Millions of sweet-toothed British men could be making themselves anxious and depressed by consuming too much sugar, a study suggests.
Scientists found that men who consumed more than 67 grams of sugar per day increased their risk of mood disorders by more than a fifth compared with those with an intake of less than 39.5 grams.
Since the average British man has a 68.4 gram per day sugar habit, the findings do not bode well for the mental health of the UK male population.
The study ruled out the possibility that the results can be explained by unhappy men comforting themselves with sugary treats.
Lead researcher Dr Anika Knuppel, from University College London's Institute of Epidemiology and Health, said: "High sugar diets have a number of influences on our health but our study shows that there might also be a link between sugar and mood disorders, particularly among men.
"There are numerous factors that influence chances for mood disorders, but having a diet high in sugary foods and drinks might be the straw that breaks the camel's back.
"There is increasing evidence for the physical damage sugar has on our health. Our work suggests an additional mental health effect."
For reasons that are unclear, the study which looked at thousands of civil servants of both sexes found no link between sugar intake and new mood disorders in women.
The findings are based on data from Whitehall II, a major long-term investigation into physical and mental health problems encountered by people working at different levels of the UK civil service.
Sugar consumption was compared with rates of common mental disorders in more than 5,000 men and 2,000 women between 1983 and 2013.
Participants were placed into three groups according to their daily sugar intake. After five years, men in the top group were 23% more like to have developed a common mental disorder such as depression or anxiety than those in the bottom group. The top tier men consumed more than 67g of sugar per day and the bottom group less than 39.5g.
British adults consume roughly double recommended levels of added sugar, three quarters of which comes from sweet foods and drinks, said the researchers.
According to the National Diet and Nutrition Survey published in 2013, the average man in the UK has a daily sugar intake of 68.4g.
Dr Knuppel added: "Sweet food has been found to induce positive feelings in the short-term. People experiencing low mood may eat sugary foods in the hope of alleviating negative feelings. Our study suggests a high intake of sugary foods is more likely to have the opposite effect on mental health in the long-term."
Co-author Professor Eric Brunner, also from UCL, said the new sugar tax on soft drinks which takes effect in April 2018 was a "step in the right direction".
He said: "Our findings provide yet further evidence that sugary foods and drinks are best avoided ... The physical and mental health of British people deserves some protection from the commercial forces which exploit the human 'sweet tooth'."
The results appear in the journal Scientific Reports.
Experts commenting on the research urged caution.
Catherine Collins, from the British Dietetic Association, said: "Whilst the findings as reported are interesting, the dietary analysis makes it impossible to justify the bold claims made by the researchers about sugar and depression in men. More surprising is the lack of reported effect in women, who have a far more emotional relationship with food.
"Reducing intake of free sugars is good for your teeth, and may be good for your weight, too. But as protection against depression? It's not proven."
Professor Tom Sanders, a nutrition expert at King's College London, said: "This is an observational study not a clinical trial and its interpretation needs to be treated with caution. While the authors have tried to adjust for the effects of social factors there still is a risk of residual confounding. There is also a major problem in that sugar intake is under-reported in the overweight and obese, which the authors acknowledge."
Rob Howard, Professor of old age psychiatry at UCL, said: "This study is important because it is the first to be able to show that an increase in risk of about a quarter in common mental disorders, mostly mild anxiety and depression, in men who eat the most sugar cannot be explained by those who were already anxious or depressed using sugar as a form of comfort."
But he said more work was needed before depression and anxiety could be added to the list of health problems known to be linked to excess sugar consumption.