Cholesterol Controversy

annie-spratt-710486-unsplashWe all probably know someone who has high cholesterol. Or maybe you have been recently diagnosed with hypercholesterolemia or elevated levels of cholesterol in the blood.
For decades we have been told we should watch the amount of egg we eat per week (especially egg’s yolk), to avoid fat meat like bacon and be careful with butter. But lately experts are telling us the fats in our diet are not a necessarily bad thing and we shouldn’t avoid it. Contrary, today we know egg’s yolk will not raise cholesterol levels in most of individuals and yolk actually contains components (phospholipids) that impair cholesterol absorption in the body. Likewise, for years HDL cholesterol (high-density lipoprotein) was called “a good cholesterol” (compared to the “bad cholesterol” LDL) and having too much of HDL was considered as something good for your health. But a few months ago, a team of scientists suggested that very high blood levels of HDL cholesterol may be linked to a higher risk for heart attack in patients who already had heart problems.
So who should we listen to? And if your cholesterol levels are not within the “normal” range, what should you do?

Some facts about cholesterol

And as much as word “cholesterol” sometimes has a bad connotation, we need cholesterol as it is essential for life.

Cholesterol is a fatty substance synthesized in our bodies, and an essential component of all cell membranes, brain and nerve cells. It is a lipid-like molecule. Chemically, cholesterol is an organic compound belonging to the steroid family (it is a sterol or steroid alcohol). Within our bodies, it is a precursor for the formation of important molecules like steroid hormones (corticosteroids and sex hormones), bile acid and vitamin D. And if you look at the chemical structure of cholesterol and for example testosterone or bile acid, you will notice how similar they are.

Cholesterol chemical structure

Cholesterol can be synthesized in our bodies and obtained from the diet. The majority of cholesterol in our systems is synthesized in the liver and intestines. The majority of cholesterol in our body actually comes from biosynthesis, not from the foods we eat. In fact, most cholesterol from foods does not get absorbed unless the body needs it. But effects of dietary cholesterol on serum LDL cholesterol levels vary from one person to another. Significant amounts of cholesterol in food occur in eggs, meat, and milk products. Egg yolk, for example, contains about 200 mg of cholesterol (just for reference, prior recommendation for dietary cholesterol was 300 mg per day). But in most individuals cholesterol from the food is poorly absorbed as the body compensates for any extra absorption of cholesterol by reducing its synthesis in the body.

Cholesterol and lipids are insoluble in water-based fluids such as blood. That is why they are transported in the blood plasma within specific proteins called apoproteins. These molecules, structured from cholesterol, triglycerides (three molecules of fatty acid combined with glycerol) and apoproteins are called lipoproteins. There are several types of lipoproteins, among others Low-Density Lipoprotein or LDL.

LDL contains a high level of cholesterol and it delivers cholesterol to cells, where it is used in membranes or for the synthesis of hormones. It is often considered as “bad cholesterol” because it can become part of plaque that can clog arteries and cause a heart attack or stroke.  Lately, the scientists claim that is the size of LDL cholesterol that matters as LDL exists in a variety of forms. Small-sized LDL molecule is the type of LDL cholesterol that is associated with heart disease.

Also, lipoproteins rich in triglycerides (chylomicrons) and Very Low-Density Lipoproteins or VLDL are both associated with the formation of plaque in arteries (although VDLD in greater extent).

And there is, of course, High-Density Lipoprotein or HDL or “good cholesterol”. HDL carries cholesterol away from the tissues and arteries back to the liver where it can be recycled or removed from the body (the liver removes cholesterol from the body by converting it to bile salts or putting it into the bile where it can be eliminated in a stool). This is why HDL is considered as “atheroprotective” or it protects against the hardening and narrowing of the arteries.

What is hypercholesterolemia?

The presence of high levels of cholesterol in the blood is called hypercholesterolemia. It is not always easy to determine the cause of elevated cholesterol in the blood. Diet, age, stress, hormonal status, obesity, smoking all have influence on how the body processes cholesterol. The occurrence of some diseases, like type 2 diabetes or hypothyroidism, can have influence too. People with diabetes, for example, have an increased risk of complications associated with abnormal cholesterol levels. Diabetes tends to lower the “good” HDL cholesterol levels and raise LDL cholesterol, which is associated with the elevated risk for stroke or heart problems.

Also, a number of medications (for example blood pressure medication) can cause high cholesterol as a side effect.
There are also gender differences in cholesterol metabolism. Men are at greater risk of having high cholesterol levels because women in their childbearing years are protected by the hormone estrogen. But as we age the cholesterol levels in both sexes rise.

In a small percentage of people hypercholesteremia is caused by an inherited genetic disorder, a condition called familial hypercholesterolemia. Because of mutations on certain genes, people with this condition have slightly different body biochemistry and usual methods for cholesterol control are not as effective as in people who don’t have familial hypercholesterolemia. For example, in one type of familial hypercholesterolemia, a mutation in a gene that regulates LDL receptors within the cell cause inherited high cholesterol. The low-density lipoprotein receptors bind LDL cholesterol and remove the LDL cholesterol from the bloodstream. That is why these receptors have a critical role in the control of cholesterol levels in the body. In some people, gene mutations cause a reduction in the number of LDL receptors in the cells. In other, mutations interfere with the receptors’ ability to remove LDL cholesterol from the blood. The result is the excess of cholesterol that circulates through the body and is deposited atypically in tissues such as the skin, tendons, and arteries.
So some cases of hypercholesteremia are caused by genetic abnormalities and are inherited. People with diagnosed familial hypercholesterolemia should avoid cholesterol-rich foods. But in most cases, high cholesterol is a result of a combination of lifestyle choices and variations in certain genes and dietary cholesterol is not as problematic as once believed.

So what food should be avoided if you have familial hypercholesterolemia?

Even though dietary cholesterol isn’t the biggest worry, you should be careful with foods that are high in saturated fats or trans fats as they have a much bigger impact on raising cholesterol levels. Saturated fats are mostly found in food of animal origin (cheese, lard, cream, some meat….), but they can also be found in some plants like palm oil or coconut oil. Many manufactured and packaged foods like cakes, pies, fatty snacks or deep-fried takeaway foods are usually also high in saturated fats. Trans fats are something you should really pay attention to. According to new findings, increased intake of trans fats is associated with an increased risk of cardiovascular diseases. Trans fats reduce levels of HDL and increased levels of LDL cholesterol.  If you would like to find out more on trans fats please see one of my previous articles “Why should we pay more attention to trans fats”.
Eating excessive carbohydrates can also lead to an increase in triglyceride levels in the blood as the liver transforms the excess of glucose into fat. Increased carbohydrate consumption and increased intake of food with a high glycemic index cause higher glucose and insulin concentrations after meal. This may lead to insulin resistance which raises triglycerides concentrations and reduce HDL levels (risk factors for developing coronary heart disease, metabolic syndrome, and diabetes).

Food that can be beneficial

  • A high-fiber diet is beneficial for health in many ways, first of all for the health of the digestive system. Our body can’t fully digest fiber, but a diet high in fiber can provide many health benefits, such as lowering risk of diabetes, maintain healthy body weight and prevent heart disease and some types of cancer. Dietary fiber can be found mostly in vegetables, fruits, legumes, and wholegrain. There are two types of fiber: soluble fiber (which dissolves in water and form a gel-like material) and insoluble fiber (that does not dissolve in water, but helps with constipation and bowel movement). Soluble fiber is a type of fiber that helps lower blood cholesterol and glucose levels. It binds with cholesterol in the intestines and interferes with its absorption in the body. It can slow the absorption of carbohydrates, helping maintain normal blood sugar levels. This type of fiber can be found in foods like oat, psyllium, peas, apples, barley, and carrots. But be careful, adding too much fiber too quickly can cause cramps and bloating, so increase fiber intake in your diet gradually.
  • Foods rich in unsaturated fats are recommended for cholesterol lowering. Unsaturated fats such as those contained in olive, sunflower, nut and seed oils should replace saturated fat in the diet. Mediterranean diet, rich in these fats, is often recommended for heart health. Similarly, omega-3 fatty acids found in fish and flax seeds suppress synthesis of triglycerides and VLDL cholesterol and increase HDL cholesterol in the blood, which is beneficial in minimizing the occurrence of cardiovascular disease.
  • Do not forget to add fruit and vegetable on your plate.  Plant-based foods such as vegetables and fruits tend to be high in polyphenols (chemicals that naturally occur in plants).  Consumption of polyphenols from vegetables and fruit increases antioxidant levels in plasma which protects the vascular system, improve lipid profile and act as anti-inflammatory agent.
  • Plant Sterol/Stanol Esters. Plant sterols are molecules similar in structure to the cholesterol. They can be found in all plant foods, with the highest concentrations occurring in vegetable oils. Plant stanols have been proven to reduce cholesterol in a number of clinical trials. Because of their cholesterol-like structure when ingested plant sterols inhibit the absorption of cholesterol in the small intestine, resulting in a decrease in overall cholesterol. Because of their properties today many foods are being fortified with plant sterols (orange juices, margarine, energy bars). They also occur naturally in fruits, vegetables, nuts, and seeds, but at low levels.

In conclusion

Cholesterol metabolism is extremely complex so there is no universal “one size fits them all” treatment for high cholesterol. But high cholesterol is just one peace in a puzzle in development of coronary and heart disease.  Depending on the type of hypocholesteremia, the treatment should be adjusted to an individual, especially if a person has a family history of heart disease and diabetes. The first line of defense is lifestyle changes like change in diet and an increase in physical activity. Dietary changes that may be beneficial are reducing saturated and trans fats, losing extra weight and switching to more of a plant-based diet.  In some people, this will be enough, but in others, the only combination of medicines, change in diet and exercise will produce the results.