Haematococcus (astaxanthin)

What is Haematococcus?

Haematococcus pluvialis is a freshwater microalga that turns blood red when stressed by strong light or lack of nutrients. That red color comes from astaxanthin, a carotenoid pigment related to beta-carotene. Astaxanthin is also what gives salmon, shrimp and flamingos their pink hue. Haematococcus is the main commercial source of natural astaxanthin used in supplements.

What the research says

Astaxanthin is a strong antioxidant in laboratory tests, and human trials have looked at whether that translates into measurable benefits. A 2022 meta-analysis of 12 randomized controlled trials with 380 participants found that astaxanthin significantly lowered malondialdehyde, a marker of oxidative damage, and lowered interleukin-6 in people with type 2 diabetes. It did not significantly change C-reactive protein or tumor necrosis factor alpha. The authors described the effects as mild.

For weight, the evidence is not encouraging. A 2025 meta-analysis of nine clinical trials found no significant reduction in BMI or body weight with astaxanthin compared with control, and no dose-response relationship. Animal studies are more positive, but those findings have not carried over to people so far.

In short, astaxanthin may modestly influence some markers of oxidative stress, but there is no good human evidence that it helps burn fat or meaningfully changes how mitochondria handle calories.

How it’s used in supplements

Astaxanthin is sold as softgels, often in oil because it is fat-soluble and absorbed better with dietary fat, and as dried algae powder in capsule blends. Supplements usually state the astaxanthin content in milligrams. In a blend that lists only “Haematococcus” without an amount, consumers cannot tell how much astaxanthin they are getting.

The trials pooled in the meta-analyses were short, and long-term safety data on concentrated astaxanthin are limited. Data in pregnancy and breastfeeding are also lacking. As with any concentrated supplement, people taking prescription medication or managing a health condition should check with a doctor before use.

It is also worth keeping in mind that “Haematococcus” on a label refers to the algae itself, not to a fixed amount of astaxanthin. Algae powders and oil extracts can differ in astaxanthin content, so the same ingredient name can mean very different doses from one product to the next.

Bottom line: astaxanthin is a well-characterized antioxidant with modest effects on some laboratory markers of oxidative stress and inflammation in human trials. Pooled studies do not show that it reduces body weight or BMI. For people interested in antioxidants, a product that states its astaxanthin content in milligrams is the only way to know what you are getting, and expectations for weight loss should be low.