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Is lowering LDL Cholesterol by diet helpful?
A recent google search provided me with the following top results:
- 11 Foods that Lower Cholesterol – Harvard Health Publishing…
- How to Lower Cholesterol with Diet: MedlinePlus
- Top 5 lifestyle changes to improve your cholesterol – Mayo Clinic
- Cholesterol: Top foods to improve your numbers – Mayo Clinic
- 10 Tips to Lower Cholesterol With Your Diet – Healthline
- 13 Cholesterol-Lowering Foods to Add to Your Diet Today
- …. and the list is much longer
Clearly, none of these articles was able to answer my question.
However, there is no doubt that we can lower LDL cholesterol by changing our diet. The most effective way to do so is probably by reducing the intake of saturated fats.
Indeed, this is the reason why reducing the amount of saturated fat in our diet has been a central theme of public health recommendations since the late 1970s (1).
But, lowering a number is one thing. The big question is whether lowering LDL cholesterol by diet improves health and reduces the risk of heart disease.
LDL Cholesterol and Heart Disease
Scientific evidence certainly shows a positive association between serum cholesterol and the risk of dying from cardiovascular disease (2,3,4).
It is also evident that LDL particles play a causal role in developing of atherosclerotic cardiovascular disease (ASCVD) (5).
Furthermore, a consensus panel of respected scientists recently concluded that any mechanism of lowering plasma LDL particle concentration should reduce the risk of ASCVD events proportional to the absolute reduction in LDL cholesterol (6).
But the same panel also concluded that this is true “provided that the achieved reduction in LDL cholesterol is concordant with the reduction in LDL particle number and that there are no competing deleterious off-target effects.”
I want to emphasize these two key issues:
- provided that the achieved reduction in LDL cholesterol is concordant with the reduction in LDL particle number
- and that there are no competing deleterious off-target effects
Saturated Fats, LDL Particle Size and Number
Low-density lipoprotein occurs as large buoyant LDL particles, and as small dense LDL particles (7).
Large LDL particles are more cholesterol-enriched, whereas small dense LDLs carry less cholesterol per particle.
Large LDL particles have a much weaker association with ASCVD than do smaller LDL particles (8,9).
Lowering LDL cholesterol by reducing the intake of saturated fats primarily reflects reduced levels of large LDL particles, whereas, in most individuals, the number of small LDL-particles is not reduced by reducing saturated fats (10).
Many recent studies have concluded that the number of LDL-particle present is a strong predictor of cardiovascular risk.
It is possible indeed, that the association between the number of small LDLs and heart disease reflects an increased number of LDL particles in patients with predominantly small particles. Therefore, the number of LDL particles could be more significant in terms of risk than the particle size itself (11).
Lowering LDL cholesterol by reducing the intake of saturated fats primarily reflects reduced levels of large LDL particles, whereas, in most individuals, the number of small LDL-particles is not reduced by reducing saturated fats
Moreover, decreasing saturated fat intake also lowers the levels of high-density lipoprotein (HDL) cholesterol which may have a negative impact on the risk of ASCVD (12).
Also, as recently pointed out in a blog article here, a low-fat, high-carbohydrate diet may increase lipoprotein (a) levels compared to a high-fat, low-carbohydrate diet(13). Lipoprotein(a) is strongly associated with the risk of ASCVD.
The PURE study reported that the association between saturated fat and ASCVD events does not fit a relation with plasma LDL cholesterol but is related to the ratio of apolipoprotein B (apo B) to apo A1(14).
Interestingly, ApoB correlates with LDL particle number (15).
In fact, several randomized trials have shown that changes in LDL cholesterol achieved by modulating the intake of saturated fat do not correlate with the risk of ASCVD (16,17,18)
This is brilliantly discussed by Arne Astrup and colleagues in a state-of-the-art-review published last year in the Journal of the American College of Cardiology (10).
As the review article points out, “the potential benefit of dietary restriction of saturated fat could be substantially overestimated by reliance on the change in LDL cholesterol levels alone.”
Is There A Downside of Diets that Lower LDL Cholesterol?
Dietary guidelines usually recommend replacing saturated fatty acids with cis-unsaturated fatty acids.
The recently published guidelines for Americans 2020-2025 discuss the importance of limiting intakes of saturated fat to support healthy dietary patterns (19).
The major purpose of these measures appears to be to lower blood cholesterol and reduce the risk of cardiovascular disease.
Among other things the guidelines suggest using lean meats and low-fat cheese or substituting beans in place of meats as the protein source.”
It is also pointed out that “saturated fat can also be reduced by substituting certain ingredients with sources of unsaturated fat (e.g., using avocado, nuts, or seeds in a dish instead of cheese). Cooking with oils higher in polyunsaturated and monounsaturated fat (e.g., canola, corn, olive, peanut, safflower, soybean, and sunflower) instead of butter also can reduce intakes of saturated fat.”
However, it is often forgotten that saturated fats are a heterogenous group of fatty acids that differ on the basis of their carbon chain length.
Furthermore, saturated fats are obtained from foods that have other ingredients that may modify their health effects.
In my opinion, judging the health effects of foods based on their amount of saturated fat is unwise and may promote bad food choices.
Also, remember that a Mediterranean-style diet appears to reduce the risk of ASCVD without reducing LDL cholesterol (20).
So, if we are to recommend food choices that lower LDL cholesterol, we have to be sure that the same recommendations do not include any competing deleterious off-target effects.
Is Lowering LDL Cholesterol Helpful?
So, let’s go back to the initial question.
Is Lowering LDL Cholesterol by Diet Helpful?
As my google search showed, there are tons of articles explaining how we can lower our cholesterol by changing our diet.
But, is it helpful?
Does it lower our risk of developing heart disease?
Frankly, I’m far from convinced. And, due to the fact that I have been studying the scientific data for more than thirty years, I believe I’m entitled an opinion.
I think that LDL cholesterol is a lousy surrogate marker and I fear that letting it control our dietary choices may lead to more harm than good.
And, yes. I know I am a cardiologist.