Some things are well-understood to be healthy for our bodies: fruits, vegetables, exercise.
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And some things are almost universally agreed as a danger to your well-being: smoking, drug use, driving without a seatbelt.
But not everything is so clear-cut. Not every food we eat or activity we do can fall neatly into the category of “good for you” or “bad for you.” There are gray areas. Questions of quantity. Matters of how you personally react to one thing or another.
That’s the case with the artificial sweetener aspartame.
On one hand, aspartame can be a saving grace for people with diabetes (“Sweet taste without the calories, and no impact on your blood sugar!”). On the other, there’s reason to be cautious.
Amid reports declaring aspartame a possible carcinogen (cancer-causing agent), we talked with oncologist Dale Shepard, MD, PhD, about aspartame — the good, the bad and what to do about it.
Aspartame is an artificial sweetener that goes by brand names like NutraSweet®, Equal® and Sugar Twin®.
Like other artificial sweeteners — including saccharine (Sweet’n Low®) and sucralose (Splenda®) — it’s a common ingredient in foods labeled “sugar-free” or “no added sugar.” That can include products like:
Aspartame and other non-nutritive sweeteners are popular among people looking for a sugarless route to satisfying their sweet tooth. That includes people with diabetes, people on sugar-restricting diets like keto and people who are trying to lose weight.
A gram of aspartame contains 4 calories, which is the same as sugar. But aspartame is 200 times sweeter than sugar. So, you don’t have to use nearly as much to get the same sweetness factor.
So, if you switch from sugar to aspartame, you essentially cut the calories to zero. And aspartame doesn’t impact your blood sugar, so it’s marketed as a good choice for people with diabetes and other people who need to be monitor their blood sugar.
The latest scientific evidence suggests that aspartame may be associated with cancer. And the World Health Organization (WHO) lists aspartame as a possible cause of cancer. None of that means that aspartame directly causes cancer. There’s a difference.
Let’s look at the research.
In the largest trial to date on the effects of aspartame, researchers followed more than 100,000 people over about eight years and documented what they ate and drank. They found that people who consumed aspartame at high levels were about 15% more likely to develop cancer than people who didn’t have aspartame in their diet. That included an increased risk of:
“When we research foods and their connection to cancer, we can see when people who eat a particular type of food are more likely to develop cancer, but that’s not proving a causal relationship,” Dr. Shepard clarifies. “We don’t know necessarily whether aspartame causes cancer.”
It’s a complicated question to research. Do people who eat a lot of aspartame get cancer because of aspartame? Or do high-aspartame consumers have something else in common — like a chronic health condition, vitamin deficiency or lifestyle choices — that leads to their increased cancer risk? After all, aspartame use is likely to be higher among people living with diabetes and obesity. Might those conditions be the root cause of a higher cancer risk?
As of now, we don’t know for sure, and the WHO’s designation of aspartame reflects that uncertainty.
The WHO ranks carcinogens into four groups based on how likely they are to cause cancer. Aspartame is listed as a “Group 2B carcinogen.” That’s the designation reserved for things believed to possibly cause cancer but that don’t have sufficient evidence to say they do for sure.
“Group 1 carcinogens are things we know cause cancer, like tobacco use and sun exposure,” Dr. Shepard explains. “Then, there’s Group 2A, which are things that probably cause cancer, like red meat. Group 2B is a step below that and includes things like car exhaust, lead and aspartame.”
In addition to its association with cancer, aspartame can come with some other unwanted effects.
Some scientists and physicians say sugar and artificial sweeteners like aspartame can be addictive in a way. They light up your nervous system, sending loads of feel-good hormones, like dopamine, throughout your body. It makes your body want more and more of the sweet stuff, which can lead to overconsumption.
What’s more is that some people may not react well to aspartame and other artificial sweeteners. The sugar alcohols used in making some artificial sweeteners can cause stomach discomfort, like bloating, cramps and diarrhea. And one common sugar alcohol, erythritol, has been linked to increased risk for heart attack and stroke.
Research on the long-term effects of aspartame has also linked it to a range of health conditions, like:
But keep in mind that, like the connection between cancer and aspartame, more research is needed to determine the extent of the association between aspartame and those conditions.
The WHO says that up to 40 milligrams (mg) of aspartame per kilogram (kg) of body weight is an acceptable daily intake. For context, one can of diet soda contains about 200 mg of aspartame. So, an adult who weighs 150 pounds (68 kg) could, in theory, drink about 13 diet sodas a day and stay within that limit, if they didn’t have any other aspartame in their diet.
But based on our current understanding of aspartame, Dr. Shepard advises caution and moderation. As in, even if the limits suggest 13 cans of diet soda is “acceptable” for you, it’s not recommended. Especially when you factor in the other potential effects of aspartame on your health.
“The risks of aspartame don’t mean that you should never have another diet soda or that you have to avoid aspartame at all costs,” Dr. Shepard clarifies. “But I see it as a reminder that moderation is important to lowering your risk.”
If you’re looking to cut back (or cut out) sugar, aspartame and other artificial sweeteners, there are some better-for-you options to satisfy your sweet tooth.
Fresh and frozen fruit are the best choices for sweetening your food and drinks. That’s because, in addition to natural sugars, they’re packed with nutritional benefits, like fiber, vitamins and minerals. Try infusing water with sliced strawberries or slice of lime.
When considering your intake of aspartame, sugar, sugar substitutes and other less-than-ideal foods, Dr. Shepard says it’s a matter of being mindful about how you’re treating your body.
“It’s all about taking stock of whether, on balance, you’re doing good things for your body,” he continues. “Are you avoiding things that we know are very serious health risks? Are you managing your health conditions? Are you watching your weight? I don’t recommend doing anything drastic because most people aren’t likely to stick highly restrictive diets. Just be mindful that the things you eat and drink come with risk.”