Tuesday, April 22, 2008

Eggs related to mortality, more so in diabetics


The Confusion

According to the Heart and Stroke Foundation of Canada, “Most people can eat eggs in moderation without concern for any harmful effects on blood cholesterol. However, those with high blood cholesterol, are advised to limit their intake of eggs to two per week”.

But wasn’t the recommendation to reduce egg intake to less than 4 a week? Or was it 2 a week? Or was it "an egg a day is ok"?

The egg recommendations keep changing and the research behind the effects of eggs on our health is as confusing.

Cholesterol in our Food and in our Blood

Eggs have more cholesterol than any other single food- all of it in its yolk. The white has no cholesterol. There's around ~210mg cholesterol per egg.

It’s true that saturated and trans fats increase blood cholesterol to a greater extent than cholesterol found in foods, but dietary cholesterol still plays an important role and shouldn’t be dismissed.

Our body makes cholesterol naturally, so we actually don’t need to get any from our diet. But we do. Foods from animal sources have cholesterol- like egg yolks, meat, poultry, milk, dairy products…

The Scientific committee behind the 2004 Dietary Guidelines for Americans said: “the relationship between cholesterol intake and cholesterol concentration is direct and progressive, increasing the risk of coronary heart disease”.

According to the American Heart Association, the average man consumes 337mg cholesterol a day and the average woman, 217mg. The American Heart Association and The Heart and Stroke Foundation of Canada recommends limiting cholesterol to less than 300mg.day, less than 200mg if you’ve had a heart attack or stroke, if you have diabetes and if you have high LDL (bad) cholesterol.

Now, it gets a bit confusing because the amount of cholesterol in your blood doesn’t necessarily reflect the amount of cholesterol you’re eating. Saturated and trans fats increase your blood cholesterol level more effectively than cholesterol in food. Moreover, unsaturated fats, fibre found in fruits, vegetables, lentils and whole grains help lower cholesterol levels. Exercise also helps lower your bad cholesterol (but helps increase your good HDL cholesterol). When researchers study the effect of eggs on blood cholesterol, they need to be taking all these other factors into account… not very easy to do!
On top of that, some people can eat a lot of cholesterol with no effect on their blood cholesterol- others are not so lucky!

The Research

A recent study published in the American Journal of Clinical Nutrition looked at egg intake of 21 327 men from the Physicians’ Health Study, excluding those that had a history of heart disease, heart attack, stroke, cancer and other serious health problems.
Egg intake was self-reported at baseline, 2 years, 4 years, 6 years. 8 years and 10 years.
Average egg consumption was 1 egg a week.
Egg consumption of up to 6 eggs a week was not associated with increased risk of death but, compared with those that ate eggs less than 1 time a week, those that at eggs more than 7 times a week had a 22% greater risk of death (excluding those that had diabetes and after adjusting for confounders).
Risk of death when diabetes was present was 100% (2 times) greater for those that ate more eggs!

Unfortunately, this study didn’t collect much dietary information, including intake of saturated fat, trans fats, fibre (fruits, veggies, whole grains), fish, unsaturated fats- all factors that could influence blood cholesterol levels and mortality.

However, this isn’t the first study to report an increased risk for diabetics that eat eggs.

Harvard investigators looked at egg consumption of 120 000 people and found that those that ate up to one egg a day had no increase in risk of heart disease or stroke. However, those with diabetes doubled their risk of heart disease with one or more egg/day.

A 1999 study published in JAMA showed a 2 time greater risk of heart disease with consumption of more than 1 egg a week compared to less than 1 egg a week in 37851 diabetic men from the Health Professionals Follow-up Study.

Explanation

It’s known that type 1 diabetics absorb more cholesterol but this has not yet been shown in type 2 diabetics. Nonetheless, it can be assumed that dietary cholesterol leads to a less favourable lipid profile in diabetics- meaning that when they eat foods that have cholesterol, it has more of an effect on their blood cholesterol, increasing their bad or "lousy" LDL cholesterol, than for non-diabetics.

Bottom line

If you must have eggs with the yolks, eat them in moderation, ideally less than 4 a week. If you do eat an egg a day, be careful to reduce your intake of other cholesterol-containing foods (foods made with eggs, meat, dairy, etc.)
If you have diabetes, limit your egg intake even more.

Sources:
http://ww1.heartandstroke.ca/Page.asp?PageID=1562&ArticleID=1363&Src=&From=SubCategory#what_if_high
http://www.americanheart.org/presenter.jhtml?identifier=4488
Djoussé, L; Gaziano, JM. Egg consumption in relation to cardiovascular disease and mortality: the Physicians Health Study. Am J Clin Nutr 2008. 87:964-69.
Eckel, RH. Egg consumption in relation to cardiovascular disease and mortality: the story gets more complex.
Nestle, M. What to Eat. North Point Press 2006.
Willett, WC. Eat, Drink and Be Healthy: The Harvard Medical School Guide to Healthy Eating. Free Press 2005.

2 comments:

nc said...

I have an egg question. If you only eat the egg white of an omega 3 egg, will you reap the benefit????

Sybil Hebert, RD said...

Thanks for the egg question nc.
Omega 3 is found entirely in the yolk. So, if you eat just the white of an omega 3 egg, you're not getting any of the omega 3.

However, on the market now are liquid eggs that contain pasteurized egg whites and a small amount of pasteurized egg yolk. (four tablespoons (50 ml) is equivalent to one large egg).
These products usually contain ~80%less cholesterol than a regular egg.
Some of these liquid eggs have either fish oil or algal oil added to them so they are a source of DHA omega 3.
Examples are Naturegg Break-Free Omega 3 from Burnbrae Farms and Gold Circle Farm's DHA Omega 3 liquid eggs.

http://www.cholesterol-and-health.com/Egg_Yolk.html

lesliebeck.com

http://www.goldcirclefarms.com/news/jan2005.html

http://www.burnbraefarms.com/consumer/our_products/liquid_bf_omega.htm