Acceptable daily intakes and reference health standards
Some substances found in or added to foods can potentially harm your health if eaten in high enough amounts. To minimise this risk, experts set reference health standards such as acceptable daily intakes (ADIs). These act as a guide to tell you how much of a substance you can safely eat over your life. Learn about the standards and how they're set.
What are reference health standards?
Reference health standards are the amount of a specific chemical – like a food additive or agricultural compound – that experts have decided is safe for a person to eat each day over their lifetime. These standards are used to help calculate safe limits for additives and chemical contaminants in foods.
The most commonly used reference health standards are:
- the acceptable daily intake (ADI)
- the potential daily exposure for food, or PDE (food).
Both ADIs and PDEs are based on one kilogram of body weight.
How reference health standards are set
ADIs and PDEs are decided after taking into account all your likely exposures to a specific chemical – including through the environment and diet.
In New Zealand, the Environmental Protection Authority (EPA) determines the overall exposure to a chemical then works out how much of that exposure is likely to come from food. MPI uses this to set safe limits for specific chemicals in food.
Where the EPA hasn't set a PDE (food), MPI uses ADIs set by international experts convened by the World Health Organization and the Food and Agriculture Organization of the United Nations. There are 2 committees:
- the Joint Expert Committee on Food Additives (JECFA) - evaluates food additives, environmental contaminants, natural toxins and veterinary drugs
- the Joint Meeting on Pesticide Residues – evaluates pesticides.
If these committees haven't set an ADI, MPI will set one.
ADIs are set after extensive research and testing
ADIs are set after extensive tests are carried out to see how much of a chemical can be eaten without it causing harm. Researchers try different doses on animals to see which dose of the chemical first has a toxic effect.
The dose just below that is called the 'no observed adverse effect level' (NOAEL). This is the level used to work out the ADI for humans – and is at least 100 times lower than the highest safe dose fed to animals. While the usual safety margin is 100 times the NOAEL, if there is any uncertainty, the ADI can be set at 1,000 or 10,000 times the NOAEL.
The size of the safety margin depends on:
- the quality and extent of the research
- the severity of any effect seen
- whether the exposure is will also apply to infants - in which case, higher safety margins are used.
ADIs also apply to children
Substances in foods can potentially have a greater impact on very young children (less than 12 weeks) because:
- their body systems are not fully developed
- they eat greater quantities of food relative to their body size, so have more than the average dietary intake of a chemical residue.
However, ADIs are set based on consumption over an entire lifetime, and the large safety margins help protect children and people sensitive to particular chemicals. And while children's organs and body systems are less developed and may be damaged more easily, their bodies usually have better repair mechanisms.
NZ diets regularly checked against ADIs
Every 5 years, MPI surveys foods sold in New Zealand to assess New Zealanders' exposure to chemicals such as agricultural compounds and chemical contaminants. New Zealanders' intakes are compared with ADIs to help us identify if any potential health risks.
Provisional tolerable weekly intakes (PTWIs)
Some food contaminants that can accumulate in the body, like heavy metals, may have a provisional tolerable weekly intakes (PTWI) rather than an ADI. For example, PTWIs have been set for cadmium, mercury and lead.
These intakes are 'provisional' because there's not yet enough research to set safe levels, and PTWIs must be reviewed regularly.
Find out more
Who to contact
If you have questions about reference health standards, email firstname.lastname@example.org.