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.

Too much blood sugar, too bad for your ears

Audiologist, Sakhile Nkosi, unpacks whether there is a link between diabetes and hearing loss.

Every person living with diabetes worldwide knows upon diagnosis that there are different types of diabetes e.g. Type 1 and Type 2 diabetes. Your doctor likely provided rigorous counselling, explaining all the clinical manifestation present in diabetes, such as loss of sensation in the feet (neuropathy), vision disturbances, kidney problems, etc. and the importance of taking medication and maintaining a healthy lifestyle to prevent these complications.

Most research conducted, so far, gave concrete evidence on what can possibly go wrong with an individual living with diabetes. Though, one of the unfamiliar complications that the diabetic community isn’t often made aware of, is the effect of diabetes on the ear structure. Hence, hearing and balance.

The ear

The ear is one of the most important organs in the human body. It provides two basic functions: hearing and to balance. Hearing itself is a special sense, just like vision; it forms basis of communication.

Hearing loss occurs as a result of damage either in the outer, middle or inner (retro-cochlear) part of the ear. If hearing loss is left untreated, it can have negative consequences on an individual’s life. This includes physical, emotional and social health and can cause disturbing effects in relationships with colleagues, family and friends.  In children, hearing loss can cause a delay in speech and language development.

The link between diabetes and hearing loss and balance

Current research reveals the link between diabetes and hearing loss. As early as 2008, the National Health and Nutrition Examination Survey results found that individuals with diabetes are at risk of developing hearing loss compared to those without diabetes.

The results of the survey revealed that individuals with diabetes are prone to a degree of hearing loss ranging from mild to moderate. The type of hearing loss common in diabetic patients is sensorineural in nature, implying the hearing loss is caused by damage to the inner ear or the hearing nerve that carries sound to the brain.

In terms of balance, patients who are diagnosed with diabetes may be at a higher risk for falls. This happens because of how diabetes affects the normal function of vision, sensation in feet, ankles, knees, hips, and inner ears.

As you may be aware, diabetes can affect the normal function of the retina of the eye. If the retina is damaged by diabetes and vision is distorted, the brain is deprived of information and needs help to maintain your balance.

Diabetes also can affect whether you have sensation in your feet. If your feet are numb (due to diabetes), you’ll not be able to sense when you are leaning forward, backward or side to side. In darkness, this becomes a larger problem because you lose the help that you normally would get with vision. This becomes a larger problem, a fall risk, if you also lose function in the inner ears.

Signs and symptoms of hearing loss

One might experience a few or a combination of symptoms.

  • Speech and other sounds are perceived muffled.
  • Difficulty understanding words or speech in a presence of background noise or crowd.
  • Frequently asking other to speak more slowly, clearly and loudly.
  • Constantly turning the TV/radio volume up.
  • Often withdrawing from conversations.
  • Avoiding certain social settings.

How to protect your hearing and balance?

You might have not yet experienced symptoms related to hearing and balance, but prevention is better than cure. Take charge of your diabetes by:

  • Controlling your blood sugar by taking your prescribed medication.
  • Noise can damage your hearing. At home, wear ear plugs when you are running the lawn mower or any other loud appliance. Take ear plugs with you when you attend concerts and sporting events that may be too loud.
  • Have your hearing tested by an audiologist on a regular basis. At least annually or sooner if you notice changes.
  • If you have a hearing impairment, your audiologist might fit you with hearing devices that will improve your ability to converse with others (e.g. hearing aids and assistive hearing devices).
  • Reduce background noise when you have a conversation (radio, TV, etc.)
  • Your doctor may recommend that your inner ears be evaluated by an audiologist to diagnose why you are dizzy and whether it is vertigo. Referrals will be made to other professionals, such as physiotherapists and occupational therapist.
  • Work with your doctor to determine whether changes in your medications might explain changes in your balance.


The Audiology Project

Bainbridge, K., Hoffman, H., & Cowie, C. (2008). Diabetes and Hearing Impairment in the United States: Audiometric Evidence from the National Health and Nutrition Examination Survey, 1999 to 2004. Ann Intern Med

Akinpelu, O., Mujica-Mota, M., & Daniel, S. (2014). Is type 2 diabetes mellitus associated with alterations in hearing? A systematic review and meta-analysis. Laryngoscope, 767-76.

Arlinger, S. (2003). Negative consequences of uncorrected hearing loss – A review. International Journal of Audiology, 42(2), S17–2 S20.

Hlayisi, V., Petersen, L., & Ramma, L. (2018). High prevelance of disabling hearing loss in young to middle-aged adults with diabetes. Int J Diabetes Dev Ctries, 39(1), 148-153. doi:10.1007/s13410-018-0655-9.


Sakhile Nkosi is an audiologist in the public sector. He has been exposed to lots of conditions that are in line with the global burden of diseases, one of them is diabetes. Currently, Sakhile holds a portfolio as a public sector representative at the South African Association of Audiologists (SAAA) and is also part of The Audiology Project (TAP), South African Cohort. 

Sugar tax is here

Sugar tax in South Africa came into effect on 1st April 2018. Abby Courtenay recaps what sugar tax is, the aims and how it will affect you.

Firstly, what is sugar tax?

We all know (or should know) what tax is. It is a compulsory payment you make to the South Africa Revenue Service (SARS) on a regular basis to fund the South African government and their initiatives.

Sugar tax is similar but rather than being compulsory it is a method to dissuade consumers on a household level (this means you) from purchasing and subsequently consuming less healthy sugary choices by making them more expensive.

Whilst we are currently unsure of how South African’s will react to these increases, studies from around the world have shown that only when a hefty sugar tax (up to 20%)1 is implemented does this truly have an impact on consumer spending.

In some countries, when foods become more expensive, consumers tend to look for less expensive substitutes. In this case, beverages that are light/zero or sugar-free (usually artificially sweetened) may be a cheaper (but similar) substitute that consumers might lean towards.

This tax might also drive manufacturers to find innovative ways to reduce the amount of sugar in their products to prevent the tax from affecting their sales.

In a modelling study in South Africa it has been predicted that a sugar tax increase of 20% may reduce obesity rates by 3,8% in males and 2,4% in females.2

What are the sugar tax charges?

Currently, sugar tax is to be implemented only to sugar sweetened beverages (SSBs), syrups and other concentrates, not food nor 100% fruit juice or milk. Sugar tax will be charged at the following rates:3,4

  • There is a threshold of 4g sugar/ 100mL of beverage below which sugar is not taxed.
  • SSBs in excess of 4g sugar/ 100mL beverage will be taxed at 2,1 cents per gram above this rate (this is approximately 11% for the most popular soft drink).
  • Syrups and concentrates in excess of 4g sugar/ 100mL beverage will be taxed at 1,05 cents per gram above this rate.

What will happen with this extra money?5

The revenue generated from sugar tax should ideally be used to fund further investigations and interventions, to help reduce obesity in our country. Obesity is rapidly growing out of proportion, much the same as many South African’s waist lines.

Why is it important to reduce your intake of free and added sugars?

Firstly, let’s define what free and added sugars are:

Free sugars are energy-providing sugars, such as monosaccharides (e.g. glucose, fructose, galactose) and disaccharides (e.g. lactose, maltose and sucrose – called table sugar), that are added to foods and drinks during processing by food manufacturing companies, cooks or consumers, as well as sugars naturally present in honey, syrups, fruit juices and fruit juice concentrates – so free sugars include added sugars.

Free sugars do not include intrinsic sugars, which are sugars incorporated within the structure of intact fresh fruits and vegetables, and sugars naturally present in milk.5

There is a large body of evidence that links a high intake of free and added sugars (especially in the form of SSBs) to an increased overall energy intake and subsequently weight gain (and an increased risk of becoming overweight or obese).6,7

Obesity in South Africa

We know that this is a huge (pun intended) problem for South Africans; with up to 65,1% of women and 31,2% of men being overweight or obese and alarmingly, 22,9% of children aged 2-14 years are already overweight/obese.8 Obesity substantially increases your risk for diseases, such as diabetes, heart disease, cancer and respiratory diseases.

In addition to this bleak picture, a high intake of free sugars also increases your risk for dental caries a.k.a rotten teeth.6,7 Treating and managing these diseases places a huge financial burden, not only on the patient and their family but the South African healthcare system as a whole.

The World Health Organization (WHO) recommends that no more than 10% of your total energy intake should come from free/added sugars, and they recommend a further reduction to 5% for additional health benefits. In household measurements, this equates to < 6 – 12 tsp added sugar per day (and to put this into context, 1 x 330mL tin of popular soft drink can contain up to 9 tsp added sugar).

We must always remember that many sugar sweetened products are high in energy and do not contain a significant amount of beneficial nutrients (vitamins and minerals). Thus, when you consume them, you’re displacing more nutritious food options thus decreasing the overall quality of the diet and placing the risk of micronutrient deficiencies.8

So, will sugar tax alone help decrease the burden of disease in our country?

It is important to note that whilst price is a major determining factor for many, it is not the only one. Factors, such as taste and cultural norms, also shape purchasing decisions. Interestingly, only 1 in 7 women consider health aspects when purchasing food.8 Just as taxing tobacco does not reduce or stop people from smoking, taxing SSBs will not reduce or stop all purchasing and consumption of SSBs and reduce obesity on its own. So, on its own it is not enough, however, it is potentially a step in the right direction as part of an overall strategy to tackle a complex problem.5


  1. Powell, LM., Chriqui JF, Khan T, Wada R, Chaloupka FJ. Assessing the potential effectiveness of food and beverage taxes and subsidies for 
improving public health: a systematic review of prices, demand and body weight outcomes. Obesity Reviews, 2013; 14:110-128
  2. Manyema M, Veerman LJ, Chola L, Tugendhaft A, Sartorius B, Labadarios D, et al. (2014) The Potential Impact of a 20% Tax on Sugar- Sweetened Beverages on Obesity in South African Adults: A Mathematical Model. PLoS ONE 9(8): e105287. doi:10.1371/journal.pone.0105287
  3. Economics Tax Analysis Chief Directorate. Taxation of Sugar Sweetened Beverages: Policy Paper. 8 July 2016. 
  4. Republic of South Africa, Minister of Finance. Draft: Rates and Monetary Amounts and Amendment of Revenue Law Bill. 22 February 2017. 
  5. Association of Dietetics in South Africa (ADSA). Position Statement on the Proposed Taxation of Sugar-Sweetened Beverages in South Africa. April 2017.
  6. World Health Organization. Guideline: Sugars intake for adults and children. Geneva: World Health Organization; 2015 
  7. Scientific Advisory Committee on Nutrition. Carbohydrates and Health. 2015, London, TSO 
  8. Shisana O, Labadarios D, Rehle T, Simbayi L, Zuma K, Dhansay A, Reddy P, Parker W, Hoosain E, Naidoo P, Hongoro C, Mchiza Z, Steyn 
NP, Dwane N, Makoae M, Maluleke T, Ramlagan S, Zungu N, Evans MG, Jacobs L, Faber M, & the SANHANES-1 Team (2014) South African National Health and Nutrition Examination Survey (SANHANES-1): 2014 Edition. Cape Town: HSRC Press. (


Abby Courtenay RD (SA) is an associate dietitian at Nutritional Solutions Grayston and Melrose. She graduated with a Bachelor of Dietetics at University of Pretoria and also holds a Masters’ degree in Nutrition from the University of Stellenbosch. Abby has a special interest in: women’s health, infant feeding and oncology.

The low down on South Africa’s sugar tax

The Minister of Finance announced in the February 2016 National Budget a decision to introduce a tax on sugar-sweetened beverages (SSBs), with effect from 1 April 2017, to help reduce excessive sugar intake by South Africans. A revision of the proposed tax was discussed in the February 2017 Budget Speech, where it was announced that the tax will be implemented later in 2017 once further consultations have taken place. The Association for Dietetics in South Africa (ADSA) welcomes this step as one part of the solution to address the obesity problem and improve the health of South Africans.

How much sugar do South Africans really consume?

When you think of sugar-sweetened beverages, the first thing that comes to mind is the regular fizzy drink, but the term encompasses far more than that. SSBs are beverages containing added sweeteners that provide energy (calories or kilojoules) such as sucrose, high-fructose corn syrup or fruit-juice concentrates. This includes carbonated drinks (fizzy soft drinks and energy drinks), non-carbonated drinks (sports drinks, iced teas, vitamin water drinks and juice concentrates), sweetened milk drinks and sweetened fruit juices. And, many of us do not realise just how much sugar is found in these drinks. For example, a 330ml bottle of iced tea has a little over six teaspoons of sugar.

ADSA is concerned that the intake of added sugars (sugars added to foods and drinks during processing by the food manufacturing companies, cook or consumer) is increasing in South Africa, both in adults and children. Some estimate that children typically consume approximately 40-60g/day of added sugar, possibly rising to as much as 100g/day in adolescents. High intakes of added sugar, particularly as SSBs, has been shown to lead to weight gain and cause dental caries. The added sugar in these drinks makes them high in energy (kilojoules). Because these drinks don’t make us feel full in the same way that eating food does, most of us don’t reduce our food intake to compensate, making it easy to consume too many kilojoules. Over time, these extra kilojoules can cause one to become overweight, putting us at risk for diabetes, heart disease and certain cancers. Obesity is already a massive problem in South Africa, with two in three women and one in three men being overweight or obese, as well as almost one in four children.

What is ADSA’s recommendation for sugar intake?

ADSA supports the recommendations by the World Health Organisation (WHO) and the South African Food-Based Dietary Guidelines that we need to reduce the intake of beverages and foods that contain added sugars, such as sugar-sweetened beverages, sweetened yoghurts, frozen desserts, some breakfast cereals, ready-to-use sauces, cereal bars, health, savoury and sweet biscuits, baked products, canned or packaged fruit products, sweets and chocolates. The WHO advises reducing the intake of free sugars found in foods and beverages (including added sugars, but excluding sugars naturally present in fresh fruits, vegetables and milk) to less than 10% of total energy (kilojoule) intake for the day (i.e. 50g of sugar, which is approximately 12 teaspoons per day), with a conditional recommendation to further reduce intake to 5% of total energy (approximately six teaspoons per day) for additional health benefits. The South African Food-Based Dietary Guidelines also advise to ‘use sugar and foods and drinks high in sugar sparingly’. To put this into perspective, a 500ml bottle of a carbonated drink will provide your maximum sugar allowance for an entire day!

The sugar tax – is it a good idea?

The proposed tax on SSBs will mean an additional tax will be added on to the purchase price of sugary drinks, which is intended to decrease the purchase and consumption of SSBs. Encouragingly, in Mexico, a sugar tax has reduced sugary drink sales by 12% in the first year. The sugar tax is likely to affect shelf prices, but will also motivate manufacturers to reduce the amount of sugar added to their products. Initially, the proposal was for a tax rate of 20% on the added sugar content of a beverage. But in the February 2017 Budget Speech, it was announced that the proposed tax rate has been reduced to about 11%. ADSA is concerned that the lower tax rate might not be sufficiently high enough to have a significant impact on purchasing behaviour, and has submitted comments to National Treasury to motivate to strengthening the tax. ADSA welcomes the proposed tax on SSBs, but acknowledges that the sugar tax is only part of the solution to address the growing obesity problem. Just as taxing tobacco does not reduce or stop smoking by all people, taxing SSBs will not reduce or stop all purchasing and consumption of SSBs and reduce obesity on its own. Obesity is a complex condition, and sugar is not the only cause. There is a need for multiple interventions across a variety of different sectors to address unhealthy diets and lifestyles and have an impact on the obesity epidemic. ADSA recommends that revenue generated from the tax should go towards health promoting interventions, such as subsidies to reduce the costs of fruits and vegetables, education around healthy choices, and creating an enabling environment to make those healthier choices easier.

In addition to reducing the consumption of SSBs to prevent obesity and promote long-term health, ADSA continues to recommend a healthy diet which includes whole grains, fruit, vegetables, nuts, legumes, healthy oils, proteins such as lean meats and seafood, and a reduced intake of processed meats and salt, accompanied by regular physical activity.

To find a registered dietitian in your area, visit

ADSA’s detailed Position Statement on the Proposed Taxation of Sugar-Sweetened Beverages, with references, can be accessed here:

This article was written by The Association for Dietetics in South Africa (ADSA).