Independent scientists advising the European Union have for the sixth time found no cause-and-effect relationship between probiotic products and improved immune systems.

The Panel on Dietetic Products, Nutrition and Allergies, part of the European Food Safety Authority, yesterday posted its assessment of 800 health claims, including some from manufacturers whose products include so-called functional ingredients like probiotics–food additives they claim can stimulate the immune system to aid digestion or inhibit pathogens.

EFSA, Europe’s food-safety watchdog, has previously published five negative opinions on claims relating to probiotics.

Probiotics are live microorganisms, considered to be “friendly” bacteria that can confer health benefits. They’re commonly consumed in fermented foods with added live cultures, such as yogurt.  EFSA, however, doesn’t use the term probiotics, which it says is not scientifically valid.

In this latest assessment of probiotic products, the EFSA panel said the data the industry submitted to support its claims were either too general, or there was no evidence of demonstrable benefits.

A separate ruling was a particular blow to Yakult, the popular probiotic beverage from Japan.  The EFSA panel reviewed 12 studies submitted for the company’s proprietary strain of probiotic bacteria, Lactobacillus casei shirota.  Yakult claims its product strengthens the immune system to help prevent colds; EFSA said the research was inadequate to support that claim.

Yakult responded to the EFSA opinion by saying it wants to discuss the evaluation process with the agency and expressed optimism of some future, positive opinion.  The company stood by its own science: “The claim was supported by well-designed, double-blind, placebo-controlled human studies,” it said in a statement. 

According to a report in the British newspaper, The Guardian, Danone, the leading manufacturer of probiotic products, withdrew its immune-boosting claims for Actimel and Activia from EFSA review after the earlier negative rulings on other manufacturers’ products.

The Guardian said Danone has since dropped most of the “immune health” claims from its advertising.  Danone’s assertion that the probiotic Lactobacillus casei in fermented milk reduces the presence of Clostridium difficile toxins associated with acute diarrhea is now the company’s only claim awaiting EFSA review.

Probiotic claims continue to be an issue in the United States.  In December 2009, the Food and Drug Administration issued a letter to Nestlé, warning the company that it was marketing its  probiotic-fortified BOOST Kid Essentials Drink as a drug.  The FDA, however, treated the matter as a misbranding issue, and didn’t challenge the health claims.

In July, the Federal Trade Commission weighed in on the matter and Nestlé agreed to stop making the claims.