Spirulina: How Healthy Are The Microalgae Really?

Spirulina is a frequent target of consumer regulators and other critics. Microalgae was long considered a superfood and is now regularly devalued in times of fact-checkers. We explain which allegations are justified and which are not. We present the health effects and benefits of spirulina and show in which situations and for which people it is really worth taking the microalgae.

Spirulina: microalgae with high nutritional content

Spirulina is a food that is considered a superfood due to its high content of nutrients and vital substances. Spirulina is a cyanobacteria. However, this was only found out when spirulina was already classified as an alga.

That is why Spirulina is still referred to as microalgae or blue-green algae to this day – as blue-green algae because it contains various colorings, e.g. the blue pigment phycocyanin. Together with the green dye chlorophyll, which is also contained, a blue-green color is created.

Unlike the macroalgae that we report on in our Seaweed article, microalgae are microscopic. There are around 35 species of Spirulina, the best known of which is Arthrospira platensis (also called Spirulina platensis).

The cyanobacteria grow in freshwater and saltwater lakes with a high pH between 9 and 11 and are native to Australia, Southeast Asia, Africa, and Central America, where they have served the population as a food and nutrient source for centuries.

Spirulina is known to us as a dietary supplement and is sold dried in the form of powder, capsules, tablets, or pellets. The species Arthrospira platensis (Spirulina platensis) is mainly used for this.

Spirulina from Germany

Spirulina is mostly grown in aquaculture. These have not only existed in the home regions of the algae for a long time but also in Europe, and even in Germany. That is why the frequent point of criticism – the alga has a bad ecological balance due to the great distance – does not count in every case.

Coffee, tea, cocoa, and bananas also come from far and wide without making a fuss about it – and a serving of spirulina provides significantly more nutrients than a cup of coffee, which is purely a stimulant.

Criticism of Spirulina

The life cycle assessment is not the only point of criticism. For years, spirulina has been the target of consumer regulators, as well as a number of other critics. In the following sections, we will clarify whether there is any truth to the allegations or not. If you have already had positive experiences with the alga yourself and are convinced of its effect, you will find all the information about taking it below from the paragraph “Spirulina: the right way to take it”.

Does spirulina contain a lot of chlorophyll and therefore help against diseases?

The consumer advice center writes on its website right at the beginning: “Spirulina with a lot of chlorophyll and protein is said to help against a wide variety of diseases and with weight loss, but this has not been proven.”

Not only SHOULD the blue-green algae be rich in chlorophyll, but it is also. The green substance is generally found in large quantities in algae: 100 grams of spirulina powder can provide up to 1500 mg of chlorophyll. With 4 grams of spirulina – the usual daily dose – this would correspond to 60 mg. For comparison: A bunch of parsley (approx. 30 g) provides just as much chlorophyll. However, the green botanical is heat sensitive and few people would eat a bunch of parsley raw. Spirulina is therefore a very good alternative for supplying chlorophyll for people who do not like to eat dark green leafy vegetables and herbs or do not get around to it every day.

If you think you’re consuming a lot of the substance with regular lettuce or iceberg lettuce, that’s hardly the case. Iceberg lettuce only provides 2 mg of chlorophyll per 100 grams, so not worth mentioning. See our chlorophyll article (link below) for a table showing the chlorophyll content of some foods.

Consumer Advice: Chlorophyll is unimportant

The consumer center is of the opinion that chlorophyll is ” nutritionally unimportant ” because it is not a nutrient. Chlorophyll is not one of the essential nutrients, but denying the substance all of its health effects is quite stretching – especially since chlorophyll-rich plants have been part of the natural diet of humans and many other animals since the beginning of time.

Studies then also show that the green natural substance is a potent antioxidant that can intercept carcinogenic substances in the body. Many other research contributions on the health properties of the green substance – e.g. e.g. its detoxifying effects – we cover in our in-depth article on chlorophyll. Of course, chlorophyll is not a panacea, but a substance that can be integrated into any prevention and therapy concept and can contribute to the prevention and healing of diseases.

Does Spirulina really contain that much protein?

The blue-green algae is a protein bomb because it has been dried and is therefore low in the water, which also increases the nutrient content. It consists of 60 percent protein – as you can also see in our nutritional value table. But because you’re only eating 4g of it a day, you end up with just 2.4g of protein, which would be 5 percent of the protein needs of a 130-pound person. However, for people who generally eat low protein, this small amount is a welcome extra portion of protein — especially since it’s a particularly high-quality protein with a very good biological value of 103.

A value above 100 means that one could meet one’s protein needs with relatively small amounts of the food in question (for spirulina algae it is between 80 and 90 g that one would have to eat daily, which is an excellent value for a non-animal food).

For comparison: tofu also has a good biological value (107). However, because it’s not a dried product like spirulina, tofu has a high water content and only about 16 percent protein. One would therefore have to eat 330 g of tofu daily in order to provide oneself with all the necessary amino acids.

However, there is nothing wrong with consuming MORE spirulina algae. Therefore, many people choose a daily dose of up to 10 g of Spirulina (subject to tolerance). In this case, you will of course consume more nutrients and vital substances, namely 2.5 times the amount.

Spirulina is strongly alkaline

Unlike most other protein sources – whether animal or vegetable – spirulina is a strongly basic protein source. Meat, fish, cheese, nuts, and soy products, on the other hand, are acid-forming. The PRAL value can serve as a rough guide for the base potential. Negative values indicate the food is basic, positive values indicate acidic food. (You can look up PRAL values at

  • Spirulina dried: -22.1
  • Spirulina fresh: -2.9
  • Salmon: +10.1
  • Steak: +8.6
  • Oatmeal: +7.1
  • Gouda: +18.9
  • Tofu: +2.6

Does Spirulina Contain Relevant Nutrient Levels?

The consumer advice center believes that “the amounts of nutrients contained are not relevant in view of the usual daily dose of spirulina”. And if they are, then they must be added, which can be seen from the list of ingredients.

Do you eat a balanced, healthy, and nutritious diet every day?

Apart from that, nowadays very few people are able to eat an optimal and balanced diet. Or do you and your family eat your five portions of fruit and vegetables every day? Do you eat any processed products? And do you prepare two to three meals a day for the whole family from fresh ingredients? Do you make sure that everyone in your family is supplied with all the nutrients? You can do that maybe two or three days a week – but every day?

Vitamin deficiency, therefore, affects more people than you think – you can read about it under the previous link. Anyone who advises against high-quality food supplements such as spirulina is keeping people away from a solution that could provide them with important nutrients despite a suboptimal diet. (Of course, it doesn’t have to be spirulina, other high-quality food supplements can also be used).

Is the vitamin B12 contained in spirulina usable for humans?

Spirulina is not said to be a good source of vitamin B12, since most of the vitamin B12 it contains is not usable by humans. Blue-green algae used to be considered a good source of vitamin B12.

In a study from 2019, however, rats suffering from vitamin B12 deficiency showed that the algae led to numerous improvements in the typical deficiency symptoms, which could now speak for an effect – at least in rats. B12 deficiency-related tissue changes in the spleen, lungs, and testicles regressed under the administration of spirulina, so the Indian scientists wrote that the alga could serve as a bioavailable plant source of vitamin B12.

However, the animals had been given between 32.5 and 65 g of spirulina per kg of feed, so with an average adult food intake of 1.8 kg per day, this would equate to between 60 and 120 g of spirulina per day.

Iron deficiency from spirulina?

You saw above that spirulina algae can contain quite a lot of iron. Nevertheless, the consumer center warns: “Spirulina binds to iron, frequent consumption could lead to an iron deficiency.” We could not find any evidence of this in the list of sources from the consumer center.

However, there are various studies in the literature that show exactly the opposite of what the consumer advocates write, namely that the microalgae not only optimize the iron supply but can also specifically help to remedy an existing iron deficiency:

  • In 1998, rats fed five different diets (two containing spirulina) showed increased iron levels in rats fed spirulina in particular.
  • In 2020, an Indonesian study of 60 pregnant women with low hemoglobin found that spirulina increased half of the women from 10 to 13.3 within 8 weeks. (A score below 12 indicates anemia). The other half had received a conventional iron supplement that did not lead to any improvement in the value. What is interesting about this study is that the daily dose of spirulina was only 300 mg, so its iron content could hardly have been decisive. However, we explain how chlorophyll can raise iron levels in our chlorophyll article — and seaweed is known to be a very good source of chlorophyll.
  • In 2021, 47 young women with iron deficiency anemia were given 3g of the algae or a placebo daily for 90 days. Neither the ferritin level (iron stored) nor the hemoglobin level changed. Although Spirulina was not successful here, the values ​​did not deteriorate either.
  • Also in 2021, a study of 240 Kenyan children aged 6 to 23 months showed that spirulina is excellent for treating iron deficiency anemia. The children received a soy-corn porridge three times a day. Some of the children were given spirulina (0.4%) with porridge. More of the children who received spirulina recovered from iron deficiency anemia, and much more quickly. The children’s recovery rate also exceeded the minimum values ​​set by the WHO for a food intervention). So it seems unlikely that spirulina leads to iron deficiency – quite the opposite.

Are there studies that show how well spirulina works?

No matter what studies and evidence are presented to spirulina critics, they are either ignored or labeled as grossly flawed and untrustworthy.

One could probably wait forever for one perfectly designed study with a large number of participants. Because behind Spirulina there is no multi-billion dollar industry that can afford large-scale, expensive studies, as is the case with pharmaceuticals. Methodological deficiencies in science also occur again and again – not only with food and food supplements but also with medicines.

Scientific research is also never conclusive. New findings are constantly being published. It is unscientific to disregard all previous studies and deny all effects of spirulina algae due to the lack of large-scale human studies.

Are allergic reactions to spirulina possible?

“In addition, allergic reactions to spirulina are possible,” the consumer center said. However, allergies are possible to almost any food, especially dairy products, eggs, peanuts, fish, soy, apples, celery, and many more. Why should the blue-green algae be an exception here? Nevertheless, there are at most individual case studies that deal with a spirulina allergy, so this occurs rather rarely and if it does, it usually occurs in people who already have other allergies, e.g. B. against pollen or house dust.

However, a review from 2011 states that spirulina can be particularly useful for people with allergies, as it has anti-inflammatory properties and inhibits the release of histamine. Even with a quantity of 1 to 2 g per day for 12 weeks, relevant allergy markers in the hay fever patients improved – and in a placebo-controlled double-blind study, the algae relieved the typical hay fever symptoms, such as runny nose, itchy eyes, etc.

For people who eat little or no chlorophyll-rich green leafy vegetables or have sensitive digestion, spirulina can cause digestive problems when first started, but this is not related to an allergy or intolerance and should subside after a few days.

Is spirulina loaded with toxins?

According to the consumer center, spirulina can be contaminated with heavy metals, PAHs, and toxins. (PAH is the abbreviation for Polycyclic Aromatic Hydrocarbons).

Like almost every food (especially fish, which is surprisingly classified as a healthy food by the consumer advice center), algae can of course also be contaminated with pollutants.

However, the danger here is even significantly lower than with other foods. Spirulina in particular is preferably cultivated in closed systems in controlled aquaculture. A load is as good as impossible here. Only if the algae comes from open lakes could it be contaminated with heavy metals and other pollutants.

It is best to buy organic spirulina, as this ensures that the algae come from controlled aquaculture and, moreover, does not contain any pesticides such as ethylene oxide. If the source of the algae is not clear on the label, check with the manufacturer to determine if it is from open or closed aquaculture systems.

Also, ask about current studies on heavy metal pollution.

The risk of possible contamination with other algae (e.g. green algae) with other cyanobacteria or intestinal bacteria (e.g. via bird droppings) – as the consumer center fears – is lower in closed aquaculture systems. Because in open aquaculture systems, where the water in the aquaculture is not separated from natural bodies of water, other bacteria and microorganisms can of course also get into the aquaculture. Of course, responsible manufacturers have regular microbial analyzes carried out.

Spirulina: the right intake

For the correct intake of spirulina, please note the following information:

Who is Spirulina recommended for?

Spirulina algae can be taken by almost everyone who wants to consume more protein, chlorophyll, iron, magnesium, etc. The alga helps to cover the daily requirement for nutrients and vital substances and to prevent or remedy deficiencies, e.g. B. Iron deficiency.

This makes it just as suitable for fast food lovers as it is for all people who cannot eat enough green leafy vegetables every day. Of course, spirulina does not replace a diet rich in vegetables in the long run, but it can at least partially compensate for the lack of vegetables – together with other individually suitable food supplements.

On the other hand, if you like to eat a lot of green leafy vegetables such as lamb’s lettuce, herbs, rocket, spinach, dandelion, nettles, kale, and so on and make sure you eat a balanced diet made of fresh ingredients, you certainly don’t need spirulina.

Drug Interactions

Almost as a matter of routine, warnings are given in connection with dietary supplements (and thus also with spirulina algae) about interactions with medicines, in particular with antidiabetics, immunosuppressants, and anticoagulants (blood thinners).

That’s interesting because, in the case of spirulina, the alga officially denied any effect. It is food, nothing more, and without relevant amounts of nutrients. But then it can apparently have such a strong effect again that you have to warn against it when you are taking medication. So ask your doctor or pharmacist whether or not you can take spirulina algae with your medication.

However, we are not aware of any studies that show that the algae interacted with the drugs mentioned above. In a study of a particular spirulina extract containing 40% phycocyanin (the blue pigment found in spirulina), there was no effect on blood clotting. (Normal spirulina supplements provide only 1% phycocyanin). Phycocyanin-rich spirulina supplements (1 to 2.3 g per day) are known to relieve joint pain.

How and when to take spirulina?

Most investigations were carried out with daily doses of 2 to 4 g of the algae. Compacts or tablets usually consist of 500 mg of powder; Capsules usually contain 400 mg of powder, so you can take up to 8 pellets (e.g. 2 times 4) or up to 10 capsules (e.g. 2 times 5).

At what time of the day (morning, midday, evening) you take the blue-green algae does not matter – nor does it matter whether you spread the intake over the day or take the entire daily dose at once.

It is best to take the algae on an empty stomach. If you have sensitive digestion, then better before or after meals. A green coloring of the stool is quite normal – this is due to the high chlorophyll content.

In studies, daily doses of up to 10 g were also used less frequently. If you want to take higher amounts of cyanobacteria due to a vital substance deficiency or for prevention, you should start with 4 g and then slowly increase this amount. This gives your body the opportunity to slowly get used to the algae.

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Written by John Myers

Professional Chef with 25 years of industry experience at the highest levels. Restaurant owner. Beverage Director with experience creating world-class nationally recognized cocktail programs. Food writer with a distinctive Chef-driven voice and point of view.

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