While my blog is often dedicated to deep dives on skincare science, I’ve decided to also include some overviews like this one for topics where I feel like a comprehensive guide may be helpful to you all.

This post covers the retinoid family – the Vitamin A derivatives that we use topically in skincare but that are also naturally occurring in the body. We will cover which ones are most proven, their potency, conversion, and some favorite products.

Comment at the end if you want to see one for Vitamin C!

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Vitamin A in the Body

Vitamin A is an oil soluble vitamin and key nutrient that’s essential for the function and health of our bodies. Because our body cannot produce it, it must be consumed through diet. It can be found in foods like liver and dairy as well as fruit and vegetables rich in carotenoids which are Vit A precursors.

In the body, it plays a role in everything from vision to bone formation. 11-cis-retinal and the protein opsin combine to form rhodopsin, the light sensitive pigment in the rods of our eyes. It’s also important for countless cellular processes, including gene expression. When it comes to bone absorption and resorption, the relationship is a little trickier as vitamin A can both stimulate and inhibit osteoclasts. Studies even shown that too much or too little of this vitamin in our diet is linked to an increased risk of fracture.

While Vitamin A is important for the body and there’s some studies on its benefit for the skin orally, I don’t recommend supplements unless directed by your physician. Because it’s oil soluble, it’s stored in our own adipose tissue and you can store enough to last for months. For this same reason, it can build up to toxic levels. Unless directed by a medical provider, you want to just ensure you’re meeting the minimum required intake through diet.

Retinoid Conversion

Retinoids come in all different forms and in order for them to be useable by the skin, they must be able to be converted to retinoic acid. This is done via oxidation, meaning they undergo an oxidation-reduction (redox) reaction.

Unless a retinoid is in the form of retinoic acid, meaning it can be utilized immediately, it will have to get into the skin and then undergo oxidation. The more conversions away from retinoic acid a retinoid is, the longer it will take to see results and the less potent it will be.

If you look at the visual above, you can see the change in structure that the derivatives undergo. Retinol is an alcohol, which we know by the name and its “-ol” ending. When it’s oxidized to retinaldehyde, the OH group becomes an aldehyde as indicated by its name as well . And then lastly, the “-oic” in retinoic acid tells us that the prior aldehyde group becomes oxidized to a carboxylic acid.

Vitamin A Derivatives

There are many examples of Vit A derivatives that fall under under the retinoid umbrella but we will be focusing on the ones that we see in skincare. I’ve listed the categories in the following graphic and they’re listed in order so that you can count the number of conversions from retinoic acid.

Beta-Carotene
Also known as Provitamin A, beta-carotene is part of the carotenoid family and a retinoid precursor. We know it increases retinol esters in the skin, indicating that it undergoes conversion and will eventually be fully oxidized to retinoic acid. At 4 conversions away, it’s not very active but is a decent antioxidant.

Retinol Esters
This includes retinyl palmitate, retinyl acetate, and retinyl propionate. 3 conversions from retinoic acid, they’re gentler yoptions than retinol but less proven and less effective. Retinyl propionate was no better than placebo in one study on skin aging though helpful for actinic keratoses where retinyl palmitate has limited data on anti aging as well but may be a helpful antioxidant per a few studies though there has been some controversy.

Retinol
2 conversions from retinoic acid, retinol is the most studied and proven of the over-the-counter retinoids. It may have better penetration than retinoic acid and the research we have comparing the two indicates it has similar effects but at a smaller magnitude in addition to the other research done.

Retinaldehyde
At only a single conversion from retinoic acid, retinaldehyde is a very promising OTC retinoid. It’s important to remember though that it’s not just about the structure but rather the research – and retinol has more long term studies. That being said, early research indicates it works quicker than retinol while also being more gentle and may be just as effective as retinoic acid.

Retinoic Acid Esters
Consisting of retinyl retinoate and hydroxypinacolone retinoate, the retinoic acid esters are lacking research still like the retinol esters. They do seem to be more promising since they’re more active while still being gentle. RR is one conversion away and converts to both retinol and retinoic acid in the skin and there is one trial showing it was more effective than both placebo and retinol while a clinical study showed it may be helpful for acne. While HPR can actually bind directly to retinoic acid receptors without conversion, the research is less promising with one controlled trial on its anti aging ability done with skin models and another two done with the HPR combined with other provide ingredients like niacinamide or retinol here and here.

Retinoic Acid
The most effective and studied is definitely retinoic acid, the active form of Vitamin A that can bind directly to the RA receptors without conversion. All-trans retinoic acid, or tretinoin, is the gold standard in regards to anti aging and decades of research showing that as well as its benefit for acne, hyper pigmentation, and scarring. Then we also have second, third, and fourth generation synthetic retinoids like adapelene and tazarotene that bind directly to RA receptors but are mainly researched for acne.

You can read more on retinoids here.

How Retinoids Benefit the Skin

As we’ve covered above, retinoids act on retinoic acid receptors in the skin and influence many different cell processes like cell proliferation. They’re also antioxidants and can both protect the skin and also help repair photodamage.

Retinoids help with photoaging in the following ways:

1) initiating the increase of epidermal proliferation leading to epidermal thickening

2) compaction of the stratum corneum

3) biosynthesis and deposition of the glycosoaminoglycans (like hyaluronic acid)

Source

Tretinoin especially helps with hyper pigmentation by better distributing pigment in the skin and retinoids enhance the effects of pigment inhibitors alone. Because they stimulate cell proliferation and normalize skin function, they also have a strong track record with acne. Abnormal desquamation and inflammation are two factors involved in acne that retinoids can address for example.

The bottom line is that in addition to sunscreen, retinoids are some of the most proven skincare ingredients on the market and help with a wide variety of skin concerns from hyper pigmentation, acne, texture and scars, and anti aging.

Which Retinoid is for You?

Need help selecting the right retinoid for you? I’m here to help.

Sensitive Skin and Retinoid Newbies
Rather than settling for less proven retinoids, I would suggest a retinol that is in a low percentage or encapsulated.

• Stratia Skin Night Shift .015% (get $10 off your $35 order here)
• NCN Pro Skincare All Trans Retinol 2% Formula I or Formula II (you get 2.5 oz so they end up being very affordable)

Anti Aging Concerns
This is where you really want to go with the most proven and effective retinoids which will be tretinoin first then retinol then retinaldehyde. Tretinoin is prescription so you’ll need to go to your regular doctor, derm, or online telemedicine site like Curology. If you’re working your way up to tretinoin or can’t tolerate it, my OTC retinol and retinal favorites are:

• Obagi Medical Retinol Serum 1.0 (code MIRA20 to save 20%)
• Truth Treatments 5% Retinol Gel with THD (code MIRA20 to save but while I love this, you don’t need to spend that much for a good retinoid if you’re on a budget)
• Geek and Gorgeous A-Game .1 Retinal Serum (newer find but very impressed so far)

Acne and Hyper Pigmentation
If you also have anti aging concerns then I would go with tretinoin as it has research supporting its efficacy for all three concerns. Tretinoin with a pigment inhibitor like hydroquinone or even paired with azelaic acid will be most effective for hyper pigmentation. If tretinoin isn’t an option, then retinaldehyde with its antibacterial properties or adapalene which targets the epidermis and hair follicles will be best for acne.

• Differin Gel 15g (or the larger size)
• Osmosis Renew (code MIRA20 to save)

Was that helpful? Comment below and let me know, especially if you’d like to see more overviews. Thanks for reading!