Of all the colorful natural supplement powders and pills out there, two of the most memorable ones are chlorella and spirulina. Both have a deep green hue (and spirulina has a bright blue offering, too), and both have had their share of attention as more and more people learn about their unique and powerful health benefits.

Chlorella and spirulina are types of single-celled microalgae, so they’re in the same family as seaweed, but — as the “micro” classification suggests — smaller. Like so many colorful plant foods, these microalgae can thank their phytochemical content for their blockbuster colors. More specifically, the credit goes to chlorophyll, a natural green pigment critical to photosynthesis but also linked with numerous health benefits.

The similarities between chlorella and spirulina don’t end there. For instance, they’re both a surprising source of vegetarian protein, containing about 4 grams of protein per tablespoon. What’s more, their protein is complete, meaning it contains all nine essential amino acids — which is hard to find in vegetarian food.

Beyond protein, both chlorella and spirulina are a good source of several other essential nutrients including vitamins B1, B2, folate, and the mineral magnesium.

Here’s how they measure up:

*Percent Daily Values (DV) are based on the FDA’s updated 2020 Nutrition Facts Label for a 2,000 calorie diet. Your needs may be higher or lower depending on your calorie needs.

While both are very nutrient dense, you’ll notice that chlorella has much higher levels of iron, Vitamin A, and zinc. If you know you are deficient in one of these nutrients then you may want to take chlorella instead of spirulina. One other note is that chlorella is rich in Vitamin K1 which can affect blood clotting (usually decreases) so consult with your healthcare provider if you take blood-thinning medications.

Spirulina has higher levels of copper. If you are one of the rare individuals that have a copper deficiency, this might be one reason to take spirulina over chlorella.

Here are some other notable differences between the two that could help you determine which microalgae might be the right supplement choice for you.

Here’s what you should know.

What is Chlorella

Chlorella is a freshwater green algae that has been used as a nutrient-dense food source for many years. Nowadays, thousands of tons of dried chlorella are produced each year in the U.S. and Asia for use as a natural functional food. Chlorella has a unique and beneficial nutritional composition: 55-60% protein (with all nine essential amino acids), 9-18% dietary fiber, and a significant amount of vitamins and minerals, according to the Handbook of Marine Microalgae.

Here’s what else experts have learned about chlorella in more recent years.

Chlorella is Higher in Healthy Omega-3s

While chlorella and spirulina have comparable (and low) amounts of fat, the type of fat they contain is significantly different. Chlorella has been shown to have much higher levels of omega-3 fatty acids — essential “good” fats that the body uses to moderate or reduce inflammation — whereas spirulina has higher levels of omega-6 fatty acids, which are typically used by the body to promote inflammation.

The type of omega-3 fatty acid found in chlorella is alpha-linolenic acid (ALA), the type also found in many seeds and oils such as flax seeds. Most studies on omega-3 fatty acids have been done on EPA and DHA omega-3s which are generally thought to be more absorbable and potent omega 3s than ALA. If you need significant omega-3 support, an animal-based option like krill oil or fish oil is likely what you want, however, you can still benefit from the ALA omega-3s found in chlorella as well.

While some inflammation is good — it helps fight off microscopic invaders and heal injuries, for example — too much inflammation can damage healthy cells and contribute to just about every illness you can think of.

Chlorella is a Chlorophyll Powerhouse

“Chlorella has one of the highest chlorophyll contents found in nature,” according to a paper in the International Journal of Advanced Research and Publications, which is compelling for a host of reasons. For one, chlorella seems to have impressive detoxification capabilities.

Research suggests chlorophyll molecules bind to toxins in the GI tract and hold them there, preventing them from being absorbed into your tissue so they are excreted rather than stored. These toxins include organic-type ones such as herbicides, pesticides, and possibly mycotoxins from molds, as well as heavy metals and plastics such as BPA and phthalates, which are being increasingly credited as endocrine disruptors and carcinogens.

Chlorophyll also may have other cancer-fighting effects as well. It has strong antioxidant properties, which help counter the cellular damage caused by free radicals that can increase inflammation and the risk of all sorts of aging-related illnesses. In an in vitro and small animal study, researchers in the Czech Republic found that chlorophyll helped inhibit the proliferation of pancreatic cancer cells.

Chlorella Contains Unique Gut-Nourishing Components

Chlorella contains Chlorella Growth Factor (CGF), which isn’t one thing, but rather a unique mix of amino acids, peptides, proteins, vitamins. Working in harmony, the nutrient complex in CGF helps stimulate the growth of healthy cells as well as beneficial gut bacteria, which in turn helps balance the gut microbiome.

Chlorella also has the potential to be a good prebiotic thanks to its fiber and other nutritional content. That means it can act as a food for the good bacteria in your gut to feast on, according to lab research published in the Journal of the Science of Food and Agriculture — making this one more way chlorella contributes to gut microbiome balance. Finally, the enzymes in chlorella, including pepsin, help break down protein to promote healthy digestion.

Chlorella May Promote Heart Health

Taking chlorella regularly may help promote healthy cholesterol levels. In a randomized, double-blind, placebo-controlled, human study, participants with high cholesterol who took 5 grams of chlorella a day saw a reduction in their triglycerides and total cholesterol after a month, compared to people who received a placebo. The researchers at Ewha Womans University in Seoul, Korea, posit that chlorella may inhibit lipid absorption in the intestines at least in part due to carotenoids present in chlorella.

Chlorella Modestly Boosts Immune Health

Chlorella may help you stave off illness or recover more quickly by boosting the activity of natural killer cells, immune system cells that help remove sick or infected cells, as well as other markers of a healthy immune system. A human study published in Nutrition Journal found that taking 5 grams of chlorella per day in the form of tablets for just 8 weeks had an immunostimulatory effect in healthy people.

What is Spirulina

Spirulina is blue-green algae (a.k.a. cyanobacteria) that’s grown in both freshwater and saltwater. Like chlorella, spirulina has long been considered a functional food. Unlike chlorella, spirulina is a photosynthesizing bacteria, rather than a true plant aglae.

In the Central African country of Chad, people have been harvesting spirulina in Lakes Bodou and Rombou for centuries. And if you’ve ever toasted St. Patrick’s Day with a green beer, it may have been brewed using spirulina. So yes, it’s a surprisingly festive microalgae, but it’s better known for some of its other qualities.

Spirulina Contains Phycocyanin, an Impressive Protein

Spirulina contains the protein phycocyanin, which researchers at Qingdao University in China and elsewhere describe as having promising anti-cancer activity, among other benefits such as antioxidant and anti-inflammatory properties. Scientists believe that phycocyanin may contribute to helping stop cancer cells from spreading while killing off some of the cells themselves. Perhaps most encouraging, unlike traditional cancer therapies, phycocyanin appears to have few to no side effects.

Spirulina Has Higher Levels of GLA, a Healthy Omega-6

The Gamma-Linolenic Acid (GLA) contained in spirulina is an omega-6 essential fatty acid, “essential” meaning that the body doesn’t produce it naturally and so it must be consumed in food. In general, people have an imbalanced proportion of omega-6 to omega-3 fatty acids, however, GLA behaves more like an omega-3. You may have heard of GLA as a beneficial omega-6 fatty acid found in seed oils like borage and evening primrose. The GLA in spirulina may have mild benefits for decreasing inflammation in the body.

GLA seems to have an anti-inflammatory effect, which is why it’s being investigated for improving a host of conditions, including reducing the pain and swelling of rheumatoid arthritis, improving allergic reactions, aiding in breast cancer treatment, getting blood pressure under control, treating menopause-related hot flashes, and staving off osteoporosis.

Spirulina Can Sometimes Contain Toxins

Under certain growing circumstances – such as warm, brackish water contaminated with heavy metals or bacteria — spirulina can produce high levels of toxins called microcystins that are toxic to the liver. If you’ve ever been to a beach that’s closed due to an algae bloom, that’s likely because the levels of these microcystins are too dangerous for humans (and often kills the fish and other marine life).

I don’t want to scare anyone as it’s not an enormous worry, but one study from the Université de Montréal in Canada found that, out of 18 products the researchers analyzed, 8 contained cyanotoxins that exceeded tolerable daily intake values. Given that concern and the fact that harvesting and processing chlorella is an easier process using fewer chemicals, I generally prefer chlorella over spirulina.

The Bottom Line

Though both chlorella and spirulina are nutrient-dense microalgae that share a number of health benefits, I recommend chlorella as being the healthier choice for gut health, detoxification, and dense nutritional support. Chlorella contains more chlorophyll, and other vitamins and micronutrients, plus it offers the unique benefits of Chlorella Growth Factor — all without the potential danger for toxins that spirulina carries.

When sourcing high-quality chlorella, look for one with broken cell walls which increases nutrient absorption and I prefer Chlorella pyrenoidosa over Chlorella vulgaris due to its higher amounts of Chlorella Growth Factor, protein, and vitamins.

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