Scientists are warning too much Christmas pudding, mince pies and yule log this festive season could trigger depression.
A team from the University of Kansas looked at a range of studies that analysed the link between the sweet stuff and the mental-health condition.
While indulging in brownies, ice cream or cake may initially boost your mood, expect to feel worse later on, they warn.
Too much sugar may also have an “inflammatory effect on the brain”, which could leave you blue.
“Bad” bacteria in our gut also thrive on the sweet stuff, “pushing the brain into a state of depression”.
Nearly one in five (19.7%) people over 16 in the UK showed signs of depression or anxiety in 2014, a 1.5% increase on the year before, Mental Health Foundation statistics show.
In the US, around 17.3 (7.1%) of Americans battled at least one “major depressive episode” in 2017, according to the National Institute of Mental Health.
Cold winter months may leave people particularly vulnerable.
“For many, reduced sunlight exposure during the winter will throw off circadian rhythms, disrupting healthy sleep and pushing 5-to-10% of the population into a full-blown episode of clinical depression,” study author Dr Stephen Ilardi said.
“One common characteristic of winter-onset depression is craving sugar and now they're constantly confronted with holiday sweets”.
To learn more about the effect of sugar on mood, the scientists analysed research including the Women's Health Initiative Observational and the NIH-AARP Diet and Health studies.
They found inflammation is linked to both sugar intake and the onset of depression.
“A large subset of people with depression have high levels of systemic inflammation,” Dr Ilardi said.
“When we think about inflammatory disease we think about things like diabetes and rheumatoid arthritis, diseases with a high level of systemic inflammation.
“We don't normally think about depression being in that category, but it turns out it really is, not for everyone who's depressed, but for about half.
“We also know inflammatory hormones can directly push the brain into a state of severe depression.
“So, an inflamed brain is typically a depressed brain and added sugars have a pro-inflammatory effect on the body and brain.”
The scientists also looked at the microbiome, a growing area of research.
“Our bodies host over 10 trillion microbes and many of them know how to hack into the brain,” Dr Ilardi said.
“The symbiotic microbial species, the beneficial microbes, basically hack the brain to enhance our wellbeing. They want us to thrive so they can thrive.
“But there are also some opportunistic species that can be thought of as more purely parasitic, they don't have our best interest in mind at all.
“Many of those parasitic microbes thrive on added sugars, and they can produce chemicals that push the brain in a state of anxiety and stress and depression. They're also highly inflammatory.”
While sugar may be doing us no good, quitting could be easier said than done.
“When we consume sweets, they act like a drug,” Dr Ilardi said.
“They have an immediate mood-elevating effect, but in high doses they can also have a paradoxical, pernicious longer-term consequence of making mood worse, reducing wellbeing, elevating inflammation and causing weight gain.”
READ MORE: 10 surprising foods full of hidden sugar
When it comes to sugar consumption, moderation may be key, like with alcohol.
“We have pretty good evidence one alcoholic drink a day is safe and might have beneficial effect for some people,” Dr Ilardi said.
“Alcohol is basically pure calories, pure energy, non-nutritive and super toxic at high doses.
“Sugars are very similar. We're learning when it comes to depression, people who optimise their diet should provide all the nutrients the brain needs and mostly avoid these potential toxins.”
To minimise your risk of depression, the scientists recommend opting for plant-based, non-processed foods most of the time.
“There's no one-size-fits-all approach to predicting exactly how any person's body will react to any given food at any given dose,” Dr Ilardi said.
“As a conservative guideline, based on our current state of knowledge, there could be some risk associated with high-dose sugar intake, probably anything above the American Heart Association guideline, which is 25g of added sugars per day.”
The NHS recommends sugar makes up no more than 5% of our calorie intake a day, around 30g for those aged 11 and over.
Sugar is low in nutrients but high in calories. This can lead to weight gain, and ultimately heart disease, type 2 diabetes and stroke.