Aspartame is a nonnutritive artificial sweetener. It is used as a sugar substitute in soft drinks, candy, chewing gum, and low-calorie foods and is also available as a tabletop sweetener (e.g., Canderel, Hermesetas Gold, NutraSweet, and Pal Sweet).
Aspartame is most often used for
Last Updated:April 2, 2024
Aspartame is a nonnutritive artificial sweetener used as a food additive in foods, drinks, and some drugs. It is a dipeptide of the naturally occurring amino acids L-aspartic acid and L-phenylalanine.[15][16][3][2]
Aspartame is most commonly used as a sugar substitute in soft drinks, candy, chewing gum, and low-calorie foods and is also available as a tabletop sweetener, sold under brand names like Canderel, Hermesetas Gold, NutraSweet, and Pal Sweet.
It is often claimed that aspartame (and other nonnutritive sweeteners) can suppress appetite, cause weight loss, and improve aspects of cardiometabolic health (e.g., blood glucose control and cholesterol). Because aspartame is a nonnutritive sweetener that is used to replace sugar in some foods and drinks, some people with weight loss goals use aspartame-containing foods and drinks as part of an energy restriction diet. Reducing sugar intake as a way to lower total daily energy intake can help support a weight loss strategy,[17][18][19][20] and some,[21][22][23] but not all,[24][25] studies show that a single dose of aspartame can acutely reduce food intake at the next meal. However, the current evidence does not show long-term health benefits of aspartame on energy intake, weight loss, or cardiometabolic health.[26][27] Consequently, there does not appear to be any direct benefit from ingesting aspartame.
Some studies link aspartame with cancer risk, but the evidence is inconsistent. For example, some observational studies show an association between greater aspartame intake and increased cancer risk,[28] whereas others do not.[29] While observational studies can help evaluate the likelihood that a substance — a food additive, nutrient, pollutant, etc. — is involved in disease risk, they cannot prove causality. Observational studies also rely heavily on self-reported dietary intake data, which introduces recall bias. Other types of studies — cell experiments, animal studies, and randomized controlled trials — can help evaluate whether a substance causes a disease. Regulatory bodies then evaluate the strength of all known evidence to determine whether a substance can theoretically cause disease in humans.
Accordingly, regulatory bodies such as the International Agency for Research on Cancer (IARC) and the Joint Food and Agriculture Organization and World Health Organisation Expert Committee on Food Additives (JECFA) have concluded that aspartame is “possibly carcinogenic” to humans — i.e., there is limited, but not convincing, evidence for aspartame causing cancer in humans and less than sufficient evidence for aspartame causing cancer in experimental animals.[2] Accordingly, food regulatory bodies including the US Food and Drug Administration (FDA) and the European Food Safety Authority (EFSA), which determine whether foods (and additives) are safe to eat, currently conclude that aspartame is safe for human consumption at current exposure levels.[3] That said, given that some evidence suggests potential adverse effects, regulatory bodies also conclude that further high-quality studies are needed.
So, in the amounts people are likely to consume, aspartame is unlikely to pose a major risk. However, if people want to reduce their exposure to any potential hazard that might be posed by aspartame, they can choose to avoid foods containing aspartame. For more information, read Does aspartame cause cancer in humans?.
When ingested, aspartame is broken down into its constituent amino acids, L-aspartic acid and L-phenylalanine. Further metabolism of these products produces methanol, formaldehyde, and formic acid in small quantities These chemicals can cause adverse effects in large doses and may, therefore, be implicated in some of the reported adverse effects of aspartame. However, the precise modes of action and fates of these metabolites in the body are not completely understood.[15][16][3][2]
Like all nonnutritive artificial sweeteners, aspartame has a sweet taste because it activates taste receptors on the tongue.[30] This mechanism might influence sweet taste behavior and increase motivation for sweet foods, but the evidence is mixed and further work is needed to make a firm conclusion.[31][32] Some studies have also shown that a single dose of aspartame can acutely decrease food intake at the next meal.[21][22][23] The current evidence shows that this effect is not driven by changes in the secretion of appetite-regulating gut hormones,[33] but it has been suggested that the increase in blood phenylalanine concentrations following aspartame ingestion may regulate appetite because phenylalanine can cross the blood-brain barrier and can influence neurotransmitter synthesis.[34]
Although a direct causal effect of aspartame on cancer in humans is unlikely at the current exposure levels, it has been associated with cancer in some observational studies, so it is important to explore the plausible mechanistic bases for a causal link. One possibility is that L-aspartic acid and L-phenylalanine (breakdown products of aspartame) could enter cellular protein synthesis pathways and affect mTOR signaling, which is known to regulate cell growth.[35] L-aspartic acid (aka aspartate) has also been shown to directly regulate cancer cell growth.[36][37] However, these are speculations, and evidence for this comes mainly from in vitro cell experiments.[36][37] Furthermore, humans are exposed to L-aspartic acid and L-phenylalanine every time protein is eaten, and cancer cell metabolism is also regulated by many other metabolites — other amino acids, glucose, etc. — that are essential for life.[35][36][37] This does not mean that such metabolites cause cancer.
Dosage Information
In the US, aspartame and other artificial sweeteners are regulated by the FDA, and products containing aspartame must be approved before they can be used. Because of the potential health risks of aspartame consumption, the FDA has set an acceptable daily intake, which is the maximum amount considered safe to consume each day over a person's lifetime.
In the US, the FDA has set the acceptable daily intake for aspartame at 50 milligrams per kilogram of body weight per day (mg/kg/day). Meanwhile, the EFSA and the Joint Food and Agriculture Organization and World Health Organisation Expert Committee on Food Additives (JECFA) have set the acceptable daily intake for aspartame at 40 mg/kg/day.[2][3]
To put these acceptable daily intake values into context, a person weighing 70 kg would have to consume approximately 9–14 cans of diet soda per day to exceed an intake level of 40 mg/kg/day.
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It does not inhibit fat loss at all, and may actually suppress appetite that could help fat loss (although it does not induce fat loss per se either). Diet soda, in regards to body fat, is a carbonated inert beverage.
First, let's define 'diet soda' as any drink that is sweetened with low to no calorie sweeteners (like sucralose, aspartame, acesulfame-potassium, etc.) in order to taste like regular (sugared) soda.
In short, there are no direct causative studies that show the use of artificial sweeteners slows your metabolism or promotes fat storage.[46]
The CHOICE randomized study, lasting 6 months and observing how different diet changes affect weight loss adherence, found that diet soda is an effective substitution for regular soda and had no significant differences in health or weight loss relative to water.[47]
Data from the NHANES (03-04) study suggest that increased servings of non-caloric beverages are not related to an increase in total calories.[48] Additionally, the PREMIER trial found that a reduction in intake of non-caloric beverage is not associated with weight loss.[49]
The real problem is that people tend to under-estimate caloric intake. By thinking about the zero calories in the soda, they end up eating an excess of calories, thus increasing fat storage[50]. This makes the well known correlation (relationship) between diet soda and obesity; one does not cause the other, but they tend to co-exist. Drinking diet soda does not make one fat, but people with obesity tend to drink diet soda.
In regards to insulin, diet soda can potentially increase insulin secretion by both an anticipatory response and the artificial sweetener aspartame can (through the amino acid, phenylalanine). However, both of these insulin spikes are too small to matter practically, and the latter mechanism doesn't seem to occur at all with many commonly ingested dosages.
As mentioned on our Aspartame and Appetite page, aspartame (via phenylalanine) might also suppress appetite.
Research suggests that diet soda is unlikely to be detrimental to metabolic health or body composition. Further controlled trial evidence is needed to explore other possible detriments.
Currently available research into diet soda and long-term health risks is insufficient, although there are specific areas where risks are unlikely. Contrary to popular belief, diet soda (defined as calorie free carbonated beverages sweetened with aspartame, sucralose, acesulfame-potassium, or other non-caloric or minimally caloric sweeteners) doesn't inhibit fat loss, or spike insulin levels.
Current research that attempts to link diet soda with type 2 diabetes and metabolic syndrome[51][52] did not have equal caloric consumption. Excess caloric consumption has a direct correlation with many health issues, and in fact one of the studies[51] distinctly states:
Consequently, the previously observed diet soda–metabolic syndrome associations are generally speculated to be the result of residual confounding by other dietary behaviors, lifestyle factors, or demographic characteristics (1,2). Biological mechanisms possibly explaining these associations are few and largely focus on artificial sweeteners in beverages/foods increasing the desire for (and consumption of) sugar-sweetened, energy-dense beverages/foods (3) or disrupting consumers' ability to accurately estimate energy intake and remaining energy needs (4). Thus, diet soda consumption may result in overconsumption, increased body weight, and consequent metabolic dysfunction.
In short, many people who have bad diets may consume diet soda in an attempt to do "less damage" - this could result in an incorrect association of diet soda consumption with health conditions.
That was most likely a survey or epidemiological research. This is research that aims to find correlations (relationships) between two variables, and sets up future studies to find which variable causes what.
There are many studies that note that diet soda is frequently consumed by unhealthy people,[51][52] but no studies that compare people with equivalent diets. One study (Northern Manhattan Study) was able to control a fair number of variables and found a weak correlation between diet soda and vascular events, but these differences disappeared when 'pre-existing health conditions' were considered.[53]
When comparing diet soda against other non-caloric beverages in an intervention study, and you control the rest of the diet, no difference in weight loss is noted. This suggests that the problem is likely the habits of people who drink diet soda, rather than the diet soda itself.[51] The Northern Manhattan study suggested that diet soda use may be correlated with disease as it its consumption was an attempt by (already unhealthy) individuals to reduce calories and take control of their health.[53]
Soda (in general) has been linked to poor dental health numerous times, especially children.[54][55] Although sucrose (sugar) plays a major role, the general acidity of diet sodas can also negatively influence dental health.[54] Overconsumption of soft drinks without adequate dental intervention may result in cavities and yellowing of teeth, and this applies to both sugared and diet sodas; although sugared are worse in this regard.[56]
Like most things, overconsumption may not be a good idea, especially for your teeth. Otherwise if you want to enjoy a Diet Coke, Coke Zero, Diet Pepsi, or whatever diet soda you enjoy most, don't feel guilty about it.
Full FAQ and database update
We fully updated this page, and have added a number of new FAQs, including ones about how aspartame is made, whether it causes headaches and cancer, and how industry involvement may influence the findings of the studies we cite.
