This Doctor's DIY Experiment Will Have You Speed-Buying Her Vitamin C Serum Pick

If you're into skin care, you've probably heard that vitamin C serums are worth their weight in gold. But in case you still need a visual demonstrating how they're effective, one vitamin C fan has shared the results of a fascinating experiment.

Zion Ko-Lamm, M.D., an internal medicine doctor, posted a video on Instagram showing the effect that a vitamin C serum has on the flesh of an apple. In the video, she squeezes some drops of the serum onto one half of the apple, leaving the other half bare. Cut to three hours later, the half that didn't get the serum is visibly more brown. (

The explanation of why one side browned faster has to do with vitamin C's antioxidant properties. Think about the way apples brown in the first place — they'll stay fresh for a while, but as soon as you cut one open and the flesh becomes exposed to oxygen, it starts rapidly browning, right? That's because "the influx of oxygen triggers an enzyme called polyphenol oxidase (PPO) to 'oxidize' the organic compounds in the apple called polyphenols, to become o-quinones," Dr. Ko-Lamm tells Shape. Those o-quinones then generate reactive oxygen species (ROS), which damage the apple tissue's amino acids, she says. After a series of reactions, the o-quinones form a brown pigment called melanin, hence the apple's brown flesh.

When you add the vitamin C serum to the sliced apple, though, it helps to neutralize the ROS, making them less reactive, Dr. Ko-Lamm explains. This is exactly why people add lemon juice (which is rich in vitamin C) to precut apple slices when trying to prevent them from turning brown right away.

Ok, now to connect the dots. Vitamin C's ability to neutralize ROS, as shown in the apple experiment, is what makes it so beneficial to your skin. "A similar concept applies to your skin — in fact, vitamin C is already the most plentiful antioxidant in your skin," Dr. Ko-Lamm says. As you go throughout your day, exposure to UV rays and air pollution causes the skin to generate those pesky ROS, she says. Vitamin C neutralizes many of those ROS to repair damaged skin cells and prevent future damage, she explains. This translates to skin-care products that prevent signs of aging, fight hyperpigmentation, and prevent the breakdown of collagen. (

Now that you're aware of vitamin C serums' benefits, you might be wondering how to choose from the boatload of options. There are a few key factors that might help you narrow it down. "The stability of the vitamin C is maintained by keeping the pH under 3.5," Dr. Ko-Lamm says (skin-care products sometimes detail their pH level in the product description). Also, "the term to look for in the active ingredients is ascorbic acid, specifically L-ascorbic acid, which is the chemically active [and most potent] form of vitamin C," she adds. Dr. Ko-Lamm also likes formulas that combine the ingredient with vitamin E and ferulic acid since research suggests vitamin C is more effective as part of an antioxidant combo.

If you'd rather skip the research and/or mini-experiment, you can shop Dr. Ko-Lamm's top picks below.

SkinCeuticals C E Ferulic

A longstanding cult favorite, this is the serum that other serums tend to get measured up against. SkinCeuticals C E Ferulic combines 15 percent L-ascorbic acid with vitamin E and ferulic acid.

Buy It: SkinCeuticals C E Ferulic, $166, dermstore.com

Drunk Elephant C-Firma Vitamin C Day Serum

With a pH of 3.3, this Drunk Elephant vitamin C serum is another option combining 15 percent L-ascorbic acid, vitamin E, and ferulic acid. It also contains pumpkin ferment, another source of antioxidants.

Buy It: Drunk Elephant C-Firma Vitamin C Day Serum, $80, sephora.com

Vichy LiftActiv Vitamin C Serum

If you'd rather test the waters with an under-$50 pick, you can go with Vichy LiftActiv Vitamin C Serum. The formula has 15 percent L-ascorbic acid, vitamin E, and hydrating hyaluronic acid.

Buy It: Vichy LiftActiv Vitamin C Serum, $29, dermstore.com

Drmtlgy Advanced C E Ferulic

The vitamin C serum that Dr. Ko-Lamm used in her apple video, Drmtlgy Advanced C E Ferulic is an option with 15 percent L-ascorbic acid, vitamin E, ferulic, and hyaluronic acid. The vitamin C is formulated within a 2.2-3.2 pH range.

Buy It: Drmtlgy Advanced C E Ferulic, $69, drmtlgy.com