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LETTERS TO THE EDITOR |
Research Center on Aging
1036 Belvedere Street South
Université de Sherbrooke
Sherbrooke J1H 4C4
Canada
E-mail: stephen.cunnane{at}usherbrooke.ca
Dear Sir:
Cordain et al (1) are to be congratulated on a succinct and topical overview, recently published in the Journal, of the perils of a Westernized diet with respect to the risk of chronic degenerative diseases in humans. Indeed, there is widespread support for reinstituting several aspects of the so-called Paleolithic diet, especially higher fiber and lower content of refined, adulterated, or synthetic constituents. However, the authors do not seem to have made reference in their article to the effect of diet on a defining feature of modern humans—namely, the brain—whether that effect is related to brain development, advanced brain function, or risk of degenerative brain disease. Several micronutrients are discussed, but iodine seems to have been overlooked, despite the fact that it is 1 of the 2 nutrients (the other is iron) from which humans globally are considered to suffer the most common deficiency (2).
The most serious consequence of iodine deficiency is impaired neurologic development, a problem that most developed countries have avoided only by legislating the use of iodized table salt; commonly preferred food choices that exclude seafood simply do not provide enough iodine. Indeed, publications from Australia, the United States, and Europe during the past decade show that mild-to-moderate iodine deficiency is reemerging as people in developed countries consume less table salt, dairy products, meat, fish, and seafood (3–5).
Cordain et al gave an overview of the nutrient density in various major food groups in Table 4 of their article, but they made no mention of the relatively poor bioavailiability of micronutrients, especially minerals, from some of these food groups. The concentration in plants of zinc or iron, without consideration of the phytate content of those plants, exaggerates the true value of plants as sources of these nutrients. Although iodine is not shown in Table 4, goitrogens in many cultivated plants greatly reduce the availability of iodine from plant-based diets. Hence, the overall ranking in Table 4 of seafood second to vegetables as a source of micronutrients underestimates the true value of seafood in protecting against the risk of the major nutrient deficiencies that affect humans. Among the food groups shown in the table, seafood actually has the highest available content of several minerals needed for brain development, including iodine, iron, zinc, copper, and selenium (6).
The focusing of some attention on the human health implications of declining iodine and seafood intakes is warranted because those declining intakes are directly linked to brain development. The modern-day vulnerability of the developing human brain to inadequate intakes of iodine, iron, docosahexaenoic acid, and several other brain-selective nutrients shows that, if seafood had not been a significant component of the Paleolithic diet, the modern human brain probably would not have evolved in the first place (6, 7).
ACKNOWLEDGMENTS
The author had no conflicts of interest.
REFERENCES
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