The truth about ‘forbidden foods’ and what it means for your heart

Ultra-processed, ready-to-eat or prepackaged foods can have bad long-term effects on your heart health.
Ultra-processed, ready-to-eat or prepackaged foods can have bad long-term effects on your heart health.
Getty Images/Filadendron
  • Fast foods may be convenient and affordable, but they can negatively affect your health.
  • They're generally high in salt and contain unhealthy fats while lacking essential nutrients your body needs.
  • Slow foods, however, are what you should aim for, as they can support good health.

The risk of death from non-communicable diseases (NCDs), including heart disease, increases by 18% with just one extra serving of ultra-processed food daily.

The second and fourth leading causes of mortality in South Africa are stroke and ischemic heart disease.

There are many risk factors for heart disease, including high blood pressure, physical inactivity, smoking, overweight and obesity, and a diet high in energy, fat, salt and sugar.

With Heart Awareness Month observed nationally in September, here’s a look at the impact of fast food on your heart health.

What qualifies as fast food?

Fast food describes ultra-processed, ready-to-eat, ready-to-heat, or prepackaged foods, such as takeaway burgers, chips, chocolate, or foods like instant noodles.

The nutrition reality is changing rapidly through the increased consumption of fast foods, which conveniently serve the fast-paced lifestyle of many South Africans.

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These foods are ultra-processed and high in processed meat, refined carbohydrates, total fat, saturated and trans fat, cholesterol, and salt (sodium) while lacking essential nutrients and dietary fibre.

These foods increase the risk of overweight and obesity, which can lead to poor blood glucose control, high cholesterol and blood pressure. These conditions collectively contribute to an increased risk of metabolic syndrome and cardiovascular disease (CVD).

What are “slow foods”?

“Slow foods”, as opposed to fast foods, are considered foods that take more time to prepare using whole or minimally processed foods. These are rich in nutrients and complex carbohydrates and low in saturated fat, trans fat and sodium.

Slow foods are, therefore, prepared at home using ingredients like fresh, frozen or dried fruit and vegetables, fish, meats, beans, dairy products like unsweetened milk, plain unsweetened yoghurt and cheese, unsalted nuts and grains.

Eating slow foods can support cardiovascular health by lowering cholesterol and blood pressure, controlling blood glucose levels, and decreasing the risk of obesity. This is because slow foods are likely to contain less energy, sugar, salt, saturated and trans fats, be higher in fibre, and contain more vitamins and nutrients compared to fast foods.

How do fats contribute to heart disease? 

There are two main groups of fats - ‘healthy fats and ‘unhealthier’ fats.

The healthy fats are Mono-Unsaturated Fatty Acids (MUFA) and Poly-Unsaturated Fatty Acids (PUFA).

The ‘unhealthier’ fats are Saturated fatty acids and Trans fatty acids. Fats have important functions in the body as they provide energy, protect organs, support cell growth, control cholesterol and blood pressure levels, and help the body absorb vital nutrients.

However, fast food contains high amounts of fat, predominantly saturated and some trans fatty acids (unhealthier fats). Saturated and trans fats are responsible for increasing LDL-cholesterol (the bad cholesterol) and decreasing HDL-cholesterol (the good cholesterol).

If ‘unhealthier’ fats are consumed in high amounts, it can result in too much LDL-cholesterol building up in the blood vessels, causing increased blood pressure and a reduced flow of blood to the heart and brain. This reduction in blood flow can cause cardiovascular problems such as heart attacks and strokes.

In addition, high saturated and trans fat intake can lead to weight gain, development of insulin resistance and cardiovascular events. This explains why higher consumption of fast food is linked to an increased risk of CVD and related mortality.

With so-called slow foods prepared at home, you can control the amount and type of saturated fat in the diet, making it easier to include more of the ‘healthy fats’ (MUFAs and PUFAs), and less of the ‘unhealthier fats’ (saturated and trans fats).

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MUFAs are found in plant foods such as avocados, nuts, and vegetable oils. These fats can lower LDL-cholesterol levels and therefore reduce one’s risk for cardiovascular disease.

PUFAs are found in plant and animal foods, such as fish, vegetable oils, sunflower seeds, and walnuts. By replacing saturated fats with PUFAs, one can achieve lower cholesterol levels, slightly lower blood pressure and controlled blood sugar levels.

What's the hype around carbohydrates? 

Fast food contains high amounts of refined carbohydrates, including added sugar, which are rapidly digested by the body, resulting in unwanted spikes in blood sugar levels and hormonal insulin release.

If your blood sugar is continuously spiking, it can change the body's normal insulin response, leading to the development of insulin resistance and type 2 diabetes. A high intake of refined carbohydrates increases triglycerides (a type of fat), which increases the risk for CVD.

READ MORE | Everything you must know about carbohydrates

The type of carbohydrates found in whole foods are ‘complex’ carbohydrates, meaning they are digested slower by the body and therefore do not cause spikes in blood sugar levels. Complex carbohydrates are found in whole grains, beans, fruit, and vegetables. Fibre is a type of complex carbohydrate that the body cannot digest.

Fibre is beneficial for cardiovascular health as it can lower blood pressure and cholesterol levels and control blood sugar levels. Fibre also makes one feel fuller for longer, which can prevent overeating and reduce the risk of obesity. Eating complex carbohydrates can therefore help to prevent the onset of CVD, type 2 diabetes, and obesity. 

Which micronutrients affect heart health?

Fast foods are often high in sodium (salt), which largely contribute to the development of high blood pressure. A high intake of sodium increases blood volume, thereby increasing blood pressure. High blood pressure is dangerous as it can increase the risk of stroke and heart attack and further aggravate existing heart disorders.

As slow foods consist largely of fresh fruit, vegetables and whole grains, they are typically rich in vitamins and minerals, including antioxidants. Diets that include antioxidants can reduce oxidative stress-related cardiovascular disease, type 2 diabetes, and obesity.


In a nutshell, these are the three things to contemplate the next time you evaluate your eating habits:

1. Fast foods often contain high amounts of unhealthier fats

Replacing unhealthier fats with healthy fats (MUFAs & PUFAs) to decrease LDL-cholesterol can reduce your risk of stroke or heart attack.

2. Fibre is an important food component

Reducing consumption of refined CHO found in fast foods and increasing fibre intake through slow foods can reduce cholesterol, control blood glucose levels and lower blood pressure. These can lead to better weight management and reduce the risk of developing NCDs.

3. Fast foods are often high in salt and low in essential micronutrients

High salt diets are associated with high blood pressure, significantly contributing to heart disease. Therefore, consuming slow foods, which are high in vitamins, minerals and antioxidants, is beneficial to heart health. 

I think you can agree that slow (food) but steady wins the race! 

Keri Lambooy and Megan Lee are final year BSc Dietetics students at Stellenbosch University. 

This resource is for educational purposes only and cannot replace individual assessment by a healthcare professional. ADSA is the Association for Dietetics in South Africa. Visit to find more dietitians in your area.

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