Research review: Eggs and cholesterol
Oh sure, he looks cute. But is the Easter Bunny carrying a basket of cholesterol-laden artery bombs? Or has he gotten a bad rap along with Humpty Dumpty?
When you talk to most people about eggs, here’s the first thing they’ll say: Eggs are full of cholesterol. The second thing they’ll say is: That’s why I don’t eat them, or That’s why I only eat the whites.
The message is clear: If you don’t want high cholesterol, don’t eat whole eggs.
Back in 1972, the American Heart Association recommended that people limit their egg intake to less than 3 a week -– yes, a week, not a day. If you want to eat eggs daily, according to the recommendation, you can safely have 0.43 of one.
Interestingly, eggs are the only food-specific dietary restriction ever suggested by the American Heart Association.
Think about that. Of all the crappy food you could possibly eat, eggs end up being restricted!
Do eggs raise blood cholesterol?
In this case, the American Heart Association made the same assumption as the people you talk to on the street: eggs are high in cholesterol; I don’t want high cholesterol; so I don’t eat eggs.
At first glance, that does seem kind of logical. Eggs are indeed high in cholesterol. They have about 235 mg per egg, which makes them one of the most abundant per-serving sources of cholesterol.
(Unless you’re a fan of eating brains; 3 ounces of cow brain provides 2635 mg of cholesterol — about ten times one egg. Probably not a huge issue if you’re not a zombie, and they’re already dead anyway.)
But does that dietary cholesterol in the egg translate to higher cholesterol — and by extension, arterial plaque buildup — in your body?
I guess it would be similar to saying that spinach is green and I don’t want to be green so I don’t eat spinach. Okay, that’s a bit of a stretch, but eggs being high in cholesterol doesn’t necessarily mean that eating eggs will increase your cholesterol.
It seems that a few proteins in eggs block the cholesterol in eggs from being completely absorbed.
How cholesterol works in the body
As a quick reminder, here’s the current model of how cholesterol works in the body.
First of all, it’s a bit of a misnomer to talk about “cholesterol levels”. In fact, what doctors usually mean by that is the levels of the transport proteins that carry cholesterol around.
You see, cholesterol is a lipid (aka fat-based), which means it’s not soluble in water. Your bloodstream is water-based.
Just like a vinaigrette, the oil-based and water-based components separate without something to either emulsify them or grab the oily bits and hang on to them.
Since injecting Dijon mustard or dish soap are both bad ideas, the body’s evolved transport proteins instead. These proteins can carry lipid-based substances around the bloodstream, getting them where they need to go.
In this case, we’re usually talking about three kinds of transport proteins: high-density lipoprotein (HDL, aka “good cholesterol”); low-density lipoprotein (LDL, aka one of the “bad cholesterols”); and very low-density lipoprotein (VLDL, the second so-called baddie).
When we say “high cholesterol” we usually mean high levels of the bad stuff, and often low levels of the good stuff.
Recently, researchers have discovered that the bigger culprits in raising “bad” cholesterol levels are trans fats (of which eggs have nearly 0g/egg) and saturated fats (of which eggs have 1.5g/egg).
In other words, eggs are actually low in the substances that do cause problems.
Meanwhile, eggs are a relatively cheap and good source of protein and eggs may help you lose weight.
In a recent study, eggs have also been shown to enhance weight loss when used with a calorie restricted diet — meaning that people who both reduced their calories and ate 2 eggs a day lost more weight (65% more weight loss & 16% more bodyfat lost ) than people who just reduced calories.
The study I review this week looks at the effects of eating one egg a day on cholesterol levels, among other blood measures. They also compare “regular” eggs and eggs with omega-3s – so you know whether the extra money for the omega-3 eggs is worth it.
Ohman M, Akerfeldt T, Nilsson I, Rosen C, Hansson LO, Carlsson M, Larsson A. Biochemical effects of consumption of eggs containing omega-3 polyunsaturated fatty acids. Ups J Med Sci. 2008;113(3):315-23.
The study examined 19 volunteers: 8 males and 11 females -– not a huge group, but not bad either. The volunteers were all over 45 years old, healthy and taking no medication that could affect blood lipids. They were also not allowed to take any estrogens, non-steroidal anti-inflammatories (NSAIDs), statins, fibrates or steroids (except inhaled).
For the study, half the volunteers (randomly assigned) ate one “regular” egg each day for a month and the other half ate one omega-3 enriched egg a day for a month.
After a month, the groups were switched: Group 1 ate the omega-3 eggs and Group 2 ate the regular eggs, again for a month. Besides the egg requirement, the volunteers could eat whatever they wanted.
Before we get into what happened to the volunteers it’s important to understand what the omega-3 enriched eggs are, and how they are different from regular eggs. Omega-3 eggs are often produced by feeding hens with something like flax seed; or in this case, with rapeseed (canola is a type of rapeseed oil).
What’s interesting is that there are indeed more omega-3 fatty acids in these eggs compared to regular eggs, but there are also less omega-6 fatty acids than in regular eggs.
Table 1: Omega-3 and omega-6 fatty acid content in eggs
||Alpha-linolenic acid (ALA)||Eicosapentaenoic acid (EPA)||Docosahexaenoic acid (DHA)|
||Arachidonic acid (AA)||Linoleic acid (LA)|
Here are all the things the researchers measured:
- Apolipoprotein A1 (ApoA1)
- ApoB lipoprotein
- Cystatin C
- C-reactive protein
- Total cholesterol
- High density lipid (HDL) cholesterol
- Low density lipid (LDL) cholesterol
- Serum amyloid A
And the exciting conclusion? Nothing!
After one month of eating one regular egg a day there were no changes in any of the things tested. This includes no change in ApoA1, total cholesterol, HDL nor LDL.
Now, before you ask “What is the point of a study that showed nothing?” remember the Seinfeld Principle: Talking about nothing is actually kind of interesting, especially when you do expect to find something.
(After all, wasn’t it interesting when no weapons of mass destruction were found when people went looking for them?) Sometimes, in science, finding nothing or no change is actually quite significant.
Okay, now that’s out of the way, what happened with the omega-3 eggs? Well, there was an increase in ApoA1, a decrease in ApoB/ApoA1 ratio and a decrease in plasma glucose and serum amyloid A.
Oh and by the way, just to make sure everybody was eating their eggs, they checked omega-3 levels in the blood (ALA) and omega-6 levels (arachidonic acid).
Omega-3s were up in the group eating omega-3 eggs and omega-6 went up in the group eating regular eggs (see Table 1.)
There were no changes in total cholesterol or triglycerides in either egg group. Thus it seems that eating one egg per day for a month will not affect your cholesterol or triglycerides negatively, regardless of what type of egg.
The increase in ApoA1 and the decrease in ApoB/ApoA1 ratio in the omega-3 egg group is a very good thing. ApoA1 and ApoB/ApoA1 ratio seem to be better indicators of cardiovascular disease than total cholesterol, HDL or LDL (2-4).
After a month of eating Omega-3 eggs there was no change in cholesterol but positive changes in ApoA1 levels and ApoB/ApoA1 ratios. This means that the omega-3 eggs seem to be improving cardiovascular health!
One other positive benefit from omega-3 egg consumption was that blood plasma glucose was lowered. In diabetics, lower blood glucose could be helpful.
When we consider these findings together, we can see that there are two key messages:
- Eggs in general don’t seem to have a negative effect on any of the blood measures surveyed. That means no increase in bad cholesterol or decrease in good cholesterol.
- Omega-3 eggs, however, seem to have a beneficial effect since they improve key blood proteins that are indicators of cardiovascular disease and decrease blood glucose.
Fantastic! I haven’t been wasting my money on omega-3 eggs all these years. And the evidence from this study shows that Humpty Dumpty was indeed framed.
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