI think eggs are wonderful. They are little balls of nutrition that can be prepared in numerous fascinating ways to make breakfast interesting and delicious. I particularly like omelets.  Alas, when I was training as a medical student the medical establishment had embraced the diet-heart hypothesis. It was felt that dietary cholesterol and fat (subsequently modified to saturated fat) by increasing levels of cholesterol in the blood (subsequently modified to raising levels of bad or LDL cholesterol) were responsible for the increasing rate of coronary heart disease that was being observed.

This certainly made sense at the time: If you eat too much cholesterol, of course it’s going to raise your blood cholesterol levels and contribute to the buildup of those nasty cholesterol plaques that would clog your arteries and give you heart attacks and strokes.

Since egg yolks contain 210 mg of cholesterol on average (more recent data suggest they only contain 184 mg/egg), eggs became a target of the dietary police.

The American Heart Association (AHA, the same organization that until recently endorsed sugar-laden cereals like Cocoa Puffs as  “heart healthy”) had decided decades ago to recommend restricting egg consumption. In 2010, AHA guidelines restricted everybody’s total cholesterol to <300 mg per day on the flimsiest of evidence.  From the AHA guidelines:

“Although there is no precise basis for selecting a target level for dietary cholesterol intake for all individuals, the AHA recommends <300 mg/d on average. By limiting cholesterol intake from foods with a high content of animal fats, individuals can also meet the dietary guidelines for saturated fat intake. This target can be readily achieved, even with periodic consumption of eggs and shellfish. As is the case with saturated fat intake, reduction in cholesterol intake to much lower levels (<200 mg/d, requiring restriction of all dietary sources of cholesterol) is advised for individuals with elevated LDL cholesterol levels, diabetes, and/or cardiovascular disease.”

The official US dietary guidelines on the topic of dietary cholesterol read as follows

“the body uses cholesterol for physiological and structural functions, but it makes more than enough for these purposes. Therefore, people do not need to eat sources of dietary cholesterol. Cholesterol is found only in animal foods. The major sources of cholesterol in the American diet include eggs and egg mixed dishes (25% of total cholesterol intake), chicken and chicken mixed dishes (12%), beef and beef mixed dishes (6%), and all types of beef burgers (5%). Cholesterol intake can be reduced by limiting the consumption of the specific foods that are high in cholesterol. Many of these major sources include foods that can be purchased or prepared in ways that limit the intake of cholesterol (e.g., using egg substitutes). Cholesterol intake by men averages about 350 mg per day, which exceeds the recommended level of less than 300 mg per day. Average cholesterol intake by women is 240 mg per day.

Dietary cholesterol has been shown to raise blood LDL cholesterol levels in some individuals. However, this effect is reduced when saturated fatty acid intake is low, and the potential negative effects of dietary cho- lesterol are relatively small compared to those of saturated and trans fatty acids. Moderate evidence shows a relationship between higher intake of cholesterol and higher risk of cardiovascular disease. Independent of other dietary factors, evidence suggests that one egg (i.e., egg yolk) per day does not result in increased blood cholesterol levels, nor does it increase the risk of cardiovascular disease in healthy people. Consuming less than 300 mg per day of cholesterol can help maintain normal blood cholesterol levels. Consuming less than 200 mg per day can further help individuals at high risk of cardiovascular disease.”

Americans were being told to severely restrict their egg consumption, especially if they had high cholesterol levels, diabetes, or heart disease. Even one egg a day seemed too much. As a cardiologist in training I dutifully took these recommendations to heart. I can’t tell you how many egg beater or egg white omelets I cooked over the next 25 years.

As more evidence accumulated, however, the bulk of the scientific evidence was coming down clearly on the side of eggs and the lack of effect of dietary cholesterol on blood cholesterol levels. As The Skeptical Cardiologist I began embracing the heresy of eating eggs, yolk and all, about two years ago.

Several large epidemiological studies have examined the association of egg consumption and serum cholesterol. The Framingham Heart Study examined the serum cholesterol in high versus low egg consumption and found no significant difference in either men or women. The association between self-reported dietary intake of eggs and serum cholesterol was examined in a population of 12,000 men in the Multiple Risk Factor Intervention Trial. Paradoxically, the men who consumed more eggs had lower serum cholesterol than those who consumed fewer eggs.In the Third National Health and Nutrition Examination Survey (NHANES III), the diets of 20,000 participants were evaluated.

“Compared to egg consumers, nonconsumers  had higher rates of inadequate intake (defined by Estimated Average Requirements (EAR) or < 70% Recommended Dietary Allowance (RDA)) for vitamin B12 (10% vs. 21%), vitamin A (16% vs. 21%), vitamin E (14% vs. 22%) and vitamin C (15% vs. 20%). After adjusting for demographic (age, gender and ethnicity) and lifestyle variables (smoking and physical activity), dietary cholesterol was not related to serum cholesterol concentration. People who reported eating > or = 4 eggs/wk had a significantly lower mean serum cholesterol concentration than those who reported eating < or = 1 egg/wk (193 mg/dL vs. 197 mg/dL, p < 0.01”

Study after study in the next 20 years showed that egg consumption was not associated with coronary heart disease and strokes. A more recent study from Spain shows no association of egg consumption on cardiovascular disease. A meta-analysis of all prospective cohort studies published in 2013 concluded that there was no association between higher egg consumption and coronary heart disease or stroke. Studies (randomized controlled trials) that  actually prove that egg consumption causes cardiovascular disease are totally lacking. Nutritional guidelines should have concluded  that there was no reason to restrict egg consumption in the vast majority of Americans.

Unfortunately, the AHA guidelines (and mainstream nutritional advisors) to this day continue to embrace the 300 mg/ day limit on cholesterol (although most other countries have dropped it). Most of my patients, having heard that eggs are bad for the heart, mistakenly try to restrict the amount they eat or eat egg whites. I see my fellow doctors in the doctors’ lounge taking boiled eggs out of the refrigerator, scooping the yolk out and eating only the egg white.

Why doesn’t more cholesterol in the diet lead to higher blood cholesterol level and subsequently to heart attacks? The answer is complicated, beyond the scope of this blog, but it illustrates how amazingly complex the body’s regulation of lipids and lipoproteins is, as well as how complicated the process of atherosclerosis is.

There are at a very basic level 3 main types of fat that doctors measure in the blood to help us gauge heart disease risk: the low density lipoprotein (LDL)  cholesterol portion or “bad”, the high-density lipoprotein (HDL) cholesterol or “good,” and the triglycerides (esterified fatty acids). On a very simplistic level, we tell patients that higher LDL levels tend to build up fatty plaques, whereas higher HDL levels can be thought of as reducing fatty plaques. When we eat an egg there is a complex reaction to the fats, proteins, sugar, and cholesterol absorbed into the blood stream.cholesterol graphic Although the LDL rises (which might increase coronary artery disease (CAD) risk), the HDL also rises (which might lower CAD risk) and there is a variable response of triglycerides. To further complicate things, each of the cholesterol fractions has  good forms and bad forms. LDL can be in a large, “fluffy” state that is not prone to promoting plaque formation or a small, dense form that does promote plaque formation. Eggs seem to promote the less atherogenic forms of both LDL and HDL. In addition, inflammation plays an important role in the process of atherosclerosis. Certain components of egg yolks may actually reduce inflammation, making plaque formation less likely.

Certain components of eggs may be beneficial and outweigh any theoretical concern about cholesterol consumption.. Eggs are the major sources of lutein and zeaxanthin, two potent anti-oxidants, which in addition to their recognized protective effects against macular degeneration and cataract formation, may also reduce LDL oxidation.

Eggs also contain choline, a nutrient that is needed for membrane formation, methylation and acetylcholine biosynthesis, which plays a major role in normal fetal development. Some studies suggest a role of choline in protecting against Alzheimer’s disease

Eating eggs may contribute to weight loss compared to eating carbohydrates. A recent study compared two different breakfasts, a bagel-based and an egg-based breakfast. During the egg period, men had a significantly lower caloric intake not only in the next meal, but also in the following 24 hours.

To make things more complicated, all eggs are not created equal. Hens that are allowed to range freely on a farm and eat grass, bugs and what might be considered their normal diet, have a different amount of omega-3 fatty acids than those that are fed grain. Given America’s current obsession with fish oil supplements (see my prior post), this makes these eggs perceived as healthier. By manipulating the diet of hens, even those stuck in cages, the omega-3 content of eggs can be increased. Is this healthier?

The limit on dietary cholesterol of 300 mg imposed by the AHA and the USDA in their guidelines, unnecessarily has my patients worrying about cholesterol in all the things that they eat. For example, there is a lot of cholesterol in shellfish. There is no evidence that eating shellfish is bad for the heart or your cholesterol profile. For example, this recent study showed no effect of eating cold water prawns on plasma cholesterol or lipoproteins.

The Bottom Line:

Eggs are an affordable (15 cents/egg) source of high quality protein and fat. Although they contain a lot of cholesterol, there is no evidence (with the possible exception of diabetics) that egg consumption is related to risk of coronary heart disease; they may in fact reduce the risk of stroke.

Since this new evidence has emerged, I regularly enjoy the deliciousness of a three egg omelet with cheese and other ingredients without guilt and I encourage my patients to do the same.photo Personally, especially in my home kitchen, I try to eat eggs that come from hens that are raised under more natural and humane circumstances as I view them as healthier than eggs from factory farms.

Not everyone is an egg lover and I’m fine with that. There is no evidence that you have to eat them. You could feel towards them as did Alfred Hitchcock :

“I’m frightened of eggs, worse than frightened, they revolt me. That white round thing without any holes … have you ever seen anything more revolting than an egg yolk breaking and spilling its yellow liquid? Blood is jolly, red. But egg yolk is yellow, revolting. I’ve never tasted it.”hitch

Milk Drinking and Your Risk For Heart Disease

In my previous post, I referenced USDA guidelines which recommend consuming dairy but only in a low-fat form. How did the mainstream nutritional community decide the American public should shift from full fat dairy to low or no fat dairy? Prior to the 1950s there was little concern in nutritional research about fat in the American diet. Beginning in the 1950s, it became apparent that heart disease, coronary artery disease (the cause of heart attacks) in particular, had become the major cause of mortality in western countries.

The American epidemiologist, Ancel Keys, became convinced in the mid 1950s that dietary fat and cholesterol were related to heart disease. In 1970 published his “Seven Countries Study” which found a correlation between per capita fat consumption and the prevalence of heart disease in seven cherry-picked countries. These kinds of studies can be useful for developing theories about which factors might cause disease, however, they cannot prove that a dietary factor causes the disease.

Messerli recently published a tongue-in-cheek analysis of the relationship between per capita chocolate consumption in a particular country and the number of Nobel Laureates produced by that same country that illuminates the weakness of this type of study.
This is the main figure from that study: Chocolate Consumption and Nobel Laureates

There is a very nice relationship demonstrated which suggests that the more chocolate consumed in a particular country, the more Nobel Laureates produced. However, no one would seriously believe that chocolate consumption causes the kind of brilliance needed to do achieve a Nobel prize. Clearly, there are confounding variables or factors. Sometimes, confounding factors are clear and can be accounted for, but often they are not clear and cannot be accounted for.

Early studies of this type demonstrated that there was a relatively strong association between the per capital supply of milk or some component of milk and heart disease mortality. In other studies, changes in gross milk production over time and changes in heart disease deaths were shown to correlate.

Despite the weakness of such studies in proving causation, as Gary Taubes pointed out ,

“the National institute of Health (NIH) had begun (by 1988) advising every American old enough to walk to restrict fat intake, and the president of the American Heart Association (AHA) had told Time magazine that if everyone went along, “we will have (atherosclerosis) conquered” by the year 2000. The Surgeon General’s Office itself had just published its 700-page landmark “Report on Nutrition and Health,” declaring fat the single most unwholesome component of the American diet.”

Such recommendations have resulted in a whole industry devoted to developing low-fat food-like substances which the public has perceived as healthier than the natural high fat original foods. Arguably, adoption of highly processed low-fat foods, which usually increase palatability by adding refined carbohydrates , sugar, or high-fructose corn syrup have contributed to America’s obesity epidemic. This, in turn through increasing obesity-associated diabetes, hypertension, and abnormal lipid profiles could have the unintended consequence of increasing heart disease.

The major focus of low-fat dietary recommendations has been to lower red meat consumption due to the high levels of saturated fat found in pork and beef. However, despite having a significantly different saturated fat composition, dairy products have been tarred with the same brush, so to speak. This has progressed to the point where, if one enters a frozen yogurt establishment (these businesses have proliferated at an alarming rate in the last few years) it is virtually impossible to find a full fat formulation of yogurt. Prominently featured are the words “no-fat” or “low-fat” with the implication that this is healthy for you. Instead of the natural fat of dairy , you have now been convinced to eat a form of dairy that has been highly processed, depleted of most nutrients and full of sugar and unrefined carbohydrates. To make up for the fat calories which might have left you more satiated without sharp peaks in blood glucose, you can substitute a whole panoply of sugary materials, chocolate, candies, or fruit.

It turns out that when the best epidemiological studies are examined in this area, the evidence suggests a protective effect of dairy on heart disease risk. Dr. Peter Elwood, a highly respected epidemiologist at the University of Wales, has consistently pointed this out based on his and other researchers’ studies.
To quote Elwood, the best epidemiological studies are “prospective cohort studies, based on data for individual subjects within a single community, with detailed attention given to confounding” variables. Such studies “give a much better basis for the examination of independent associations between food items and disease incidence than studies based on either ecological data or relationships with risk factors.”

In 2004, Elwood published a review of such studies which was published in the European Journal of Clinical nutrition. He found 10 studies worthy of inclusion. All but one study suggested that milk protects against heart disease. Those subjects consuming the most milk were less likely to have a heart attack or stroke than those consuming no milk. The relative risk for high volume milk drinkers versus those drinking no milk for “ischaemic heart disease” (this refers to coronary artery disease , the major cause of heart attacks) was 0.87. In other words, if you drank a lot of milk you were 13% less likely to have heart disease than if you drank none.

Elwood’s original research on this was called the Caerphilly Prospective Study. Between 1979 and 1983, 2500 men completed a food frequency questionnaire. During the following 21 years, the relative risk in men who drank more than a pint of milk per day, compared with the risk in men who drank no milk was 0.66 for ischemic heart disease and 0.84 for ischaemic stroke. In other words, high milk drinkers were 34% less likely to develop coronary heart disease, the major cause heart attacks.

All the studies reviewed were set up at times when reduced-fat milk was unavailable or scarce therefore the conclusion from the best available evidence in 2004 should have been that full fat dairy lowers your risk of heart attack and stroke.

For both the general public and for my cardiac patients I, therefore, differ strongly in my advice regarding dairy consumption from most published dietary guidelines. Keeping in mind that “all things in moderation” applies just as much in this area as any other, I advise full fat dairy consumption. This means that they can consume butter, milk, full-fat cheese and yogurt. I strongly advise utilizing dairy that comes from grass-fed , pasture-raised cows for reasons I will examine in subsequent posts. Each of these dairy products has a different fatty acid profile and therefore, likely a different effect on cholesterol profiles. Butter, in particular, may warrant separating out from the other dairy products because it is a very highly concentrated fat. However, since reviewing the published data on butter consumption and cardiovascular disease, I have personally gone back to fairly liberally applying butter (again, hopefully from grass-fed, pasture-raised cows) to a lot of my foods because there are few data suggesting that butter raises my risk of cardiovascular disease and the stuff tastes awesome.

Does Eating High-Fat Dairy Cause Heart Disease or Obesity

Dietary guidelines recommend the consumption of milk and dairy products as an important part of a healthy, well-balanced diet The 2010 USDA Guidelines state:
“Milk and milk products contribute many nutrients, such as calcium, vitamin D (for products fortified with vita- min D), and potassium, to the diet. Moderate evidence shows that intake of milk and milk products is linked to improved bone health, especially in children and adolescents. Moderate evidence also indicates that intake of milk and milk products is associated with a reduced risk of cardiovascular disease and type 2 diabetes and with lower blood pressure in adults.”

However, dairy fat has been portrayed as the unhealthy component of milk and dairy products, largely because it is energy dense and a rich source of saturated fatty acids . Therefore, typical dietary advice recommends fat-reduced milk and dairy products.

Shockingly, and despite expert and government-backed recommendations, the advice to change to fat-reduced or skim milk and dairy products is not supported by any prospective scientific studies.

The main reason cited for the recommendations is that the consumption of saturated fatty acids is related to an increase in total cholesterol which in turn has been related to increased coronary heart disease-the major cause of heart attacks. As we discuss this topic more, we will discover that this logic is flawed because 1) saturated fats are a diverse family of compounds with varying effects on the cholesterol profile and 2) the cholesterol profile itself is incredibly complex and simple measurements of “bad” (HDL) and “good” (LDL) cholesterol alone probably don’t tell us enough about the risk of heart disease .

Partially as a result of these guidelines, the pattern of dairy fat intake has changed considerably in the last 40 years, a time frame during which the modern obesity epidemic has developed in the United States Butter consumption has dropped considerably and low fat milk has supplanted full fat milk as the preferred product. In parallel, dairy fat consumption from other, possibly less healthy sources such as prepared foods, pizza, industrially produced margarine.

When epidemiologists have scientifically reviewed the relationship between high fat dairy consumption and heart disease or obesity, almost invariably they have found an inverse relationship. That is, the more dairy consumed, the lower the risk of heart disease and the less obesity.

In subsequent posts we’ll look in more detail at the evidence supporting dairy consumption in reducing heart disease and obesity.