From our email:
I have read about sugar in the diet causing glycation, but what about sugar in skin care products? My facial sunscreen contains decyl glucoside. Is this a cause for concern? -W
It is absolutely true that ingesting sugar can result in prematurely aged skin. Sugar ages your collagen, making it brittle and weak and less elastic. Sugars do this in a very specific process:
1. A blood sugar glycates (attaches to) a protein molecule, forming a Schiff base.
2. The Schiff base either falls apart or forms a more stable product called an Amadori product. Examples of Amadori products include the molecule used to measure blood sugar levels, glycated hemoglobin (Hb1ac), in red blood cells.
3. The Amadori product forms an advanced glycation product (AGE), either directly or through the action of oxoaldehydes, such as methylglyoxyal.
4. The advanced glycation endproduct (AGE) undergoes glycoxidation, a process that is accelerated by the presence of free radicals. This is the super-dangerous part: Through glycoxidation, AGEs cross-link into a second, neighboring protein. These cross links have proven to be responsible, at least in part, for the hardening of cardiovascular structures, improper filtering of the kidneys, and, when the AGE is glucosepane, the hardened, stiffened collagen within aged skin. Cross links of the AGE glucosepane alter the structure of the collagen within the skin and accumulate as you age, progressively making collagen harder and more inflexible.
It Is True Sugar Can Be Absorbed By Your Skin
When it comes to chemical compounds (like sucrose), the size of molecules matters. The 500 Dalton rule dictates that any ingredient greater than 500 Daltons in size cannot penetrate the skin (read more). Sucrose (or sugar) is 342 Daltons (source), so its molecular size is small enough for it to be absorbed by the skin.
…But the Effects are Not As Deleterious When Sugar is Topically Applied
Fortunately, despite what some clever natural and organic companies will tell you, food is not skincare. In fact, when it comes to absorption, they’re actually opposites: The skin evolved to protect your internal organs from potential harm. On the other hand, the digestive tract evolved to absorb as many key nutrients as possible.
In Fact, Sugar May Have Some Benefits When Applied Topically in Low Amounts
Sugar has been used in wound healing and moisturization for years. For wound healing, sugar was added to iodine and applied to wounds in humans and pets for years. Its action was a “hyperosmotic” effect, meaning that it would facilitate the movement of bacteria out of the wound. (That is, so long as the wounds weren’t too large).
In moisturization, sucrose is a humectant, meaning that it helps absorb moisture from the environment and keeps existing moisture locked into the area.
That Said, Sugar In Too High of Concentration Can Be Bad
If you apply sugar in too high of concentrations to the skin (think leaving on a sugar scrub overnight), it can be a source of bacterial growth and pretty much is begging for infection. You may also attract bugs (ew, gross, I know).
When using ingredients like ascorbyl glucoside or decyl glucoside, you’re dealing with concentrations of sucrose that are likely to be hydrating and that may even contribute mildly to wound healing. Think about it: in a lotion with 5% decyl glucoside, you’re getting less than 2% sugars. It is certainly very unlikely to attach to collagen within your skin and deform it, the way that sugar that is ingested and absorbed into the bloodstream can over time, and it also should not attract bacterial growth, the way higher concentrations of sugar can when applied to the skin.
Hope this helps!