How harmful is Sugar?

How harmful is sugar? Is hidden sugar a particular health risk? Are some sugars healthier than others? How much sugar should we be consuming?

Action on Sugar was launched in the UK in 2014. Supported by 23 expert advisors it is working to persuade manufacturers to reduce the amount of sugar added to food and soft drinks.

So how harmful is sugar really? And what do we mean by ‘sugar’ anyway?

Is this just the sugar we add to tea and coffee?

No, that’s just one type of sugar i.e sucrose, which comes from sugar cane or sugar beet. There are other types of sugar, like glucose (from carbohydrates), fructose (from fruits) and lactose (from milk).

Some occurs naturally, for instance in fruit. However other sugars are often added to food. These days most soft drinks, fruit drinks and energy drinks contain added sugar. 

High fructose corn syrup in particular is an ingredient in many processed foods - like biscuits, ice cream, cereal bars, yoghurt drinks, cakes, pastries, bread rolls and cereals. Many products advertised as low fat contain high levels of sugar. For example a low fat fruit flavoured yoghurt can contain up to ten tea spoons of fructose based sweetener in one pot. 

Sugar is also found in food that you may not think of as sugary - like soups, cereals, tomato ketchup and coleslaw. A 2016 US study reports that ultra-processed foods (containing additives like flavouring, colours, sweeteners and emulsifiers) often have a particularly high sugar content.

Most food labelling in the UK specifically identifies how much of the carbohydrates in a product are made up of sugar. It is in the small print – but worth checking.

So, is ‘hidden sugar’ a health risk?

We may be consuming a lot more sugar than we realise – which makes it important to know how harmful sugar really is. Is it, as American Professor Richard Johnson claims, ‘an environmental toxin with major health implications.’

Research in recent years has linked sugar with a range of serious health risks and illnesses. These include:

Diabetes - Regularly consuming sugar sweetened drinks was associated with a greater incidence of type 2 diabetes. That was the conclusion of an analysis of 17 studies, published in the British Journal of Sports Medicine in 2016. 

High Blood Pressure – Sugar-sweetened drinks and sugars were significantly associated with raised blood pressure. That’s according to both an American study published in 2010 and a UK study published in 2011. These findings were confirmed in a 2014 review of the evidence. 

Becoming Overweight and Obese – Rapid weight gain occurs after increasing sugar intake. However, a 2012 systematic review advised, ‘Fructose does not seem to cause weight gain when it is substituted for other carbohydrates in diets providing similar calories.’ This suggests the risk is through sugar consumption leading to increased calorie intake.

Coronary Heart Disease (including Heart Attack and Stroke) A study of over 42,000 men, published in 2012, suggested that consumption of sugar-sweetened beverages was associated with increased risk of Coronary Heart Disease While in 2017 the American Heart Association issued a Scientific Statement which concluded that strong evidence supports the association of added sugars with increased cardiovascular risk in children.

A 2011 article in the European Journal of Internal Medicine highlighted, ‘how an excess of dietary carbohydrates, particularly fructose, alongside a relative deficiency in dietary fats and cholesterol may lead to the development of Alzheimer’s Disease.’ However, a study published in 2017 suggests that it is artifically sweetened drinks which are associated with an increased risk of Alzheimer's - so for the moment the evidence suggests that the four health risks sugar is associated with are Type 2 Diabetes, High Blood Pressure, Obesity and Coronary Heart Disease.

Might the risk from sugar be exaggerated?

Some commentators believe so. Here are some of their reasons:

  • It is probably simplistic to blame sugar and sugar alone for a range of diseases which are more complicated than that. As NHS Choices points out, other dietary factors may be at work, such as fat and salt – and, as we have reported elsewhere on Age Watch, lack of exercise may also be implicated.
  • Fructose is associated with a range of serious medical conditions but clinical trials have yet to prove beyond all doubt that it causes them  - a point made by the Senior Editor of Harvard Health in 2011.

However, this ‘defence’ of sugar is usually relative rather than absolute – typically seeing sugar as one of a number of health risks rather than the only one.

Are some sugars better for us than others?

The sugars (fructose) which occur naturally in most fruit grown in the UK seem healthiest, as they have a relatively low glycemic index. Eating whole fruits is healthy because of the fibre they contain (particularly in the skins). This slows the rate at which the sugars are absorbed by the body.

Conversely, sugar sweetened drinks have a high glycemic index and are associated with a number of health risks. In addition they don’t make us feel full in the same way as more solid forms of sugar, making it easier to consume too much sugar and become overweight. 

How much sugar should we be consuming?

A maximum of 10% of our energy should come from sugar. That’s what a 2013 editorial in the British Medical Journal described as a realistic practical target.

That’s 50 grams (or around 12 teaspoons a day). This may seem like quite a lot. However, the average American consumes nearly twice that amount just through the hidden sugar in their food and drink – before any sugar they add themselves.

In 2015 the World Health Organisation suggested that reducing our sugar consumption even further (to below 5% of our total energy intake) would provide additional health benefits. 


  • High sugar consumption is associated with a range of serious health risks.
  • We may not realise how much sugar we are consuming because much of it is ‘hidden’ in processed foods and soft drinks.
  • Be wary of 'low fat' and ultra-processed products, as they often contain high levels of sugar. 
  • Sugar may be only one of a number of risk factors – with salt, fat and lack of exercise other examples.
  • However, it is likely to be safer to limit our sugar intake.
  • We can do this, for example, by choosing water rather than soft drinks, limiting how much sweet food we eat (like biscuits, cakes and pastries) and checking the levels of sugar in apparently ‘healthy’ foods like cereals, low fat yoghurt and energy drinks. 

Revised and updated by Viktoria Semanov, October 2017. Next review due September 2021.