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Capsules of astaxanthin being poured onto a wooden table


Astaxanthin can increase testosterone levels in men by blocking its conversion to dihydrotestosterone (DHT). Since testosterone can also be converted by the body to estradiol, an estrogen hormone that, in excess, can lead to breast enlargement in men (gynecomastia), concern has been raised that astaxanthin may indirectly increase the risk of gynecomastia by increasing testosterone levels. However, there is no evidence that taking astaxanthin increases levels of estradiol or the risk of breast enlargement. For more details, see the Concerns and Cautions section of our Astaxanthin Supplements Review.

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