The sun's ultraviolet rays can be punishing to human skin. Sunblock can mitigate the potential damage, but when it comes to protecting our body's largest organ, more help is always appreciated. A new study from researchers at the University of Alabama, Birmingham (UAB) may have just the thing: They've just discovered that the consumption of grapes can significantly increase the skin's resistance to UV rays.
Grape consumption may act as an 'edible sunscreen,'" lead author of the study Allen Oak of the UAB School of Medicine says. "This does not mean that grapes should be used in lieu of sunscreen, but they may offer additional protection which we are eager to continue learning more about. This research is exciting because our current findings provide building blocks for additional studies that may eventuate in an oral photo-protective product from a natural source."
The study
Credit: Maciej Serafinowicz/Unsplash/Big Think
For the study, published in the Journal of the American Academy of Dermatology, the researchers fed 19 healthy volunteers a powder of freeze-dried grapes for 14 days. This is the equivalent of 2.25 cups of grapes per day.
The participants' sensitivity to UV light was assessed before the trial period, and again afterward. Each individual's skin was assigned a Minimal Erythema Dose (MED) value — the threshold beyond which UVC radiation causes visible reddening to skin after 24 hours. After the test period, the amount of UV light required to redden each participant's skin was 74.8 percent greater than it had been before. This is the first study demonstrating this effect.
Biopsies also revealed fewer skin-cell deaths and fewer inflammatory markers. These slow down healing and may be linked to skin cancer.
The enhanced resistance to UV light came courtesy of an increase of polyphenols in their skin. Polyphenols are a naturally occurring family of compounds found in grapes, berries, and other fruits. They're also in products derived from them, such as wine, chocolate, tea, and legumes.
"Study results indicate that oral consumption of grapes has systemic beneficial effects in healthy adults," says Oak, citing prior research showing that polyphenols repair UV-ray damage, and that they can also reduce inflammation.
The researchers also found that a topical application of a grapeseed extract containing the polyphenol proanthocyanidins inhibited the formation of sunburn cells.
Avoiding skin cancer?
An estimated one in five Americans develops skin cancer by age 70, with most cases being linked to sun exposure, including 90 percent of nonmelanoma skin cancers and 86 percent of melanomas.
The study finds early indications that grape consumption may also help a person avoid skin cancer, though these findings are just preliminary, cautions Oak, and require further investigation before a definitive conclusion may be drawn.
Principle investigator Craig Elmets, also of UAB, tells the California Table Grape Commission, "We saw a significant photoprotective effect with grape consumption and we were able to identify molecular pathways by which that benefit occurs — through repair of DNA damage and downregulation of proinflammatory pathways. Grapes may act as an edible sunscreen, offering an additional layer of protection in addition to topical sunscreen products."
One of the internet's favorite mysteries has been what happens to an everyday grape nearly split in halves and put in a microwave: After about five seconds the grape produces a dramatic flash of plasma. Here's what it looks like. Has this mystery been keeping you up at night? Even if it hasn't, it's been a puzzler. Now, though, a paper from three Canadian physicists has been published in Proceedings of the National Academy of Sciences, and it finally explains what's going on.
What’s plasma, anyway?
Plasma is the fourth state of matter, the others being solids, liquids, and gases. Most of the material in the universe, by a long shot, is plasma. Plasma starts with gas into which enough energy is introduced that it heats up and its electrons become excited to the point that they're ripped away from their atoms and molecules. The result is plasma, a dynamic stew of negatively charged electrons frantically bouncing around positively charged air molecules and positively charged nuclei, or ions. Plasma's light comes from its electrons flipping back and forth between excited and de-excited states in response to the energy driving the whole process. It's technically a light-producing ionized gas.
Turning grapes into plasma
What the authors of the new paper wanted to figure out is what makes an innocent halved grape spit plasma when it's microwaved. A popular theory has been that the production of plasma had to do with microwaves charging electrolytes in the water of each grape, leading to a sudden exchange of energy across the bridge of skin remaining between the two haves, resulting in a flash of plasma. The new research debunks this idea.
How is the plasma being generated?
According to the paper, it's the grapes' size that's ultimately responsible, since it turns out that a grape is the perfect size for capturing and holding microwaves. As microwaves collect inside one, they add to each other, becoming amplified to the point that they need to release all that energy and heat. The midpoint between two grapes side-by-side becomes a hot spot at which both halves release their energy, and plasma is produced.
In carefully documented experiments, the researchers tried different materials, sizes, and skins/coverings, and interrupted the plasma generation at different stages to reveal the progression of the process. Apparently a grape's skin has nothing to do with it at all. The authors were able to produce plasma using a simple pair of hydrogel beads as well as gooseberries, large blackberries, and even quail eggs. They concluded that lots of things about the size of a grape with sufficient water content can produce plasma as long as the two objects are less than three millimeters apart.
What's interesting about all this, in practical terms, is that grapes' odd microwave-amplification ability could potentially be scaled up in size and lead to the development of passive microwave antennas that collect microwaves like man-made, oversized, synthetic, well, grapes.
A new mystery
The researchers answered one riddle and wound up with another: They noticed that when two grapes or grape stand-ins are side by side in a microwave, they oscillate away and then back toward each other. Why? That's the next thing the scientists plan to investigate.
