Mushrooms, Antioxidants and ORAC Values The current focus on antioxidants in brightly colored tropical fruits and berries has left mushrooms in the dark so to speak. For example, while a serving of blueberries may boast of an ORAC (Oxygen Radical Absorbance Assay) value of 9000, a 100 gram serving of fresh mushrooms would have an ORAC value of only 400 to 700 on a fresh weight basis (or around 4500 on a dry weight basis). Thus, based on this assay, mushrooms would appear to be not so very impressive in the antioxidant category. However, there is much to be considered when evaluating the antioxidant value of foods and dietary supplements. First off, there is really no “gold standard” when it comes to the measurement of the antioxidant capacity of a food or supplement. Brunswick Labs, which developed and owns the ORAC assay, has done an extremely effective job of marketing this assay. They charge $250 per sample for an ORAC assay but the results have never really been proven to correlate to anything. The assay is a test tube spectroscopy chemistry test which analyses for chromaphoric chemicals, specifically polyphenols. The drawbacks of this method: 1. It measures only the antioxidant activity against particular (peroxyl) radicals 2. The nature of the damaging reaction is not characterized 3. There is no conclusive evidence that free radicals are even involved in the reaction that is being measured 4. There are literally thousands of other bioactive compounds in foods that are not polyphenols that have antioxidant activity 5. It is neither an in vitro nor an in vivo test (no living cells are involved in the test) 6. There is no correlation between ORAC values and what actually happens in the body at the cellular level when the product is consumed Mushrooms do not score very high ORAC values relative to those of berries and tropical fruits. However, ORAC values do not tell the full antioxidant story particularly when it comes to the biological relevance of what actually happens in our bodies. Biochemically, mushrooms are considerably more complex than fruits and berries. Mushrooms contain approximately 2000 functionally specific enzymes which assist in at least 30 different stress pathways within our body’s cells. These enzymes, especially significant in mycelial biomass products which contain both intra- and extra-cellular fungal enzymes, catalyze many antioxidation processes in the body. This intricate biochemical complexity may “mask” some of the actual antioxidant capacity of mushrooms as it is measured by the test tube ORAC analysis methodology (Frankel, 2000) Mushrooms also contain significant levels of the extremely powerful antioxidant L-ergothioneine (LE). LE is a membrane-impermeable thiol compound that is specifically accumulated in cells via an active transport system (the organic cation transporter OCTN1). LE cannot be synthesized by humans and therefore is only available from dietary sources. LE is synthesized only by fungi and certain soil-inhabiting bacteria. Specialty mushrooms contain the highest levels of LE of any food source. LE is important not only in protecting cells from oxidative damage but also serves an important role in energy regulation. The role of L-ergothioneine as an antioxidant and cell protectant is well documented. LE has several unusual biological properties that make it unique among naturally occurring antioxidants. The antioxidant properties of LE appear to be related to the molecules ability to: - directly scavenge reactive oxygen species - chelate various divalent metallic cations
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activate antioxidant enzymes such as glutathione peroxidase (Se-GPx) and MnSOD and inhibit superoxide generating enzymes affect the oxidation of various hemoproteins such as hemoglobin and myoglobin
In addition to polyphenol antioxidants and LE, mushrooms also contain significant amounts other classes of antioxidants such as selenomethionine compounds and glutathione. An antioxidant study on horses was performed where the antioxidant potential of blood samples taken after 30 days of supplementation with a medicinal mushroom powder blend were analyzed. A different assay was used to evaluate the antioxidant status, the Acute Oxidative Potential (AOP) assay which better represents the combined actions of all antioxidants in a living body vs. focusing only on the peroxyl radical in a test tube as in the ORAC assay. The mean increase in the antioxidant status in the blood of the 14 horses tested was 16.45%. In a previous initial human trial, several individuals showed an increase in their antioxidant potential after only 2 weeks of receiving the mushroom blend supplement fortified with synthetic LE (1 mg LE/2 g) at a daily dose of 2 grams per day. So although mushrooms may not score as high of ORAC values as some other foods, when mushrooms are consumed as a complete whole food nutritional matrix, the actual antioxidant effect in the body at the cellular level is probably much higher than the so-called “Super Antioxidant” foods and supplements that base their efficacy on the over-rated ORAC assay. However, communicating these complicated processes and concepts to the public is a marketing challenge. - SF References: Frankel, N. and Meyer, A., 2000. “The problems of using one dimensional methods to evaluate multifunctional food and biological antioxidants”. Journal of the Science of Food & Agriculture. 80(13): 1925-1941.