The article, originally published in 2015, was just updated for 2020 with new research and product recommendations. Updates to the article will be highlighted in purple.
Beautiful skin doesn’t happen by accident.
Beautiful, healthy skin is the culmination of a lifetime of decisions about the foods you eat, your lifestyle and your skin care practices. Yes, there’s a genetic component to great skin, but genetic factors are vastly outweighed by your nutrition and lifestyle decisions.
Skin care is an every-day, all-year project - but it takes on extra significance during the summer when sun exposure increases dramatically for most people.
This article ahead is the product of hundreds of hours (and $$$) spent looking for the perfect sunscreen. Spoiler: It doesn't exist (yet?). Once this became clear, I started investing my time in figuring out the best skin protection strategy given the reality of the products currently available.
But first, let’s look at why we should care about this project at all.
UV Radiation And The Danger For Our Skin (and DNA)
It’s a bit ironic that the same gaseous orb responsible for all life on the planet is also perhaps the single biggest threat to the health of our skin.
Both the UV-A and UV-B radiation produced by the sun can result in significant damage if the skin is exposed in large doses. This is because both UV-A and UV-B will damage fats and other molecules in the skin to create reactive oxygen species, otherwise known as oxidative toxins.
When allowed to accumulate, reactive oxygen species will damage and kill skin cells. In short, it's this oxidative damage that makes skin look old and weathered.
UV-B radiation is even more problematic as it will directly damage DNA in skin cells, leading to cell death and greatly increased risk for skin cancer. 
We’ve Got Sunscreen Issues
Here are the problems with each of the three common types of sunscreens.
1. Conventional Sunscreens Contain Toxic Ingredients - Conventional “chemical sunscreens” use synthetic compounds known as photostabilizers that absorb the UV radiation before it damages your skin cells. The problem is almost all of the commonly used photostabilizers are also potentially toxic if absorbed into the skin.
By far the most problematic of these is oxybenzone. Oxybenzone has been shown in multiple studies to disrupt endocrine function by mimicking estrogen in the body.  If allowed to accumulate in the body, oxybenzone can lead to disrupted reproductive function in both sexes and endometriosis in women.
Unlike some of the other photostabilizers, Oxybenzone is particularly problematic because it absorbs readily into the skin, where it can then move easily into the bloodstream and be stored in fat throughout the body. Up to 9% of the oxybenzone you apply to your skin will be absorbed. For these reasons, oxybenzone is at the top of my list of sunscreen ingredients to be completely avoided. 
Other common chemical photostabilizers like octinoxate (octylmethoxycinnimate) and homosalate have also been shown to have estrogenic activity in the body. However, because both of these are absorbed into the skin at a rate of less than 1%, they don’t set off alarm bells quite in the same way oxybenzone does for me.
If allowed to accumulate in the body (with regular use), both octinoxate and homosalate will certainly have hormone-disrupting effects, but because the absorption rate is so low, I relax ever-so-slightly from the avoid-at-all-costs approach I take with oxybenzone.
[2020 update] Since this article was originally written, avobenzone has become the photostabilizer of choice in the chemical sunscreens that market themselves as being "less toxic".
The research on avobenzone is still sparse, but there is some research showing it can mimic glucocorticoid and anti-androgenic hormones in certain doses.  We also know avobenzone absorbs into the skin and blood , but at levels that are nowhere near as alarming as oxybenzone. All in all, I put the practical risk level of avobenzone on par with octinoxate and homosalate.
2. Mineral Sunscreens [used to!] Provide A Terrible User Experience - I have tried literally dozens of the best-reviewed mineral sunscreens (some for upwards of $50/bottle) and I can report that every single one sucks in its own way.
[2020 update] Hey! I'm happy to report this has improved significantly over the past 5 years, and is what primarily inspired me to update the article.
Mineral sunscreens use either zinc oxide or titanium oxide to reflect UV away from the skin. They're very effective and essentially non-toxic when applied topically, so on paper they're the ideal sunscreen.
But, 5 years ago even the best of these products invariably left your skin tinted white and feeling like you have a thin layer of clay covering your body.
Now, thankfully, there are some really good mineral sunscreens available.
Brush On Block uses zinc oxide powder plus a natural tint (so it doesn't show up white on the skin), applied with a makeup brush. The application is a bit tedious, so it's best used on the face. Once applied, it's very effective and essentially unnoticeable. Brush On Block goes on my face any day I'm expecting to get even a little sun.
As much as I love Brush On Block, the brush applicator makes it impractical to use on the whole body, so until recently I was still occasionally (begrudgingly) using a chemical sunscreen on other areas. Thankfully, this piece of the puzzle is now filled by Babo Botanicals Sheer Spray Sunscreen.
Babo's product uses zinc oxide also, and is easily the best experience of any (non-powdered) mineral sunscreen I've tried. It definitely still has a bit of a white tint (even when rubbed in thoroughly), but it's significantly better than any other mineral sunscreen I've tried, and definitely not noticeable enough to discourage me from using it.
More impressively in my estimation, Babo has formulated their product to somehow avoid feeling oily or cakey like every other mineral sunscreen. It dries quickly and feels totally fine on the skin in my opinion. A big step forward for mineral sunscreens.
3. Natural SPF Oils Are Rarely Adequate - In the past few years, the idea of using plant-based oils that contain natural photostabilizers has become popular. I was admittedly bullish on the idea myself for a while, as some sources claimed that oils like red raspberry seed oil and carrot seed oil had SPF in excess of 30.
[2020 update] The more I used oils like red raspberry for sun protection, the more my confidence in them eroded.
The short version of the story is that while these oils might contain compounds that are effective photostabilizers under labratory/experimental conditions, the real world reality doesn't reflect this.
My guess is that the levels of these compounds vary wildly from batch to batch of a given oil, making it a gamble as to whether the oil you're applying to your skin will offer any sun protection at all.
I've also noticed that any protection offered by the oils seems to be short lived, likely because these photostabilizing compounds break down after a comparatively short period of UV exposure and cease to offer any protection.
Solving The Sunscreen Dilemma
Given the far-from-perfect sunscreen landscape, this is what I believe to be the most intelligent strategy for protecting the skin from UV radiation:
1. Minimize Your Sunscreen Use, Cover Up! - Covering your skin is always the best strategy for protection from UV radiation. Even the best sunblocks still let significant UV reach your skin.
Hats, umbrellas and scarves/shawls are great wardrobe choices for sun protection on hot days where it would get sweaty to have a lot of clothing close to the skin.
[2020 update] There are a number of breathable, sweat-wicking long sleeve shirts made from fabric with SPF 50+ that stay reasonably cool even in the heat. I still prefer using sun sleeves paired with a t shirt/cycling jersey when I'm hiking/riding, as this set up ventilates much better than a long sleeve garment.
2.[2020 update] Use An Agreeable Mineral Sunscreen!
In 2015, points two and three were devoted to instructions for choosing the least-toxic traditional chemical sunscreen, and then recommendations to use it as infrequently as possible.
3. Wash Your Skin Thoroughly - The best thing you can do to prevent absorption of these photostabilizers is to deeply clean your skin after you use them.
[2020 update] Absorption of chemical photostabilizers need not be a concern anymore! Zinc oxide and the tints and oils used in the sunblocks recommended above don't carry toxicity concerns, but that doesn't make them great for skin. I still recommend washing skin thoroughly as soon as you're out of the sun.
This is a good opportunity to point out that most “soaps” on the market are actually detergents that linger in the skin and can damage skin cells. I highly recommend choosing an additive-free true soap like Dr Bronner’s Liquid Soap.
4. Dry Brushing - Washing your skin thoroughly will remove any octinoxate and homosalate still sitting on your skin, but to clear chemicals that have already absorbed into the skin, you need to support your skin’s detoxification systems.
[2020 update] Similar to number four, removing octinoxate and homosalate from lymph is thankfully not a concern with mineral sunscreens, but there's still a lot to be gained from dry brushing. UV-damaged lipids and proteins accumulate in our skin and lymph after a day in the sun (these are what produce a "sunburn"), and flushing these should still be a priority.
Dry brushing stimulates blood flow and lymphatic fluids to clear these damaged compounds from the skin. See The Synchro Guide To Truly Healthy Skin [Part One]: Dry Skin Brushing.
5. Moisturize - Yes, using a moisturizing oil makes your skin look nice - but more importantly it keeps your outermost layer of skin (epidermis) hydrated which, in turn, improves clearing of toxins.
[2020 update] I've tried dozens of natural oils over the years, and my current favorites are jojoba oil (for cooler weather and/or drier skin) and sweet almond oil (warmer weather, less dry skin) My favorites are here and here.
6. Antioxidants - No sunscreen - mineral or chemical - absorbs even close to 100% of the UV radiation that will hit your skin during a day in the sun. This means that oxidative toxins will always be formed in the skin during prolonged sun exposure, and neutralizing these oxidative toxins is just as important as removing potential endocrine disruptors.
Oxidative toxins in the skin aren't neutralized until they come into contact with antioxidants. Using a product that supports endogenous antioxidant production (like Gold Liposomal Turmeric) or contains super high levels of plant-based antioxidants (Genesis Powerfood) will help mitigate the damage done from your day in the sun.
Every Day Is A Skin Care Day
If your goal is truly healthy, glowing skin (not to mention minimized skin cancer risk), skin care can’t be something you focus on only when you’ve spent a day in the sun.
From the list above, numbers 1, 5, 6 and 7 should be practiced every day.
I specifically omitted number 4 here - as I don’t recommend using soap on the skin every day. Soaps (and detergents) pull natural oils out of our skin and make it more difficult for our skin to maintain it’s natural oil balance.
Our skin is “designed” to have a certain level of oils in/on it, so a hypothetical “clean” skin free of oils is NOT actually healthy skin.
Dry brushing, moisturizing and showering (sans soap) every day is a much better practice for keeping the skin healthy and “clean”.
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