One of the fears some have in adopting a low carb diet is the possibility that LDL cholesterol will increase. And indeed, in the typical blood test we take, there is sometimes an increase in this so-called bad cholesterol. But what is the real relationship between carb consumption and LDL particles in the bloodstream?
Dr. William Davis of the Heart Scan Blog has some clarification for us:
1) Increase triglycerides and very low-density lipoprotein particles (VLDL)
2) Triglyceride-rich VLDL interact with LDL particles, making them smaller. (A process mediated by several enzymes, such as cholesteryl-ester transfer protein.)
3) Smaller LDL particles are more oxidizable–Oxidized LDL particles are the sort that are taken up by inflammatory white blood cells residing in the artery wall and atherosclerotic plaque.
4) Smaller LDL particles are more glycatable–Glycation of LDL is an important phenomenon that makes the LDL particle more atherogenic (plaque-causing). Glycated LDLs are not recognized by the LDL receptor, causing them to persist in the bloodstream longer than non-glcyated LDL. Glycated LDL is therefore taken up by inflammatory white blood cells in plaque.
Of course, carbohydrates also make you fat, further fueling the fire of this sequence.
Dr. Davis’ main concern is the impact eating carbs has on your cardiovascular health … not fat, but carbs. He focuses on the most recent scientific evidence and techniques to shepherd his patients past heart disease and toward longer, healthier lives. Is he concerned that the standard blood test may show a rise in LDL cholesterol? Not at all.
The standard blood test uses the Friedewald calculation rather than measuring the blood lipids directly. We have several articles on LDL and the Friedewald calculation for your edification.
Johns Hopkins has been doing research and clinical trials on ketogenic diets for seizure disorders in children for years. The diet they use is much more carb-restricted than we find in PP, and probably higher in fat content. The article in Diabetes in Control describes it this way:
The ketogenic diet, consisting of high-fat foods and very few carbohydrates, is believed to trigger biochemical changes that eliminate seizure-causing short circuits in the brain’s signaling system. Used as first-line therapy for infantile spasms and in children whose seizures cannot be controlled with drugs, the diet is highly effective but complicated and sometimes difficult to maintain. It can temporarily raise cholesterol, impair growth and, in rare cases, lead to kidney stones, among other side effects.
The Hopkins Children’s Hospital used the diet for 16 months to 8 years to reduce or eliminate the seizures. The study being referenced is a follow-up to see if any lasting health problems from the diet are revealed.
There don’t seem to be any long-term effects:
Only two of the 101 patients reported kidney stones after stopping the diet, the same rate found in the general population not treated with the ketogenic diet, the researchers say.
None of the 25 patients who had liver and kidney function tests had abnormal results. Among the 26 patients who had their cholesterol tested, the average level was 157 milligrams per deciliter of blood (less than 200 is considered normal), with three of the 26 having abnormal levels. Most patients’ cholesterol levels go up while on the diet, but are believed to return to normal thereafter. The Hopkins study now confirms that this is the case.
In 2008, Johns Hopkins Children’s Hospital described the results on cholesterol this way:
While most children developed high cholesterol after starting the diet, in half of them, cholesterol gradually improved returning to normal or near-normal levels, with or without modifications to their diet to reduce fat intake.
Interestingly, efforts to reduce saturated fat saw no greater decrease in cholesterol levels. In other words, doing nothing and reducing saturated fat had the same effect over time. That might be good news for low carbers that are worried about an increase in cholesterol in the early years of the new way of eating.
Since 2005, Hopkins has noted that a modified Atkins low carb diet plan has nearly the same benefits as their more restrictive ketogenic diet for children with seizure disorders. In effect, any diet that puts the patient into ketosis restricts the seizure activity.
Statins are a class of drugs that lower cholesterol levels, and, the reasoning goes, should reduce the risk of heart attack. But the reality has been less illuminating than the promise. This morning word of another study showing that the popular statins containing ezetemibe, Vytorin and Zetia, do not lower the risk of heart disease. As the LA Times reports:
For the second time in as many years, a large clinical trial has found that the key ingredient in the heavily advertised drug Vytorin provides little or no benefit in preventing heart disease compared to a competing product. The ingredient is ezetemibe, which blocks the absorption of cholesterol in the intestines. It is sold alone under the brand name Zetia or in combination with the cholesterol-lowering drug simvastatin under the brand name Vytorin. The combination of drugs has been shown to reduce cholesterol more than simvastatin alone, but that apparently does not translate into a lower risk of heart disease.
Statins are often credited with a number of unpleasant side effects, including uncomfortable muscle aches. And evidence is mounting that while they may lower LDL cholesterol numbers, they aren’t providing the reduction in heart attacks that “should” result.
Another article has been posted to our Research pages, this time recapping a study that compared a standard LCD (low carb diet) to the American Heart Association diet that emphasizes low fat. The study was published in the Nutrition, Metabolism and Cardiovascular Diseases journal, and is posted here.
The study selected 39 individuals and divided them into two groups. One group ate a carb-restricted diet for 12 weeks. The other group ate a carb-restricted diet for 6 weeks, and then switched to the AHA diet for the remaining 6 weeks.
In this study, the low carbohydrate diet followed the recommendations of most of the low carb diets: 20 to 25% of calories from carbs. The AHA diet, by comparison, doubles that amount with 50 to 55% of the calories from carbs.
One concern often expressed about eating low carb and increasing saturated fat in the diet is that LDL can rise using the normal calculated value
. This study looks specifically at the type of LDL that each of the diets produces, using direct measurements rather than an inaccurate calculation.
The short version of the results is that the low carb diet “had a better effect on atherogenic VLDL and HDL than the low fat diet recommended by AHA.” Atherogenic
VLDL and HDL are particles that lead to the formation of atheromas on the walls of the arteries, or what we commonly call atherosclerosis.
This is just one study, and won’t immediately change the dietary recommendations of nutritionists, doctors and the American Heart Association. But the “Low Fat Age” is seeing its reign come to an end, and the Low Carb Age
is upon us.
My medical history includes a high triglyceride level over 400, and my doctor asked for a direct measurement of my LDL. Usually, the labs calculate the LDL by using a formula rather than measuring it directly. As Dr. Michael Eades says in his blog:
… Friedewald substituted triglycerides (TGL) divided by 5 for VLDL in the above equations, giving us the so-called Friedewald equation for calculating LDL.
LDL = Total cholesterol – HDL – TGL/5
And this is how it is still done in labs all over the world 27 years after Friedewald’s paper. If you’ve had a lab report showing an LDL figure, I can guarantee it was calculated by the Freidewald equation and not measured directly.
It has long been recognized that if the triglycerides are over 400, the calculation does not work. So you have to measure the level directly. In that same blog post, Dr. Eades explains his experience that LDL calculations are inaccurate when the triglycerides are low as well. I have linked two articles Dr. Eades identifies as supporting that position in our new LDL Research Page.
Many studies show marked improvement in patients HDL, triglycerides and glucose levels with low carb diets. Often, the low carb dieter has a rise in total cholesterol and LDL. Researchers are not concerned with the higher total cholesterol number, but the LDL level increase does concern them. But most studies use the Friedewald calculation that may not give an accurate picture of the true LDL level.
If my LDL gets too high, I’ll be certain to ask for a direct measurement of it, rather than a calculation. The extra cost for the test is probably cheaper than taking statins.