Aspartame: Is it safe?

Aspartame is commonly used as a sweetener in food and beverages. But is it safe?

Aspartame is often called number 951 on food labels in New Zealand.  It is one of the most widely used and popular alternative sweeteners in food and beverages and has 200 times the sweetness of sugar.

Made from two amino acids (the building blocks of proteins), it breaks down at high temperature so it can’t be used in baking or cooking.

It is commonly used in cold beverages and is one of the most studied sweeteners. It does have an energy value (64kJ per gram) but as so little is used to sweeten food, the energy contribution is virtually zero. Used as a table top sweetener, in drinks and in foods.

The health impacts

If you Google ‘aspartame’ and start reading, you could be forgiven for becoming very nervous about your health: it seems that ingesting aspartame will cause an extraordinarily wide range of complaints, pretty much from A to Z. Why is this additive allowed in our food supply, you ask yourself?

Aspartame is broken down into aspartic acid, phenylalanine and methanol in our bodies. One popular piece of misinformation about aspartame is that it causes methanol toxicity which mimics multiple sclerosis, but there is simply no evidence for this, nor any logical explanation of why it should be so. The methanol and other compounds mentioned are not in any way sinister, they are found naturally in other foods and our bodies are able to absorb, metabolise and excrete them.

A large Italian study raised concerns suggesting a link between aspartame and an increased risk of cancer in rats. This report received wide media coverage. The European Food Safety Authority (EFSA) assessed this aspartame study along with currently available evidence and concluded that there is no need to further review the safety of aspartame nor revise the acceptable daily intake (ADI) for aspartame. The National Cancer Institute in the US recently conducted a beverage consumption study with nearly half a million people and the results indicated that there is no relationship between aspartame use and cancer in humans.

There is a requirement to label any food containing aspartame or aspartame-acesulphame to the effect that the product contains phenylalanine.

What is phenylketonuria?

You may have seen the warning on the label of foods and beverages containing aspartame: “Contains phenylalanine”. 

Phenylketonuria (PKU) is a rare genetic disorder that prevents the body breaking down the essential amino acid phenylalanine which is one of the amino acids found in aspartame. In people with PKU the phenylalanine builds up in the tissues of the body and can cause irreversible brain damage.  We are all tested for this disorder at birth. 

People with PKU must follow a special limited diet which strictly limits their intake of phenylalanine, especially in the early and teenage years.

Acceptable daily intake

The acceptable daily intake (ADI)* is an estimate of the amount that could be consumed every day over a lifetime without adverse effects. It’s worth noting that the ADI is set at a very conservative level. And usual intake is well below the acceptable daily intake.

The ADI for aspartame is 40mg per kg of body weight per day. For a 68kg person, this equates to 12 cans of diet soda per day.

* Note: This volume is related to the safety of aspartame and does not imply that such large daily volumes of carbonated drinks are appropriate in a balanced diet. 

The bottom line

Aspartame has its place when used sensibly. It is useful to help satisfy a desire for sweet foods without adding the kilojoules. Used in moderation, it is safe and effective for reducing the energy value in food and beverages that would otherwise contain sugar.