Many of the concepts presented below are taken from Chris Kresser’s “Diet-Heart Myth”, which I strongly recommend. For very current information, on cholesterol I strongly recommend Chris Masterjohn’s website www.cholesterol-and-health.com.
In 1984, Time magazine came out with an article titled “Cholesterol and Now the Bad News.” It was based on an assumption that dietary cholesterol and saturated fat intake will increase our risk of heart disease. In order to lower your risk of heart disease, you will be better served to eat low-fat meals, avoiding meals from animal products such as butter and bacon. Then these thoughts were reinforced with the original food pyramid that we should consume large amounts of grains and breads with very little consumption of fats and oils. Since that time, people have not gotten healthier; we have gotten fatter, become diabetic and rates of chronic disease have significantly increased. We may be living longer but in many ways we are just existing longer and our actual “Living-span” has probably decreased.
On the other hand, there are the cholesterol skeptics, who believe that cholesterol has nothing to do with heart disease risk and that those markers should be ignored.
With most things the truth lies in the middle.
Regardless of which camp you may side with, there are fundamental questions that we need to ask ourselves:
- Does dietary cholesterol affect blood cholesterol levels?
- Does saturated fat intake increase blood cholesterol levels?
- Does dietary cholesterol and saturated fat increase heart disease risk?
- Does high blood cholesterol increase heart disease risk?
Does Dietary Cholesterol affect Blood Cholesterol levels?
The answer is for the most part a resounding “NO.” This first question is actually fairly easy to answer because there have been very good studies that address the topic directly. Our body’s cholesterol status is supposed to be tightly controlled. Depending on our cholesterol needs, the body will either make more cholesterol or make less cholesterol, typically only about 25% of cholesterol will come from diet.
In certain studies, volunteers were fed 2-4 eggs per day, they found that dietary cholesterol did not rise for 75% of the volunteers. The other 25% were labelled as hyper-responders and they did see an increase in blood cholesterol. However, in this group the ratio of LDL to HDL remain unchanged.
Does saturated fat intake increase blood cholesterol levels?
Some studies have shown that saturated fat intake raised blood cholesterol levels. But these studies are almost always short-term, lasting only a few weeks. Longer-term studies have not shown an association between saturated fat intake and blood cholesterol levels. In fact, of all of the long-term studies examining this issue, only one of them showed a clear association between saturated fat intake and cholesterol levels, and even that association was weak.
In addition, studies on low-carbohydrate diets (which tend to be high in saturated fat) suggest that they not only don’t raise blood cholesterol, they have several beneficial impacts on cardiovascular disease risk markers. For example, a meta-analysis of 17 low- carb diet trials covering 1,140 obese patients published in the journal Obesity Reviews found that low-carb diets neither increased nor decreased LDL cholesterol. However, they did find that low-carb diets were associated with significant decreases in body weight as well as improvements in several risk factors, including decreases in triglycerides, fasting glucose, blood pressure, body mass index, abdominal circumference, plasma insulin and c-reactive protein, as well as an increase in HDL cholesterol.
Does dietary cholesterol and saturated fat intake increase heart disease risk?
There have been a variety of studies to test this theory but they have not found an association between dietary intake of cholesterol and saturated fat and heart disease risk. In fact, A Japanese prospective study that followed 58,000 men for an average of 14 years found no association between saturated fat intake and heart disease, and an inverse association between saturated fat and stroke (i.e. those who ate more saturated fat had a lower risk of stroke).
Dietary cholesterol has been shown to increase the level of blood cholesterol in chickens and rabbits but it does not have the same effect on humans. In humans, increasing dietary cholesterol to a cholesterol-free diet raises the blood level, but when added to an unrestricted diet, it has a minimal effect.
Patients must keep in mind that studies are looking at patterns among populations and not specific individuals. It is possible for dietary cholesterol and saturated fat intake to increase your blood cholesterol levels. However, if this is the case, the patient must keep in mind that there may be another underlying cause for this phenomenon that may require further investigation.
Does high blood cholesterol cause heart disease?
This is where the discussion gets a little more complicated. The truth is there are associations between blood cholesterol levels and heart disease but the answers are not very cut and dry. Just because you have high blood cholesterol, this does not mean that you are at risk for heart disease. Likewise, if you have low cholesterol, you may still be at risk.
Most people have become familiar with the different cholesterol categories, such as HDL, LDL, VLDL, and triglycerides. Many people associate LDL as bad cholesterol and HDL as good cholesterol, and this is somewhat true. Studies have linked high LDL cholesterol with heart disease but it is still not a definitive marker. LDL stands for low density lipoprotein. In order for cholesterol to be transported through the blood it must be carried by special proteins called lipoproteins. When we measure LDL-cholesterol we are measuring the concentration of cholesterol in each LDL particle.
Imagine that your bloodstream is a highway. The lipoproteins are like cars that carry the cholesterol and fats around your body, and the cholesterol and fats are like passengers in the cars. Scientists used to believe that the number of passengers in the car (i.e. amount of cholesterol in the LDL particle) is the driving factor in the development of heart disease. More recent studies, however, suggest that it’s the number of cars on the road (i.e. LDL particles) that are most significant.
Based on the above example, LDL particle number may be a better predictor of heart disease risk than LDL cholesterol. However, even LDL particle number is only a marker for disease and it is not a disease in itself. Everything we measure must always be taken into context. For example:
Imagine two people with an LDL-P above 2,000, which puts them in the highest risk group. Person A follows a Paleo diet and lifestyle, gets plenty of sleep, manages stress and has no other significant risk factors for heart disease. Person B eats a Standard American Diet, doesn’t exercise, doesn’t get enough sleep, is stressed out and has several other risk factors for heart disease. Logic would dictate that Person A would be at much lower risk for heart disease than Person B, but there isn’t any comparative data to quantify the difference in risk and it’s unlikely such a study will ever be done.
When it comes to heart disease it is a combination of factors that will determine each individual’s risk. Do not make the mistake of assuming your overall health and your risk of heart disease can be captured by a single number. Each individual must take into consideration their diet, lifestyle, stress management, etc. when assessing their own individual risk.
Where this all comes full circle and why you shouldn’t be concerned with increasing your saturated fat and cholesterol intake is because heart disease is truly caused by oxidation. Oxidation is the degeneration of chemicals. If you have ever witnessed a chair rusting when left outside, then you have witnessed oxidation. Oxidation is occurring in our bodies all the time, whether from injuries, infections, or just normal life, oxidation is a process that is constantly occurring. Oxidation does not always become a problem because we have a lot of built in mechanisms to control it.
When LDL oxidizes it is more likely to create a cascade of events that lead to heart disease. Therefore, it makes sense that LDL-cholesterol could show a correlation to increased heart disease risk. However, if your body can clear out LDL before it oxidizes or control the oxidative process, than it is likely that your LDL-cholesterol number will not be a good indicator of heart disease risk.
Guess what? The dietary fats that are most resistant to oxidative stress are saturated fats. Also, in order to have good control over the oxidative process we want to consume a diet rich in bioavailable nutrients. Animal products such as meat and eggs (foods often associated with higher saturated fat content) are some of the best sources for bioavailable nutrients, especially the fat soluble vitamins A, D, E, K which are particularly beneficial to preventing the oxidation of LDL.