Evolution of dietary antioxidants
The evolution of oxygen-producing cells was probably one of the most significant events in the history of life. Oxygen is a potent oxidant whose accumulation in terrestrial atmosphere resulted from the development of photosynthesis over three billion years ago, in blue-green algae (Cyanobacteria), which were the most primitive oxygenic photosynthetic organisms. Brown algae (seaweeds) accumulate inorganic iodine to more than 30,000 times the concentration of this element in seawater, up to levels as high as 1-3 % of dry weight (1, 2). Protective endogenous antioxidant enzymes and exogenous dietary antioxidants helped to prevent oxidative damage (3, 4). In particular, mineral antioxidants present in the primitive sea, as some reduced compounds of metalloproteins of Rubidium, Vanadium, Zinc, Iron, Cuprum, Molybdenum, Selenium and Iodine, which play an important role in electron transfer and in redox chemical reactions (5). Most of these substances act in the cells as essential trace-elements in redox and antioxidant metallo-enzymes. When about 500 million years ago plants and animals began to transfer from the sea to rivers and land, environmental deficiency of marine mineral antioxidants and iodine, was a challenge to the evolution of terrestrial life (6).
Terrestrial plants slowly optimized the production of “new” endogenous antioxidants such as ascorbic acid, polyphenols, flavonoids, tocopherols etc. A few of these appeared more recently, in last 200-50 million years ago, in fruits and flowers of angiosperm plants. In fact Angiosperms (the dominant type of plant today) and most of their antioxidant pigments evolved during the late Jurassic period. Plants employ antioxidants to defend their structures against reactive oxygen species (ROS) produced during photosynthesis (7).
The human body is exposed to the very same oxidants, and it has also evolved effective antioxidant systems. Plant-based, antioxidant-rich foods traditionally formed the major part of the human diet, and plant-based dietary antioxidants are hypothesized to have an important role in maintaining human health. Moreover, chordates, the primitive vertebrates, began to use also the “new” thyroidal follicles, as reservoir for iodine, and to use the thyroxine in order to transport antioxidant iodide. Iodide is one of the most abundant electron-rich essential element in the diet of marine and terrestrial organisms. Iodide, which acts as a primitive electron-donor through peroxidase enzymes, seems to have an ancestral antioxidant function in all iodide-concentrating cells from primitive marine algae to more recent terrestrial vertebrates (8, 9).
1. Venturi S, Venturi M. Iodide, thyroid and stomach carcinogenesis: evolutionary story of a primitive antioxidant? Eur J Endocrinol. 1999 Apr;140(4):371-2. N PMID: 10097259
2. Küpper FC, Feiters MC, Meyer-Klaucke W, Kroneck PMH, Butler A (2002) Iodine Accumulation in Laminaria (Phaeophyceae): an Inorganic Antioxidant in a Living System? Proceedings of the 13th Congress of the Federation of European Societies of Plant Physiology, Heraklion, Greece, September 2-6, p. 571
3. Küpper FC, Schweigert N, Ar Gall E, Legendre J-M, Vilter H, Kloareg B (1998) Iodine uptake in Laminariales involves extracellular, haloperoxidase-mediated oxidation of iodide. Planta 207:163-171; DOI 10.1007/s004250050469
4. Ar Gall, E., Küpper, F.C. & Kloareg, B. (2004). A survey of iodine content in Laminaria digitata. Botanica Marina 47: 30-37.
5. Cocchi M, Venturi S. Iodide, antioxidant function and omega-6 and omega-3 fatty acids: a new hypothesis of a biochemical cooperation? Progress in Nutrition, 2000; 2 :15-19
6. Venturi S, Donati FM, Venturi A, Venturi M. Environmental iodine deficiency: A challenge to the evolution of terrestrial life? Thyroid. 2000 Aug;10(8):727-9. PMID: 11014322
7. Venturi S. and Venturi M. “Iodine and Evolution”. DIMI-MARCHE NEWS, Dipartimento Interaziendale di Medicina Interna della Regione Marche (Italy), published on-line, Feb. 8, 2004: http://web.tiscali.it/iodio/
8. Venturi S, Donati FM, Venturi A, Venturi M, Grossi L, Guidi A. Role of iodine in evolution and carcinogenesis of thyroid, breast and stomach. Adv Clin Path. 2000 Jan;4(1):11-7. PMID: 10936894
9. Venturi S, Venturi M. Evolution of Dietary Antioxidant Defences. European EPI-Marker. 2007, 11, 3 :1-12