An extract of the seaweed Lithothamnion corallioides from Ireland has been the subject of a clinical trial with patients suffering from osteoarthritis of the knee.[1] The seaweed extract containing minerals was compared to glucosamine sulfate, and both products demonstrated improvements in those taking them.

Comparing 6-Minute Walking Distances and the WOMAC Knee and Hip Osteoarthritis Index, 70 subjects with moderate to severe osteoarthritis of the knee were placed into 4 random groups and took either the seaweed mineral extract (2400 mg), glucosamine sulfate (1500 mg), both, or a placebo. The seaweed mineral and glucosamine groups demonstrated significant improvements in 6 minute walking distances, but the placebo and combination groups did not.

The WOMAC index grades pain, stiffness and physical function over specific activities. Significant differences were found between groups for pain scores after 12 weeks of treatment. The seaweed extract treatment group showed significantly improved WOMAC pain, stiffness, activity and composite scores over the course of the 12-week treatment. No significant improvements were found for subjects in the placebo group or for subjects in the combination treatment group.

The authors hypothesize that there could be an interaction in the stomach between the alkaline seaweed minerals and the acid glucosamine, which has to ionize in the stomach to be effective.

NAP Phytocal and Clearcal contain minerals from Lithothamnion corallioides, and are suitable for specific or all blood groups.

References:
1. Frestedt JL, Walsh M, Kuskowski MA, Zenk JL. "A natural mineral supplement provides relief from knee osteoarthritis symptoms: a randomized controlled pilot trial." Nutr J. 2008 Feb 17;7:9. PMID 18279523