Aspartame: is it safe?

What is aspartame?

Aspartame, first discovered in 1965, is a high-intensity sweetener. It is around 200 times sweeter than sugar and is used to replace sugar in a whole range of foods and drinks, including sugar-free cookies, jams and jellies and carbonated drinks. Aspartame-containing foods and drinks may be useful for those who wish to reduce their sugar intake, for example diabetics or those on a weight-reducing diet.

Aspartame is made by bonding together the two amino acids, aspartic acid and phenylalanine to form a dipeptide; this is then esterified with methanol.

These constituents are commonly found in every day foods. Amino acids are the building blocks of proteins, and aspartic acid and phenylalanine are found in a range of protein foods, including meat and dairy products. Methyl esters are found in fruits and vegetables.

What happens when aspartame is eaten?

When aspartame is eaten it is broken down in the body into aspartic acid, phenylalanine and methanol. These components are all naturally present in common foods and are handled by the body in the same way as when they are derived from food.

Is there any scientific evidence for adverse effects?

You’d probably be quite alarmed if you did a Google search on ‘aspartame’, as it has been linked to a wide variety of conditions, including; brain tumors, headaches, memory loss, vision loss, depression, seizures, coma, allergic reactions, epilepsy, cancer and weight gain. There is, however, no sound scientific evidence that aspartame is a causative factor for any of these conditions. Aspartame does not enter the blood stream and there is no plausible physiological reason why it could cause adverse health effects.

Is aspartame really safe?

There have been numerous studies into the safety of aspartame, however, research from the Italian-based Ramazzini Foundation of Oncology and Environmental Sciences has received particular attention in recent years. Two reports have been released since 2005, each claiming to have found a significant increase in lymphomas and leukaemias in rats exposed to a diet containing aspartame.

Food safety authorities worldwide have evaluated these studies. The US Food and Drug Administration issued a statement in 2007 to say that significant shortcomings had been identified in the design, conduct, reporting, and interpretation of this study, and that the data do not appear to support the aspartame-related findings reported by Ramazzini Foundation. The European Food Safety Authority evaluation of the results concluded that the increased incidence of lymphomas/leukaemias reported in treated rats was unrelated to aspartame and there was no reason to revise the established Acceptable Daily Intake. The same conclusion was independently reached by Food Standards Australia New Zealand, the United Kingdom Food Standards Agency and the Canadian Food Inspection Agency.

Overall, more than ninety countries world-wide, including New Zealand, Australia, the United States, Canada, and countries of the European Union have reviewed aspartame and found it to be safe for human consumption.

How is the safety of aspartame assessed?

The use of aspartame is tightly regulated and rigorously assessed for safety. In New Zealand, the Food Standards Code sets out which foods are permitted to have aspartame added to them. These permissions are the result of a comprehensive assessment and review of all food additives, undertaken by Food Standards Australia New Zealand (FSANZ).

FSANZ safety assessments are based on evaluations and acceptable daily intakes established by the Joint World Health Organisation and Food and Agriculture Organisation’s Expert Committee on Food Additives (JECFA).

Phenylketonuria (PKU)

Some people in New Zealand have a rare inherited disorder called phenylketonuria (PKU). Such people are unable to metabolise the amino acid phenylalanine effectively, potentially leading to high levels of phenylalanine in the blood stream, which is very harmful. Usually people with PKU are diagnosed shortly after birth and will be following a strict diet to limit intake of phenylalanine. Products containing aspartame will be clearly labeled and such products can be easily avoided by people with PKU.

What is the Acceptable Daily Intake for aspartame?

The Acceptable Daily Intake (ADI) is the amount of an additive that can be consumed daily over a lifetime without causing any adverse effects. It is expressed in relation to body weight to take account of different body sizes, for example children of different ages will have different body sizes. The ADI for aspartame is 40mg per kg body weight. Average intake in New Zealand has been estimated by the New Zealand Food Safety Authority to be 2mg per kg body weight, which is much lower than the ADI. Even high consumers have less than 10mg per kg body weight.

How do I know if a food contains aspartame?

Aspartame may be listed on food ingredients either by its name, or by the number 951. Products containing aspartame may also list phenylalanine on the list of ingredients.


Overall, there is no sound scientific evidence to show any adverse effects of aspartame on human health when consumed at levels below the ADI. Even at high doses the metabolites of this sweetener do not accumulate in toxic amounts. However, just as a precautionary measure, it is recommended that pre-prepared foods and drinks served to infants are free of sweeteners.

Further Information

European Food Safety Authority

Food Standards Australia New Zealand (FSANZ) – Aspartame fact sheet

Health Canada

New Zealand Food Safety Authority (NZFSA), Aspartame – what is it and why is it used in our food?

New Zealand Food Safety Authority (NZFSA) submission to the Health Select Committee 2007

UK Food Standards Agency

US Food and Drug Administration (USFDA)

This Science Byte was peer-reviewed by Jenny Reid, Assistant Director at the New Zealand Food Safety Authority.