Could the sugary drinks we consume make us feel more anxious? A new study looking at the effects of a popular sweetener, aspartame, on mice suggests this is a possibility worth investigating further.
Approved by the US Food and Drug Administration (FDA) in 1981, aspartame is widely used in low-calorie foods and beverages. Today, it is found in nearly 5,000 different products consumed by adults and children.
When a sample of mice were given unlimited access to water laced with aspartame equivalent to 15% of the maximum daily amount recommended by the FDA for humans, they generally exhibited more anxious behavior in specially designed mood tests.
What’s really surprising is that the effects of this popular sweetener can be seen in the offspring of animals for up to two generations.
A popular sweetener is proving increasingly dangerous
“This study shows us that we need to look back at environmental factors, because what we see today is not just what is happening today, but what happened two generations ago and maybe even longer,” says neuroscientist Pradeep Bhide , from Florida State University, in the USA.
Anxiety was measured by a variety of maze tests in several generations of mice. The researchers also performed RNA sequencing on key parts of the rodent’s nervous system, depending on how the tissues’ genes were expressed. The researchers found significant changes in the amygdala, a part of the brain associated with regulating anxiety.
We know that when consumed, aspartame breaks down into aspartic acid, phenylalanine and methanol, which can affect the central nervous system. There have already been questions about potential adverse reactions to the sweetener in some people.
When the mice were given doses of diazepam (a drug once marketed as Valium, which is commonly used to treat anxiety in humans) the anxiety-like behaviors ceased across all generations. The drug helps regulate the same pathways in the brain that are altered by the effects of aspartame, he writes Science Alert.
The results were very clear
Although monitoring anxiety-like behaviors in mice is only an approximation of similar moods in humans, the researchers observed clear changes in the animals’ behavior, which they linked to changes in gene activity.
“It was such a pronounced anxiety-like feature that I don’t think any of us anticipated we would see. It was completely unexpected. You usually see subtle changes,” says Sara Jones, a research assistant at Florida State University.
The research is based on previous works by the same team on the generational effects of nicotine use on mouse behavior: again, these effects can apparently be passed down from generation to generation due to non-coding epigenetic changes in mouse sperm cell genes.
Something similar could be happening here, the team suggests. In other words, it’s not just those who consume this popular sweetener that could be at risk, but so are their children and their children’s children. How this might happen is not yet fully understood, but it fits with emerging evidence suggesting that epigenetic marks can indeed remain intact over many generations.
This popular sweetener has previously been linked to other health problems as well
Researchers have considered links between aspartame and anxiety before, and while plausible, other animal studies have found no change in anxiety-like behavior in rats given artificial sweeteners, suggesting much more work is needed to understand what is happening.
Even so, based on these results, Jones, Bhide and their colleagues urge caution. Previous research has linked artificial sweeteners to cancer and changes in gut bacteria that lead to glucose intolerance; maybe anxiety is now another thing to consider.
The population at risk of health problems may be larger than previously thought
While these results must first be tested in humans, finding signs of anxiety in mice is a very good reason to investigate further.
“Extrapolation of the findings to humans suggests that consumption of aspartame at doses below the maximum recommended daily intake by the FDA may produce neurobehavioral changes in aspartame users and their offspring,” the researchers write in the paper.
“Thus, the human population at risk for potential mental health effects of aspartame may be larger than current expectations, which include only people who currently consume aspartame,” they wrote.
The research was published in PNAS.