Cholesterol and Fat

I had a conversation with a friend last night about milk and how I like organic whole milk in comparison to skim milk. She was stunned that as a trainer I advocate the higher fat version of milk. However, I stick to my guns because the whole milk is more natural, has less added sugar and less refinement. Besides the milk fat and protein (casein and whey) is good for you. The discussion took a turn when she said what about clogging your arteries? Well let's look at the role of fat intake, cholesterol, and "clogging" our arteries. Here goes....

Let's begin with cholesterol. There is an overall fear of it in America and westernized countries, that we need to control our cholesterol levels, and the dogma seems to be that lower is better. I have to disagree, but let's save that for later. First, what is cholesterol? Cholesterol is a solid alcohol (not that kind) chemical that is soapy to the touch. Only a small percentage (around 7%) is circulated in the blood, the other 90-something percent is stored in every cell of the body as one of the constituents of the cells membranes (the things that regulate the flux of nutrients and hormones in and out of the cell, basically the liner of the cell). Also, cholesterol is used to make hormones, literally the building blocks. These hormones are involved in blood pressure, sex hormones (testosterone and estradiol), etc. If there is a lack of cholesterol you could test pathologically low for sex steroids (not good if you like a normal sex life, sex characteristics, and normal moods). Furthermore, cholesterol is involved in brain and peripheral nervous system development among other things. At any rate, the bottom line is we need cholesterol to do a bunch of things, and lowering it to extreme levels would not be advantageous to chasing health. What about cholesterol and it's respect to food intake? Well it's a lot smaller than we think. Read on....

Only a fraction of the cholesterol in our body comes from dietary intake (~15-20%), and the rest is produced by the body (mainly the liver, but also the intestines and skin). What's more, if you decrease your cholesterol and cholesterol stimulating foodstuffs intake, your body will just rev up the cholesterol production to meet its needs, and if you eat more cholesterol/cholesterol producing foodstuffs your body will ramp down the production. In people with very high cholesterol levels (over 220-250ng/dL or similar) simply eating less cholesterol will not warrant a significant change. What we need to address is the internal mechanism of cholesterol production. The actual main issue with cholesterol levels, is that too high levels in the blood can cause some issues (we'll get to that later), and the body can't regulate the blood levels. Cells constantly need cholesterol for repair and regeneration, but don't always just take it from the blood, sometimes they just make their own. Also, cells don't know how much cholesterol is floating around outside that specific cell, they just know what they have. So if they need to get some cholesterol for various processes, they'll just make it, completely oblivous to any aberration in blood cholesterol levels.

So we have this cholesterol floating around, and it's usually in one of 3 forms. VLDL, LDL, and HDL. At this point, most people know that LDL is the bad cholesterol, and they carry around mostly all cholesterol molecules to body tissues. It can do one of 3 things, be removed from circulation via the liver, absorbed by tissues needing cholesterol, or be deposited in the arteries. So how do we lower LDL blood levels so none is laid down in the arteries? Well to remove as much LDL as possible we need to get them in contact with as many LDL receptors (in the liver and other tissues) as possible. Cells that need more cholesterol send receptors (LDL receptors) to the cell surface to aquire the LDLs. Then they pull them inside and remove them from the blood. So, simply enough, we just need to increase the LDL receptors in tissues to get rid of LDL in the blood. However there is another side of the equation, if we can't significantly increase LDL receptors in each cell, we need to limit the production of cholesterol inside the cell, so that at least we give ourselves a shot at scavenging LDL particles with our few LDL receptors. At the same time we start sending our LDL receptors to the cell surface, we crank up the machinery to produce cholesterol within the cell. How does this happen?

When we have our LDL receptors out trying to get LDL from the blood, we are simultaneously acruing the raw materials to make cholesterol within the cell to meet the demand. There is one enzyme that is crucial to this in-cell synthesis, and it's HMG-CoA. Most cholesterol lowering drugs (statins) reduce this enzymes activity, and thus lower cholesterol production. However, we can do this naturally, without the need for expensive drugs, side effects, and do a lot better job anyway. It should be noted, that if we slow down in-cell production of cholesterol, then we will concurrently make more LDL receptors in make up for the lag in cholesterol production. Good right?

There are certain hormones that increase HMG-CoA activity, and certain hormones that reduce or blunt its activity (what we want). Insulin, stimulates HMG-CoA activity, and glucagon blunts it. Also of importance, insulin trumps glucagon in all cases, so an increase in insulin for whatever reason means glucagon is relegated to the red headed step child. So if we can keep insulin levels low (which they are normally without ingestion of refined sugars, grains, and high starch intake) we will make a plethora of LDL receptors that will scavenge all that nasty LDL out of the blood and keep our arteries safe.

Now this is only one part of the story, what about HDL? The good cholesterol, HDL is responsible for collecting the extra cholesterol from tissues (including atery linings) and converts this extra to LDL. So you see, it's important to still be able to get rid of the LDL when HDL is normal or high. In fact, we would like to see a shift of more HDL than LDL so that the net activity is removing extra cholesterol from tissues rather than depositing it in arteries or having it circulate looking at places to deposit it.

Now, what about all this low-fat recommendation we hear and preach (and what I was talking about in the introduction)? Remember, if we lower fat, we concommitantly lower protein intake (since protein is generally associated with fat-think animal meats, milk, etc) and since you have to give to get, low fat equals high carbohydrate. Some may argue, but you have to eat something, and a diet low in fat, is high in carbohydrates, and moderate or low in protein as well. It's just a balanced equation here, let's not get too misty eyed over this.

Most studies show that a high carb, low fat diet lower LDL (which is good right?) but also lower HDL, by an even greater percentage (uh oh!). This is bad news. How are we supposed to clean up the extra cholesterol laying around with even less HDL, and our LDL is still doing its job, floating around depositing it on arteries and such (now with even more lag time until its cleaned up by the lower HDL levels)?? What about a low carb, high fat diet (and higher protein, naturally)? We see an overall lowering of total cholesterol (although slightly less than a low fat diet), but a greater reduction in LDL cholesterol percentage-wise, and an INCREASE in HDL! So while low fat diets offer a lowering of LDL and HDL, we get the best of both worlds with low carb diets which offer a lowering of LDL and an increase in HDL. This is ultimately what will help people stave off the effects of high cholesterol (atherogenic plaques, circulatory obstructions, etc).

So the gist of it is this, high fat, high cholesterol diets won't in and of themselves make you have clogged arteries. If your carbs are restricted (say under 120g a day), and you don't have a metabolic disorder involving insulin, then your cholesterol levels will improve, and you won't have to worry about HDL, VLDL, LDL, or any other DL thing-a-ma-jig the rest of your life. So tip your glasses to whole milk....mmm mmmm good.