Sabinsa scientists scrutinized samples of the company’s Curcumin C3 Complex and found low levels of oxalate, which the AJCN article suggested existed at high levels in some commercial samples.
“The amount of oxalic acid in a dose of Curcumin C3 Complex is 88 times lower than the lowest level needed for a food to be classified as ‘high oxalate’,” Sabinsa said in a statement.
Oxalate is a form of oxalic acid and has been linked to kidney disease when consumed at high levels. High oxalate foods are those with 22-99mg of oxalic acid per standard food serving. Low oxalate foods have between 5-10mg per serving.
Sabinsa said the AJCN had fed speculation that dietary supplements containing turmeric extract could increase the risk of kidney stone formation in susceptible individuals.
“The inference was based on a human clinical study, wherein subjects received supplemental amounts of turmeric spice powder,” Sabinsa said. “The published paper does not cover research on carefully standardized extracts of curcuminoids from turmeric. It only refers to the raw spice that contains numerous natural compounds, in addition to the curcuminoids.”
It added: “…we did not anticipate to find significant amounts of oxalic acid in the standardized extract. Actual experimentation confirmed this presumption.”
The company employed HPLP analysis to test the products. It noted that trials involving turmeric supplement doses of up to 12.5g had turned in oxalate levels of 20000ppm (245mg of oxalate). But supplements using Curcumin C3 Complex at its own recommended doses of 500mg registered only 250ppm (0.025mg) – well within low oxalate levels.
Curcumin C3 Complex is comprised of curcumin at 70-80 per cent; demethoxycurcumin at 15-20 per cent and bisdemethoxycurcumin at 2.5-6.5 per cent.
Sabinsa said the complex was being utilized by a number of clinical researchers and had been granted Investigational New Drug status by the Food and Drug Administration (FDA) as well as “other regulatory organizations overseas”.
Sabinsa had assisted the United States Pharmacopeial Convention (USP) build recently published monographs for both turmeric and curcuminoid extracts.
An eight-week clinical trial involving Curcumin C3 Complex and published last year found consumption of curcumin can benefit advanced pancreatic cancer sufferers.
The study, published in the American Association for Cancer Research's Clinical Cancer Research, was conducted by researchers at the University of Texas – MD Anderson Cancer Center.
They found Curcumin C3 Complex, despite possessing what they called limited absorption potential, had anti-cancer potential albeit in a small number of participants.
“A key question related to treatment with curcumin is its poor bioavailability after being taken orally. Our results also indicated that only low levels of curcumin are detectable in plasma (steady-state level at day 3 is f22-41 ng/mL),” the researchers wrote.
“Nevertheless, some of the patients had biological activity of curcumin as evidenced by the anti-tumor effects in two patients and by effects on cytokine levels and on NF-nB, COX-2, and pSTAT.”
Curcumin C3 Complex is produced from dried rhizomes of turmeric.