Cholesterol in food, cholesterol in the blood

A top nutrition advisory committee says people no longer have to be concerned about eating foods that are high in cholesterol. The committee’s report, which was released today, will help shape the next version of the U.S. Dietary Guidelines, set to be released later this year.

High levels of “bad” cholesterol in the blood, which have been linked to heart disease, are still a health concern. What’s changed is that many researchers and physicians now believe that eating cholesterol-rich foods such as eggs may not affect the cholesterol that is in your blood.

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 For the majority of people with raised cholesterol there is no reason to limit cholesterol containing foods that are otherwise low in saturated fat.  Why? Because the focus of our dietary advice is to lower saturated fat and replace it with healthy calories from unsaturated fats and wholegrain foods.  This is because saturated fat has a greater influence on cholesterol levels than eating the foods that contain cholesterol.  

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• The biggest influence on blood cholesterol level is the mix of fats and carbohydrates in your diet—not the amount of cholesterol you eat from food.

• Although it remains important to limit the amount of cholesterol you eat, especially if you have diabetes, for most people dietary cholesterol is not as problematic as once believed.

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Myth #1: Eating cholesterol and saturated fat raises cholesterol levels in the blood.

Most of us grew up being told that foods like red meat, eggs and bacon raise our cholesterol levels. This idea is so deeply ingrained in our cultural psyche that few people even question it. 

But is it really true?

The diet-heart hypothesis—which holds that eating cholesterol and saturated fat raises cholesterol in our blood—originated with studies in both animals and humans more than half a century ago. However, more recent (and higher quality) evidence doesn’t support it.

On any given day, we have between 1,100 and 1,700 milligrams of cholesterol in our body. 25% of that comes from our diet, and 75% is produced inside of our bodies by the liver. Much of the cholesterol that’s found in food can’t be absorbed by our bodies, and most of the cholesterol in our gut was first synthesized in body cells and ended up in the gut via the liver and gall bladder. The body tightly regulates the amount of cholesterol in the blood by controlling internal production; when cholesterol intake in the diet goes down, the body makes more. When cholesterol intake in the diet goes up, the body makes less.

This explains why well-designed cholesterol feeding studies (where they feed volunteers 2-4 eggs a day and measure their cholesterol) show that dietary cholesterol has very little impact on blood cholesterol levels in about 75% of the population. The remaining 25% of the population are referred to as “hyper-responders”. In this group, dietary cholesterol does modestly increase both LDL (“bad cholesterol” and HDL (“good cholesterol”), but it does not affect the ratio of LDL to HDL or increase the risk of heart disease. (2)

In other words, eating cholesterol isn’t going to give you a heart attack. You can ditch the egg-white omelettes and start eating yolks again. That’s a good thing, since all of the 13 essential nutrients eggs contain are found in the yolk. Egg yolks are an especially good source of choline, a B-vitamin that plays important roles in everything from neurotransmitter production to detoxification to maintenance of healthy cells. (3) Studies show that up to 90% of Americans don’t get enough choline, which can lead to fatigue, insomnia, poor kidney function, memory problems and nerve-muscle imbalances. (4)

What about saturated fat? It’s true that some studies show that saturated fat intake raises blood cholesterol levels. But these studies are almost always short-term, lasting only a few weeks. (5) 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. (6)

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PURPOSE OF REVIEW:

The perceived notion that dietary cholesterol is associated with increased risk for coronary heart disease (CHD) has led to dietary recommendations of no more than 300  mg/day for healthy populations in the USA. This study will review the recent evidence that challenges the current dietary restrictions regarding cholesterol while it presents some beneficial effects of eggs (an icon for dietary cholesterol) in healthy individuals.

RECENT FINDINGS:

The European countries, Australia, Canada, New Zealand, Korea and India among others do not have an upper limit for cholesterol intake in their dietary guidelines. Further, existing epidemiological data have clearly demonstrated that dietary cholesterol is not correlated with increased risk for CHD. Although numerous clinical studies have shown that dietary cholesterol challenges may increase plasma LDL cholesterol in certain individuals, who are more sensitive to dietary cholesterol (about one-quarter of the population), HDL cholesterol also rises resulting in the maintenance of the LDL/HDL cholesterol ratio, a key marker of CHD risk.

SUMMARY:

The lines of evidence coming from current epidemiological studies and from clinical interventions utilizing different types of cholesterol challenges support the notion that the recommendations limiting dietary cholesterol should be reconsidered.

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