Saturday, January 22, 2011

The Incredible, Egg Yolk

Yolks are good for you

Egg yolks? But they're full of cholesterol!

I'm sure you've heard it before. When you think of a "health freak," you don't think of someone eating egg yolks and discarding the white.

Think again.

Egg Nutrition: Yolk vs. White

Egg yolks are indeed full of cholesterol. Like most cholesterol-rich foods, they are jam-packed full of important nutrients, especially the fat-soluble vitamins and essential fatty acids.

In fact, the slew of nutrients in an egg yolk is so comprehensive that a few a day would offer better insurance than a multi-vitamin. Most importantly, the yolk contains most of the nutrients in an egg.

Egg whites, on the other hand, contain far fewer nutrients. The only thing that could justify their consumption is their attachment to their companion yolk.

Don't believe it? Below is a table that compares the nutritional value of egg whites and yolks, with data provided by the USDA. Also  included are the additional analysis in the last two columns that provides the percentage of the total nutrition found in the yolk and the percentage of total nutrition found in the white.

Table 1: Egg Yolks Versus Egg Whites

Nutrient White Yolk % Total in White % Total in Yolk
Protein 3.6 g 2.7g 57% 43%
Fat 0.05g 4.5g 1% 99%
Calcium 2.3 mg 21.9 mg 9.5% 90.5%
Magnesium 3.6 mg 0.85 mg 80.8% 19.2%
Iron 0.03 mg 0.4 mg 6.2% 93.8%
Phosphorus 5 mg 66.3 mg 7% 93%
Potassium 53.8 mg 18.5 mg 74.4% 25.6%
Sodium 54.8 mg 8.2 mg 87% 13%
Zinc 0.01 mg 0.4 mg 0.2% 99.8%
Copper 0.008 mg 0.013 mg 38% 62%
Manganese 0.004 mg 0.009 mg 30.8% 69.2%
Selenium 6.6 mcg 9.5 mcg 41% 59%
Thiamin 0.01 mg 0.03 mg 3.2% 96.8%
Riboflavin 0.145 mg 0.09 mg 61.7% 48.3%
Niacin 0.035 mg 0.004 mg 89.7% 9.3%
Pantothenic acid. 0.63 mg 0.51 mg 11% 89%
B6 0.002 mg 0.059 mg 3.3% 96.7%
Folate 1.3 mcg 24.8 mcg 5% 95%
B12 0.03 mcg 0.331 mcg 8.3% 91.7%
Vitamin A 0 IU 245 IU 0% 100%
Vitamin E 0 mg 0.684 mg 0% 100%
Vitamin D 0 IU 18.3 IU 0% 100%
Vitamin K 0 IU 0.119 IU 0% 100%
DHA and AA 0 94 mg 0% 100%
Carotenoids 0 mcg 21 mcg 0% 100%

As you can see from the table, the yolk contains 100% of the carotenoids, essential fatty acids, vitamins A, E, D, and K (6 items). The white does not contain 100% of any nutrient.

The yolk contains more than 90% of the calcium, iron, phosphorus, zinc, thiamin, B6, folate, and B12, and 89% of the panthothenic acid (9 items). The white does not contain more than 90% of any nutrient, but contains over 80% of the magnesium, sodium, and niacin (3 items).

The yolk contains between 50% and 80% of the copper, manganese, and selenium, while the white contains between 50% and 80% of the potassium, riboflavin, and protein.

It should also be kept in mind that the yolk of an egg is smaller than the white. Where the white contains a slim majority of nutrients, such as protein, this is not due to a greater concentration in the white, but simply to the fact that there is more white in the egg than yolk.

Finally, eggs are an excellent source of carotenoids. These are primarily highly absorbable forms of lutein and its partner zeaxanthin. These carotenoids accumulate in the back of the eye and appear to protect against age-related macular degeneration. There is no RDA for them, as researchers are still trying to understand their importance. All of the lutein and zeaxanthin in an egg is contained in the yolk

But what about the cholesterol in eggs?

Let's begin with how important cholesterol is to the human body. Cholesterol belongs to a group of fats referred to as Sterols. Chemically it is not a fat, although Sterols are found in all fats and oils especially animal fat.

The chief sources are eggs, egg yolk, liver, kidney, brain, fish oil  and oysters. It is also found in a lesser degree in meat, whole milk, cream cheese and butter. Cholesterol is commonly thought of as a poison and something to be avoided at all cost. Nonsense! This is a mistruth.

# Did you know that the majority of the dry weight of the brain is comprised of cholesterol?
# Did you have any idea that the sheath nerve endings from the top of your head to the bottom of your spine are wrapped in cholesterol?
# Did you know that cholesterol serves as a conductor for the transmission of all nerve ending throughout the body?
# Did you know that if you received even the slightest 1/4 inch cut, you would bleed to death if not for cholesterol?
# Did you know that the cholesterol found in your blood comes from two sources: cholesterol in food that you eat and cholesterol that your liver makes from other nutrients. What's interesting is that the amount of cholesterol that your liver produces varies according to how much cholesterol you eat. The more cholesterol you eat, the less your liver produces. And vice versa - the less cholesterol you eat, the more your liver produces. This is why a low cholesterol diet does not decrease a person's blood cholesterol by more than a few percent.

Cholesterol manufactures every hormone in the human body, every one of them: progesterone, estrogen, testosterone, T1, T3 by the thyroid, etc. It's a natural function of your body. Your liver manufactures cholesterol all day long. You couldn't have sex without cholesterol.

It is the very important part of fluid in the body. If you eat an egg or butter, your liver ceases to produce the same substance, cholesterol. When you don't eat eggs, butter, or cheese, your liver starts to manufacture cholesterol. If you eat vegetables, it will start to manufacture cholesterol.

So you see that your body has a check and balance, it's a very wonderful thing. The medical profession doesn't know much about it because it's nutritionally based information and medical doctors are only given 30 hours of nutritional guidance during their entire medical education.

Egg Yolks Contain Essential Fatty Acids DHA and Arachidonic Acid

One important set of nutrients that should not be overlooked is the long-chain essential fatty acids. Egg yolks contain the long-chain omega-3 fatty acid DHA, which is necessary for the brain and proper retinal function in the eye, and the long-chain omega-6 fatty acid arachidonic acid, which is required for the healthy skin, hair, libido, reproduction, growth and response to injury. These fatty acids are primarily needed by young children, pregnant and lactating women, and people with degenerative diseases involving oxidative stress, especially those of the nervous system such as Alzheimer's. While fatty fish and cod liver oil supply DHA in larger amounts, egg yolks have an advantage over these foods because they also contain arachidonic acid and because they do not contain EPA, which interferes with arachidonic acid metabolism.

According to one egg yolk contains 75 mg of arachidonic acid (AA), 20 mg of DHA, but no EPA. As I describe in my Special Report, How essential are the fatty acids? DHA and AA are the two fatty acids essential to humans and other mammals, while EPA interferes with the body's use of AA and probably does not belong in the mammalian body at all.

Animal foods from animals raised on pasture are likely much richer in DHA. In all eggs, both the DHA and AA are contained in the yolk.

To Cook, or Not to Cook? The Benefits of Raw Egg Yolks

Many people believe that the health benefits of egg yolks are greater when the yolks are consumed raw. Heat destroys enzymes, reduces the amounts of certain nutrients, and may make the amino acid cysteine less available, which is needed to synthesize the master antioxidant of the cell, glutathione.

Those who eat raw egg yolks report easier digestion, increased stamina, and resistance to illness — not to mention a quicker snack if they're on-the-go.

That said, there is little evidence beyond such anecdotes that egg yolks are truly more beneficial when consumed raw.

There is also little evidence to support the common belief that consuming raw egg yolks is dangerous.

Raw Egg Whites Contain Digestive Enzyme Inhibitors and Anti-Nutrients

Raw egg whites should not be consumed. They contain inhibitors of the digestive enzyme trypsin, which are destroyed by heat. Consuming 100 grams of raw egg white with one egg yolk compared to consuming the same food cooked was shown in one study  to reduce protein digestion from 90 percent down to 50 percent.
Raw egg whites also contain an anti-nutrient called avidin. Avidin is a glycoprotein that binds to the B vitamin biotin, preventing its absorption. Biotin is necessary for fatty acid synthesis and the maintenance of blood sugar, and is especially important during pregnancy when biotin status declines.

Residual Egg White Avidin — Cooking Does Not Fully Destroy the Anti-Nutrients

It is a myth that light cooking completely destroys the avidin.

According to a study, poaching eggs only destroys one third of the avidin while even frying leaves 30 percent of it behind.

This raises the question of whether there is a net nutritional advantage to eating any egg whites at all. Most likely, it depends on the individual person. There is controversy over whether biotin produced in the intestinal tract is absorbed — if intenstinal biotin production is indeed nutritionally important, then people whose intestinal flora are less avid producers of biotin probably need to be more concerned about the potential adverse effects of consuming egg white.

Back to the Basics: Taste!

The truth is that most satisfying meals one could make with eggs just don't taste right without both the yolk and the white. Most baked goods come out with a richer taste and a better texture when the yolks are included. Food should provide good nutrition — for which inclusion of the yolks is necessary! — but it should also taste good.

Food should be fun. It should be rewarding to cook, delicious to eat, and relaxing to indulge in.
The anti-cholesterol establishment upholds its poor theory and unjustified conclusions only to condemn us to a bland and unsatisfying diet, the cornerstone of which is "light cooking" with bland and taste-challenged "foods" like the notorious, emasculated, yolkless egg white.

Fear not.

You are now armed with the raw facts from the USDA's nutrition database that shows that missing out on the egg yolks means missing out on the nutrition in your breakfast. Take heart in this the next time you enjoy the incredible, egg yolk.

- Chris Masterjohn
Add to My Yahoo!


  1. very true bro. i started to include 2 yolks every morning in my 8 egg omlet when in the past i used to do 8 whites and 0 yolks. now i do 2 full eggs and 6 whites. very good info here and nice blog. if you like football, check me out at -- following/supporting :D

  2. This was really very interesting - I haven't eaten an egg in a few years, but if I can find a good source I might start up again. Thanks! Following, etc.

  3. that was a very informative read thank you for posting this

    your friend,