December 11, 2019

Diet & Nutrition – Are Food Additives Safe?

Many people are put off from food additives simply because they do not know enough about them or the extreme testing that they must go through before being permitted for use. There is a particular suspicion towards E Numbers and their association with cancer, hyperactivity and allergies.

A food additive is a substance (natural or synthetic) that is added to food to improve colour, flavour, texture, stability or functional properties of food. Food additives can be put into 3 different categories:

  • Natural chemicals (Pectin, Citric acid, Lecithin)
  • Nature identical chemicals (Limonene, Vanillin, Calcium propionate)
  • Synthetic chemicals (Saccharin, Tartrazine, Butanene hydroxy toluene)

Each food additive is assigned an E number so that it can be widely recognised.

  • E100-E199 are colours
  • E200-E299 are preservatives
  • E300-E399 are antioxidants
  • E400-E499 are emulsifiers and stabilisers

How can we be sure that these E numbers are safe?There are 3 main stages in the safety evaluation of a chemical intended for use as a food additive:

  • Toxicological testing
  • Determination of ADI
  • Determination of potential human exposure.

Toxicological Testing

Acute toxicity tests:

These are required to identify target organs of the chemical. EU directives require an LD50 value for the chemical. (An LD50 value is the dose required to cause lethality in 50% of test animals over a certain period of time). The chemicals should be tested at 3 or more doses extending well above the expected human exposure range and the chemicals should be tested in 2 or more species. A 14 to 28 day feeding test is done to provide information of cumulative toxicity and to identify the target organs. These results act as a basis for settling dose levels for longer tests.

Metabolic studies:

These studies are done on test animals (rats, mice or hamsters) to obtain information on absorption, distribution, metabolism and excretion of the chemical. Sub acute toxicity studies can then be carried out. This is a 90-day feeding study that begins after the weaning of the rodent and extends through a period of rapid growth. Both male and female animals are studied. At least 3 dose levels of the chemical should be fed to different groups of the animals. Ideally the top dose should be within the minimum toxic dose range that was determined by the acute toxicity and target organ tests. A control is also included.

The NOEL (No Observable Effect Level) and the MTD (Maximum Tolerable Dose) can be determined after the animals have been sacrificed.

Long-term toxicity studies:

This lifetime animal bioassay is often the cornerstone of the risk assessment process. The test substance is fed for a lifetime at the MTD, ½ MTD and ¼ MTD. Even at ¼ MTD the dose is likely to greatly exceed the expected exposure to humans.

Reproductive and Teratogenicity studies:

These studies are designed to identify the adverse effects of the chemical on the embryo or foetus. Again, at least 2 species of test animal are used. The effects of fertility and breeding performance, and embryo toxicity and teratogenicity tests are all studied.

Determination of ADI

The ADI is determined by dividing the NOEL by a safety factor (~100).This is an arbitrary number and unless other information is presented it is believed that this margin of safety is adequate. The extrapolation from animal to man must account for species differences, individual variations, incompleteness of available data, the numerical difference between the test animals and the human population. Also to be taken into consideration during this extrapolation is the synergistic action among other chemicals in the diet, the fact that the chemicals will be consumed by people of all ages and health status and wide variations in individual dietary patterns. The ADI is defined as the daily intake of a chemical, which during an entire lifetime appears to be without appreciable risk on the basis of all known facts at the time. It is expressed as mg/kg body weight.

Determination of potential human exposure

This is calculated by multiplying the intake of the food containing the chemical by the concentration of the chemical in the food.

Methods such as:

  • Food disappearance data
  • Food purchase data
  • Dietary recall studies
  • Food frequency questionnaires

Can be used to estimate the intake of the food in a population.

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