Are there links between sugar, cancer and diabetes?

Dietitian, Berna Harmse, unpacks the evidence on the effects sugar has on our bodies and the direct and indirect links it has with cancer and diabetes.

Researchers are continuously investigating the connection between sugar and cancer. Unfortunately, the topic causes a lot of anxiety and misinformation in the media and on the internet. There is no strong evidence that directly links sugar to increased cancer risk, but there is an indirect link.

What is the indirect link?

All the cells in our body, including cancer cells, need sugar (glucose) from our bloodstream for fuel. We get this blood glucose from carbohydrate-containing foods, including fruit, vegetables, starch, wholegrains and dairy. Some glucose is also made in our bodies from protein.

Sugar doesn’t make cancer grow faster. As stated in a Mayo Clinic article, “All cells, including cancer cells, depend on glucose for energy. But giving more sugar to cancer cells doesn’t speed up their growth. Likewise, depriving cells of sugar doesn’t slow down their growth.”

Eating high-sugar foods increase our body weight and body fat, which is linked to some kinds of cancer. For that reason, the American Institute for Cancer Research recommends increased intake of wholegrains, vegetables, fruit and beans; and reducing intake of sugary beverages and sweets.

Influence on weight and metabolism

Let’s look at the influence on weight and metabolism. The Academy of Nutrition and Dietetics reinforces that much research shows that higher insulin (a hormone) levels and related growth factors may influence cancer cell growth the most, as well as increasing the risk for other chronic diseases.

Different types of cancer cells have high amounts of insulin receptors, making them respond more than normal cells to insulin’s ability to promote growth.

All the food we eat gets broken down to smaller bits, in the process we call digestion. Glucose sits in the veins, and insulin working like a key, unlocks the veins so the energy can get to the rest of the body to be used.

When insulin levels are high, it is a signal to the body that there is plenty of food available, and that these kilojoules should be used to grow and build reserves for future times of starvation.

Insulin levels rise quickly when we eat unrefined carbohydrates (white bread and sweets) and leads to a drop in blood glucose levels. Low blood glucose is the biggest appetite stimulant in the world. It makes you overeat, which again causes a release of more insulin and thus a cycle of eating more and gaining weight and body fat continues.

Inactivity and being overweight also increases insulin levels, and so insulin resistance is caused. If no intervention is launched at this stage, diabetes soon follows.

Is there a link between cancer and diabetes?

Research is being done to investigate the direct link between cancer and diabetes, with some researchers speculating that the underlying metabolic factors, like long-term stress and the inflammation that comes with it, underpins some of the patterns behind it.

So, what do I eat considering all this information?

If you can keep your food portions controlled and maintain your weight, you are on the right track.

Avoid refined carbohydrates, like take-aways, white bread products, and sweetened foods and beverages. Rather choose high-fibre carbohydrates, like wholegrains, fruit, vegetables and legumes. Higher fibre foods are the cornerstone of blood glucose management.

The five-a-day approach is still best – try to have at least two fruits and three vegetables per day, or vice versa. This ensures the adequate intake of antioxidants which plays a big role in terms of fighting and preventing chronic diseases.

Vegetables and salad should take up half of your dinner plate, and carbohydrate and proteins should be the side dishes of the meal.

Try to have breakfast every morning and do not skip meals

Aim to do some form of physical activity most days of the week.


Berna Harmse is a private practicing dietitian in Cape Town, she holds a MSc in Dietetics and has a special interest in oncology nutrition. She is also an external lecturer at Stellenbosch University Division of Human Nutrition.

Sleep apnoea and diabetes – is there a link?

Adele Duvenage, the Snore Sister, explains the link between sleep apnoea and diabetes.

Why do people snore?

During normal sleep, the muscles that control the tongue and soft palate hold the airway open. If these muscles relax, the airway becomes narrower. As one breathes in, the soft or floppy part of the throat vibrates; snoring being the result. In some cases, snoring can be very loud and unpleasant for the person sleeping next to the snorer. But usually, this is the only way snoring is recognised – by a friend or partner who observes the person sleeping.

Worryingly, more complex conditions, such as sleep apnoea, can be consistent with snoring. Snoring is recognised as a more serious symptom of obstructive sleep apnoea (OSA). Before relying on techniques that may mask symptoms but not treat the underlying condition, people who snore should seek professional medical advice.

Even the loudest snoring does not mean that an individual has sleep apnoea. The symptom that is most suggestive of sleep apnoea is when the snoring stops. A simple apnoea screen test, in the comfort of your own home, will confirm or exclude the presence of sleep apnoea.

What is OSA?

Obstructive sleep apnoea is a sleep disorder, characterised by abnormal pauses in breathing or instances of abnormally low breathing, during sleep. Your airway may: narrow – limiting airflow as you breathe; vibrate – commonly heard as snoring; or collapse – you stop breathing.

Each pause in breathing, called an apnoea, can last from ten seconds to minutes, and may occur five times or more an hour, or several hundred times during the night. Similarly, each abnormally low-breathing event is called a hypopnea.

In OSA, breathing is interrupted by a physical block to airflow despite respiratory effort, making snoring common. A person with sleep apnoea is rarely aware of having difficulty breathing, even upon awakening. Symptoms may be present for years (or even decades) without identification, during which the sufferer may become conditioned to the daytime sleepiness and fatigue associated with significant levels of sleep disturbance.

There are several factors that can cause or worsen throat narrowing during sleep, such as being overweight, drinking alcohol, abnormalities of the nose and throat, smoking, and the use of sleeping pills.

Mild occasional sleep apnoea, which people experience if they have an upper respiratory infection, may not be worrying, but chronic severe obstructive sleep apnoea requires treatment to prevent low blood oxygen (hypoxemia), sleep deprivation, and other complications.

Is OSA life-threatening?

OSA has been linked to be the possible cause of several serious life-threatening conditions, including Type 2 diabetes, high blood pressure, high cholesterol, hypothyroidism (underactive thyroid), heart disease, heart attack, stroke, and depression.

Because of severely disrupted sleep, many people suffering OSA are excessively tired during the day. Studies have linked this tiredness to increased occurrence of traffic accidents.

The link between sleep apnoea and diabetes

It’s common for people with Type 2 diabetes to have sleep apnoea. Sleep apnoea and Type 2 diabetes often co-exist because of shared risk factors like obesity. The more severe the untreated sleep apnoea in a person with Type 2 diabetes is, the more difficult it is to control glucose levels.

The cause of sleep apnoea and how it connects to Type 2 diabetes has a lot to do with weight. People with Type 2 diabetes may be obese, insulin resistant, and have large amounts of visceral fat (the fat deep inside the body that surrounds the organs). The extra weight causes the tissues in the neck and throat to narrow the airway.

Sleep apnoea can also increase blood sugar levels because of the stress associated with chronic sleep deprivation and abrupt awakenings in the night. When you get stressed, your body releases stress hormones that can release stored glucose into the liver. Over time, the increase in blood sugar levels can contribute to insulin resistance.

Treatments and benefits

Getting a good night’s sleep, often for the first time in years, can lead to significant improvements in other aspects of a person’s life, including psychological health and happiness.

Treatment of OSA can lead to a reduction in snoring, which benefits the person with OSA as well as his/her bed partner. Improved sleep leads to an improved quality of life, as treatment reduces OSA- related symptoms.

Effective treatment of OSA reduces cardiovascular risk, which also results in better control or resolution of hypertension, and may have positive effects on diabetes control. In some people, lifestyle changes are enough to manage snoring and possible OSA. Some recommendations include losing excess weight, quitting smoking, and avoiding alcohol or sedatives in the evening.

Other methods used to treat OSA include oral appliances. For moderate to severe sleep apnoea, the most common treatment is the use of a continuous positive airway pressure (CPAP) or automatic positive airway pressure (APAP) device. These devices ‘splints’ the patient’s airway open, during sleep, by means of a flow of pressurised air into the throat.

The patient typically wears a facial mask, which is connected by a flexible tube to a small bedside CPAP machine. The CPAP machine generates the required air pressure to keep the patient’s airways open during sleep.

Advanced models may warm or humidify the air and monitor the patient’s breathing to ensure proper treatment. There are many different types of masks, and finding the most comfortable one is detrimental to effective CPAP treatment. It can be compared with buying a shoe that is comfortable – will you be able to wear that shoe every day? Will you be able to sleep with that mask every night?

Who is more likely to get sleep apnoea?

  • Males more than females
  • Obesity BMI>40
  • Age 40 – 64
  • Smoker>40/day
  • Family history of snoring
  • Neck circumference male ≥ 43 cm female ≥ 40 cm
  • Degenerative medical conditions
  • Nasal obstruction neuromuscular diseases

Symptoms of sleep apnoea

  • Feeling excessively sleepy or tired during the day in spite of a full night’s sleep.
  • Gasping, choking or snorting during sleep.
  • Waking up tired or with a headache.
  • Falling asleep in inappropriate situations (movies, church, sitting quietly) or without meaning to sleep.
  • Problems with memory and concentration.
  • Being ill-tempered or irritable.
  • Personality changes.
  • Aggressiveness, anxiety or irritability.
  • Depression.
  • Recurrent awakening at night.
  • Night sweats.
  • Weight increase.
  • Impotence.
  • Decreased libido (1/3).
  • Dry mouth/drooling.

MEET OUR EXPERT - Adele Duvenage

Adele Duvenage is a registered nursed. She is known for her expertise in OSA, its diagnosis and treatment and was responsible for successful negotiation for the performance of home-based sleep studies and tests to treat OSA by most major medical aids.