Carotenoids, the precursors of vitamin A, are natural pigments supplied with regular highly conjugated π-bond systems, providing the natural yellow, orange, or red colors of many vegetables and fruits. Until now, more than 750 naturally occurring carotenoids have been found. Based on their structure, carotenoids can be compiled into two main groups:

  • the carotenes also called carotenoid hydrocarbons, which only contain carbon and hydrogen,
  • the xanthophylls or oxygenated carotenoids that may contain different functional groups (epoxy, methoxy, hydroxy, carbonyl, and carboxyl acid groups).

Besides the unique carotenoid, β-carotene, another carotenoid has been receiving great attention lately: astaxanthin, which is extensively produced by Haematococcus Pluvialis (where it accumulates up to 3.8% on the dry weight basis).

Astaxanthin is a fat-soluble nutrient (it incorporates into cell membranes) with increased absorption when consumed with omega-3-rich seed oil. Astaxanthin stretches through the bilayer membrane with its unique molecular structure, providing resilient protection against oxidative stress. It can scavenge and quench ROS and free radicals (superoxide anion, hydrogen peroxide, singlet oxygen, etc.) in both the inner and outer layers of the cellular membrane, unlike most antioxidants, which work either in the inner (e.g., vitamin E and β-carotene) or the outer side of the membrane (e.g., vitamin C). Astaxanthin derived from the microalgae H. Pluvialis has been approved as a color additive agent and a dietary supplement for human consumption for more than 20 years in dosages up to 12 mg per day and up to 24 mg per day for no more than 30 days.

Recent human studies elaborate on the safety perspectives of natural astaxanthin, and so far, no documented negative effects have been found over its 20 years of consumption as a dietary supplement. Clinical studies have found that natural astaxanthin supplementation improved blood flow in humans and enhanced blood rheology by increasing the flexibility of erythrocyte membranes.

Astaxanthin emerged in the spotlight because of its potential pharmacological effects, including anticancer, antidiabetic, anti-inflammatory, immune-stimulating effects, and antioxidant activities as well as neuro-, cardiovascular, ocular-, and skin-protective effects. Studies found that astaxanthin reduces the oxidative stress caused by hyperglycemia in pancreatic β-cells and improves glucose and serum insulin levels in diabetes.

Furthermore, it has been suggested that astaxanthin is a potential therapeutic agent against atherosclerotic cardiovascular disease. Astaxanthin can directly cross the blood-brain barrier to reach different mammalian brain regions”. Here, we summarize the effects of astaxanthin on metabolism, insulin resistance, and type-2 diabetes mellitus; furthermore, its advantages on muscle performance, recovery, and atrophy, and effects on the central nervous system and the skin will also be discussed.