Basing criteria for substantiating health claims solely on evidence from human intervention studies is impractical, according to the International Alliance of Dietary/Food Supplement Associations (IADSA).

Commenting on the latest draft Codex Alimentarius recommendations for the scientific basis of health claims, IADSA said that while the clinical trial model is one source of scientific data, it is not practical when applied to the reduction of risk of disease in “healthy” people.

The recommendations, which are being revised by an electronic working group of which IADSA is a member, states that short-term human intervention studies in healthy subjects should be the prime source of evidence in claims substantiation. Text also makes no reference to evidence based on traditional knowledge and history of use.

The previous draft was sent back to the drawing board last year following concerns over the structure of the document and the weight given to the different types of evidence required for scientific substantiation.

“It is scientific dogma to state that health claims should be based primarily on well designed human intervention studies,” said David Richardson, scientific adviser to the UK Council for Responsible Nutrition (CRN) and IADSA. “Much of what is already known about human health cannot be validated using ‘gold standard’ clinical trials. These studies are, of course, important, but they provide only one source of information. All sources of scientific data have inherent limitations, hence the need to focus on the totality of the available data and weighing of the evidence.”

IADSA referred to the approach taken in the draft as “medicine-based, aimed at deciding whether a drug can prevent, cure or alleviate a disease or medical condition in the treatment of well-defined groups of people at high risk of disease or already with a disease.” However, IADSA argued that nutrition studies in healthy people require a large sample size, long-term follow up, high rates of compliance and must account for other lifestyle factors.

“The scientific evidence to support the diet and health relationships for dietary guidelines and health claims for fruits and vegetables, and for whole grain cereals, are based mainly on human observational studies, not clinical interventions,” Mr. Richardson said.

The text, which will go through an eight-step process to completion, will be presented at the next Codex Nutrition Committee meeting this November.