Thinking Nutrition

Let food be thy sunscreen

July 27, 2021 Dr Tim Crowe Episode 75
Thinking Nutrition
Let food be thy sunscreen
Show Notes Transcript

You are what you eat. This is more than a trite phrase, as this mantra may have some direct relevance to the area of skin protection from UV sun damage. And here, it is the carotenoid family of vitamin A precursors which give many fruits and vegetables their vivid rich red, orange and yellow colours that could be getting into our skin to prevent the oxidative damage from the sun. In this podcast, I’ll look closer at those carotenoids and profile the latest research on how they could protect your skin. And as an extra reason for why you may want to eat more of these foods, I’ll explain why they could even help you get a date. 

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You are what you eat. This is more than a trite phrase, as this mantra may have some direct relevance to the area of skin protection from UV sun damage. And here, it is the carotenoid family of vitamin A precursors which give many fruits and vegetables their vivid rich red, orange and yellow colours that could be getting into our skin to prevent the oxidative damage from the sun. In this podcast, I’ll look closer at those carotenoids and profile the latest research on how they could protect your skin. And as an extra reason for why you may want to eat more of these foods, I’ll explain why they could even help you get a date. 

Vitamin A is a versatile vitamin and is known to influence over 500 genes. Its major roles include promoting vision, participating in protein synthesis and cell differentiation, and supporting reproduction and growth. Vitamin A in our body can come from two different sources: animal foods and plant foods. It is vitamin A in the form of a precursor found in plant foods that belongs to a family called carotenoids. These carotenoids can be converted, with varying degrees of efficiency, to vitamin A in the body. The family of carotenoids include alpha- and beta-carotene, beta-cryptoxanthin, lycopene, lutein, and zeaxanthin.

Beta-carotene is the one you know the best. It is a rich, deep yellow, almost orange, compound and is why carrots are the colour they are. There is also lots of beta-carotene in leafy dark-green vegetables but its colour is masked by the large amounts of the green pigment chlorophyll. Dark leafy greens (such as broccoli and spinach) and rich yellow or deep orange vegetables and fruits (such as cantaloupe, carrots, and sweet potatoes—but not corn or bananas) help people meet their vitamin A needs.

You’ll find lycopene abundant in tomatoes, carrots and watermelon. While lutein and zeaxanthin are abundant in green leafy vegetables, broccoli and capsicums. In nature, lutein and zeaxanthin absorb excess light energy to prevent damage to plants from too much sunlight. These carotenoids are also found in high amounts in the macular of our eyes and this is the reason why they are popular in supplements directed towards eye health. It is believed that lutein and zeaxanthin in the macula block blue light from reaching the underlying structures in the retina, thereby reducing the risk of light-induced oxidative damage that could lead to macular degeneration.

But if we look at the whole field of carotenoid research, there certainly is good evidence that diets high in these compounds as part of food are linked to a reduction in the risk of many diseases and earlier death, with people with higher blood levels of these compounds having a lower risk of cancer and cardiovascular disease mortality. Of course, this is observational evidence and can’t prove it is carotenoids that are doing this as there are lots of other beneficial phytochemicals in plant foods too.

But for today, I’m going to dig into one super interesting role that carotenoids could have in the body, and that’s as a defence against UV light-induced skin damage. A natural sunscreen if you will.

The damage to the skin from too much UV light from the sun is well described. In the absence of any topical photoprotective agent such as sunscreen, the skin's primary defence solely rests on endogenous protection and for this, it is antioxidants that are stored in the skin that come into play. This defence mechanism can be boosted by dietary phytonutrients found in fruits and vegetables, such as carotenoids. It is already known that dietary carotenoids can end up in the skin and if you consume enough of them, this can actually be visible – more about this and a bunch of fun facts later in the podcast.

With quite a bit of research now conducted showing that at least supplemental carotenoids can reduce UV skin damage, a just-published review has looked at all this evidence. And I’ll link to this study in the show notes. https://onlinelibrary.wiley.com/doi/10.1111/phpp.12690

Here’s what you need to know: the review covered 25 intervention studies (13 of which were randomised controlled trials) that looked at the effect of carotenoid supplementation on markers of skin health. Carotenoid supplementation not only improved resistance to sunburn but also reduced lipid peroxidation and other markers of oxidative stress, inhibited reactive oxygen species and collagen degradation, and benefitted skin hydration, wrinkling, and elasticity. That ticks all the boxes for some level of sun protection and protection against signs of photoageing. Note: the review is not saying that a bag of carrots can substitute for sunscreen and other sunsmart habits, only that these carotenoids can offer an additional layer of sun protection that covers your whole body and is always with you.

Now, this review only looked at studies that used supplemental carotenoids – I’ll talk a bit more about diet near the end of the podcast, but there is little reason to think that getting carotenoids natively in your diet from food won’t give similar results as they end up in your skin the same. And there have been some safety concerns raised for taking high doses of carotenoids in isolation. None such concerns exist for getting them from food.

As for how the doses of carotenoids used in the studies may compare to foods, there isn’t an easy answer here as each study used different doses and types of carotenoids, but to give a bit of a ballpark figure, if you’re eating several hundred grams of the carotenoid-rich foods each day of dark leafy greens such as spinach, carrots, sweet potato, pumpkin, cantaloupe, capsicums, apricots, tomatoes (tomato paste is a super high source of lycopene), and watermelon then you’ll be travelling very well. And being lipid-soluble, absorption and ultimate skin deposition of dietary carotenoids are improved if eaten at the same time as a dietary lipid source – so don’t be stingy with the extra virgin olive oil.

The more of these carotenoid-rich foods in your diet, especially if they are replacing more highly processed and less nutritious foods, then the more it will be a big overall health win, all while helping to protect your skin.

Carrots, flamingos and fish

Now for those promised fun facts.

It is not an urban myth, you can turn yourself orange if you eat a lot of carrots. It is a condition called hypercarotenemia and can be common in children. Just how much you have to eat is something I’ve searched high and low for, but that research still eludes me. The best estimate I’ve seen is at least 500 grams of carrots for an adult each day for some months. Please don’t try this at home.

Hypercarotenemia is considered harmless, even though it can give the appearance the person has liver disease causing jaundice but in hypercarotenemia, the eyes retain their natural white colour, but in jaundice they’re yellow. There’s your useless bit of trivia for the day.

And while we’re on the topic of myths and trivia, you certainly would have heard that carrots are good for your eyesight. Well, of course, there is some truth to this as loss of night vision is one of the first clinical signs of vitamin A deficiency which if left unchecked, can progress to irreversible blindness. But that doesn’t mean the more carrots you eat, the better your eyesight will be. Where a lot of this advice came from was way back in World War II where the British, as a way to hide the fact that they had developed radar and this was giving them an edge in intercepting and shooting down German planes, spread the propaganda that they were feeding their pilots lots of carrots to improve their eyesight and this was the reason. Now, I always thought this was a nice story that was plausible, but likely a myth, until one day I was doing a radio talkback segment on nutrition myths and this one came up. And low-and-behold an elderly gentleman called up and said he was actually based at a RAF fighter base in England during the war and they were fed lots of carrots in the mess hall for this very reason. I’m calling this myth: confirmed.

One of the popular carotenoid supplements is astaxanthin and that was part of the review into skin protection benefits as well. Astaxanthin is a reddish pigment and occurs naturally in certain algae. It is the direct cause of the pink or red colour in salmon, trout, lobster, shrimp, and other seafood because of the food they eat as the astaxanthin moves up the food chain from microalgae (also known as phytoplankton). It’s also why promoters of krill oil reckon their product is better than fish oil because of the small amounts of astaxanthin naturally found in it – which is why these pills are normally red in colour. Commercial astaxanthin supplements are made directly from harvesting and processing species of algae that make astaxanthin.

So, fun fact. Farmed fish, especially salmon, need to be supplemented in their feed with astaxanthin. You may sometimes read that this is somehow manufacturers adding some type of toxic chemical to the fish to make them change colour and on how unnatural all this is. Just no. All that is happening here is adding missing astaxanthin back to the diet of the fish because without it, the colour of the fish flesh would be white. And do you know what the commercial market is for white smoked Atlantic salmon? It’s zero. Because consumers’ taste expectations are that such fish should be orange, and colour can influence taste expectations.

And one more fun fact for the day. If I say the word flamingo, you’ll likely think of a pink, elegant bird. You could even have some plastic ones in your front yard. No judgements. Well, flamingos are naturally white-feathered birds as that is how they are born. It is their diet of….you guessed it, of algae, shrimp and crustaceans that contains astaxanthin, that stains them pink.

Attractiveness

And one final reason you may want to consider getting more carotenoid-rich foods in your diet is: it can make you look more attractive. I’ve already covered how carotenoids can cause colour changes in the skin of both humans and animals if you take in enough of it. Well, a study published in the American Journal of Public Health which I’ll link to in the show notes found that eating more fruit and vegetables can change skin tone, lending it a healthier glow, within a matter of weeks. https://ajph.aphapublications.org/doi/10.2105/AJPH.2011.300405 

For the study, 35 students were recruited and their diet and changes in skin colour were monitored over 6 weeks. They also monitored how much of a change in skin colour had to take place before it was noticed by others. The results showed that participants that increased their consumption of fruits and vegetables over the 6 weeks showed a change in skin colour, toward more of a golden healthy glow. Those whose diets went the other way, with less fruit and veg eaten, showed a reduction in skin tone. Just two extra portions of fruit and veg a day for six weeks was enough to cause a detectable change in skin tone. And it doesn’t matter what your skin colour is to start with – either very pale or very dark, the tint given by carotenoids can still be observed.


And extending this research, one novel study looked at how skin colouration, as far as changes in the tint and tone of a person’s current skin colour, can boost attractiveness. In the study, volunteers who were blinded to what the study was about, were asked to rate the attractiveness of a range of faces. Using digitally enhanced methods, they changed the skin tone to enhance what the skin colour would look like with a tan representative of more melanin production versus skin colour if it was tinted by the yellow/red/orange tones of carotenoids. It was the carotenoid colouration that was consistently rated as more attractive over the tan. And I’ll link to this study in the show notes and if you go to the link, it will show you one of the examples of the pictures used. https://www.semanticscholar.org/paper/Fruit-over-sunbed%3A-Carotenoid-skin-colouration-is-Lefevre-Perrett/6e81e0652bcc638acb9f16401b82bc2dfbaed856 

So, there you have it – eating more foods rich in carotenoids is good for your health, good for your skin, and may just help you get more right swipes on your dating profile pics.

So that’s it for today’s show. You can find the show notes either in the app you’re listening to this podcast on if it supports it, or else head over to my webpage www.thinkingnutrition.com.au and click on the podcast section to find this episode to read the show notes.

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I’m Tim Crowe and you’ve been listening to Thinking Nutrition.