Antioxidant potential of astaxanthin

When we look at the antioxidant potential of different pigments the question arises, what is the most powerful and most health-promoting of them all?

We know that food synergy plays a role and that we should eat them all but also, we know that some plants are much better than others and that some pigments are much more potent than others. So, from yellow to orange to red, what is the strongest of them all? What is the healthiest plant?

The answer is red pigment astaxanthin in a special type of microscopic algae that we would never be able to consume in higher amounts in our normal diet.

These types of algae have developed a defensive mechanism to combat UV radiation because they were exposed to sunlight during the entire day in areas where there is heavy UV radiation. The richest commercial source for natural astaxanthin is freshwater microscopic algae Haematococcus pluvialis. These microscopic algae Haematococcus pluvialis, when exposed to strong light or when any other environmental stressor is present like for example increase in salinity, will start to accumulate a bright red carotenoid pigment that is known as astaxanthin.

It is a very well-researched molecule. So far there are more than 3000 studies done on it both in vitro and in vivo. It is a carotenoid same as lycopene or beta carotene. The big difference is that it is the most powerful pigment known in science.

It is much more potent than curcumin for example. It is 6000 times more potent than vitamin C and 550 times more potent than vitamin E, 5000 times more powerful than green tea, 800 times that of coenzyme Q10, 200 times that of polyphenols, 150 times that of anthocyanins (water-soluble blue pigments in berries), and 75 times that of α-Lipoic acid (1).

Astaxanthin properties

Like other carotenoids, it is oil-soluble so which means it will accumulate in tissues.

In nature, it will accumulate in a food chain starting with animals that consume these types of algae. Red trout, salmon, red sea bream, flamingos, shrimps, krill, crab, and lobsters all are born white. Flamingos will become red from the effects of astaxanthin accumulation in their tissues. When shrimps and other crustaceans eat this type of algae, they will accumulate this pigment and their shells will become red. As the biomagnification process happens in the food chain, the level of astaxanthin and color becomes more concentrated as it moves up creating the beautiful reds and pinks we see in fish such as salmon and marine birds like flamingos. That nice red meat of salmon is nothing more than astaxanthin accumulation. In wild salmon, the amount of accumulated astaxanthin is in the range of 20 to 40 mg/kg of body weight.

Another unique characteristic is that it can pass the blood-brain barrier and also the retina and will accumulate in the brain and the eyes. When examined the xanthophylls (yellow pigments, one of two major divisions of the carotenoid group which includes astaxanthin, lutein, and others) accounted for 66-77% of total carotenoids in all brain regions examined (2). 

What this also means is that once assimilated it will remain in the cells offering long-lasting protection. Water-soluble antioxidants could not do that because they do not have the means to remain in the body. The problem is that our body is not just water or fat. It is both so to provide overall protection we need both of them. Ideally, we would consume water-soluble antioxidants in every meal during our evolution from whole plant foods so that was not an issue in the past. Today we eat animal products, oil, and refined sugar. What we need today is an oil-soluble antioxidant that can accumulate in the cells but will also protect other parts of our cells that are not made out of fat. And that is exactly what this pigment can do.

It is unique in that matter that is both oil and water-soluble.

This is not 100 percent correct but it is sort of true. It is an oil-soluble antioxidant but it is a very long molecule that when integrated into a cell membrane the end of that molecule will stick out of the cell membrane into the watery parts of the cells. So, although it is oil soluble the shape of the molecule will allow for it to protect both parts of the cells in fats and water. And will go through the entire body including the brain. The molecular structure also enables it to quench free radicals at the polar end groups, while the double bonds of its middle segment remove high-energy electrons. These unique chemical properties explain some of its features, particularly a higher antioxidant activity than other carotenoids (3).

In addition, astaxanthin protects the redox state and functional integrity of mitochondria.

It is extremely strong, it is a universal antioxidant (both oil and water-soluble), it passes through the blood-brain barrier, and one more thing the most important of them all.

It can never turn itself into a pro-oxidant.

After it gives all of its electrons it does no damage to DNA. Astaxanthin cannot become pro-oxidant, it just gives electrons and leaves so there is no danger in taking it. It is a molecule that is almost perfect in its design. It offers complete and lasting protection against oxidation and toxins. Everything that other pigments do like curcumin, astaxanthin will do as well and is much stronger.

Besides this, there is one more benefit. There are three main enzymes that our body produces to fight free radicals. These are superoxide dismutase, catalase, and glutathione peroxidase. In studies, both three were significantly upregulated in irradiated cells in the presence of astaxanthin (4). Therefore, it exerts significant antioxidant activities not only via direct radical scavenging but also by upregulating our body defenses. It activates the cellular antioxidant defense system through modulation of the Nrf2 pathway. Nrf2 is a protein that regulates the expression of antioxidant proteins that is triggered by injury and inflammation. Several synthetic drugs that stimulate the Nrf2 pathway are currently being tested for the treatment of diseases that are caused by oxidative stress. Astaxanthin does this much more than any other antioxidant tested so far. Curcumin has the potential to stimulate only catalase. Astaxanthin is even more potent in this regard than curcumin.

Also, so far there are no serious negative side effects associated with it that were ever reported.

Androgenicity

The only one I can think of would be its potential to neutralize the enzyme 5-alpha-reductase (5αR) in the body to some extent. That is the enzyme that turns testosterone into DHT (dihydrotestosterone). It can lower the androgenicity in the human body by lowering DHT levels and increasing testosterone levels meaning it can protect the prostate, increase lean muscle mass and slow down balding in men but as a side effect, it could potentially lower the libido. DHT is five times more androgenic than its parent hormone testosterone with zero anabolic effects. Skeletal muscles have an enzyme that neutralizes DHT. Boosting testosterone levels can help with muscle mass preservation in elderly people. This also helps in cases of prostate enlargement and prostate cancer.

Bodybuilding and endurance

It is a good supplement for bodybuilding and athletes in general. And it is not on a doping substance ban list. It increases physical strength and endurance significantly and minimizes muscle recovery time following exertion (16). The only reason why it is not banned in professional sports is that it is a naturally occurring dietary carotenoid and there is no possible way for the industry to ban athletes from regular eating. When we exercise there is inflammation in the muscles due to the overproduction of free radicals due to the high rate of oxygen consumption. Heavy breathing exists due to the increase in demand for energy. Because of this, protein, lipid, and nucleic molecules can become damaged due to an overproduction of reactive oxygen and nitrogen species. To prevent this supplementing with strong antioxidants like astaxanthin has become a strategy for many professional athletes and active health-conscious individuals.

There was a study that investigated the testosterone-boosting supplement that contained astaxanthin and saw palmetto berry extract. A study examined the effect of astaxanthin on levels of dihydrotestosterone (DHT), testosterone, and estradiol (5). These three hormones can have a role in the development of an enlarged prostate and prostate cancer as well as andropause (male menopause). Investigators gave a supplement that contained astaxanthin and saw palmetto berry extract for 14 days. The analysis showed a significant increase in testosterone and a significant decrease in DHT and also a significant decline in estradiol as well. Because testosterone is a base hormone that enzymes in the body convert to DHT and estrogen usually if you block conversion to DHT you can expect a rise of estradiol. Because of xenoestrogens and high dairy consumption levels of estrogen are elevated in most of the population. Astaxanthin lowers DHT and lowers estrogen and boosts testosterone. All of the improvements in hormone levels seen in this study bode well for men and prostate health and also male pattern baldness and exercise and bodybuilding and even other androgenic problems like acne vulgaris. But it can also potentially lower the libido. There are no reports found on this so this is just anecdotal right now. If you already taking some of the enzyme 5-alpha-reductase blockers like finasteride for hair loss or dutasteride for prostate enlargement you can still add astaxanthin to your list of supplements but keep taking your medication as well. So far there are no real clinical studies for hair loss prevention using this pigment so I don’t know how potent it is regarding this issue.

UVA protection, skin diseases, and collagen production

It all started when some researchers got the idea that they can use astaxanthin in a sunscreen lotion as a topical product. The reasoning was if it is a strong pigment and it absorbs UV radiation and protects algae from the Sun then it will do the same thing for our skin if applied topically. They got much more than they hoped for. This pigment offered photoprotective, antioxidant, and anti-inflammatory effects providing it to be much more beneficial. Free radical damage is what in reality destroys our skin and leads to skin aging. The mechanisms of both internal and external (photo-) aging include the generation of reactive oxygen species via oxidative metabolism and exposure to Sun ultraviolet light. The process of skin aging in the first step involves damage to DNA caused by free radicals, then comes the inflammatory response and the generation of matrix metalloproteinases that degrade collagen and elastin in the dermal skin layer(6).

It has been shown that astaxanthin in the skin will act on several different pathways of the oxidative stress cascade (7). Besides UVA protection its protective role will slow down the DNA damage to the skin and increase collagen production and will contribute to skin rejuvenation and appearance and in skin diseases. It was shown that it will help in a wide range of skin conditions where inflammation plays a role such as psoriasis and atopic dermatitis and will also help with excessive dryness and pruritus.

Like glutathione, it will lighten the skin and the eyes and will help with hyperpigmentation suppression, melanin synthesis, and photo-aging inhibition. It will increase the rate of healing of injuries, skin irritation, and tumor incidence (8).

And for cosmetic purposes besides the already mentioned effects, it was shown that it will reduce wrinkle formation almost at the level of retinol creams (9).

In this study, they gave 6mg of astaxanthin as an oral supplementation plus a topical cream and at the 8-week mark the subjects showed significant improvements in skin condition in all layers, corneocyte layer, epidermis, basal layer, and dermis.

This is a clinical trial, not just some “alternative medicine“. For skin so far this is maybe the best thing that nature has to offer. It lightens the skin and removes hyperpigmentation, will protect the skin from UV radiation and free radical damage, will reduce wrinkles and increase elasticity, and will give you a “golden glow“ like beta carotene.  In some anecdotal reports, people on high dosages of astaxanthin were very resilient to sunburn so much so that in some cases they will just stop using sunscreen. Sunscreen products just by themselves are very toxic but in most cases are necessary even with astaxanthin supplementation.

It is not just astaxanthin that does this, there are many other dietary antioxidant sources including polyphenols and carotenoids but astaxanthin has some unique properties and is the strongest of them all. Comparative studies examining the photoprotective effects of carotenoids have demonstrated that astaxanthin is a superior antioxidant, having greater antioxidant capacity than canthaxanthin and β-carotene in human dermal fibroblasts. That is the reason why there is so much research into it.

People especially ladies always ask me what regimen I recommend for skin rejuvenation.

It starts with a healthy diet and lifestyle but on top of that astaxanthin supplementation with micro-needling and with retinol cream can improve a skin condition visibly. The skin has an unlimited amount of stem cells so you can do a micro-needling with no problems also retinol will increase cell turnover and astaxanthin will protect the skin and will increase collagen production. The only side effect that is possible if you overdo it because it accumulates in the skin is that you might go past the “golden glow“ into carotenemia. So far there is no actual case reported of astaxanthin-induced carotenemia except some anecdotal reports of skin turning pink in between the fingers and palms. You will have to take substantial amounts of this pigment to stain your skin in a more visible manner but theoretically, it is possible. It does accumulate and it does have a strong red color.

This is a reason why it failed as a sunscreen product. Not in research, it has strong ultraviolet absorbing properties but as a skin product, it failed. When applied to the skin as a cream it has a red color. Putting something that looks like ketchup on your skin is not consumer friendly. We also need to keep in mind that there is nothing unique about astaxanthin except its potency and if we want to protect our skin from solar radiation, we could also do it by consuming adequate amounts of other antioxidants from food. For example, there was a line of studies that proved that alcohol consumption decreases the protection efficiency from antioxidants and increases the risk of sunburn (10). This is because alcohol is a pro-inflammatory toxin that burns up the body’s antioxidant defense. The results showed a significant decrease in the carotenoid concentration in the skin after alcohol consumption, but no significant decrease after a combined intake of alcohol and orange juice.

Neuroprotective properties

One other area where astaxanthin has more to offer than other antioxidants is in brain-protective properties. These features have led experts to label astaxanthin as a natural brain food.  

Unlike many other antioxidants, astaxanthin crosses the blood-brain barrier and accumulates in the brain.

Astaxanthin also directly combats the oxidative impact of abnormal proteins in both Alzheimer’s and Parkinson’s diseases.

Besides this, it is an excellent supplement to combat age-related cognitive decline.

In research in vivo in mice and clinical trials in humans besides anti-apoptotic, anti-inflammatory, and antioxidant effects, it showed potential to promote or maintain neural plasticity and to increase the rate of neurogenesis, the rate of creation of new neurons from stem cells in the hippocampus (14).

The nervous system is rich in both unsaturated fats (which are prone to oxidation much more than saturated fats, regular fat you see in your abdomen) and iron (that can easily oxidize and is very reactive). These, together with the intense metabolic activity and rich blood supply with a lot of blood vessels, make tissues particularly susceptible to oxidative damage. The brain consumes 20 percent of all calories that we eat and 20 percent of oxygen as well. Keep in mind that the weight of the entire brain in humans is around three pounds. The problem with the brain is that it has to protect itself from toxins and unwanted chemicals much more than the rest of the body because neural cells are very sensitive and need to have a pristine environment to work properly hence there is a blood-brain barrier that keeps a lot of bad stuff out.

Only two of the 20 or so dietary carotenoids, carotenoids circulating within the blood, lutein, and zeaxanthin, are typically found in the retina.

At the same time, they are found in millimolar concentrations (the highest accumulation of carotenoids in the body). The retina is part of the central nervous system. Not only are lutein and zeaxanthin in ocular tissue in high amounts, but their exclusive presence also makes it clear that they are concentrated via some active mechanism. The brain, like the retina, appears to accumulate xanthophylls not simply through passive diffusion but actively because that is the only possible way to explain high concentrations of lutein and zeaxanthin in the retina. In the rest of the brain lutein is also a dominant carotenoid. When you have low consumption of lutein and other carotenoids it will increase cognitive decline (11) and especially if you have low lutein consumption that will increase age-related macular degeneration (12).

Pigments create color by absorbing and reflecting the different wavelengths of visible light. Lutein has the ability to filter blue light, thus reducing phototoxic damage to photoreceptor cells in the retina.

Lutein intake varies and depends on vegetable consumption. Low habitual consumption of fruit and green leafy vegetables is one of the risk factors for increasing the rate of age-related macular degeneration.

Macular degeneration

Same as lutein, astaxanthin is also found to slow down age-related macular degeneration and glaucoma.

These two carotenoids are very important because they are the primary carotenoids that saturate our brains. Eating high amounts of antioxidants is beneficial but if we strictly talk about brain and eye health, these two are the main ones. In addition to protection, the xanthophylls may serve other functions in brain tissue that range from epigenetic regulation to cellular communication. Both astaxanthin, lutein, and zeaxanthin are xanthophylls. But be careful, there was one reported case of a woman that had developed crystals in the retina after excessive lutein supplementation. Lutein as a supplement also has shown an increase in lung cancer risk(13). In the study use of supplemental beta-carotene, retinol, and lutein supplements was associated with a significantly elevated risk of total lung cancer. This is so far just an association but until more research is done, I will suggest whole food sources.

Astaxanthin, however, does not suffer from this effect probably because of its potency. It is a single phytochemical that microalgae use, or the primal phytochemical that microalgae use with potent effects just on its own. So far it is shown to be an effective and safe product.

Astaxanthin does everything that other antioxidants do

Besides protecting the brain, skin, and eyes astaxanthin does everything that other antioxidants do as well, but these are more unique characteristics of this pigment. Besides this, it does all the same things as curcumin even at a higher rate because it is more potent and it accumulates in the cells.

It also has cancer-fighting effects, protects the cholesterol from oxidizing and improves its profile, and protects cardiovascular health this includes stroke prevention as well, boosts the immune system, helps with infertility, helps with diabetes, helps with wounds, burns, ulcers, and sores, protects against influenza and bacterial inflammation, helps with autoimmune diseases and other inflammatory diseases, helps with inflammation in the liver, overall liver functioning, and non-alcoholic fatty liver disease helps alleviate menopausal symptoms, can help reduce pain symptoms and inflammation related to rheumatoid arthritis and carpal tunnel syndrome.

I won’t analyze all of the studies, there are more than 3000 of them so far but I will say that the benefit it provides with no real side effects makes this one of the most health-promoting molecules science has ever found. It is the strongest universal antioxidant that nature has to offer. If you don’t have any disease it is still a beneficial supplement for life extension.

Life extension

It prolongs longevity by protecting DNA from damage and by increasing and regulating autophagy, a self-eating mechanism of damaged cells and cellular repair that our body does when we go into fasting mode (15). Up-regulation of autophagy comes into consideration as one more cancer prevention strategy and especially in individuals that already practice some form of intermittent fasting or calorie restriction. On top of autophagy which cleans up already damaged and pre-cancerous cells when we lower the rate of oxidation in the body in the first step, we live longer because there is no need for DNA repair. Every time DNA splits it halves telomers in half and when there are no telomeres there is no splitting only death. By protecting DNA, we prolong life. If there is an unlimited amount of stem cells that our body can produce, we will never die. Because there isn’t, the only thing we can do is to slow down the oxidation.

Dosage

Recommended dosages range from 4mg to 12mg a day depending on the desired effect. 8 mg astaxanthin per day is equivalent to a consumption of 1.6 kg of fresh salmon. We would never be able to consume this amount naturally. This also implies that this would be a wild-caught salmon.

Because fish in farms only consume the feed, they lack astaxanthin. For instance, pink flamingos are born white. In farming conditions, fish are fed with special forms of die since they don’t naturally consume the large range of phytochemicals found in the ocean. Salmon from industrial farms only contains dye or the meat would be completely colorless whit is proven by research as not desirable by consumers. Dye is synthetically produced astaxanthin that is used as a colorant. Synthetic astaxanthin made in laboratories from petrochemicals has not been approved for human consumption but you will be consuming it through salmon. It also comes in a variety of hues, from Roche’s carophyll pink to BASF’s lucantin pink. Because consumers won’t buy salmon if it is not a in nice natural pink color these dyes are used as a scam. They provide no dietary function. Their sole objective is to deceive you, the customer, into believing the product is tasty, nutritious, and natural-looking.

If we look at the dosages that are used in most of the studies they are lower than what most people would consume. A study specifically designed to investigate the safety of astaxanthin (17) concluded that 6 mg of astaxanthin per can be safely consumed by healthy adults. A  daily consumption of just 4 mg of astaxanthin provided significant protection of the skin against the effects of UV radiation. This is because it would accumulate in the skin in time even with that low dosage. What would happen if you go to 100 mg I don’t know. A dosage of 6 mg per day showed an improvement in skin elasticity, wrinkles, dry skin, age spots, and eyes. For more serious health issues like chronic pain, neuroprotection, and immunomodulation higher dosages would be necessary.

Major athletes use minimum doses of 16 mg per day. This is a bare minimum for them on daily bases and in some cases, dosages go up high as 200 mg before an event. The half-life of astaxanthin in the plasma is approximately 16 h after oral administration. But they also abuse steroids and other substances so they are not a representative sample for the rest of the population.

Among the scientific publications reporting the efficacy of astaxanthin, some have been conducted with high doses: from 40 mg to 100 mg per day. A dose of 40 mg per day is shown to be effective in improving gastric reflux syndrome, particularly in people infected with Helicobacter pylori. However, keep in mind that astaxanthin is like all other carotenoids, a fat-soluble molecule that accumulates. There will be probably some threshold of how much our body can accumulate and the lower the dosage the longer it will take. In most cases, people just take one 12mg pill a day a never see any signs of carotenemia. This is a dosage that I take. If you see signs of carotenemia only way to reverse it is to lower the dosage.

In wild salmon, astaxanthin tissue concentration can go as high as 40mg/kg. For 80kg human that will translate into 3200mg. If you take 12mg a day that means you will go to this level of wild salmon concentration in 267 days if your body doesn’t utilize any of the ingested astaxanthin and that is not the case. More realistically it would be hard to reach full body saturation with a 12mg dose. It is more of a maintenance dose if you are not a smoker, and have a whole-food, plant-based, antioxidant-rich diet. What I recommend is to start with a loading phase of 3 months of 40mg/day and then see how you feel. This would be a total of 3600mg and then you can transition to the maintenance phase. Another way is to go as long as you don’t see visible signs of carotenemia before lowering the dose. This would be an individual approach that might be the most optimal one. Also, there are synthetic and natural astaxanthin.

Synthetic astaxanthin is used as a food additive for farmed salmon. It is used as a tissue die to give a farmed salmon a natural-looking pink color of the meat. Synthetic astaxanthin from petrochemicals and astaxanthin derived from genetically mutated phaffia yeast has never been proven beneficial and have not been proven safe for direct human consumption. One more thing to keep in mind. Because astaxanthin, beta carotene, and other carotenoids are oil-soluble the absorption is greatly increased if we consume them with food or oil (18).

Side Effects

• Increased skin pigmentation
• Altered hormone levels
• Changes in sex drive
• Possibility of decreased blood pressure in megadosing
• Red stool color
• Increased bowel movements
• Research is limited on the safety of astaxanthin supplements in women who are pregnant or breastfeeding

Conclusion:

• There are only a few supplemental antioxidants that are proven to be effective and safe like liposomal vitamin C, curcumin, or astaxanthin.
• Astaxanthin is the most powerful natural antioxidant, 6000 times more potent than vitamin C.
• Astaxanthin is produced by a special type of microscopic algae that we would never be able to consume in higher amounts in our normal diet.
• These types of algae use astaxanthin as a defensive mechanism to combat UV radiation when they get exposed to heavy sun radiation or when any other environmental stressor is present.
• These types of microscopic algae produce astaxanthin as a monotherapy defense against DNA damage without any other phytochemical synergies.
• So far there are more than 3000 studies done on it both in vitro and in vivo.
• Astaxanthin is a universal antioxidant (both oil and water-soluble).
• It can never turn itself into a pro-oxidant.
• There are three main enzymes that our body produces to fight free radicals and both three were significantly upregulated in the presence of astaxanthin.
• As an oil-soluble catenoid, it will accumulate in tissues.
• Astaxanthin protects the redox state and functional integrity of mitochondria.
• Unlike many other antioxidants, astaxanthin crosses the blood-brain barrier and accumulates in the brain. Only two of the 20 or so dietary carotenoids, lutein, and zeaxanthin, are typically found in the retina.
• Besides anti-apoptotic, anti-inflammatory, and antioxidant effects, it showed the potential to promote or maintain neural plasticity and to increase the rate of neurogenesis.
• Astaxanthin is also found to slow down age-related macular degeneration and glaucoma.
• It also has cancer-fighting effects.
• Protects the cholesterol from oxidizing and improves its profile, and protects cardiovascular health this includes stroke prevention as well.
• Boosts the immune system.
• Helps with infertility.
• Helps with diabetes.
• Helps with wounds, burns, ulcers, and sores.
• Protects against influenza and bacterial inflammation.
• Helps with autoimmune diseases and other inflammatory diseases.
• Helps with inflammation in the liver, overall liver functioning, and non-alcoholic fatty liver disease
• Helps alleviate menopausal symptoms.
• Help reduce pain symptoms in chronic and acute diseases like rheumatoid arthritis.
• It prolongs longevity by protecting DNA from damage and by increasing and regulating autophagy.
• Recommended or approved doses vary in different countries and range between 2 and 24 mg.
• Supplemental antioxidants are not a substitute for a bad diet with a nonexisting ORAC score even if it is whole food plant-based diet, learn your ORAC values.

Passages selected from a book: “Go Vegan? Review of Science: Part 3” [Milos Pokimica]

1. Quenching activities of common hydrophilic and lipophilic antioxidants against singlet oxygen using chemiluminescence detection system. Carotenoid Science. 2007;11(6):16–20
2. Carotenoid, tocopherol, and retinol concentrations in elderly human brain. J Nutr Health Aging. 2004;8(3):156-62
3. Astaxanthin: a review of its chemistry and applications. Crit Rev Food Sci Nutr. 2006;46(2):185-96
4. Astaxanthin attenuates total body irradiation-induced hematopoietic system injury in mice via inhibition of oxidative stress and apoptosis. doi: 10.1186/s13287-016-0464-3
5. An open label, dose response study to determine the effect of a dietary supplement on dihydrotestosterone, testosterone and estradiol levels in healthy males. doi: 10.1186/1550-2783-5-12
6. Oxidation events and skin aging. doi: 10.1016/j.arr.2015.01.001
7. Preventive effect of dietary astaxanthin on UVA-induced skin photoaging in hairless mice. doi: 10.1371/journal.pone.0171178
8. Effective inhibition of skin cancer, tyrosinase, and antioxidative properties by astaxanthin and astaxanthin esters from the green alga Haematococcus pluvialis. doi: 10.1021/jf304609j
9. Cosmetic benefits of astaxanthin on humans subjects. Acta Biochim Pol. 2012;59(1):43-7
10. Alcohol consumption decreases the protection efficiency of the antioxidant network and increases the risk of sunburn in human skin. doi: 10.1159/000343908
11. Low macular pigment optical density is associated with lower cognitive performance in a large, population-based sample of older adults doi: 10.1016/j.neurobiolaging.2013.05.00
12. The Effect of Lutein on Eye and Extra-Eye Health, doi: 10.3390/nu10091321
13. Long-term use of beta-carotene, retinol, lycopene, and lutein supplements and lung cancer risk: results from the VITamins And Lifestyle (VITAL) study. doi: 10.1093/aje/kwn409
14. Neuroprotective mechanisms of astaxanthin: a potential therapeutic role in preserving cognitive function in age and neurodegeneration, doi: 10.1007/s11357-017-9958-x
15. Astaxanthin Modulation of Signaling Pathways That Regulate Autophagy. doi: 10.3390/md17100546
16. Astaxanthin in Exercise Metabolism, Performance and Recovery: A Review, doi: 10.3389/fnut.2017.00076
17. Safety of an Astaxanthin-Rich Haematococcus pluvialis Algal Extract: A Randomized Clinical Trial doi.org/10.1089/109662003765184741
18. Bioavailability of astaxanthin in Haematococcus algal extract: the effects of timing of diet and smoking habits. Biosci Biotechnol Biochem. 2009 Sep;73(9):1928-32

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