Aspartame – a guide to artificial sweeteners

Aspartame (E 951) is one of our most common sweeteners. It is also one of the most researched ingredients out there. Nevertheless, aspartame can not shake off its bad reputation. Why is that?

8 September 2020 • and

In our series ‘Guide to arti­fi­cial sweet­en­ers’, we start with one of the most famous sweet­en­ers avail­able: aspar­tame. Aspartame has become some­thing of the industry’s ‘bad boy’ or scape­goat. Perhaps it is a sym­bol of con­sumers hes­i­ta­tion about arti­fi­cial sweet­en­ers in gen­er­al. At the same time, ‘sug­ar-free’

is increas­ing­ly in demand. How is it all con­nect­ed, and what is the solution?

Aspartame – a discovery by chance

The year is 1965 and James Schlatter is a young chemist at the phar­ma­ceu­ti­cal com­pa­ny DG Searle & Co. He is work­ing on devel­op­ing a new med­i­cine for stom­ach ulcers and has no idea that he will soon lay the foun­da­tions for a revolution.

One day he is stand­ing in his lab­o­ra­to­ry with a mix­ture of the two amino acids pheny­lala­nine and aspar­tic acid. For some rea­son (which he him­self has not been able to explain) he puts his fin­ger in the mix­ture to taste it.

What hap­pened then? In an inter­view with the Washington Post sev­er­al years lat­er, he says:

– I licked my fin­ger and it tast­ed good.

There and then, the idea was born for the sweet­en­er aspar­tame, which still con­sists of these two amino acids.

Aspartame consists of two amino acids

Amino acids are the build­ing blocks that form pro­teins. Protein, in turn, is used to build cells, mus­cles and hor­mones, and more in your body.

There are about 20 amino acids that make up pro­tein. Nine of these amino acids are called essen­tial. That means you have to have them, they are nec­es­sary for you, but your body can­not form them by itself. You have to get them through your diet. One of these essen­tial amino acids is pheny­lala­nine, which is found in aspartame.

The non-essen­tial amino acids are also nec­es­sary for us. They are called non-essen­tial because the body itself can man­u­fac­ture them when needed.

One of these non-essen­tial amino acids that the body can pro­duce itself is aspar­tic acid. It is the sec­ond amino acid found in the sweet­en­er aspartame.

How to make aspartame?

You start by cre­at­ing the raw mate­r­i­al, the two amino acids pheny­lala­nine and aspar­tic acid. This is done by cul­tur­ing the bac­te­ria Brevibacterium flavum and Corynebacterium glu­tam­icum, which in turn pro­duce amino acids.

Here’s how: Bacteria are fer­ment­ed in a nutri­tious soup, stir­ring con­stant­ly for sev­er­al days. At the same time as the bac­te­ria grow and become more numer­ous, they form large amounts of amino acids.

When it’s time to har­vest, the soup is put in a cen­trifuge that sep­a­rates the amino acids from the bac­te­ria. The amino acids are then placed in an ion exchang­er, where you can pick out (iso­late) the desired amino acids for fur­ther processing.

The next step in the process is to place the amino acids in a crys­tal­liza­tion reac­tor, where crys­tals formed dur­ing the process are cen­trifuged away. Then the amino acids are allowed to dry.

Then comes the syn­the­sis – bring­ing the amino acids togeth­er to cre­ate aspar­tame. This takes place in sev­er­al steps, where, among oth­er things, the amino acids are heat­ed to 65 degrees and then cooled down to -18 degrees. Then new crys­tals are formed which are mixed with acetic acid, hydro­gen and pal­la­di­um under high pres­sure for 12 hours. This caus­es the two amino acids pheny­lala­nine and aspar­tic acid to fuse together.

The whole process ends with fur­ther purifi­ca­tion where the added sub­stances are fil­tered and dis­tilled. What remains is a hard mass which is dis­solved with ethanol, after which the amino acids are crys­tal­lized again, fil­tered one last time and then allowed to dry.

A crooked path to success

When James Schlatter licked his fin­ger in 1965, he had no idea it would change his whole life. Instead of devel­op­ing a med­i­cine for stom­ach ulcers, he had dis­cov­ered an arti­fi­cial sweet­en­er that many years lat­er would turn over hun­dreds of mil­lions of dol­lars a year. But get­ting there was not an easy task and fraught with controversy.

In 1973, an appli­ca­tion was made to the FDA (US equiv­a­lent of the National Food Administration) to use aspar­tame as an addi­tive in food. Together with the appli­ca­tion, the com­pa­ny sent Searle 150 stud­ies, and a year lat­er, in 1974, aspar­tame was approved, albeit with cer­tain restrictions.

In 1983, aspar­tame was approved as a sweet­en­er in soft drinks, which laid the foun­da­tion for a rev­o­lu­tion in ‘light’ bev­er­ages. It was the big break­through for aspartame.

But right from the start, in the ear­ly ’70s, the FDA’s deci­sion to approve aspar­tame as a food addi­tive was crit­i­cized by Dr John W. Olney and the author of The Chemical Feast, James S. Turner, who had researched the effect of amino acids on the brain.

They ques­tioned the safe­ty of aspar­tame and point­ed out, among oth­er things, that peo­ple with the dis­ease phenylke­tonuria (PKU) can not break down the amino acid pheny­lala­nine, which is found in aspartame.

This opened up a wide range of stud­ies on aspar­tame. It has made aspar­tame one of the most researched ingre­di­ents in the world.

Is aspartame dangerous?

Today, the Swedish Food Agency rec­om­mends that peo­ple with the dis­ease phenylke­tonuria (PKU) should be care­ful with their intake of pheny­lala­nine, espe­cial­ly children.

Otherwise, there are no restric­tions as long as we stay below the rec­om­mend­ed dose. On the Swedish Food Agency’s web­site, we can read:

‘Aspartame-sweet­ened soft drinks may con­tain a max­i­mum of 0.6 grams/​litre. This means that a per­son weigh­ing 60 kg can drink four litres of aspar­tame-sweet­ened soft drink/​day.’

Over the years, stud­ies have emerged that point to an increased risk of can­cer with a large intake of aspar­tame. Some of these stud­ies have been wide­ly cir­cu­lat­ed in the media, which is one rea­son why many con­sumers are hes­i­tant about aspartame.

The EU’s equiv­a­lent to the Swedish Food Agency is called EFSA (European Food Safety Authority). According to them, these stud­ies have had major short­com­ings and unre­li­able results. On the Swedish Food Agency’s web­site, we can read:

‘All stud­ies involve life­long expo­sure to dos­es up to 8 g aspartame/​kg body weight and day. This dose, con­vert­ed to an adult, is equiv­a­lent to approx­i­mate­ly 2,400 cans of aspar­tame-sweet­ened soda each day through­out life.’

Sceptical consumers

Although numer­ous stud­ies have shown that aspar­tame pos­es no dan­ger nor seri­ous side effects, many peo­ple claim that they do not tol­er­ate aspar­tame. Common symp­toms are headache, dizzi­ness, fatigue and mood swings.

The research done in this area has not been able to demon­strate such a con­nec­tion. At the same time, researchers can­not com­plete­ly rule out the pos­si­bil­i­ty that indi­vid­u­als may have increased sen­si­tiv­i­ty to aspartame.

In a dou­ble-blind test con­duct­ed by researchers from sev­er­al dif­fer­ent uni­ver­si­ties, main­ly in the UK in 2015, 48 peo­ple who said they were sen­si­tive to aspar­tame ate two bars at one-week inter­vals, some con­tained aspar­tame and oth­ers did not. Results showed that there were no dif­fer­ences in symp­toms between those who ate aspar­tame and those who did not.

In 1984, The Center for Disease Control (CDC) con­duct­ed a four-month study of about 500 indi­vid­u­als. The par­tic­i­pants had var­i­ous ‘gen­er­al prob­lems’ with their health, but noth­ing that the study could link to the use of aspartame.

Despite the fact that ‘food agen­cies’ around the world have declared aspar­tame safe, there is still a great deal of uncer­tain­ty left. The scep­ti­cism comes, among oth­er things, from finan­cial con­nec­tions between indus­try and author­i­ties and sus­pi­cions of bribery.

If you delve into the sim­pli­fied descrip­tion above on how to make aspar­tame, you will find anoth­er expla­na­tion for con­sumer scep­ti­cism. It is a prod­uct invent­ed in the lab­o­ra­to­ry and man­u­fac­tured in a factory.


Within the EU, aspar­tame is used in a num­ber of dif­fer­ent prod­ucts, includ­ing bev­er­ages, desserts, ice cream, sweets, chew­ing gum, yoghurt, break­fast cere­als, jams, sauces and dietary supplements.


Aspartame is as high in calo­ries as sug­ar (4 kcal per gram), but in prac­tice, it is basi­cal­ly free of ener­gy. Because it is 180-200 times sweet­er than sug­ar, small amounts are need­ed to give the same sweet­ness as sug­ar. The taste is sweet but not bitter.


Aspartame is a com­pound of sev­er­al amino acids. When the pH val­ue becomes too high or at high tem­per­a­tures, the amino acids go their sep­a­rate ways and the sweet­en­ing effect dis­ap­pears. In prac­tice, this means that aspar­tame is unsuit­able in bak­ing or in foods that require long shelf life.

If you despite this, use aspar­tame in bak­ing, you may need to add oth­er ingre­di­ents to keep it sta­ble. Fat or mal­todex­trin may work to some extent. In prod­ucts that require long shelf life, you need to add oth­er ingre­di­ents to ensure the qual­i­ty of the food. To improve the shelf life of soft drinks, sac­cha­rin can be used.

The bad reputation persists

Although research sys­tem­at­i­cal­ly dis­pels myths and neg­a­tive notions about aspar­tame, the dubi­ous rumour remains. Therefore, from a mar­ket­ing per­spec­tive, it is dif­fi­cult to argue for aspar­tame, at least if you want to clear­ly strength­en your brand.

Consumers pre­fer foods that are per­ceived as nat­ur­al or at least do not con­tain any­thing unnat­ur­al. A close rel­a­tive is the glob­al free from-trend, which means reduc­ing or remov­ing ingre­di­ents that, for var­i­ous rea­sons, are not in line with the norms and pref­er­ences that many con­sumers have.

But there are alter­na­tives to aspar­tame that come from nat­ur­al sources: sweet ste­vi­ol gly­co­sides, which are extract­ed from the ste­via plant.

It is a calo­rie-free alter­na­tive that does not raise blood sug­ar lev­els and can be used in a vari­ety of foods. And unlike aspar­tame, ste­vi­ol gly­co­sides have not faced the crit­i­cism that aspar­tame has endured.

The future is natural

The devel­op­ment of bet­ter ste­vi­ol gly­co­sides in recent years has been at a furi­ous pace as we have become bet­ter at extract­ing the rare ste­vi­ol gly­co­sides with the most sweet­ness, such as Reb M.

In the com­ing years, we will prob­a­bly see more inno­v­a­tive com­bi­na­tions of sweet­en­ers of nat­ur­al origin.

An exam­ple is thau­matin. Thaumatin is a high-inten­si­ty sweet­en­er that orig­i­nates from the West African Katemfe fruit. It cre­ates syn­er­gy effects with ste­vi­ol gly­co­sides, which enhances the sweet­ness and over­all taste experience.

Curious about stevia?

Are you curi­ous about ste­via and ste­vi­ol gly­co­sides? We devel­op ste­via extracts for dif­fer­ent appli­ca­tions. Take a look at our range of ser­vices or con­tact us if you want to know more about how we can help you.

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