The LDL-Fructose Disconnect

I believe that we can all agree that the commonly obtained Friedewald LDL cholesterol (what I call "fictitious" LDL cholesterol) is wildly inaccurate. 100%--yes, 100% inaccuracy--is not at all uncommon.

This flagrant inaccuracy, unacceptable in virtually every other discipline (imagine your airplane flight to New York lands in Pittsburgh--close enough, isn't it?), is highlighted in the University of California study by Stanhope et al I discussed previously.

32 participants consumed either a diet enriched with either fructose or glucose. Compared to the effect of glucose, after 10 weeks fructose:

Increased LDL cholesterol (calculated) by 7.6%

Increased Apoprotein B (a measure of the number of LDL particles) by 24%

Increased small dense LDL by 41%

Increased oxidized LDL by 12.6%


In other words, conventional calculated LDL substantially underestimates the undesirable effects of fructose. The divergence between calculated LDL and small LDL is especially dramatic. (By the way, this same divergence applies to the studies suggesting that calculated LDL cholesterol is reduced by low fat diets--While calculated LDL may indeed be reduced, small LDL goes way up, a striking divergence.)

This is yet another reason to not rely on this "fictitious" LDL cholesterol value that, inaccuracies notwithstanding, serves as the foundation for a $27 billion per year industry.

Genetic vs. lifestyle small LDL

Let me explain what I mean by "genetic small LDL." I think it helps to illustrate with two common examples.

Ollie is 50 years old, 5 ft 10 inches tall, and weighs 253 lbs. BMI = 36.4 (obese). Starting lipoproteins (NMR):

LDL particle number 2310 nmol/L
Small LDL: 1893 nmol/L (1893/2310 = 81.9% of total, a severe small LDL pattern)


Stan is 50 years old, also, 5 ft 10 inches tall, and weighs 148 lbs. BMI = 21.3. Starting lipoproteins:

LDL particle number 1424 nmol/L
Small LDL 1288 nmol/L (1288/1424 = 90.4% of total, also severe)


Both Ollie and Stan go on the New Track Your Plaque diet and eliminate wheat, cornstarch, and sugars, while increasing oils, meats and fish, unlimited raw nuts, and vegetables. They add fish oil and vitamin D and achieve perfect levels of both. Six months later, Ollie has lost 55 lbs, Stan has lost 4 lbs. A second round of lipoproteins:

Ollie:

LDL particle number 1810 nmol/L
Small LDL: 193 nmol/L (193/1810 = 10.6% of total)


Stan:

LDL particle number 1113 nmol/L
Small LDL 729 nmool/L (729/1113 = 65.4% of total)


Ollie has reduced, nearly eliminated, small LDL through elimination of wheat, cornstarch, and sugars, along with weight loss, fish oil, and vitamin D.

Stan, beginning at a much more favorable weight, reduced both total and small LDL with the same efforts, but retains a substantial proportion (65.4%) of small LDL.

Stan's pattern is what I call "genetic small LDL." Of course, this is a presumptive designation, since we've not identified the specific gene(s) that allow this (e.g., gene for variants of cholesteryl ester transfer protein, hepatic lipase, lipoprotein lipase, and others). But it is such a sharp distinction that I am convinced that people like Stan have this persistent pattern as a genetically-determined trait.

Saturated fat and large LDL

Here's a half-truth I often encounter in low-carb discussions:

Saturated fat increases large LDL particles


For those of you unfamiliar with the argument, I advocate a low-carbohydrate approach, specifically elimination of all wheat, cornstarch, and sugars, to reduce expression of the small LDL pattern (not to mention reduction of triglycerides, relief from acid reflux and irritable bowel, weight loss, various rashes, diabetes, etc). Small LDL particles have become the most common cause for heart disease in the U.S., exploding on the scene ever since agencies like the USDA and American Heart Association have been advising the public to increase consumption of "healthy whole grains."

This has led some to make the pronouncement that saturated fat increases large LDL, thereby representing a benign effect.

Is this true?

It is true, but only partly. Let me explain.

There are two general categories of factors causing small LDL particles: lifestyle (overweight, excess carbohydrates) and genetics (e.g., variants of the gene coding for cholesteryl-ester transfer protein, or CETP).

If small LDL is purely driven by excess carbohydrates, then adding saturated fat will reduce small LDL and increase large LDL.

If, on the other hand, your small LDL is genetically programmed, then saturated fat will increase small LDL. In other words, saturated fat tends to increase the dominant or genetically-determined form of LDL. If your dominant genetically-determined form is small, then saturated fat increases small LDL particles.

So to say that saturated fat increases large LDL is an oversimplification, one that can have dire consequences in the wrong situation.

Is glycemic index irrelevant?

University of Toronto nutrition scientist, Dr. David Jenkins, was the first to quantify the phenomenon of "glycemic index," describing how much blood sugar increased over 90 minutes compared to glucose. The graph is from their 1981 study, The glycemic index of foods: a physiologic basis for carbohydrate exchange. The research originated with an effort to characterize carbohydrates for diabetics to gain better control over blood sugar.

Since Dr. Jenkins’ original work, thousands of clinical studies have been performed by others exploring this concept. The food industry has also devoted plenty of effort exploiting it (e.g., low-glycemic index noodles, low-glycemic index cereals, etc.).

Most Americans are now familiar with the concept of glycemic index. You likely know that table sugar has a high glycemic index (60), increasing blood sugar to a similar degree as white bread (glycemic index 71). Oatmeal (slow-cooked) has a lower glycemic index (48), since it increases blood sugar less than white bread.

A number of studies have shown that when low glycemic index foods replace high glycemic index foods (e.g., whole wheat bread in place of cupcakes), people are healthier: less diabetes, less heart attack, less high blood pressure. Books have been written about glycemic index, touting its benefits for health and weight control. Health-conscious people will try to substitute low-glycemic index foods for high-glycemic index foods.

So what’s not to like here?

There are several fundamental flaws with the notion that low-glycemic index foods are good for you:

1) Check your blood sugar after a low-glycemic index food like oatmeal. Most non-diabetic adults will show blood sugars in the 140 to 200 mg/dl range. The more central (visceral) fat you have, the higher the value will be. In other words, an apparently “healthy” whole grain food like oatmeal can generate extravagantly high blood sugars. Repeated high blood sugars of 125 mg/dl or greater after eating increase heart disease risk by 50%.

2) Foods like whole wheat pasta have a low glycemic index because the blood sugar effect over the usual 90 minutes is increased to a lesser degree. The problem is that it remains increased for an extended period of up to several hours. In other words, the blood sugar-increasing effect of pasta, even whole grain, is long and sustained.

3) Low-glycemic index foods trigger other abnormalities, such as small LDL particles, triglycerides, and c-reactive protein (a measure of inflammation). While they are not as bad as high-glycemic index foods, they are still quite potent triggers.

Low-glycemic index foods trigger the very same responses as high-glycemic index foods—they’re just less bad. But less bad does not equate to good. Low-glycemic index foods cause weight gain, trigger appetite, increase blood pressure, and lead to the patterns that cause heart disease.

High-glycemic index foods are bad for you. This includes foods made with white flour (bagels, white bread, pretzels). Low-glycemic foods (whole grain bread, whole wheat crackers, whole wheat pasta) are less bad for you—but they are not necessarily good.

Don’t be falsely reassured by foods because they are billed as “low-glycemic index.” View low-glycemic index foods as indulgences, something you might have once in a while, since a slice of whole grain bread is really not that different from a icing-covered cupcake.