Relationship between fat, carbohydrate, sugar, and cholesterol

After posting my review of the Beyond meat burger, I received questions from readers, asking about the relationship between fat, carbohydrate, sugar, cholesterol. A lot has changed in the research and I wanted to review recent studies to answer the following three questions that my readers had asked:

1. What does the research today say about the relationship between fat, carbohydrate, sugar, cholesterol, whole grains and heart disease?
2. Do foods high in cholesterol raise blood cholesterol levels?
3. Does carbohydrate intake affect cholesterol?

Research on Diet and Heart Disease

Heart Disease has been the second leading cause of death in Canada, after cancer, over the last 20 years.

What we know about diet, health and heart disease has evolved over the last 50 years. The message about dietary fat and cholesterol has changed. What was true in the ’90s is not the same as what we know and how we educate the public today.

From 1974 to 2014, the primary message around the leading dietary cause of heart disease was the excess intake of saturated fatty acids in our diets. The public health message was that reducing your intake of saturated fats would reduce your risk of heart disease. In the late ’60s, the hypothesis was that dietary cholesterol contributed to the risk of heart disease. The main source of saturated fat is meat from animals and cheese. Meat and cheese are also a source of dietary cholesterol.

Carbohydrates and heart disease

By promoting the link between saturated fats and heart disease, the population was educated to reduce saturated fats in their diet. The problem that resulted is that the reduction of saturated fats increased carbohydrate intake.

In the 1970s, scientists started to look at refined carbohydrates (processed foods), sugar and low dietary fibre as dietary causes of heart disease. At the time there was weak supporting evidence for this claim, and it was not generally accepted. In 2016, a scandal was uncovered that the sugar industry, not pleased with this research, paid scientists to minimize the role of sugar in heart disease and to leave saturated fats as the main contributing dietary factor.

Finding the “sugar” in foods

Just like all fats are not equal, so it is the same for carbohydrates. For illustration purposes, I will define two different types of carbohydrates in our diets: Simple and Complex. When reading nutrition labels, you can easily distinguish between these two types by looking at the Sugar and Dietary Fibre content.

Sugar is the simplest form of carbohydrate. Sugar is easily absorbed into the bloodstream and is linked to many dietary health concerns. Processed foods have increased the sugar content in foods as well as increased our cravings and addictions to carbohydrate-rich foods.

The dietary fibre number will give you a clue of the wholeness of the food, assuming it is not added in as an ingredient. Dietary fibre is a carbohydrate that naturally occurs in foods of plant origin and is not digested or absorbed by the small intestine.

In addition, reading the ingredients of a food product will be insightful. Ingredients are listed in order of the amount they represent in the food. If sugar is listed in any of the top three positions of the ingredients, it is a sure sign that the product is not healthy.

Saturated fats and heart disease

Focusing on Saturated Fat as the leading cause of heart disease led to the public health message of replacing saturated fats with polyunsaturated fats in a healthy diet. Polyunsaturated Fat sources include vegetable oils such as flaxseed, soybean, and fatty fish such as herring, salmon, mackerel, and sardines.

Omega-6 and Omega-3 fats are polyunsaturated fats. When the public health message focused on saturated fats as the “bad fat,” we started seeing products marketed for their “omega” content.

Cholesterol and Heart Disease

Dietary cholesterol comes from animals. The primary food sources of cholesterol include egg yolk, shrimp, beef, pork, poultry, as well as cheese and butter. For years, dietary cholesterol was thought to increase blood cholesterol levels, thus leading to the elevated risk of cardiovascular disease, another form of heart disease. Eggs were considered “bad” back in the 90s because of their high dietary cholesterol content.

When comparing the nutrient value of eggs to beef, cheese, chicken, butter and shrimp (all foods that are from animals), a difference was observed. Eggs in comparison to other animal products are lowest in total fat, including saturated fat but highest in cholesterol. Beef, cheese, chicken and butter are both high in dietary cholesterol and saturated fat.

By debunking the research that dietary cholesterol does contribute to cardiovascular disease, eggs got a clean bill of health because they are low in saturated fats. Foods high in saturated fats continue to be a contributing factor to the development of heart disease.

Eggs are now a mainstay of a healthy diet. Eggs are rich in protein quality, vitamins and minerals. Egg yolk is also rich in dietary choline, which is an essential nutrient for human liver and muscle functions. Shrimp is also in the good books and an exception to a food that is high in cholesterol but contains zero saturated fat.

Around 2014, research studies showed that saturated fat intake was only weakly associated with the risk of heart disease. The most reliable indicator of risk of heart disease was the ratio of total cholesterol to HDL-cholesterol (good cholesterol formed by the liver).

So going back to my reader’s question:

1. Does dietary cholesterol raise blood cholesterol levels? The answer is no. Saturated fats are more of a risk to heart disease. High “bad” blood cholesterol levels are a result of saturated fats and cholesterol produced in the liver.
2. Does carbohydrate intake affect cholesterol? Yes. Sugar contributes to increases in blood pressure and blood lipids, both of which are major risk factors for the development of heart disease. Processed carbohydrates, added sugars and sugar-sweetened beverages are significant dietary factors which could contribute to heart disease. Whole grain cereals and dietary fibre likely reduce the risk of heart disease.

Five recommendations for a healthy heart diet.

1. Increase your intake of Dietary Fibre from whole foods and grains. Dietary fibre has been found to reduce the risk of heart disease, as well as promote regular bowel movement through the colon, thereby reducing the risk of colon cancer.
2. Reduce your intake of processed foods, including processed foods that are labelled gluten-free. Keren’s Rule, if the product is in a package and has a shelf life of more than 3-5 days, it is a processed food product. If sugar is listed in the first three ingredients, then the product is not healthy.
3. Eggs are back! Eggs are a high-quality source of protein, affordable and nutrient-dense. Don’t worry about the high cholesterol because research has shown that dietary cholesterol is not the only culprit for high blood cholesterol levels.
4. Moderation is key to any healthy diet. A diet high in saturated Fats has been linked to heart disease but does not mean that you have to eliminate animal products completely. Experiment with adding plant-based meals into your diet and focus on eating a variety of whole foods.
5. A healthy eating pattern incorporates nutrient-dense foods, balanced meals and a variety of colourful vegetables and fruits.