Research published yesterday, has found that high sugar intake from sweet foods and drinks can adversely affect long-term psychological health.
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The World Health Organization has recommended for many years that free sugars should not make up more than 5‑10% of our total calorific intake. Free sugars are those that are not part of a complex carbohydrate, such as starch, for example glucose and fructose.
They are added to many prepared foods and drinks, such as yoghurts, fruit juice, tomato sauce, ready meals. With increasing reliance on processed foods our intake of free sugars is rising, often unwittingly. The average intake of free sugars is now double the recommended level in the UK, and is even higher in the USA.
It is well known that high levels of sugar in our diets lead to health problems, such as obesity, diabetes, cardiovascular disorders, but there have also been reports that high intake of sugar can also lead to mental health problems.
Several cross-sectional studies have reported an association between high sugar consumption and the development of depression. However, it had not been determined whether high sugar intake is actually a causal factor for mental health problems.
Researchers have now analyzed prospective data collected in the Whitehall II study over 22 years to investigate whether high sugar intake from sweet foods and beverages increases the risk of mood disorders.
In 1985, the Whitehall II study recruited over 10,000 civil servants aged 35‑55 years and has been regularly collecting data from them through questionnaires ever since. Numerous publications from analyses of this study population have reported the impact of various psychosocial factors, such as stress at work, on health. It is now also studying the effects of aging.
The Whitehall II study included assessment of diet and mood using validated questionnaires. Analysis of these data has now revealed a strong positive association between sugar intake from sweet foods and beverages and common mental disorders.
The risk of developing a common mental disorder after 5 years was 23% higher among men who consumed more than 67g of sugar compared with those with a sugar intake of less than 40 g. There was also an indication that men and women with an existing mood disorder were more likely to develop depression if they had a high sugar intake, compared with those consuming low amounts of sugar.
Although an association was observed between high sugar intake and the development of depression in men and women who did not have a pre-existing mood disorder, this was lost after correction for other health behaviours, socio-demographic and diet-related factors.
Further research is required to confirm whether too much sugar can make us sad, and whether the effect is more pronounced in men than in women. However, since limiting sugar intake has already been shown to have numerous other health benefits it should remain a dietary target with the possibility of better psychological health being an added bonus.
- Knüppel A, et al., Sugar intake from sweet food and beverages, common mental disorder and depression: prospective findings from the Whitehall II study. Scientific Reports 2017; 7, Article number: 6287. Available at: http://www.nature.com/articles/s41598-017-05649-7#Tab1