Humic acids are omnipresent compounds of highly varied chemical composition and thus very different properties. They are a part of the natural human diet as they exist in our natural environment. Consequently, much research has been dedicated to the safety of these substances. Humic acids from peat are generally considered safe. (Schauss 1998)

However, some papers on this subject suggest a direct or indirect connection between intensive humic acid intake and the so-called Blackfoot disease. Therefore the question raised by the National Pharmaceutical Institute, i.e. whether the safety of long-term, oral intake of humic acids in higher concentrations has been toxicologically proven, is an essential one.

The following is known about the Blackfoot disease at present: it is endemic to the South-Western coast of Taiwan and it is characterized by peripheral vascular obstruction, gangrene and ulcerations of the lower extremities. Pathological consequences include endothelial damage and inhibition of Protein C activation and the enzyme itself (in vitro). Some early reports indicate increased endothelin production (Yang and Rostai, Amer. J. Haematol. 46, 264, 1994). Nevertheless, data available from scientific literature suggest that Blackfoot disease is a multifactoral illness, because the waters in that area clearly have extremely high arsenic content and this is much more common in this area than elsewhere: thus this disorder is strongly linked to arsenism.

The anemia associated with Blackfoot disease might be caused by the humic acid-mediated oxidative damage of red blood cells (Cheng and Rostai, Free Radical Biol. Med. 27, 470, 1999), but anemia might be a consequence of arsenism also. This study describes in detail the accelerated lipid peroxidation, the decrease in reduced glutathione and the reduced activity of the major antioxidant enzymes (catalase, SOD, G6PD), all caused by humic acids, and the possible prevention of all these reactions in the presence of Vitamin E. But the humic acid concentrations in the reaction mixtures were in the microgram/ml range, which practically never exists in nature. The same applies to the circumstances in which Protein C activity can occur. The doses measured in microgram/ml are pharmacological, experimental doses, therefore they should not be directly translated to in vivo circumstances.

We have rather poor absorption study results: the absorption test results are rather difficult to evaluate, because mainly fulvic acids prepared with the help of bacteria were used in studies involving 14C labeled humic acid, while the research team in Taiwan used iodine isotope 124I in absorption tests. In the latter study it was demonstrated that 60% of intraperitoneal humic acid was still detectable after 24 hours in the rat. Earlier animal studies demonstrated low absorption rate of around 0.1% in the rat. Humin substances certainly do metabolize in the alimentary tract - for some are produced there also - and so their concentrations in the plasma (are so low that for them to be) measurable in microgram/ml is highly unlikely, when the daily dose is approx. 75 mg.

Furthermore, the quality of humic acids and their differences in terms of origin and structure must also be taken into account. Preparations derived from peat contain pure humic acid only in parts, as they generally contain a mixture of humic acid and fulvic acid in the ratio of 1:1. The dominant chemical structures in humic acids depend on their age (date of origin) also. Furthermore, the place of origin of peats and the location of their underground or underwater deposits also influence the exact chemical structure of humin substances, since they are a complex mixture of compounds. Therefore, it is not evident that the humic acids from the area where the Blackfoot disease is endemic are identical with humic acids isolated from other areas. The fluorescent humic acid substance studied by Lu et al (Thrombosis Research 57, 747, 1990) modified the prothrombin time and APTI in such high concentrations that the direct causal relationship between the intake of this isolated humic acid and the disease - as suggested by biochemists - seems highly unacceptable.

While humic acid preparations are used in other countries as well, the Blackfoot disease occurs only in this specific part of Taiwan, where there is an overload of arsenic. As demonstrated by the researchers themselves in Taiwan, humic acids of different origins (well water, synthetic, Aldrich catalogued) produced strongly differing results in identical biological test models.

Ground waters contain humic and fulvic acids everywhere, but the Blackfoot disease was reported only in Taiwan. The As, Cu and Zn concentrations of certain sea-snails in Taiwan are good indicators of environmental exposure (Han BC et al, Arch. Environm. Contam. Toxicol. 32, 456, 1997) in the places where this vascular disease occurs. Ko Y.C. in a summary report gave a critical assessment of the epidemiology of this disease (Sangyo-Ika-Dauigaku Zasshi 8, 339, 1986) and pointed out that the disease has been known as Blackfoot Disease since 1958 and had been thought to be caused by arsenism up to that time. More recent data indicate that the incidence of the disease increased in this specific area after the replacement of artesian water supply with piped water system: a fact that points against humic acid exposure being the etiological factor.

This is by all means a multi-causal disease. Scientific research is rather contradictory, since Wang CT (Eur. J. Clin. Chem. Clin. Biochem. 34, 493, 1996) has identified arsenic as the main cause of the disease, beside the high zinc and extremely low selenium concentrations. In the particular endemic area the artesian water had 200 ppm humic acid content, and Lu and Hiung (J. Formosan Med. Assoc. 85, 352, 1986) estimated the average daily humic acid intake as 400 mg per day. Gau et al (Toxicology and Applied Pharmacol. 166, 59, 2000) conducted very sophisticated experiments to prove that humic acid inhibited the expression of lypopolysacharid-induced ICAM-1, VCAM-1 and E-selectin adhesive molecules in the human umbilical vein endothelial cell culture, depending on time duration and concentration. Nuclear factor kappa-B (NF-kB) regulates this type of expression, and thus an examination of its activation revealed that humic acid acted as the inhibitor. The same way, humic acid suppressed the endotoxin-induced immune and inflammatory reaction of these endothelial cells, which indicates that a disorder in these reactions may play a role in the development of the Blackfoot disease.

The lowest humic acid concentrations - below the efficacy threshold - that were applied were as high as 10-25 microgram/ml. In an earlier study Riede UN et al (Virchows Archive B Cell Pathol. 60, 27, 1991) demonstrated the activation of human granulocytes and increased hydrogen peroxide production as a result of naturally occurring humic acid, while no changes were seen in either the chemotaxis or the chemokinesis. Therefore, humic acids may modify inflammatory reactions as well, although any effects in these experiments were shown only for concentrations above 10 microgram/ml. Lu F.J. in an animal study on mice (-letter- Lancet 336, 115, 1990) demonstrated in 1966 that humic acid treatment can actually induce the symptoms of the Blackfoot disease in these animals. It is true that these experiments involved only 16 mice and extremely high doses of intraperitoneal humic acid, but certain typical symptoms were actually manifested.

In view of all this, the toxicological assessment of the samples recently submitted for clinical trial has been fully justified. In respect of the effect of humic acid on the haemostatic system, the articles attached hereto (Yang HL et al Amer. J. Haematol. 46, 264, 1994, Lu FJ. et al: Bull. Environm. Contam. Toxicol. 53, 577, 1994, Klöcking H-P. Recent Develop. Toxicol., Arch. Toxicol. Suppl. 14, pp.166, 1991, Lu GFJ. Thromb. Res. 58, 537, 1990, Lu FJ. Lee. YS:. Science of the Total Environm. 114, 135, 1992) clearly reveal - through in vitro experiments - the effects of humic acid of the Aldrich catalogue on the one hand and the active fractions gained from purified the humic acid isolated from the said endemic area on the other hand, on prothrombin time, plasmin, and the activity and activation of plasma Protein C, t-PA release etc. Taking into consideration this effect, humic acids have been described as anticoagulants and in respect of other effects as pro-coagulants. This also indicates that effects in both directions can be evidenced, depending on the concentrations applied.

It would seem wise to find out whether it is possible to collect data on such levels of prevalence of peripheral vasculopathies and endotheliopathies that matches that of the endemic Blackfoot disease in Taiwan, in countries where humic acid containing "health products" have been successfully sold and consumed to date.

To sum up the above information, scientific literature contains significant amounts of data and test results in favor of, and raises at least as many doubts regarding the safety of humic acid and its causal relationship to the Blackfoot disease. The reason for this is the failure of researchers to use identical substances and that they worked with doses that were different from the doses recommended current application protocols. The purified, laboratory-clean humic acid fraction and the various preparations derivable from waters and peat are products of different safety characteristics. Any safety measurements should have involved the application of the specific preparation in such experimental circumstances that match the available plasma concentrations in the given endemic environment. The so-called peat-derived humifulvate from Hungary (a mixture of humic and fulvic acids in a 1:1 ratio) did not provide any indication for endothelial damage or pro-coagulant activity.

Furthermore, the reviewer of scientific literature sees no evidence based on which objection should be raised against the administration of the preparation as a course of treatment, in a non-permanent intake pattern, in order to allow for the manifestation of "tonic" effects in the given field of application as a result of trace element supplementation.

Based on the above facts - since this opinion is given in relation to a trial aiming at developing the product into a medicine - I consider the safety data sufficient for conducting such a clinical trial. In view of the above, I do not recommend the inclusion of ad libitum application in the finalized wording of the application protocol and the patient information, but I see no major counter-indication for periodical treatment in doses up to the maximum limit specified.

Budapest, 19 February 2001. Dr. György Blaskó med habil. Doctor of Medicine