Pectin is a complex  aggregation of polysaccharides first isolated from plant matter in 1825 by French chemist and pharmacist Henri Bracconot. Pectin is the major constituent of all plant primary cell walls, contributing to the plant’s structural integrity and providing a barrier to the external environment. Consequently, pectin is a component of all omnivorous diets.

Pectin is known to be a soluble, prebiotic fibre that bypasses human digestion in the small intestine, but is readily metabolised by microbes in the large intestine, stimulating growth of bacteria that promote colonic health such as Bifidobacteria and Lactobacillus. Furthermore, consumption of pectin is associated with benefits for cholesterol and lipid metabolism, glycaemic regulation, and alleviation of dumping syndrome.

As a water-soluble fibre, home cooks and food scientists have long utilised cooked pectin as a gelling and thickening agent for making jellies and other foods. Modified citrus pectin is typically derived from the pectin-rich peel and pith of citrus fruits (like lemons, limes, and oranges), which is subsequently denatured by heat and/or pH changes. This process aims to generate smaller fragments of the pectin polymer that could potentially be absorbed in the small intestine.

Modified citrus pectin has been considered for potential therapeutic benefits such as heavy metal binding and particularly for prevention of cancer development or metastasis. Its origins arise from a theoretical model in which a monosaccharide, galactose, was found to suppress metastasis in cell culture experiments and correspondingly that pectin is a galactose-containing polysaccharide. In a single-arm trial in men with treatment-resistant prostate cancer, administration of modified citrus pectin for 12 months resulted in an increase in prostate-specific antigen (PSA) doubling time (i.e., slower rise in the PSA biomarker) in 7 of 10 patients, suggesting that these patients may have been at reduced risk for metastatic progression. In a separate study, 49 patients with a wide array of advanced solid tumors were given modified citrus pectin for 16 weeks. After treatment, 22% of the treated patients had stable disease as measured by Response Evaluation Criteria In Solid Tumors (RECIST), and 12% of treated patients had stable disease for an additional 8 weeks following treatment. To date, these are the only published trials demonstrating any clinical benefit for cancer patients.

It has been proposed that modified citrus pectin confers health benefits through interactions with a class of carbohydrate-binding lectins known as galectins. These are a conserved family of proteins that mediate a wide array of intracellular and extracellular processes including development, differentiation, and communication. Galectins display a high degree of specificity for binding of specific carbohydrate ligands, and they are involved in a wide array of functions such as neovascularization, inflammation, and regulation of immune cell activity. Since pectin is a polymer of heterogeneous polysaccharides, it is feasible that pectin fragments or degradation products could inhibit galectins via glycan-binding domains. Recent cell culture studies suggest that such interactions may occur, specifically with galectin-3.

However, biochemical analysis revealed that numerous commercially available and laboratory-produced modified citrus pectins fail to bind strongly to the family of galectins, making it unlikely that modified citrus pectins directly inhibit galectin activity in vivo . In vitro experiments demonstrated that citrus pectin fragmented by heat in a laboratory setting can induce apoptosis in human liver and lung carcinoma cells. 4,5-dihydroxy-2-cyclopenten-1-one was identified as a cytotoxic molecule that mediated the effect; additionally, as an experimental control heat-modified galactouronic acid (the primary monosaccharide comprising pectin) also yielded this molecule and equally induced apoptosis.¹⁹ This suggests that the effect may not be unique to modified citrus pectin per se, but rather it may be conferred by heat treatment of any source of galactouronic acid. 

Therefore, be aware of what you purchase, as not all modified citrus pectin products available in the market have therapeutic effects.

References:

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