Is this Retinol a bargain or do I need remedial math classes?

March 1, 2011 8:16 PM

Is this too good to be true? Is this 32 oz bottle of Retinol serum really stronger and considerably cheaper than this 1/2 oz bottle? Chemists, aestheticians, and mathematicians, lend me your ears.

I've been using this brand of Retinol for about 18 months and I have been very happy with the results. However, at $55.50 for 1/2 oz, it's pretty pricey. After searching online for wholesale retinol, I found this 32 oz bottle for $35.45. However, there's a difference in the percentage of actual Retinol, and since it looks to good to be true, I'm wondering if I'm interpreting the numbers wrong. The 1/2 oz bottle is listed as .30%, and the 32 oz bottle as .5%. I'm thinking that means the 32 oz bottle is a stronger concentration. Is it? Did I just find the deal of the century? Or are my math skills even more rusty than I think?

posted by MexicanYenta to Clothing, Beauty, & Fashion (5 answers total)

Best answer: I see two issues here. One, the cheaper stuff has alot more ingredients and you don't necessarily know how your skin would react to all of them. But the main issue is that the cheap stuff contains retinyl palmitate, which is not the same thing as retinol. From this site:

Not all forms of vitamin A are created equal. Some are more easily converted to retinoic acid than others. A typical conversion pathway looks like this:

Retinyl palmitate <> Retinol <> Retinaldehyde => Retinoic acid

It takes two and three metabolic steps, correspondingly, to convert retinol and retinyl palmitate to retinoic acid. The overall rate of conversion of retinol to retinoic acid is low and that of retinyl palmitate is lower still. Therefore a relatively large amount of retinol and even larger amount of retinyl palmitate needs to be delivered into a cell to boost retinoic acid levels and produce clinically meaningful effects.

I take this to mean that even though the retinyl palmitate concentration is higher, you are probably not going to get the same amount of the effective ingredient (retinoic acid, once your body absorbs it).
posted by cabingirl at 8:32 PM on March 1, 2011 [2 favorites]

Retinol is just vitamin A, made to sound exciting by its resemblance to prescription Retin-A, which is vastly more effective. The price of your fancy Retinol serum has nothing to do with it's Retinol content.
posted by Ery at 8:33 PM on March 1, 2011 [1 favorite]

Best answer: You could order some other base formulation such as e55 cream or whatever else you would normally use and then add the retinol into it. It can be purchased fairly cheaply from Sigma and if you're only wanting a 0.5% formulation then it would be 500 miligrams in 100g of goop. It is only 33 pounds from sigma and would net you something like the first bottle of unguent and be much cheaper. The other compounds in the first bottle are just standard things you find in any cream.

I wouldn't worry about not being able to replicate the 12000 psi that the first cream claims due to their "microfluidizing conditions". It sounds like a claim similar to the penta water people and they are just loons.
posted by koolkat at 1:31 AM on March 2, 2011 [1 favorite]

I agree with cabingirl's conclusion. That is not to say you shouldn't give it a try, but if it doesn't work as well as your expensive cream, you will know at least reason why. I think koolkat's suggestion is brilliant.
posted by lizbunny at 7:38 AM on March 2, 2011

Best answer: Biochemist here. Concerning your question about the "strength" of the two products, you can't compare them directly because they contain two different active ingredients and you need to consider the molecular weight of each.

Retinyl palmitate = 524.9 g/mol

Retinol = 286.5 g/mol

The first compound carries some extra "dead weight" due to the palmitate, so you need more of it to deliver the same amount of the "business end" of the molecule (i.e., the retinol part). So, to oversimplify a bit, retinyl palmitate is only 286.5 / 524.9 = 55% retinol.

Thus, a formulation of 0.5% retinyl palmitate is only 55% retinol, or 0.55 * 0.5 = 0.27% retinol. This is probably virtually equivalent to the 0.3% retinol product, in terms of round-off error accuracy. So the "stronger" product is not stronger, only equivalent or maybe slightly weaker.

Cabingirl's comment about the metabolic pathway is very important, but so are the excipients in each product. Topical and cosmetic formulations aren't my area, but excipients can have a huge effect on how well the active ingredient is absorbed and transported through tissues. Skin is very impermeable and not much gets through it efficiently, which is why some transdermal drugs ("patches") have to use DMSO as a carrier.

Anyway, I looked at the excipients in each product but don't know enough about skin-permeating formulations to tell which would be better. But chances are, there's a difference since the ingredient list was pretty different.

Bottom line: the "stronger" cheaper stuff comes in a small sample size, why not buy one and see how it works for you compared to your current product?
posted by Quietgal at 10:46 AM on March 2, 2011