How Much Spirulina Should I Consume?

Spirulina is a type of algae extract that is rich in a variety of essential nutrients and antioxidants.
Image Credit: Magone/iStock/GettyImages

Spirulina is a type of algae extract that is rich in a variety of essential nutrients and antioxidants. It can be consumed as a food product or taken as a dietary supplement. Although the spirulina plant is healthy, it should be consumed in moderation; even small amounts can contain heavy metals.



A February 2016 study in the ‌Journal of Nutrition Research‌ recommends consuming about 4 grams of spirulina per day. However, it's possible to safely consume about 7 grams per day, and you shouldn't regularly consume more than 15 grams per day.

Video of the Day

Read more:10 Vegan Protein Sources — Some Will Surprise You

Video of the Day

Spirulina Plant Nutrition Facts

Spirulina is an extract taken from blue-green algae that typically grows in fresh water. According to an August 2016 study in the ‌Archives of Toxicology‌, it's technically classified as a type of ‌filamentous cyanobacteria‌. There are several types of spirulina, with ‌Spirulina platensis‌ and ‌Spirulina maxima‌ being the most commonly consumed types.

According to the USDA, a tablespoon (7 grams) of dried spirulina has 20 calories, 0.5 grams of fat, 1.7 grams of carbohydrates and 4 grams of protein. A tablespoon of spirulina also contains:

  • 11 percent of the DV for iron
  • 47 percent of the DV for copper
  • 6 percent of the DV for manganese
  • 14 percent of the DV for vitamin B1 (thiamin)
  • 20 percent of the DV for vitamin B2 (riboflavin)
  • 6 percent of the DV for vitamin B2 (niacin)
  • 5 percent of the DV for vitamin B5


Spirulina plants are also well-known for being rich in beneficial bioactive compounds, particularly antioxidants.

According to a February 2016 study in the ‌Journal of Nutrition Research,‌ there can be a substantial amount of nutritional variability between spirulina plants. For example, a tablespoon of spirulina could contain as much as 5 grams of protein or as little as 3.8 grams of protein, depending on the product.


The majority of spirulina plant products are also extremely rich in certain nutrients, like vitamin A, though this also varies substantially between products. This means that as little as 4 grams of spirulina plant per day might be suitable instead of a whole tablespoon. In general, it is not recommended for people to regularly consume more than 15 grams per day. You may need to restrict your spirulina consumption, depending on the nutritional content of the product you've chosen.


Read more:11 Nutrients Americans Aren't Getting Enough Of


Benefits of Spirulina's Nutrition

Spirulina consumption is typically encouraged given how nutrient-rich it is. The ‌Journal of Nutrition Research‌ study reported that protein is one of the primary beneficial nutrients in spirulina. While your average piece of chicken is about 24 percent protein and your average fish is about 22 percent protein, spirulina powder is 65 to 70 percent protein.


This is also more than dried egg (47 percent protein), powdered milk (37 percent protein) and peanuts (26 percent protein). This means that spirulina can be a valuable protein source for people who consume plant-based diets.

On a similar note, spirulina is also rich in vitamin B12. This nutrient is typically found in animal-based products like eggs, dairy, shellfish and meat. Spirulina is one of the few vegan and vegetarian-friendly sources of this essential nutrient.


Read more:How Vegans Can Get All Their Nutrients (Without Taking Supplements)

Thanks to spirulina's nutrients and antioxidants, it can help to:

  • Combat malnutrition, even in people with chronic illness.
  • Combat viral and bacterial effects.
  • Combat heavy metal toxicity.
  • Improve cholesterol levels.
  • Improve blood lipid levels.
  • Reduce inflammation and modulate the immune system.
  • Prevent skeletal muscle damage.
  • Protect the liver.


Spirulina is also a very green food — it grows very quickly and requires less water and land compared to other protein-rich plant-based foods, like soy. It is one of the most environmentally friendly food products you can consume.

Spirulina is notably rich in vitamin A, vitamin B12 and chromium. However, even small amounts of spirulina can exceed the recommended daily values for these nutrients. The ‌Journal of Nutrition Research‌ study reported that consumption of as little as 10 grams of the average spirulina product could cause you to exceed the recommended daily consumption of these nutrients.


Dangers of Spirulina Consumption

The benefits and dangers of spirulina products both primarily come from their specific nutritional makeup. Given how nutrient-rich spirulina is, it's possible to get unhealthy amounts of certain vitamins and minerals if you consume excessive amounts of spirulina plant products.

There are no side effects associated with vitamin B12, and the National Institutes of Health has not yet established a tolerable limit for chromium consumption. However, vitamin A consumption can be bad for your health in excess. Although the USDA listing did not mention vitamin A content, the ‌Journal of Nutrition Research‌ study stated that you could reach the tolerable limit of vitamin A intake from about a single tablespoon of spirulina product.

Excess vitamin A is the main reason you should be cautious about your spirulina intake. However, spirulina primarily contains vitamin A in the form of beta-carotene. This form of vitamin A is less toxic than preformed vitamin A when consumed in excess. However, if you were to consume large amounts of spirulina plant products for a while, your skin could turn yellow or orange. Long-term consumption of excess beta-carotene may also increase your risk of lung cancer and cardiovascular disease.

Spirulina, algae, seaweed and other similar products often contain large amounts of iodine. You may need to be cautious about spirulina consumption due to its iodine content. Older adults, pregnant people, people with pre-existing thyroid problems and infants are all at particular risk for developing thyroid dysfunction from consuming products like spirulina. These people may want to avoid consuming spirulina products altogether.

Spirulina and Heavy Metals

Although spirulina can heavy metal detox your body, it is possible for your spirulina plant to contain heavy metals too. These metals are more likely to be found in spirulina grown in river water rather than farmed spirulina plant products.

Cyanobacteria like spirulina are also associated with toxins. While it's rare for spirulina to be toxic to humans, a June 2015 study in the ‌Harmful Algae Journal‌ found that spirulina can contain arsenic species and cyanotoxins like cylindrospermopsin and anatoxin-a. This study found that spirulina side effects included fatigue, dermatitis, nausea, dizziness and headache due to the presence of these toxins.

The World Health Organization states that cyanobacterial toxins can cause:

  • Skin rashes
  • Stomach cramping
  • Vomiting
  • Nausea
  • Diarrhea
  • Fever
  • Throat irritation
  • Headache
  • Muscle and joint pain
  • Oral blisters
  • Liver damage

Fortunately, spirulina side effects like these are typically due to contamination and poor production quality, rather than the spirulina itself.