Nanoparticles in the sunscreen zinc oxide...does it zap my brain?

Zinc: the good, bad and ugly.

Old timey Zinc Oxide was that stark white cream smeared over the noses of lifeguards at the beach. And on babies’ butts for diaper rash preventions. And it’s also in the calamine lotion you used on itchy mosquito bites.

A medicine cabinet staple.

But now we learn that the 'safe' Zinc Oxide sunscreen for babies, is made up of nanoparticles that get absorbed from skin into systemic circulation and then across the blood brain barrier.

Yikes.

The Good

But I thought ionic zinc was something we want in our bodies. It is an essential component in antiviral concoctions [eg with doxy and HCQ], and immune system supplements [eg EmergenC]. Zinc is a cofactor in many crucial metalloenzymes, which include carbonic anhydrase and superoxide dismutase. ‘Zinc fingers' are necessary to bind steroid hormones to receptor sites on DNA.'

The zinc-binding site of CA II. The first two ligands, H94 and H96, are on the same stand of the β-sheet. The third ligand, H119, is on the neighboring strand of the β-sheet.

The Bad

Blocking sunlight needed for vitamin D generation in the dermis is not good. Humans need about a half hour of mid day sun to get their daily dose of the vitamin. Zinc Oxide very effectively reflects and scatters both UVA and UVB waves. Too much use could cause, well in extreme cases, rickets.

Is zinc in the brain good or bad? Two theories circulate for dementia: 1. that the zinc level is too low when tested in brain tissue from dementia autopsies; 2. Zinc ions’ presence clumps beta amyloid proteins in CSF. Hmmm…

The Ugly

Med school dogma states that skin cancer arises from excess sun exposure. Adding Zn2+ ions may have the potential to generate DNA-damaging reactive oxygen species when exposed to that UV radiation.

Really? Is that dogma still true?

Martínez-Cadenas highlights that in other types of cancerous diseases, age was already identified as an important factor— "but we initially thought that in the skin, due to being exposed to the sun, the phototype and the history of chronic exposure to the sun would have more weight in mutations, and it is not true," says Martínez-Cadenas. The rest of the factors have an irrelevant incidence together with the first two. The difference between mutations in areas chronically exposed to the sun and those that are only exposed intermittently is not even significant.

In addition, the incidence of age is not linear in time, since according to the study, the trend for the appearance of mutations worsens after 60 years. Martínez-Cadenas says, "From a certain age, whatever you have done, the mutations related to the predisposition to having cancer increase." - Research Group on the Evolution of Cancer Genome of the Universitat Jaume

So… skin mutation rate is dictated by Father Time, irrespective of lifelong photo exposure. But what about beauty? It is only ‘skin deep’ so they say. Solar radiation does photoage the dermis, causing loss of elasticity. Sagging, wrinkling.

debraspence.com

Then, I guess we should all go back to using sun bonnets, muslin and linen summer togs… oh yes, and those lovely parasols.

They will definately push back against the ugly.

blog.americanduchess.com

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REFERENCES

Nanomaterials shape and form influences their ability to cross the blood brain barrier https://medicalxpress.com/news/2021-07-nanomaterials-ability- blood-brain-barrier.html

Zhiling Guo el al., "Biotransformation modulates the penetration of metallic nanomaterials across an artificial blood–brain barrier model," PNAS (2021). https://www.pnas.org/content/118/28/e2105245118

Function and Mechanism of Zinc Metalloenzymes https://academic.oup.com/jn/article/130/5/1437S/4686409

Zinc and Dementia (Does it Help?) https://readementia.com/zinc-and-dementia/

Hidaka H, et al. DNA damage photoinduced by cosmetic pigments and sunscreen agents under solar exposure and artificial UV illumination. J Oleo Sci 2006; 55: 249–261.

Age is the main explanation for the genetic mutations of skin cancer https://medicalxpress.com/news/2021-06-age-main-explanation-genetic-mutations.html

B. Hernando et al, The effect of age on the acquisition and selection of cancer driver mutations in sun-exposed normal skin, Annals of Oncology (2020). DOI: 10.1016/j.annonc.2020.11.023

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