UCL scientists found that no matter the healthy interventions of the future, flies previously fed on a high-sugar diet died earlier, as the activity of a gene associated with longevity was repressed by sugar over the long term.
The recommended daily intake of sugar for an adult with a normal body mass index is about 25 grams per day, or about 5 percent of your daily calorie intake, according to the World Health Organization. A single can of Coke has 39 grams of sugar.
Sugar, often found in ‘innocent’ foods like fat-free salad dressings or multi-grain cereals, leads to higher cholesterol, heart disease, obesity, uncontrolled growth and multiplication of cells, diabetes, metabolic syndrome and more. A logical debate has ensued about whether it should be considered white gold or white poison.
Ironically, first-world countries, where information flows abundant, like the US, Germany or the Netherlands, still consume 126, 103 and 103 grams of sugar on a daily basis respectively, occupying the three first places on the list of the top 10 sugar-consuming countries in the world.
Timelier than ever, research from the University College London, which was published in the January issue of the journal Cell Reports, now rings the alarm bells for one more overlooked danger of eating sugar at face value: Sugar over-consumption may bear long-lasting effects even after a healthy diet has been adopted.
The research team, comprising scientists from UCL and Australia’s Monash University, compared the lifespans of female flies fed on a diet containing 5 percent sugar (a healthy one) to flies given eight times this amount. Both groups of flies were fed for three weeks before going on a healthy diet.
The team found that no matter the healthy diet in the later stage, the flies previously fed a high-sugar diet started to die earlier, and on average had 7 percent shorter lifespans ( flies live up to 90 days).
At a molecular level, this was attributed to a “gene reprogramming” caused by the sugar-rich diet consumed in early adulthood. In a nutshell, sugar repressed the activity of a type of gene associated with longevity, FOXO.
“FOXO is a type of gene called a transcription factor,” Adam Dobson, a researcher at the UCL’s Institute of Healthy Ageing explained to Olive Oil Times.
“Transcription factors are interesting because they regulate other genes. So, if you change the activity of a transcription factor, in this case, by eating a high-sugar diet, you can indirectly change the activity of many other genes and cause extensive secondary effects.”
“We don’t know yet precisely what happens downstream of FOXO,” Dobson said, “but we think it is probably one of these secondary effects, with FOXO regulating genes which change the physical structure of DNA. This might explain the reprogramming of gene expression and lifespan, because the structure of DNA can affect which genes are turned on or off.”
“Importantly, flies and worms that don’t have FOXO don’t appear to be reprogrammed by sugar,“Dobson added.
With the FOXO gene contributing to longevity in a wide variety of species including humans, the UCL study’s findings are salient for our understanding of how changes in diet and gene expression are related to the pace of ageing.
Would it be arbitrary or premature to claim the damage too much sugar does to our organisms is irreversible?
“We can’t say anything about humans for certain because we have only looked in flies and worms,” said Dobson. “But we have shown that those organisms do bear long-term molecular implications of their past diets, because of sugar suppressing FOXO.
“There is some evidence that FOXO is important for human longevity and we know that sugar consumption is rocketing in humans. So while we don’t know if what we have shown in flies and worms is also true for humans, all the pieces are there.”