For many years, egg yolks were touted as evil contributors to elevated cholesterol.
I suppose it depends on the decade, first, they’re good for you, then they’re awful for you and now back to good for you.
This is not a cut and paste the article. There’s more than enough of rampant on the internet. This article and its conclusions are based on peer-reviewed information.
First, let’s go back in time for me…
In college, I learned that eating exogenousA chemical, hormone or any other substance that is made in a lab and introduced into the body. cholesterol had minimal change in endogenousA chemical, hormone or any other substance that is made within the body, e.g., endogenous insulin is made by our pancreas whereas exogenous insulin is injected with a syringe. cholesterol. Thus, I questioned my professors about the validity of people’s concerns on yolks. They agreed, under conditions.
We’ll get to the conditional part in a moment. Remember, this is before the internet became what it is today.
Sadly, the popular media heard the word cholesterol and associated it with “bad”.
These popular beliefs were wrong though.
Altering the amount of cholesterol consumed in the diet has a very minor influence on blood cholesterol. That goes for concentrations and ratios.
I dug deeper to better understand cholesterol. The topic of my studies was primarily focused on foods effect on our body chemistry. So it was very appropriate.
Egg Yolks vs. Lean Ground Beef
Before moving forward, let’s look at the breakdown of egg yolks vs 85% lean ground beef as a comparison.
Nutritional breakdown of an average size yolk:
- Total Fat: 4.6g
- Saturated Fat: 1.7g
- Monounsaturated Fat: 2.1g
- Polyunsaturated Fat: 0.8g
- Cholesterol: 195 mg
Compare 1 oz 85% ground beef (note that we typically eat 4-6 oz ground beef at a time)
- Total Fat: 7.5g
- Breakdown varies based on cut, but the majority is saturated fat
- Cholesterol: 32mg
A Simplistic Breakdown of Cholesterol
Our liver generates the different types of cholesterol in our body. This is what we measure to test blood chemistry.
Ingested (eaten) cholesterol absorption is regulated by the intestine.
It is transported to the liver via bilea fluid produced by the liver from cholesterol that is stored in the gallbladder and aids in the digestion of fats salts.
There it is broken down in the liver. Where it is finally voided from the body through the biliary system (bile production)
The liver and intestinal wall supply 90% of the plasma cholesterol. Working on a biofeedback mechanism down-regulating cholesterol synthesis and total body cholesterol increases.
Cholesterol is not an energy-producing nutrient. It is an important precursor to many important steroids in the body, such as:
- Vitamin D
- Adrenocortical hormones
- Bile acids
- And more
The balance between saturated fats, unsaturated fats, and carbohydrates ingested (eaten) plays a very large role in our liver’s production of cholesterol ratios (HDLa high-density lipoprotein is typically referred to as “good cholesterol” and has the role of carrying cholesterol and phospholipids from the cells back to the liver to be recycled. Think of them as the trash truck heading to the dump (liver)./LDLa low-density lipoprotein that circulates the body to deliver their contents (phospholipids and cholesterol) to all the cells. Think of them as the UPS driver delivering packages (good and bad).).
This is important to note in consuming large amounts of refined carbs and saturated fats.
If you’re concerned about cholestrol
The most important factor is the combination of a high sugar/starch diet mixed with a high intake of saturated fat. This has the greatest impact on elevated (↑) LDL, decreased (↓) HDL levels and elevated triglycerides. Not the level of cholesterol present in foods.
There are a select few individuals who actually respond to dietary cholesterol. This results in elevated endogenous levels, which is a genetic factor. Having your blood chemistry analyzed can help differentiate your genetic predispositions based. There’s some of the conditional part mentioned earlier.
Metabolic chemistry is far more complicated than most of us realize. Imagine a giant “if/then tree” that changes course with every different combination of food ingested and exercise executed. Resulting in massive differences in blood chemistry.
Under what circumstances are yolks bad for you?
If you’re consuming large quantities of sugar or starch (a large percentage of the population), the saturated fat in the yolk will contribute to an increase in LDL cholesterol. So, it’s totally a mixed bag.
Remember the if/then statement previously stated in the last bullet.
Also, remember the genetic factor. These may make some individuals more sensitive to ingested cholesterol.
But before we go on, remember that one yolk has a hair less than 2 grams of saturated fat. Not enough to label it as a major contributor to endogenous cholesterol levels.
Another factor is the decline in LDL receptor activity as one ages. Creating a delayed clearance of LDL from circulation. But weight gain and diet is still a more prominent factor in the elevation of LDL cholesterol.
What dietary adjustments have the largest impact on endogenous cholesterol levels?
Apple, et al showed that replacing a high saturated fat and carbohydrate diet with a diet high in protein (mixed plant and animal) and unsaturated fats reduce triglycerides, LDL cholesterol, and blood pressure while increasing HDL cholesterol 1,2.
So eat a very small amount of carbs. Replace those calories with protein and unsaturated fats.
The Conclusion on egg yolks
Enjoy the yolks if you’re keeping your sugars and starches low. But reduce the yolks if you eat a lot of starches. Let’s be honest, you should already be keeping you sugar ingestion low anyway.
Eggs, in general, contain so many great nutrients and are a great bang for the buck.
Questions for you
Have you avoided egg yolks in the past because of what you heard?
Are egg yolks a part of your regular diet?
References on egg yolks
Appel LJ, Sacks FM, Carey VJ, Obarzanek E, Swain JF, Miller ER, Conlin PR, Erlinger TP, Rosner BA, Laranjo NM, Charleston J, McCarron P, Bishop LM, OmniHeart Collaborative Research Group FT. Effects of Protein, Monounsaturated Fat, and Carbohydrate Intake on Blood Pressure and Serum Lipids Results of the OmniHeart Randomized Trial. JAMA. 2005;294(19):2455–2464. doi:10.1001/jama.294.19.2455
McAuley, K.A., Hopkins, C.M., Smith, K.J. et al. Diabetologia (2005) 48: 8.