NPR recently published an article entitled “Looks Like The Paleo Diet Wasn’t Always So Hot For Ancient Teeth” (1). In it, author Christopher Joyce summarized the results of a new study regarding hunter-gatherers and dental caries (cavities).
Up until now, it has been hypothesized that the shift from hunting and gathering to a life based on farming and agriculture correlated with an increase in dental decay. This new research, published in the journal PNAS, challenges the notion that hunter-gatherers were largely free from dental problems and instead suggests that a particular diet of wild foods can in fact lead to poor oral health (2).
If you haven’t read the NPR piece, no problem. Here’s the gist: Archaeological evidence from a Moroccan cave revealed the remains of a hunter-gatherer population that existed between 12,000 – 15,000 years ago. Archaeologists were astonished to discover a very high rate of dental caries among the bodies, claiming that acorns may have been the culprits. Acorns, according the study’s author, are very high in carbohydrates, and with their sticky texture can adhere to teeth. Dental decay is the ultimate result. This is the earliest discovery of dental caries in a population, challenging the belief that the paleo diet is inherently healthy.
Now, it would be easy to address the points Joyce makes regarding the paleolithic diet and
lifestyle – that Stone Age life was “certainly” brutal and short, that there is one single paleo diet, and that saber-toothed cats were maniacally running around everywhere – but it’s not my intention to rebut these particular issues.
Fortunately, I was able to access the original study published in PNAS, and would like to reveal what the researchers actually discovered.
As it turns out, acorns weren’t the only botanical remains found. Twenty-two different plants were discovered, including juniper, pine nuts, pistachio, wild pulses, wild oats, goosefoot, ephedra, rose, and elderberry. Sure, acorns outnumbered the other plants, but nowhere in the NPR article is another species mentioned. The researchers even specifically stated that carbohydrates found in wild pulses and wild oats may have contributed to the high prevalence of dental decay.
But let’s just assume, for the time being, that acorns were the major cause of the dental caries. The holm oak acorns discovered (Quercus ilex) are reported to be low in tannin content. Tannins are astringent compounds that can interfere with protein and mineral absorption and, unless action is taken to mitigate their effects, can be detrimental to the human body. A major finding, mentioned nowhere in the NPR article, is that the acorns were thought to have been eaten raw. According to the study:
“The rarity of charred seeds indicates that acorns were consumed raw or underwent an initial processing stage that did not involve the use of fire.”
Yes, the individuals may have used fire later on in their preparation of acorns, but the possibility exists that they were eaten raw.
Why does this matter? Acorns are almost always processed in a particular way to increase edibility. Ethnobotanical research reveals that clay, lye, lime, and water have all been used to decrease the tannin content of acorns, followed by the addition of heat. Even though holm oak acorns are low in tannic acids, wild food experts still recommend that all acorns be leached prior to consumption. Arthur Haines, a botanist who runs the Delta Institute of Natural History in Maine, writes (3):
“Despite what you may have been told, all acorns should be leached prior to consuming them in any quantity.”
There isn’t much evidence to support raw acorn consumption by healthy, indigenous populations. Rather, what we do find is that those who process acorns through proper leaching and cooking often exude the qualities of superb health, with healthy teeth and bone structures. Tannic acids affect protein and mineral absorption, and may alter the availability of certain compounds necessary for healthy teeth and bone formation, thus leading to dental caries.
The study isn’t saying that leaching was always omitted. It is possible that the North African hunter-gatherers leached the acorns and reduced the tannin content. But heat could have reduced the content even further, as shown in studies using clay to reduce the tannic acids of acorns. However, as stated above, the researchers suggested that the acorns were eaten raw, with no evidence of leaching.
There’s another issue involved with the consumption of unprocessed acorns, that being the presence of excesssive phytic acid in the diet. Phytic acid is the primary storage form of phosphorous in plants (including acorns), and when ingested, decreases the availability of certain minerals such as zinc, iron, calcium, and magnesium. Some oaks contain as much as 2.67% phytic acid by weight, similar to linseed, pinto beans, and tofu (4).
Phytic acid, unless properly dealt with, may affect mineralization involved in enamel building (5). If this population of hunter-gatherers took the necessary precautions of leaching and cooking the acorns (which they could have, but the evidence is lacking), the phytic and tannic acids would be minimized. The researchers place most of the blame on acorns as the reason for rampant tooth decay, but perhaps the issue has more to do with the processing methods (raw/leached/cooked), and less to do with the species.
The researchers also revealed other possible explanations for the oral wear and tear experienced by these hunter-gatherers. For example, land snails were part of their diet, and consumption of abrasive particles could have contributed to tooth wear. This specific population was known to use stones to pound and grind their food, and abrasive particles from the stones may have led to further tooth wear. The individuals may have also harbored virulent bacterial strains specific to dental decay that spread rapidly within the population. Without adequate oral hygiene, this could have greatly influenced the prevalence of dental caries.
It’s difficult to know exactly what led to the high prevalence of tooth decay within this Moroccan hunter-gatherer population. The NPR article focuses almost entirely on the consumption of acorns as the leading cause, however based on the evidence, only a correlation can be made (and even that is tenuous).
There is limited evidence to suggest that acorns, at least from the holm oak species, are cariogenic. If they were, we might also find a higher prevalence of dental decay among indigenous groups that relied on acorns as dietary staples. This isn’t the case, however, and instead we see acorn-eating populations throughout history who experienced great health.
Many more points could be addressed – for example, generalizing this particular diet of wild foods to all paleo diets. However, no single paleo diet exists. The real paleo diet of the past, which was a hunting and gathering wild food diet, varied greatly between different areas of the world, and was based on the biodiversity within particular ecosystems. To say that the paleo diet wasn’t always conducive to good oral health, therefore, is inaccurate. The North African hunter-gatherer diet of the Later Stone Age? Maybe. But not all.
Fear not, for the hunter-gatherer lifestyle has indeed been shown to be a bit more favorable for oral health, though this point was somehow left out of the NPR article. The researchers from this study stated:
“Frequencies of carious lesions in archaeological populations range from 2.2–48.1% of teeth for agricultural populations, but only 0–14.3% for hunter-gatherers.”
I’ll keep eating my acorns, properly processed of course. I hope you will too.
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