Astaxanthin is a naturally occuring red pigment which belongs to a family of chemicals known as carotenoids.

Astaxanthin is what gives the flesh of salmon it's orange color, and is responsible for the red appearance of shrimp, lobster, crawfish, crabs, and krill among other marine life.

It is well known to help protect against hormonal hairloss known as androgenetic alopecia. To produce this effect, it lowers Dihydrotestosterone (DHT) in the body by inhibiting the 5-alpha reductase (5-AR) enzyme.

This method of action is similar to drugs such as Finasteride and Dutasteride. Both of these drugs come with an increased risk of gynecomastia development in men. Does Astaxanthin use produce the same risk?

What causes Gynecomastia

Gynecomastia is an enlarged gland tissue of the breast in men. It is caused by an imbalance of the hormones estrogen and testosterone and can commonly occur during puberty.

Drugs that alter the ratio of estrogen to be higher than testosterone in men have the possibility to enduce gynecomastia.

Drugs used for hairloss inhibit the transformation of testosterone to DHT, which leaves more free testosterone in the body. Through another enzyme called aromatase, excess testosterone is convered to estrogen. This increase of estrogen is responsible for most cases of drug-induced gynecomastia.

Can Astaxanthin Cause Gynecomastia?

There have been speculation over Astaxanthin's ability to induce gynecomastia since it inhibits the 5-AR enzyme which can result in excess estrogen.

Drugs that target the 5-AR enzyme cause an increase in estrogen by reducing DHT which increases testosterone and subsequently increases estrogen through the aromatase enzyme.

Astaxanthin is unique because it has been studied as a potential aromatase inhibitor as well. According to a study that studied the ability of dietary supplements to inhibit aromatase, they found that both Astaxanthin and Black Cohosh acted as aromatase inhibitors.

All of the test compounds inhibited aromatase activity with astaxanthin and black cohosh demonstrating the most significant inhibition. 1

By inhbiting aromatase, Astaxanthin has the potential to prevent the excess testosterone generated by 5-AR inhibition from being converted into estrogen.

Astaxanthin appears less likely to cause gynecomastia in men than standard pharmaceutical drugs that inhibit 5-AR, while still providing some of the same benefits.

Recommended brands of Astaxanthin

When choosing a brand of Astaxanthin, it's important to select one that is derived from a natural source such as microalgae. Avoid any Astaxanthin products that are snythetically made.

For its sustainability and natural cultivation techniques, we recommend BioAstin.

Most studies on Astaxanthin administer 12mg per day, which BioAstin offers in capsule form.

Bottle of BioAstin 12mg
Purchase on Amazon

BioAstin also offers a 4mg option which can provide more control over daily dosage amounts.

Bottle of BioAstin 4mg
Purchase on Amazon


  1. National Center for Biotechnology Information (2022). PubChem Patent Summary for US-7731992-B2. Retrieved