Chlorella vs. Spirulina: Which One Is Right for You?

Chlorella and spirulina are algae with miraculous-sounding health claims. But these supplements have some fundamental differences—here's what nutrition experts need you to know.

Popular supplements

People are buzzing about chlorella and spirulina. With miraculous-sounding benefits, it’s no wonder the algae biz is booming.

Sales of spirulina are expected to jump by as much as 10.5 percent by 2026, and sales of chlorella are expected to increase by 7 percent between 2020 to 2025. But do these popular supplements live up to the hype? And which one is the better choice? Let’s take a look.

What is chlorella?

Chlorella is a freshwater alga native to Japan and Taiwan. Although it is rich in protein, fiber, and a variety of vitamins and minerals, the hard cell wall of this algae cannot be digested by humans.

The only way to gain the nutritional benefits from chlorella is to ingest it in supplement form. Chlorella supplements can be found on shelves as powders, capsules, or tablets.

The health benefits of chlorella

With its rich nutritional profile, chlorella may offer many potential health benefits.

“As a plant-based protein, chlorella provides about 50 to 60 percent complete protein, including all nine essential amino acids and many of the B vitamins, along with being a great source of vitamin A, iron, and zinc,” says Sarah Koszyk, a registered dietitian nutritionist and author of 365 Snacks for Every Day of the Year.

This is especially great news for those who follow a vegan diet. It can be challenging to meet the daily nutrition recommendations for nutrients such as vitamin B12 without consuming animal products.

The amino acid profile of this algae is responsible for many of its health benefits.

“Chlorella products contain a large amount of the amino acid arginine, which is imperative for the production of nitric oxide,” explains Lindsay Allen, a registered dietitian nutritionist and owner of Back in Balance Nutrition & Fitness. “A lack of nitric oxide is associated with heart disease, diabetes, high blood pressure, and sexual dysfunction.”

This benefit of chlorella may explain some of the health claims associated with the supplement. Research has found that chlorella supplements may help to lower cholesterol levels and improve immune function, blood pressure, and blood sugar levels.

In addition, chlorella may aid the body’s own detoxification process. “Chlorella has been shown to bind to heavy metals and toxins in the body and actually help flush them out,” says Koszyk, who is also co-founder of wellness company MIJA, which sells a supplement that includes chlorella.

What is spirulina?

Spirulina is a blue-green alga that grows in both freshwater and saltwater. Incredibly nutrient-rich, just one tablespoon provides four grams of complete protein. It’s also an excellent source of copper, a good source of iron, and has the B vitamins thiamine and riboflavin.

In fact, this tiny algae has even been used by NASA to fuel the nutrition of astronauts. Spirulina supplements are increasingly popular for good reason.

“Spirulina is full of immune-boosting vitamins and minerals as well as being one of the highest protein-containing vegetables—with about 60 percent protein content,” says Elizabeth Gunner, a registered dietitian nutritionist.

Unlike chlorella, spirulina can be digested in a whole food form and can be incorporated into the diet as an ingredient or as a nutritional supplement.

The health benefits of spirulina

Because spirulina is so nutrient-dense, it can provide many health benefits when you eat it regularly.

“Spirulina contains antioxidants such as phycocyanin, which is anti-inflammatory, immune-supporting, cancer reducing, and brain supporting,” says Koszyk.

Research has also found that spirulina may help reduce cholesterol and triglyceride levels and improve blood glucose levels.

Spirulina supplements have also increased in popularity among athletes, thanks to the potential impact they may have on exercise-induced oxidative damage. “Spirulina may offer a positive effect on athletic endurance by reducing oxidative stress, which increases the ability to train harder and longer,” explains Koszyk.

Green chlorella pills or green barley pills and powder.jirkaejc/Getty Images

Chlorella vs. spirulina

Both spirulina and chlorella supplements may offer benefits to overall health, but is one superior? “Both show very similar benefits in terms of the bioactive compounds that affect our physiology,” says Allen.

However, there are a few key differences between them. “Chlorella is higher in fat and calories when compared to spirulina, but spirulina may contain up to 10 percent more protein than chlorella,” explains Koszyk.

And the differences aren’t in the macronutrients alone. “Chlorella does appear to contain higher amounts of vitamins and minerals, especially selenium, vitamin D2, and B12,” Allen says.

The downside of chlorella and spirulina

Although these two nutritional powerhouses offer many benefits, there are a few downsides to consider.

“Although uncommon, some individuals may experience gas or nausea with chlorella supplements,” says Koszyk.

Spirulina’s negatives are more significant. “Depending on where the spirulina is grown, there could be toxins and heavy metals found within it, which is why finding a reliable source is important,” says Koszyk.

It is also important to note that some people can experience an allergic reaction to algae and therefore would need to avoid supplementation with either chlorella or spirulina.

A personal choice: chlorella vs. spirulina

Based on the research surrounding these supplements—along with their nutrition profiles—both can provide benefits to health. Which is best for you may come down to your personal needs and goals.

Talk to your health care provider before taking a new supplement. A physician or registered dietitian can help guide your decision.

When choosing a supplement, always be sure to select a high-quality brand. Purchase from trusted vitamin brands and check the label to be sure the product has been tested by an independent third party.

“Since supplements are not FDA [Food and Drug Administration] regulated, I recommend consumers purchase supplements that are third-party tested,” says Gunner.

Next, how to store vitamins and supplements.

  • 360 Market Updates: "Global Chlorella Market 2020 by Manufacturers, Regions, Type, and Application, Forecast to 2025"
  • Allied Market Research: "Spirulina Market by Type (Arthrospira Platensis and Arthrospira Maxima), Application (Nutraceuticals, Cosmetics, Food & Beverages, Animal Feed, and Others), and Drug Formulation (Powder, Tablet & Capsule, Liquid, and Granule & Gelling Agent): Global Opportunity Analysis and Industry Forecast, 2019–2026"
  • Sarah Koszyk, MA, RDN, cofounder of wellness company MIJA and author of 365 Snacks for Every Day of the Year
  • Elizabeth Gunner, RDN, registered dietitian nutritionist
  • Lindsay Allen, MS, RDN, owner of Back in Balance Nutrition & Fitness
  • Current Pharmaceutical Design: "Chlorella vulgaris: A Multifunctional Dietary Supplement with Diverse Medicinal Properties"
  • Renewable and Sustainable Energy Reviews: "Morphology, composition, production, processing and applications of Chlorella vulgaris: A review"
  • Nutrition Journal: "Impact of daily Chlorella consumption on serum lipid and carotenoid profiles in mildly hypercholesterolemic adults: a double-blinded, randomized, placebo-controlled study"
  • European Journal of Nutrition: "The effect of Chlorella pyrenoidosa supplementation on immune responses to 2 days of intensified training"
  • Nutrients: "Potential of Chlorella as a Dietary Supplement to Promote Human Health"
  • Clinical Nutrition: "Glucose homeostasis, insulin resistance and inflammatory biomarkers in patients with non-alcoholic fatty liver disease: Beneficial effects of supplementation with microalgae Chlorella vulgaris: A double-blind placebo-controlled randomized clinical trial"
  • USDA FoodData Central: "Seaweed, spirulina, dried"
  • Clinical Nutrition: "A systematic review and meta-analysis of the impact of Spirulina supplementation on plasma lipid concentrations"
  • Diabetes, Metabolic Syndrome and Obesity: : Targets and Therapy: "Quantifying the effects of spirulina supplementation on plasma lipid and glucose concentrations, body weight, and blood pressure"

Erin Palinski-Wade
Erin Palinski-Wade, RD, CDCES, CPT is anationally recognized nutrition, diabetes and fitness expert & author of 4 books including "2 Day Diabetes Diet," (Reader's Digest), "Love Your Age"(Rodale) & "Belly Fat Diet For Dummies," (Wiley). She is a frequent media guest with over 200 top-tier interviews annually & a TEDx speaker. As a busy mom of 3, she founded the 'Healthy Mom Happy Family' brand wth a combined audience of over 100,000 on social media.