Higher Sugar Intake Linked to Depression in Men

Theresa Bebbington

July 31, 2017

Men who have more than 67g of sugar per day – about the amount found in two cans of cola – could be increasing their risk of common mood disorders by 23% after 5 years, compared to those with consume less sugar, researchers say.

A study also says having a mood disorder does not make people more likely to eat foods high in sugar.

High Sugar Intake

Adults in Britain consume roughly twice the recommended level of added sugar in their diets, and previous studies have linked higher sugar consumption with an increased risk of depression.

The study, published in the journal Scientific Reports, examines the association between sugar intake and common mood disorders.

The researchers, led by Dr Anika Knüppel from the Department of Epidemiology and Public Health at University College London, analysed people's sugar intake from sweet food and drinks and the occurrence of common mental disorders.

They explain that few studies have investigated 'reverse causation', referring to the possibility that a mood disorder could lead to higher sugar intake, which they wanted to explore.

For their study, they examined repeat measures of sweet food and drink consumption and mental health to look at the association between the two.

They used data from the Whitehall II cohort, a long-term study on health (and nowageing), using participants working at different levels in the UK's civil service.

Of the 10,308 participants recruited in 1985, about two-thirds are men and one-third are women.

After the first wave of data collection, self-completed questionnaires and clinical data continued to be collected every 2 to 5 years.

Fizzy Drinks, Cakes and Biscuits

For their analysis, the researchers used data collected up to 2013 and included participants who reported their consumption of at least 8 of a list of 15 items of sweet foods and drinks such as cakes, biscuits, fizzy soft drinks and added sugar in coffee or tea.

Participants were divided into groups based on their daily sugar intake from sweet food and drinks.

For men, these were:

  • More than 67g

  • Between 67g and 39.5g

  • Less than 39.5g

For women, these were:

  • More than 51g

  • Between 30g and 51g

  • Less than 30g

Their analysis found that men in the top third group, who consumed the most sugar at more than 67g per day, were 23% more likely to have common mental health disorders after five years when compared to those in the bottom third group, who consumed less than 39.5g of sugar per day.

This finding was independent of other diet-related factors, health behaviours and socio-demographic characteristics such as marital status and pay grade.

The researchers say they could not find a similar observation among women, but this may be due to the lower number of female participants.

The researchers also conclude that from the results of their study, they "were able to exclude potential 'reverse causation' as the reason for the observed link between high sugar intake and low mood". They explain that the associations observed in their analysis were not the result of changes in consuming sugary foods and drinks.

Limitations of the Study

The study has limitations, noted by the researchers themselves.

Among them, for example, is that processed foods – which can be a hidden source of added sugar – were not included in the study; and self-reporting on questionnaires is often not reliable, with participants liable to underreport or otherwise misreport data.

In addition, nutrient content was based on food composition tables from 1991, and it is likely that food compositions have changed since then.

Reaction

Catherine Collins, a registered dietitian and spokesperson for the British Dietetic Association, agrees that "food portion sizes would have distorted the calculated sugar intake significantly".

She explains that, for example, "a muffin or doughnut has almost doubled in size over the last 10 years" and that a can of cola soda is normally 330ml but it could also be a downsized 250ml.

Ms Collins also has other concerns about the study. She notes that only one-third of the participants in the original group were female, which is not typical of the UK population. However, she says, "Women have a far greater emotional engagement with food, yet this study failed to find any correlation between sugar intake and depression short term or longer term in women."

She adds: "Whilst the food frequency questionnaire used to determine sugar intake was an appropriate tool, 'translating' this into daily sugar intake was deeply flawed…"

As an example, Ms Collins refers to the participants reporting their alcohol intake, but its contribution to sugar intake wasn't taken into account. She says, "for heavy drinkers this could have been a significant oversight, especially if the favourite tipple was beer, lager or cider".

She also mentions that there appears to be confusion on sugar intake "from both naturally occurring (e.g. milk) and added ('free' sugars, such as sugar added to hot drinks, in sweets and chocolates etc.)".

She says: "The researchers concluded boldly that 'their research confirms an adverse effect of sugar intake on long-term psychological health' and make an unproven recommendation that a lower sugar intake would improve psychological health. Neither of these statements can be justified based on major issues with the diet survey which limits their findings."

Ms Collins notes that reducing your consumption of free sugars may be good for your weight and teeth, but says "as protection against depression? It's not proven."

Tom Sanders, professor emeritus of nutrition and dietetics at King's College London, also has reservations about the results. In his response to the report, he says: "From a scientific standpoint it is difficult to see how sugar in food would differ from other sources of carbohydrate on mental health as both are broken down to simple sugars in the gut before absorption and the glycaemic index of sugar is less than refined starchy foods such as white bread and rice."

He also notes that, "When individuals reduced their sugar intake in the later follow up phases there was no change in risk of poorer mental health." He explained that he would expect "to see the association with high sugar intake to persist with long-term follow-up which was not the case".

SOURCES:

Scientific Reports: "Sugar intake from sweet foods and beverages, common mental disorder and depression: prospective findings from the Whitehall II study"

Science Media Centre

UCL Department of Epidemiology and Public Health

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