When we first covered the controversy surrounding model Gisele Bündchen's use of the word "poison" to describe sunscreen (a term her publicist later refuted as an incorrect translation), StyleList was inundated with reader comments that surprisingly shared a similar suspicion about the safety of chemicals in common sunscreens.

Combine that with the results of a study published last year that sparked fears of a cancerous relationship between a form of vitamin A found in sunscreen formulations and sun exposure, and it's no wonder people are concerned.

That got us thinking: Is there such a thing as natural sunscreen? Why do brands even use chemicals to begin with, and should consumers be wary of any of them? And what is the status on the Food and Drug Administration's investigation into the retinyl palmitate scare?

As far as natural sunscreens go, there is disagreement between the medical and holistic communities about what constitutes the word "natural."

On one hand, American Board of Dermatology President Dr. Robert T. Brodell says there is no such thing as a natural sunscreen.

"None of the products that protect the skin significantly would be considered 'natural,'" Brodell tells StyleList. "The closest thing would be 'chemical-free' sunscreens. The white paste you see on a lifeguard's nose in the summer is zinc oxide... the classic example," adds the Ohio dermatologist.

Defined as an "inorganic compound" because it's formed by chemical bonds that lack a carbon molecule, zinc oxide, and its common cousin titanium dioxide, are earth minerals often found as a physical block in sunscreen. Dermatologists consider both compounds to be safely proven ways of blocking both harmful UVA and UVB sunrays.

Yet organic expert and "The Green Beauty Guide" author Julie Gabriel, says that she is willing to consider an element like zinc oxide as natural, since it's a mineral.

"The absence of a natural sunscreen is a fairy tale of the conventional beauty industry. I've been using a basic handmade blend of beeswax, calendula oil, zinc oxide, green tea and vitamin E during my ski weekends in very high altitudes of 2,500 meters in Davos, Switzerland," Gabriel tells StyleList.

"I've had no sun damage, no tan, no marks, nothing," says Gabriel, who adds that she came up with the concoction by mixing a zinc oxide-containing diaper balm with the marigold-colored calendula plant to add a glowy finish.

If making your own blend, Gabriel recommends purchasing zinc oxide from either Ingredients to Die For or Texas Natural Supply. The organic expert says she has worked with both retailers, and considers them top, trustworthy sources.

With such nonirritating, noncontroversial sunblocks available, one wonders why brands even go the route of chemical blends. Experts say it's primarily because consumers find that physical blocks can feel heavy, smell strongly, and cast an unnatural pale tint to skin, especially on deeper skin tones.

"Because zinc oxide and titanium dioxide sit on the skin's surface without being absorbed, they are nonirritating and nonallergenic. But this is also the reason why natural sunscreens require a lot more rubbing in, and advance application time to bind with the skin to be effective," says New York State Society for Dermatology and Dermatologic Surgery President, Dr. David Bank.

Some brands turn to chemicals for lighter and seemingly more elegant formulas, which protect skin by first interacting with UV light, and then undergoing a chemical reaction that blocks out dangerous sunrays.

These chemicals are often of the multisyllabic, impossible-to-pronounce variety, with common examples being avobenzone, benzophenonone, triethanolamine, and the easier to say, though no less mired in controversy, ingredient of PABA.

Mexoryl, which enjoyed a highly anticipated debut on the US market after tremendous success in Europe, is gaining recognition as a favored chemical sunscreen. Experts attribute the ingredient's popularity to its light, easily absorbed texture, nearly non-existent scent and superior block of both UVA and UVB rays.

The newest chemical sunscreens that are currently pending FDA approval are Tinosorb S and Tinosorb M, which offer a trio of powerful actions, including absorbing, reflecting and scattering ultraviolet rays. They're both very naturally stable, which makes for a more dependable and long-lasting application, shares Bank.

And that means greater protection against the signs of aging.

"These products (chemical ingredients) also protect against the long-term problems associated with sun exposure, including wrinkling, brown spots, yellowing and thickening of the skin, precancers and skin cancers. The weight of the evidence strongly favors routine use of sunscreens, whether chemical or physical," Brodell strongly advises.

However, it's what happens during the chemical transformation phase that causes some to speculate on the overall safety of the active ingredients. It's here where the heart of the chemical sunscreen controversy exists.

"Triethanolamine has been identified as an active in promoting the release of free radicals in our bodies once the UVA and UVB radiations saturate our skin," says Los Angeles dermatologist, Dr. Ava Shamban, author of "Heal Your Skin."

Free radicals are considered by many in the beauty industry to be volatile molecules that react explosively and cause the kind of tissue damage that leads to aging and disease.

Another concern with chemical sunscreens is the potential for skin sensitivity issues in those who are suspeptible.

"The chemical most responsible for an allergic reaction to sunscreen is oxybenzone, which is also one of the most commonly used chemicals in broad-spectrum sunscreen," explains Maryland dermatologist, Dr. Noelle Sherber. "I always tell my patients with sensitive skin to avoid it, because it's the most common culprit of redness, itchiness and bumps."

But oxybenzone isn't just a problem for those who have sensitive skin. Bank says it's an ingredient that has long been questioned for its safety.

"Oxybenzone is of most concern to many scientists. In a study by the Center for Disease Control, it was proven to be absorbed into the blood stream systemically, and excreted in the urine of 97 percent of study participants. More studies are needed to give us a comprehensive understanding of how these chemicals behave in skin cells," says Bank.

Fortunately, most experts agree that the new technology found in micronized mineral sunscreen is both safer and more enjoyable to apply and wear. These nano particles block rays with zinc oxide or titanium dioxide, yet apply less white and with a sheerer finish than their traditional forms. Protection works by bouncing sun radiation waves off skin.

You should especially consider micronized mineral sunscreen for babies and children, says Sherber.

"The amount of surface area compared to body mass is very different between a baby and an adult. Whatever you apply all over a baby's skin will be absorbed more, because they have so much more skin than body mass. For example, a topical eczema-treatment cream can be given to adults without a problem, but the active ingredients are absorbed at such a high rate by children, that it can actually stunt their growth," says Sherber.

While the collective consensus between the natural and dermatology worlds seems to skew toward physical blocks, the debate on the safety of retinyl palmitate in sunscreen has moved little since the Environmental Working Group raised concerns this past year over an FDA study that showed an increase in cancer cells of mice exposed to sunlight while wearing a retinyl palmitate-containing cream.

"Retinols and retinoids in general have been a nighttime preparation, as it makes the skin sun sensitive. Some manufacturers believed that since retinols are antioxidants, then adding them to sunscreen would be beneficial," explains Bank.

However, the study in question surprised experts when it was shown that vitamin A could possibly turn photocarcinogenic under sunrays.

Yet evidence pointing to retinyl palmitate as a cause of cancer remains unproven, as the original study examined the form of vitamin A in plain skin cream, not sunscreen. Further review by the FDA this winter shed no additional light on the situation.

Sherber cautions against jumping to conclusions when other mitigating factors may have colored the results of the study.

"The possibility that the shininess of the cream could have magnified their UV exposure -- like putting on old-school baby oil in the sun -- is one of several potential confounders," says Sherber.

"It's also important to note that the mice used in NTP (National Toxology Program) studies are highly susceptible to UV radiation. They can get skin cancer within weeks of UV exposure. While this makes studies of skin cancer in these mice feasible because they can show effects within weeks rather than years of UV exposure, we have to be very careful not to assume that these mice respond to UV or other skin-directed treatments in the same way that humans do," adds Sherber.

Experts also caution consumers that just because a substance may be naturally derived, that doesn't mean it's automatically safe.

"The FDA looks at vitamins and minerals in a less stringent way than other drugs, so I am always nervous about the safety of such products," admits Brodell. Citing that the study was done on mice, and never with sunscreen, Brodell adds, "I do not worry, for myself or my family, about retinyl palmitate, but reserve the right to change my mind if more information would become available."

Yet, Shamban takes a more conservative approach in her interpretation of the same study results.

"Vitamin A has been known to make skin more sensitive, and is recommended to use at night. I do not recommend using a sunscreen with Vitamin A. Vitamin C and E is OK for sunscreen, but vitamin A is only recommended for night use because of its rejuvenating effects," says Shamban.

And so, the debate rages on. But with an industry that continually churns out sunscreen options that range the gamut of views discussed here, there's bound to be a new favorite for everyone's needs and comfort level.

Topping our experts' recommendation list are the Blue Lizard Chemical Free Sunscreen line, Skinceuticals Sheer Physical UV Defense SPF 30, Badger Balm SPF 30 Natural Sunscreen and La Roche-Posay Anthelios SX.

Whatever your choice, most experts agree that you should select an SPF 30 that specifically cites full-spectrum UVA and UVB protection. Remember, it's always best to go a little higher in SPF number, as the average person doesn't apply the full shot-glass worth of sunscreen it takes to achieve the printed SPF number.

But will all this protection deplete your vitamin D levels? Now, that's an entirely different story.