12 healthy volunteers were given 4 mg of astaxanthin daily for 9 weeks. 11 were given a placebo. At the start, and after 9 weeks a piece of skin was irradiated with UV-light. 

The skin of the astaxanthin group was significantly more resistant to the damaging effects of UV-light (as you can see in the image below). 

‘MED’ means ‘Minimal Erythemal Dose’ and is the minimal amount of UV-light that induces visible reddening (sunburn). Higher is better. 

“Dietary supplementation with astaxanthin might protect skin from damage caused by UV rays comparable to exposure to the sun for 1.5 h in the Japanese summer.”

“Because absorbed astaxanthin reaches the epidermis and dermis, it is assumed that astaxanthin directly exerts anti-oxidative activity at the epidermis and dermis to protect skin from UV-induced skin deterioration”

https://www.mdpi.com/2072-6643/10/7/817/htm

A group of 61 people with mild hyperlipidemia (high cholesterol) were given 0, 6, 12 or 18 mg of astaxanthin daily for 12 weeks. 

Triglycerides were reduced by up to 25% in the 12 and 18 mg group, while (good) HDL cholestorol was increased by up to 15% in the 6 and 12 mg group. 

“astaxanthin may be expected to treat
impaired metabolism and prevent atherosclerosis.”

https://www.fujichemical.co.jp/english/newsletter/images/1001/NutraNL.pdf

https://www.atherosclerosis-journal.com/article/S0021-9150(09)00843-0/fulltext

A group of 21 competetive cyclists were given 0 or 4 mg of astaxanthin per day for 4 weeks. The astaxanthin group increased power output by and average of 15% and were able to complete a 20 kilometer time trial 5% faster. 

“Astaxanthin improved various mechanisms associated with transporting long chain fatty acids into the mitochondria.”

“Our study does suggest that astaxanthin supplementation may be an effective supplement for improving exercise performance.”

https://www.researchgate.net/publication/51703925_Effect_of_Astaxanthin_on_Cycling_Time_Trial_Performance

Mice were given 0, 1.2, 6 or 30 mg/kg of astaxanthin for 3 weeks, and made to swim to exhaustion. The more astaxanthin the mice had been given, the longer it lasted. 

“Astaxanthin activated utilization of lipids (fats) to a greater extent than glucose as an energy source for performance.”

“There was no significant difference in body weight between groups. However, in the 30 mg/kg astaxanthin group, adipose (fat) tissue weight was significantly decreased.”

https://bpb.pharm.or.jp/bpb/200610/b10_2106.pdf

Mice were fed either normal food or food containing astaxanthin.

The mice fed astaxanthin experienced a significant increase in the activation of the FOXO3 gene in their heart tissue.

“We found a nearly 90% increase in the activation of the FOXO3 “Longevity Gene”

https://www.sciencedaily.com/releases/2017/03/170328092428.htm