Spirulina for Women: Are There Any Special Considerations

Spirulina is often positioned as a “superfood” for women: a source of iron, protein, and antioxidants, a means for weight loss and beauty. Some of these claims have a scientific basis, some are exaggerated, and certain features that matter specifically for women go unmentioned in advertising. Our editorial team examined what is known about spirulina in the context of women’s health and training.

What spirulina is

Spirulina is the dried biomass of cyanobacteria of the genus Arthrospira (most often A. platensis). Despite the popular name “algae,” from a biological standpoint these are bacteria capable of photosynthesis. They are grown in alkaline bodies of water or industrial ponds, harvested, and dried into a powder or pressed into tablets.

In the dry matter of spirulina, more than half is protein, and there are also pigments — phycocyanin (blue), chlorophyll, carotenoids — gamma-linolenic acid, minerals, and vitamins. It is phycocyanin that is responsible for most of the antioxidant and anti-inflammatory effects observed in laboratory studies.

Despite the high percentage of protein, spirulina is consumed in doses of a few grams per day, so its contribution to the daily protein requirement is modest. For comparison: to obtain 20 g of protein, about 30–35 g of spirulina is needed, and that is a lot for a product with a distinctive taste and price.

The U.S. Pharmacopeia (USP) conducted a safety assessment of spirulina in 2011 and concluded that, provided there is no contamination, it poses no serious health risk, while recommending precautionary labeling regarding pregnancy, children, and autoimmune conditions.

Iron and vitamin B12: expectations and reality

Iron. Spirulina contains a noticeable amount of iron, and this is one of the reasons for its popularity among women, who have an increased need for it because of menstrual losses. EFSA (2015) set the reference intake of iron for premenopausal women at 16 mg per day.

Several small studies have shown some improvement in blood parameters with spirulina intake, in particular in older people with anemia, but the quality of the evidence is limited. Spirulina is not a treatment for iron-deficiency anemia: with low ferritin, a doctor prescribes iron supplements in appropriate doses.

Vitamin B12. Here the situation is more complicated. A study by Watanabe and colleagues (1999) showed that spirulina tablets are dominated by pseudovitamin B12 — a compound that is detected by some assays as B12 but is not biologically active for humans. A review by Watanabe (2007) confirms: spirulina is not a reliable source of vitamin B12.

For women on a vegetarian or vegan diet this is critically important, especially when planning a pregnancy. You cannot rely on spirulina as a source of B12 — fortified foods or a supplement of cyanocobalamin or methylcobalamin are needed.

Weight, lipids, and training

A meta-analysis by Serban and colleagues (2016) of randomized trials showed that taking spirulina is associated with a reduction in total cholesterol, LDL, and triglycerides and an increase in HDL. The effects are moderate, and the studies are heterogeneous in doses and duration.

As for weight loss, some small studies describe a slight reduction in body weight, but there are no convincing data that spirulina substantially accelerates weight loss. It is not a “fat burner” and does not replace a calorie deficit and physical activity.

In a sports context, the effect of spirulina on oxidative stress and endurance has been studied. The results of individual small studies are encouraging, but insufficient to recommend it as a means of improving performance.

For women who train and follow a diet, spirulina can be part of the diet as a source of micronutrients and pigments, but it should not crowd out staple foods. The IOC consensus on REDs (2023) reminds us that excessive dietary restriction in female athletes threatens hormonal disturbances and loss of bone mass.

Pregnancy, breastfeeding, autoimmune conditions

Microcystins. The most serious risk of spirulina is associated not with it itself but with contamination. When grown in open bodies of water, other cyanobacteria that produce hepatotoxic microcystins can get into the raw material. A study by Heussner and colleagues (2012) detected toxins in some of the tested cyanobacteria-based supplements.

Therefore, during pregnancy and breastfeeding, when the risks of toxins for the fetus and child are higher, most experts advise refraining from spirulina or taking only products with laboratory-confirmed absence of toxins and heavy metals, and only in agreement with a doctor.

Autoimmune diseases. Spirulina in laboratory studies exhibits immunostimulating properties. Isolated clinical cases of exacerbation of autoimmune conditions with cyanobacteria-based supplements have been described. Since autoimmune diseases, for example systemic lupus erythematosus or autoimmune thyroiditis, occur more often in women, this caution is especially relevant for them.

Phenylketonuria. Spirulina contains phenylalanine, so it is contraindicated for people with phenylketonuria.

• Pregnancy and breastfeeding — only after consulting a doctor; it is better to refrain.
• Autoimmune diseases and immunosuppressive therapy — discuss with your treating doctor.
• Taking anticoagulants — inform your doctor of any supplements.
• Phenylketonuria — contraindicated.

How to choose and take it

In clinical studies, doses from 1 to 10 g of spirulina per day were most often used. The practical range for healthy adults is 1–5 g per day, starting with a lower dose to assess gastrointestinal tolerance.

The main selection criterion is quality. It is worth choosing products for which the manufacturer provides certificates of analysis for microcystins, heavy metals (lead, cadmium, mercury, arsenic), and microbiological purity. Growing in closed, controlled systems reduces the risk of contamination.

Possible side effects — abdominal discomfort, nausea, a change in stool color — are usually mild and pass when the dose is reduced. Allergic reactions are rare but possible.

Spirulina is convenient to add to smoothies or take in tablets. For better iron absorption, it can be combined with foods rich in vitamin C and not washed down with tea or coffee.

Editorial conclusions

Spirulina is a nutritious supplement with moderate evidence of an effect on the lipid profile and with an iron content, but it does not cure anemia, is not a source of active B12, and does not replace protein.

For women, the most important cautions concern pregnancy and breastfeeding (because of the risk of contamination with toxins) and autoimmune diseases.

If you have decided to take spirulina, choose products with laboratory-confirmed purity and stick to moderate doses.

The editorial team also recommends familiarizing yourself with our materials on spirulina after 40, on pea protein for women, and on soy protein for women.

References

1. Marles RJ, Barrett ML, Barnes J, et al. United States Pharmacopeia safety evaluation of spirulina. Crit Rev Food Sci Nutr. 2011;51(7):593–604.
2. Karkos PD, Leong SC, Karkos CD, Sivaji N, Assimakopoulos DA. Spirulina in clinical practice: evidence-based human applications. Evid Based Complement Alternat Med. 2011;2011:531053.
3. Watanabe F, Katsura H, Takenaka S, et al. Pseudovitamin B12 is the predominant cobamide of an algal health food, spirulina tablets. J Agric Food Chem. 1999;47(11):4736–4741.
4. Watanabe F. Vitamin B12 sources and bioavailability. Exp Biol Med (Maywood). 2007;232(10):1266–1274.
5. Serban MC, Sahebkar A, Dragan S, et al. A systematic review and meta-analysis of the impact of Spirulina supplementation on plasma lipid concentrations. Clin Nutr. 2016;35(4):842–851.
6. Heussner AH, Mazija L, Fastner J, Dietrich DR. Toxin content and cytotoxicity of algal dietary supplements. Toxicol Appl Pharmacol. 2012;265(2):263–271.
7. EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). Scientific Opinion on Dietary Reference Values for iron. EFSA Journal. 2015;13(10):4254.