Does a liking for sweet foods compromise a healthy diet?
Dr Anna Wittekind (PhD sports Science, University of Essex) is a registered nutritionist, lecturing at London Metropolitan University and providing freelance nutrition consultancy. Anna’s areas of expertise include sugars, sweeteners, beverages and sports nutrition/science. She has worked for the sugar industry and PepsiCo.
This interview was based on a workshop organised by ILSI Europe on ‘Dietary sweetness – is it an issue?’ held in April 2017. Dr Wittekind was a participant in the workshop and first author of the proceedings published in the International Journal of Obesity.
Some say a liking for sweetness is a relic from our hunter-gatherer past and we need to tame it to be healthy in the modern food environment. What would you say to them?
This statement assumes that we need to reduce a liking for sweetness and/or reduce our intake of sweet-tasting foods to have a healthy balanced diet, when neither is supported by the current evidence.
Regarding our innate liking for sweetness, more work needs to be undertaken to understand whether, or to what extent, various sweet taste qualities (perception threshold, intensity rating, preference etc.) can be changed.
We also need to know whether these qualities need to change. Very little research has been undertaken on the sweetness of the whole diet, with most research looking at diet quality in relation to sugars and/or sweeteners intake – the latter usually inferred by low/no-calorie beverage intake. The research which has been undertaken suggests diet quality is more related to the choice of sugars-containing foods rather than the sugars content or sweetness of those foods per se. And there is some evidence to suggest that low/no- calorie beverage consumption is associated with better diet quality. Together, this evidence does not support the idea that we need to tame our liking for sweetness or reduce the sweetness of the diet, but perhaps make better choices when it comes to which sweet foods and drinks we consume on a regular basis.
Does a ‘sweet tooth’ increase the risk for obesity, Type 2 diabetes or any other chronic illnesses? Many studies have been undertaken looking at relationships between various taste qualities and risk of obesity, diabetes and other chronic illness. Individual studies have found relationships (both positive and negative) between indicators of obesity (e.g. body mass index, or BMI) and preference for sweetness, as well as no relationship. The totality of the evidence shows no significant association between sweet taste qualities and BMI or Type 2 diabetes. However, a systematic review of the evidence in this area would be helpful.
Has the advent of non-nutritive sweeteners un-coupled sweet taste and sugar intake and how has this affected our diet?
The uncoupling of sweet taste with energy or sugar intake is a theory and unproven. And it is difficult to investigate methodologically. Aside from no or low-calorie drinks consumed in isolation, most sweeteners would be consumed along with other nutrients, including sugars. And if no or low-calorie drinks are consumed with foods, then again, the sweeteners are being consumed with other nutrients.
It has been suggested that this apparent ‘un-coupling’ means we can no longer use sweetness as a cue for energy and therefore lose the ability to control our energy intake. The main evidence against this theory comes from recent systematic reviews on non-nutritive sweeteners, which have reported beneficial (Rogers et al., 2015) or no effects (Azad et al., 2017) on body weight in intervention trials. Importantly, neither reviews found evidence for adverse effects on energy intake or body weight in intervention trials. Any effects may depend on whether the foods or drinks containing non-nutritive sweeteners are added to the diet or are being substituted for foods/drinks containing sugars or other caloric nutrients. In addition, the context may be important, such as whether the person is trying to lose weight or not. Longer-term studies are in progress and will hopefully help to answer these kinds of questions (eg The SWITCH study).
Has our taste for sweet increased over time?
As very little research has been undertaken on sweetness of the whole diet, this is difficult to answer. We know that sugars intake has increased compared to our distant ancestors. But in more recent years, very few countries have collected enough dietary records to be able to examine trends. In the few countries which have records, data suggests dietary sugars intake is generally stable or decreasing. However, with the increased use of sweeteners one might theorise that dietary sweetness may have increased.
What happens to our taste for sweet through the life cycle?
A higher preference for sweet taste has been noted in youth but appears to decrease with age and this appears to be reflected in the higher sugars intake of youth vs adults. Dietary patterns, including consumption of sweet foods and/or drinks, appear to track through childhood, but more research is needed to better understand if the same patterns continue into adolescence and beyond.
There’s a trend now to ‘quit sugar’, and many people are looking to avoid sugar completely. What advice do you have for health professionals when educating people about sweet foods? There are many diet trends encouraging people to quit certain foods or food groups from their diet, including quitting sugar. Some people seem to prefer quitting foods completely rather than consuming them in moderation, however this may not be sustainable over time. Eliminating any food group or food type should be considered carefully and preferably under the guidance of a registered/accredited dietitian or nutritionist.
There is no evidence that people need to eliminate sugar from their diet, and sugars are found naturally in many nutritious foods, including fruits, vegetables, dairy foods and grains, and are added to nutritious core foods such as dairy foods and breakfast cereals. I would suggest that sweet foods that are consumed on a regular basis should be nutritious (nutrient dense), with less nutritious foods only consumed as occasional treats.