Not so sweet after all

Last week, a comment by a friend familiar with the beverage industry that not all "diet" drinks were the same, ignited my curiosity and prompted me to scrutinise the sweeteners used in the "diet" drinks.

Like many, drinking "diet" beverages was driven by the desire to avoid weight gain. Given that obesity carries with it an increased risk of high blood pressure, diabetes mellitus, heart disease and stroke, there is an increasing propensity for many who love the sweet taste of their beverages to adopt a preference for artificial sweeteners or sugar substitutes.

The "sweet tooth" is most intense in infancy, declines in adolescence, tapers in intensity in young adults, and plateaus or declines further with increasing age. Foods that carry the labels " diet" , "sugar free" or "very low calorie" contain artificial sweeteners or sugar substitutes which replace the sweetness and calories that we obtain from natural sweeteners such as sucrose (table sugar) , corn syrups, and fruit juice concentrates.

Non-nutritive sweeteners

Non-nutritive sweeteners (NNS) or caloric sweetener replacement are also referred to as very low-calorie sweeteners, artificial sweeteners, non caloric sweeteners, and intense sweeteners. Currently, the NNS which have been approved by the US Food and Drug Administration (FDA) include saccharin (Necta Sweet), aspartame (Nutrasweet, Equal), acesulfame potassium (Sweet One) , neotame, and sucralose (Splenda). For each NNS, there is an acceptable daily intake (ADI) that can be consumed daily throughout life without significant health risk based on known scientific data.

Saccharin has sweetness 200 to 700 times that of sucrose, has no calories and has a bitter aftertaste. Early 1977 rat studies showed bladder tumours with saccharin ingestion but subsequent human studies did not show an increase in cancer . Although FDA has not imposed restrictions, some public consumer groups have urged caution in infants, children, and pregnant women in view of the animal data.

Aspartame has sweetness 160 to 220 times that of sucrose and it contains calories, albeit lesser compared to the sweetness intensity. While most regulatory authorities have approved aspartame except for those with a genetic disease phenylketonuria, controversy continues to shroud it as a result of the circumstances surrounding its approval process by the FDA , the conflicting safety data and the lack of consensus among experts. These controversies have also led to its current re-evaluation by the European Food Safety Authority.

Sucralose is a low calorie chemically created product which has sweetness 600 times that of sucrose. Acesulfame potassium has sweetness 200 times that of sucrose. Although it is FDA approved, there have been concerns that it contains methylene chloride, a potential carcinogen, and its lack of long term data in humans. Neotame is chemically similar to aspartame but safe for consumption even for those with phenylketonuria and it has sweetness 7,000 to 13,000 times that of sucrose.

Nutritive sweeteners

Nutritive sweeteners

Nutritive sweeteners include naturally occurring sugar alcohols (polyols) from fruits and vegetables, natural sweeteners and novel sweeteners such as stevia (main picture), tagatose, trehalose. They provide sweetness, though less intense than sucrose , and provide lower calories than sucrose.

Sugar alcohols are carbohydrates that are neither sugars nor alcohols and include erythritol, mannitol, isomalt, lactitol, maltitol, hydrogenated starch hydrolysates, sorbitol and xylitol. In contrast to sucrose which contains four calories per gram, polyols contains about two calories per gram on average. They can cause elevation of sugars in diabetics but do not cause dental cavities. The intensity of sweetness as compared to sucrose varies from about one third (lactitol) to 100 per cent (xylitol). The main precaution is that consumption in large quantities (greater than 50 grams/day of sorbitol or greater than 20 grams/day of mannitol) may cause diarrhoea.

Natural sweeteners are sugar substitutes which are usually processed and refined. Those that are FDA approved include honey, agave nectar, molasses, maple syrup , date sugar and grape juice concentrate. Compared to sucrose, they do not have significantly less calories and provide no significant advantage when consumed by diabetics.

Confusing Labels

Labels for sweeteners can be confusing. Some sweeteners such as stevia are labelled as "natural" although they are actually processed or refined. Sucralose is a non-natural complex compound which is not directly related to sucrose in contrast to what the name suggests. Sugar alcohols do not contain any alcoholic content. Sugar free does not mean calorie free.

Weight loss or weight gain?

While artificial sweeteners have been consumed to reduce calorie intake and thereby reduce weight or prevent weight gain, the results of studies have been conflicting. Some studies, including the Nurses' Health Study in 1970 have shown weight gain. In the 2012 American Heart Association and the American Diabetes Association statement, the benefits of calorie reduction from NNS can only be realised if there is no dietary compensation subsequently, that is, no consumption of other calorie sources to compensate for the reduction in calorie intake.

To take or not to take?

The next time you reach out for your favourite "diet" drink or calorie free snack, check the label. Be aware of the labelling which can be confusing. Choosing naturally occurring sugar substitutes may mean only slightly less calories as compared to sucrose and "natural" does not mean that it has not been processed or refined.

If calorie reduction is the aim, artificial sweeteners and sugar substitutes are only effective if you do not compensate your calorie reduction by increasing calorie intake from other sources. For pregnant women and children , despite the regulatory authorities having approved the use of the chemically produced NNS, the raging controversies surrounding some of the NNS may lead one to consider healthier alternatives.

Finally, despite the safety data supporting the NNS, excess consumption beyond the ADI over a prolonged period can potentially be detrimental to health.

Dr Lim is medical director at the Singapore Heart, Stroke & Cancer Centre. He is also editor-in-chief, Heart Asia (a journal of the British Medical Journal Publishing Group); chairman, scientific advisory board, Asia Pacific Heart Association; and honorary professor and senior medical adviser, Peking University Heart Centre.

This series is brought to you by the Heart, Stroke and Cancer Centre. It is produced on alternate Saturdays.