The chemical proof that a product contains compounds that will interfere with specific oxidizing chemical reactions drove parts of our industry into a numbers game: “My ORAC is bigger than yours.” This was related to some confusion between antioxidants and biologically active compounds. The USDA wrote this when it withdrew the ORAC database from public view: “We know now that antioxidant molecules in food have a wide range of functions, many of which are unrelated to the ability to absorb free radicals.” Whether this fact is a good reason to withdraw the ORAC database from the public domain remains debatable.
Sometimes in heated debates, the basics get forgotten. Technically speaking, an antioxidant is an electron donor. Many substances can donate electrons to chemical reactions, thereby neutralizing damaging free radicals that would otherwise destabilize cells, organs and DNA. A compound such as vitamin C may be able to act both as an antioxidant and a pro-oxidant in chemical reactions, but it is uncertain if the pro-oxidant properties have any biological role. In addition, vitamin C has immune modulating properties that seem independent of, and immensely more complex than, its ability to give or take electrons in chemical reactions. This helps illustrate that the simplistic definition of an “antioxidant” is valid but does not translate to whether or not it has a biological role that involves antioxidant mechanisms (see Figure 1).
Chemical Properties vs. Biological Value
Each type of chemical antioxidant assay has its own unique value and role in identifying what types of chemical reactions are sidetracked by a nutritional product. None of these assays have much value in terms of whether a source of antioxidants provides antioxidant protection in biological systems—with the exception of situations where biological fluids, collected before and after consuming a product, are applied in the chemical assays.
The ORAC test is a good test to see whether a product contains antioxidants; so too are the Folin-Ciocalteu (or Total Phenolics, TPH) assay, the Ferric-Reducing Antioxidant Properties (FRAP) assay and many other chemical-based assays. However, when these tests are applied directly to a natural product they don’t report any data about whether the antioxidants measured have any biological role.
In contrast, when the same tests are applied to, for example, human blood samples, the data tell a story about whether antioxidants were assimilated into the bloodstream in a form that is able to reduce free radical damage. This is a good next step, but it still does not document whether antioxidants in the starting product make it into the bloodstream in a form that can enter into and protect living cells in the body. That can be achieved by testing either the natural product or serum from a subject that consumed the product in a well-designed cellular antioxidant protection test.
A poor antioxidant status in human blood has been associated with obesity, cardiovascular disease, reduced immune function and deteriorating mental health (including suicidal tendencies and age-related cognitive decline).
Therefore, it seems poor judgment to begin questioning antioxidant claims, as long as there is an understanding of what an antioxidant is, chemically and in biological systems. If a food-based source of antioxidants has been documented to provide an increase of antioxidant capacity in serum and/or living cells, then there would be a potential value for human health.
Models for Documenting Activity in Biological Systems
Be cognizant of what you want to prove. A clear and logical stream of testing of antioxidant capacity evolves from chemical proof of antioxidant content, through biological testing in cell-based assays, to clinical studies showing antioxidant uptake, protection and evidence of downstream events. For example, if a product has a high content of polyphenols, or has shown a good ORAC value, the next steps would involve cell-based bioassays to examine antioxidant uptake and protection from oxidative stress in suitable cell models, and possibly further work in models outside the human body.
Initial cellular testing should involve a simplistic cell type that is in itself not capable of producing free radicals as part of cellular metabolism or intracellular communication. In my opinion, as the developer, one of the better cellular models for the measurement of cellular antioxidant protection is the CAP-e test, where erythrocytes are used to document cellular uptake and protection from free radical damage. The data and conclusions are not clouded by free radical production as part of mitochondrial function, because the cells do not have mitochondria.
Further cellular testing in any other cell type goes beyond a simple question of antioxidant uptake and protection, since all other cell types engage in complex free radical production. Such testing may involve examination of whether a product reduces the production of Reactive Oxygen Species (ROS), and supports mitochondrial function, cellular energy production and viability under conditions of oxidative stress. With that foundation, a placebo-controlled feeding trial can be undertaken, and blood samples can be used to evaluate whether functional antioxidants were absorbed into the body in a manner that is capable of protecting the body environment from oxidative stress. In addition to a straightforward antioxidant evaluation, testing may include outcome measures that reflect oxidative damage within the living human body (see Figure 2).
Activities Beyond Antioxidant Properties
In this contentious debate about antioxidants and antioxidant testing, one of the most interesting and important lines of discoveries pertains to the immensely large group of polyphenolic compounds. While many people believe these compounds are strictly plant-based, polyphenols are also produced by fungi such as yeast and mushrooms.
This group of compounds has simple or complex ring structures that play a role in their ability to donate electrons, and be classified as antioxidants. However, their multifaceted biological properties seem unrelated to this ability. The effects include interaction with: plasma proteins; glucose transport; fat cells; cancer cells; modulation of immune function; and direct anti-viral properties, including HIV.
There is value in antioxidants for human health and prevention of disease. If we as an industry can use our tests and data properly, as well as continue to develop better testing methods, the USDA may be approached to re-open their data banks to the public as a valuable resource for the nutritional and health sciences.
Gitte Jensen, PhD, is the founder and research director at NIS Labs. Her academic immunology background doing cancer research, and her appointments at University of Aarhus, Alberta and McGill, coupled with a lifelong interest in complementary medicine provides a bridge for the natural products industry to mainstream research. NIS Labs specializes in contract laboratory and clinical research for the natural products industry, including assay development and validation. As director at NIS Labs, Dr. Jensen works with natural products companies to design research objectives ensuring that marketing-oriented research and development is robust, ethical and effective.