Eggs and cholesterol

[tbach24]

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Why do you care? You're like 12, you can have all the crap you want to eat.

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Well this morning I was going to go make my fried eggs for breakfast and my brother told me eggs were bad for me and since my parents were asleep/at work (I dont remember which) I was forced to ask OOT for the answer.

[Cosimo]

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The majority of serum cholesterol is produced by your own body. Your liver produces 2000 mg a day; one egg has a bit over 200g.

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Oops. Liver produces 2,000 mg, and an egg is 200 mg. An egg is 1/10th of your daily production.

[Cosimo]

omg this is long.

First: the studies that showed reduced heart disease from low-cholesterol, low-fat diets showed an increase in other diseases: strokes, cancer, suicide, and violent death. Yet these studies did ten things at once, and low cholesterol intake itself has not been correlated with heart health.

I found it amusing that trying to save yourself from heart disease would lead, instead, to suicide. [img]/images/graemlins/smile.gif[/img] The reason is that cholesterol is needed for proper function of serotonin, the feel-good neurotransmitter. Low cholesterol levels leads to aggression and depression, hence more violent deaths and suicides.

Cholesterol is found in atheriosclerotic plaques because cholesterol is good at repairing damaged artery walls. The problem isn't cholesterol, it's the damage -- which is accumulated free radical damage or vitamin C deficiency.

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Specifically watch your trans fat intake, as it not only raises your LDL (bad) cholesterol, but simultaneously reduces levels of HDL (good) cholesterol.

Margarine bad.


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I've never got a decent explanation for this, you know one?

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First, some backstory.

Cholesterol sometimes acts as a fat-transport steroid. You might be familiar with the general axiom that fat is less dense than muscle tissue (protein). When cholesterol is carrying lipids, its density goes down. When it's not carrying lipids, it's high-density. Hence HDL and LDL (high- or low-density lipoproteins, "lipid" means fat). If your LDL/HDL ratio is high, that means that there's a lot of cholesterol in your blood that is carrying fats around.

A fat molecule (fatty acid) is basically a long carbon chain with a carboxyl (COOH) at one end. A triglyceride is a glycerol with the carboxyls from three fatty acids attached to the oxygen atoms in the glycerol. (Triglycerides in the blood are not from dietary fat, though; they are formed in the liver from blood sugar.)

The carboxyl end of a fatty acid will disolve in water, while the other end (a methyl group) is hydrophobic and will instead disolve in oils. ("Oil and water don't mix.") Fatty acids are the main component in soap cuz one end bonds with dirt and oil while the other end disolves in water and carries that oil right out of your clothes.

So, back to fatty acids. You have a long carbon chain. Each carbon (except for the ends) is connected to two other carbons and two hydrogen atoms. Sometimes, two of the carbons in a chain will bind closely together (a double bond), meaning that they each drop a hydrogen. A saturated fat has its full complement of hydrogens, which means no double bonds. A mono-unsaturated fat has one double bond, and a poly-unsaturated fat has two or more double bonds. The whole 'saturated' bit just refers to whether the molecule has a full complement of hydrogen atoms.

The carbon chains of fatty acids are normally straight. When there's a double bond, a bend forms (due to electrochemical factors). The double bond can form in one of two ways: cis or trans (cis is the top one). In the cis configuration, the chain curves because the two hydrogen atoms that are dropped are dropped from the same side. In the trans configuration, the hydrogens drop from opposite sides, so there's a kink in the chain. A curving fatty acid prevents multiple molecules from packing tightly together; hence, cis fatty acids tend to be liquids (oils). Trans fatty acids are more rigid than straight chains alone, so they're solids at room temperature (fat). This liquid/solid distinction is the difference between what we call an oil and what gets called a fat.

Virtually all naturally occuring and produced unsaturated fats are in the cis configuration. Trans fats are produced either by heating cis fats or by hydrogenization (bubbling hydrogen through an oil at high temperature with a bit of trace solvent that probably also picked up some of the pesticides applied to the source seed). Note that you can't trans-ify a saturated fat.

Fatty acids can be named by the location of the first double bond (from the methyl, or omega, end). Hence, Omega-3, -6, and -9 fats. There's not a strong correlation here between good and bad; some of each are good. However, the balance between them is important because they interefere with each other in important metabolic reaction. Note that most oils have a ton of different fats in them; what differs between (say) corn oil and olive oil is which fatty acids are prevelant.

Alrighty, so trans fats are rigid. Why is that bad?

(1) Because cell membranes are formed by two phospholipid layers (a phospholipid is a triglyceride where one of the fatty acids has been replaced by a phosphate). When the membrane is rigid, it interferes with transport through the cell membrane, screwing up cell metabolism, letting the bad guys in and keeping the good guys out, mutating DNA, and all the rest.

(2) Trans fats inhibit the production of the prostoglandin-1 and -3 families of hormones, which are good guys. They fight infection, tumors, high blood pressure, and other bad stuff.

(3) Some studies suggest that trans fats are carcinogens, although the mechanism is currently unknown. This might be related to prostoglandin-2 hormones, uninhibited by trans fats; by increased free radical production caused by the trans configuration; or by the interference in cell membrane function.

Final note: until recently, trans fats were lumped in with saturated fats in research studies, hence a lot of undeserved finger-pointing at saturated fats.

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Good: dietary cholesterol, saturated fat, tropical oils (olive oil, coconut oil, palm oil).

Bad: trans fats, plant oils.