Clinical trials have demonstrated the effectiveness of standardized extracts of Ginkgo biloba for the stabilization or improvement of mild to moderate Alzheimer's disease (using dosages of 120-240mg/day for 3-6months). This improvement in symptoms is comparable to or greater than that obtained with conventional synthetic drugs such as tacrine, but without the harmful side effects associated with the latter. Chemical substances with powerful antioxidant activity are thought to contribute to the effectiveness of Ginkgo biloba extract in Alzheimer's disease patients.

Antioxidants counter the damaging effects of toxic molecules produced within the body called free radicals, which have been implicated in a variety of diseases including Alzheimer's disease. A study by British scientists to compare antioxidant activity in 18 Ginkgo biloba brands has recently been published in the Journal of Alternative and Complementary Medicine. Antioxidant activity was measured using a standard laboratory test, and expressed on a per mg ginkgo basis to enable comparison between tablets of different sizes. There was a 50-fold difference in activity between the samples, with Pharma Nord Bio-Biloba having the highest level of antioxidant activity.

This variability can be partly explained by the type of Ginkgo biloba used; some products are based on dried leaf powder, while others use Ginkgo biloba in a more concentrated (standardized extract) form. However even when comparing the latter products, there is still a considerable variation in antioxidant activity, which presumably must result from differences in manufacturing processes used by different suppliers.

In addition to the above study on Ginkgo biloba, recent reports have highlighted discrepancies in stated active ingredient content for the nutritional supplements coenzyme Q10 and St John's Wort, which have been shown to be effective in the treatment of cardiovascular disease and depression respectively. These reports demonstrate the importance for consumers of purchasing supplements from manufacturers who can guarantee product content, quality, and activity. All nutritional supplements marketed by Pharma-Nord are manufactured under pharmaceutical control, which is a guarantee of product quality.