Egg yolks contain a rich array of essential vitamins and
minerals, particularly vitamins A, D, E, B12 and K, riboflavin, folate and
iron, while the whites are a great source of low-calorie protein. The nutrients
in eggs also have some interesting specific benefits. For example, a new study
found that the Vitamin D in egg yolks might be particularly good for diabetics.
People with diabetes often have Vitamin D deficiencies, and the form of Vitamin
D in eggs could be particularly beneficial. Apart from this eggs contain Omega
3 fats and antioxidants.
The egg’s tarnished reputation comes from the cholesterol
the yolk contains. I early seventies, the American Heart Association began
urging us to cut down on our egg consumption as a means of protecting against
heart disease, which is associated with increased cholesterol levels. Then, in
2000, the AHA revised its dietary
guidelines and gave healthy adults the green light to enjoy eggs once again.
The AHA's guidelines now allow an egg a day for healthy adults while still
advising a total daily cholesterol limit of 300 mg.
What is cholesterol?
Cholesterol is
a type of lipid molecule, and is biosynthesized
by all animal cells, because it is an essential structural component of all animal
cell membranes; essential to maintain both membrane structural integrity and fluidity.
Cholesterol enables animal cells to dispense with a cell wall, thereby allowing
animal cells to change shape rapidly and animals to move.
In addition to its
importance for animal cell structure, cholesterol also serves as a precursor
for the biosynthesis of steroid hormones, bile acid, and vitamin D. Cholesterol
is the principal sterol synthesized by all animals. In vertebrates, hepatic
cells typically produce the greatest amounts.
A human male weighing 68 kg normally synthesizes about
1,000 mg per day, and his body contains about 35000 mg, mostly contained
within the cell membranes. Most ingested
cholesterol is esterified, and esterified cholesterol is poorly absorbed. The
body also compensates for any absorption of additional cholesterol by reducing
cholesterol synthesis. For these
reasons, cholesterol in food, seven to ten hours after ingestion, has little,
if any effect on concentrations of cholesterol in the blood. Cholesterol is
recycled in the body. The liver excretes it in a non-esterified form (via bile)
into the digestive tract. Typically, about 50% of the excreted cholesterol is
reabsorbed by the small intestine back into the bloodstream.
The liver excretes cholesterol into biliary fluids, which is
then stored in the gallbladder. Bile contains bile salts, which solubilize fats
in the digestive tract and aid in the intestinal absorption of fat molecules as
well as the fat-soluble vitamins, A, D, E, and K. Within cells, cholesterol is
also a precursor molecule for several biochemical pathways. For example, it is
the precursor molecule for the synthesis of vitamin D and all steroid hormones,
including the adrenal gland hormones cortisol and aldosterone, as well as the
sex hormones progesterone, estrogens, and testosterone, and their derivatives.
Major
dietary sources of cholesterol include cheese, egg yolks, beef, pork, poultry,
fish, and shrimp. Human breast milk also contains significant quantities of
cholesterol.
Egg Facts
Normal
size egg may weigh about 50 grams, which gives 75 calories, 150mg cholesterol,
65 mg sodium, 62 mg potassium, 1 gm Carbohydrates and 6 gm proteins. Apart from
this it gives 5% of daily requirement of Vitamin A, 11% of Vitamin D, 10% of
Vitamin B12, 3% of Vitamin B6, 3% of calcium, 4% of iron and 1% of magnesium.
Per cent Daily Values are based on a 2,000 calorie diet. Your daily values may
be higher or lower depending on your calorie needs. An egg contains
about 5 grams of fat which may be in the form of 1.5 gm of saturated fat, 0.7
gm of polyunsaturated fat and 2.8 gm of monounsaturated fat.
The egg is a powerhouse of disease-fighting nutrients like lutein
and zeaxanthin. These carotenoids may reduce the risk of age-related macular
degeneration, the leading cause of blindness in older adults. And brain
development and memory may be enhanced by the choline content of eggs.
Heart diseases and cholesterol
When scientists learned that high blood cholesterol was
associated with heart disease, foods high in cholesterol logically became
suspect. But after 25 years of study, it has become evident that cholesterol in
food is not the culprit. But saturated fat has a much bigger effect on blood
cholesterol. Full-fat dairy products and fatty meats are examples of foods that
are loaded with saturated fat and which trigger the body to produce
cholesterol. An egg contains as low as 1.5 grams of saturated fat whereas 50
grams of chicken is loaded with 2 gms of saturated fat and 50 gms beef with
3gms of saturated fat.



