Sugar and disease

Processed sugar intake increases the risk of obesity, high cholesterol and type two diabetes (T2D), and, together with other lifestyle factors such as lack of exercise, considerably elevates the risk of heart disease, stroke, cancer and numerous other chronic diseases. This page summarises some of the evidence which links sugar and disease and offers practical lifestyle tips to help you safely keep your blood sugar within the normal healthy range.

Processed sugar and, to a lesser extent, processed carbohydrates are harmful because they lead to inappropriately raised blood sugar levels due to their high glycaemic index (GI). Foods with a high GI – ranked on a scale from 0 to 100 by the World Health Organisation (WHO) – cause marked fluctuations in blood sugar levels because they are rapidly digested and absorbed, a process which triggers a rapid insulin response. On the other hand, low GI foods, by virtue of their slow digestion and absorption, produce gradual rises in blood sugar and insulin levels.

Sugar is known to:


Reducing processed sugar intake

Whole fruits are very healthy and have relatively low sugar levels compared to processed sugar (see table below). They also contain fibre, minerals and vitamins, so should not be avoided. When fruit is juiced or put in a smoothie, its healthy structure is broken down, and sugar hits the bloodstream much faster (increases the glycaemic index- GI). Likewise, drying fruit also substantially increases the GI and should be avoided, especially on an empty stomach.

Try to stop eating sweets, mints, toffees or chocolate with added sugar. Refrain from adding sugar to tea or coffee. Avoid eating foods with added sugar such as sugary cereals. Sugar-free chocolate does exist, and this is actually full of healthy minerals and polyphenols. Avoid any sugar on an empty stomach such as first thing in the morning and eat slow-release carbs and fats instead see how to make an idea breakfast bowl.

Sometimes it’s not so obvious where sugar has been added, especially as some of these foods may be advertised as healthy – reduced fat ready meals, salad dressings, pasta sources, yoghurt or muesli cereals. Some restaurants add sugar to their curries and stews – you can instruct the waiter to ask the chef to omit the sugar – more healthy recipe ideas.

Other factors which help lower blood sugar

ex-people-smallExercise: It has long been established that exercise reduces plasma insulin levels, a biochemical response which has recently been reported in an exercise intervention study involving breast cancer survivors. If you are interested in reading a comprehensive evidence review of the 180 beneficial biochemical changes which occur in the body after exercise, click here.

polyphenolsPolyphenols: Polyphenol-rich foods have numerous health benefits, including lowering the glycaemic index of foods, lowering blood sugar and decreasing the risk of diabetes. Good examples include turmeric, cinnamon, broccoli, tea, coffee, chocolate, pomegranate, red wine and berries – read more about how polyphenols reduce blood sugar.

How to increase your polyphenol intake? Try to add colour, spice and flavour to every meal. Have a salad or leafy green vegetables with every meal, and liberally use herbs, garlic, chilli and other spices. The recipes in the cancernet blog provide examples of low sugar, polyphenol-rich meals. Additionally, consider a polyphenol-rich whole food supplement. Pomi-T, a product tested in a scientific study, containing purified, high grade, verified broccoli, green tea, turmeric and pomegranate, is our recommended whole food, polyphenol-rich supplement –  more about polyphenol-rich food supplements.

Timing and food combinations: The timing and total content of the entire meal influences GI. Wholemeal bread has a slower absorption, as well as more vitamins and fibre than typical thin white, while wholemeal or fava bean enriched pasta, as well as al dente pasta, have a slower GI than overcooked white pasta [Tunco]. Processed sugars on an empty stomach, such as first thing in the morning, are particularly harmful as they are absorbed rapidly. Conversely, a small sweet dish after a healthy meal will have less of an impact as the stomach has plenty of other food to slow the gut down.

Intermittent fasting: In humans, a study involving women with breast cancer has revealed that overnight fasting for a period of 13 hours was associated with a lower risk of breast cancer recurrence, significantly better sleep and lower levels of glycated haemoglobin (a measure of average blood sugar levels over a period of months). Another small study with female volunteers investigated intermittent energy restriction (IER) in the form of a 2:5 diet (2 days of 65 % energy restriction per week). Researchers reported a 4.8% weight reduction and an 8% reduction in total body fat over one month. 55% of subjects demonstrated changes in lipid and glycogen synthesis and reduced markers of insulin resistance.

Table of percentage sugar levels in common foods

% whole food % whole food
Table sugar 100% Low Fat Granola 28%
Brown sugar 97% Pickled Relish 29%
Fructose syrup 93% Chocolate Ice Cream 25%
Honey 82% Frozen Yogurt 24%
Butterscotch 81% Grapes 16%
Boiled sweets or mints 80% Cherries 14%
Fudge and toffee 80% Bananas 14%
Sucralose (Splenda) Sweetener 80% Apples 13%
High-Fructose Corn-Syrup 76% Pomegranate 10%
Molasses 75% Kiwi 10%
Maple Syrup 72% Pineapple 11%
Dried mango 70% Honey melon 8%
Currents/raisins 65% Figs 7%
Dates 63% Plumb 7.5%
Creamed sandwich biscuits 61% Blueberries 7%
Dried papaya 55% Blackberries 6%
Dried pear 55% Strawberries 6%
Dried fig 55% Papaya 6%
Chocolate-Hazelnut Spread, 53% Casaba melon 5.5%
Most Jams 49% Cantaloupe melon 5.5%
Frosted corn cereals 39% Tomato 2.5%
Cocoa Crispies 39% Lemon 2.5%
Chocolate Chip Cookies 37% Avocado 0.9%
Cranberry Sauce 37% Lime 0.2%


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Summary – Tips to reduce sugar and disease

  • Avoid adding sugar to tea or coffee or to food during cooking
  • Exercise and be physically active most days
  • Fast for 13 hours overnight
  • Don’t snack between meals
  • Eat some polyphenol-rich foods with every meal
  • Avoid processed foods, pre-packed ready meals or those labelled as ‘diet’
  • Avoid sugary snacks
  • Avoid sweet drinks such as cola or other fizzy drinks
  • Avoid processed fruit juices with the pulp removed
  • Avoid sugary breakfast cereals especially with added sugar or honey
  • Change from white to wholemeal bread
  • Use wild rice instead of white rice
  • Eat salad and vegetables with white pasta to slow its GI
  • Try quinoa instead of white rice or pasta
  • For a treat, consider chocolate made without sugar
  • Make cakes without sugar – use fruits such as dates or banana instead
  • If you need to add something sweet use natural alternatives (e.g. Stevia)
  • If you are craving something sweet restrict consumption to post meal times
  • Eat the whole fruit
  • Drink blended fruit and vegetable smoothies rather than juices


Sugar and cancer – Professor Robert Thomas et al 2017 ICON
The biochemistry of exercise. Robert Thomas & Stacey Kenfield 2017 BJSM
Polyphenols and cancer. Robert Thomas et al BJMP 2015
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Kim Y. Polyphenols and glycemic control. Nutrients 2016 5;8(1)
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Sun Q. Urinary excretion of polyphenol metabolites is associated with a lower risk of T2D. J. Nutr. 2015
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