Aspartame is an intense sweetener, approximately 200 times sweeter than sugar, which has been used in soft drinks and other low-calorie or sugar-free foods throughout the world for more than 25 years. It is also referred to as E951.

Safety evaluations

Sweeteners and all other food additives are tightly regulated and may only be used once their safety has been rigorously assessed.

Aspartame was first approved in the UK in 1982 following the review of its safety by the UK's Committee on Toxicity, Consumer Products and the Environment (COT), a committee of independent experts that advises the Government on the safety of food chemicals. This was reaffirmed in 1988 by the European Commission's former Scientific Committee on Food (SCF).

Following the publication of a number of anecdotal reports, which cast doubt on the safety of this sweetener, the SCF reviewed more than 500 papers published in the scientific literature between 1988 and 2001 on the safety of aspartame, including studies supporting the safety of aspartame and others pointing to potential adverse effects, which concluded, in 2002, that there was no evidence to suggest a need to revise the outcome of their earlier risk assessment or the Acceptable Daily Intake (ADI) previously established for aspartame of 40 milligrams per kilogram of body weight per day (40 mg/kg bw/day).

A study published by the Ramazzini Foundation in Bologna, Italy, in July 2005 claimed to have shown that rats given dosages of aspartame equivalent to the Acceptable Daily Intake (ADI) may develop tumours. EFSA assessed the study and raised a number of concerns regarding it. They concluded, that ‘there is no need to further review the safety of aspartame nor to revise the previously established ADI'.

The FSA supported the conclusions of EFSA's review but reiterated that all approvals of food additives should be kept under review as and when new scientific information becomes available. Indeed, as part of its systematic re-evaluation of all food additives, EFSA has re-evaluated the safety of aspartame (see External sites box). As a result, it concluded in December 2013 that 'aspartame and its breakdown products are safe for human consumption at current levels of exposure'.

Intake of aspartame

Like many food additives, the safety assessment for aspartame has led to the setting of an Acceptable Daily Intake, or ADI. This is an estimate of the amount of an additive that could be routinely consumed every day over a lifetime with no appreciable health risk. In the case of aspartame, the ADI is set at 40 milligrams per kilogram of body weight. This is equivalent to 2800 milligrams for an average British adult. For an average 3-year-old child the amount is of the order of 600 milligrams.

The ADI applies to all sections of the population, including children and infants from the age of 12 weeks. The only exception is for people suffering from a rare genetic disease phenylketonuria (PKU) (see below).

It is not necessary, however, for each person to calculate their intake of additives in order to make sure that they keep within the ADI. Indeed, it would be extremely complicated and time-consuming to do so. Instead legislation on food additives specifies the categories of foods in which aspartame can be used and the levels that can be added.

These levels are set after considering food consumption patterns and the likelihood of exceeding the ADI, combined with knowledge of the amount that is actually needed in the food to have the desired sweetening effect. In the case of aspartame, an adult would have to consume 14 cans of a sugar-free drink every day before reaching the ADI, assuming the sweetener was used in the drink at the maximum permitted level. In practice most drinks use aspartame in combination with other sweeteners so that the level is considerably lower.


There is a group of people who cannot safely consume aspartame. These are the sufferers of the inherited disease phenylketonuria (PKU), who are unable to metabolise the amino acid phenylalanine effectively, leading to the accumulation of potentially harmful levels. PKU is a serious, metabolic disorder, affecting 1 in 10,000 individuals and if untreated, it can cause serious brain damage.

Sufferers are normally diagnosed shortly after birth by a routine blood test and need to follow a very strict diet in order to limit their intake of phenylalanine, which is a normal constituent of proteins in food. Since aspartame is also a source of phenylalanine, all food products containing aspartame are clearly labelled to indicate the presence of phenylalanine so that those people who suffer from PKU can avoid consuming these products. This labelling is a legal requirement.

Because high levels of phenylalanine can harm an unborn baby, women who have PKU and are actively planning a family follow a pre-conception phenylalanine-controlled diet. In the UK, all newborn babies have been screened for PKU since 1969. It is highly improbable that anyone born before 1969 would have PKU and been unaware of their condition, especially if there is no family history of PKU. However, women who are actively planning a family who have concerns about PKU should contact their doctor.


As well as the general requirement for foods to carry a list of food additives and other ingredients, products containing sweeteners such as aspartame must show the statement 'with sweetener(s)' on the label close to the main product name.

Foods that contain both sugar and sweetener must carry the statement 'with sugar and sweetener(s)'. In addition, foods that contain aspartame must be labelled with a warning 'contains a source of phenylalanine'. This warning is specifically to aid individuals who suffer from phenylketonuria (PKU), so that they can avoid such foods (see above).

The method for calculating permitted levels of the salt of aspartame-acesulfame is available below.

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