What Nutrients are in Marine Phytoplankton?
Marine phytoplankton is one of the more nutrient-dense foods you can buy: protein, omega-3, vitamins, minerals and plant pigments, all in a form the body takes up well. What follows goes nutrient by nutrient, based on published analyses rather than the back of the tub, and it is as clear about the claims that do not hold up as the ones that do.
 | ||
 |
The macronutrients: protein, carbs and omega-3
Protein
By dry weight, marine phytoplankton is roughly 45% protein, and a complete protein at that, carrying all nine essential amino acids we cannot make for ourselves. You will see it compared with beef gram for gram, which is true on paper but a little misleading: you take it by the teaspoon, not the steak. For a plant source, though, the protein quality is hard to fault.
Carbohydrates and fibre
Carbohydrate is low, under 10%, split between simple sugars, a few polysaccharides and a trace of fibre. At a teaspoon a day that adds up to nothing meaningful in energy or fibre terms, and that is fine: carbs are not why anyone buys this.
Omega-3 fats (EPA)
This is the one that matters. Marine phytoplankton, and Nannochloropsis strains especially, is among the few plant sources of EPA itself, the long-chain omega-3 normally tied to oily fish. Most plant omega-3 arrives as ALA, a short-chain form the body has to convert to EPA and does badly. Phytoplankton supplies the EPA more or less ready-made, which is exactly why it interests vegans and anyone off fish.
The authorised wording is precise: EPA and DHA contribute to normal heart function at a combined 250mg a day (Commission Regulation (EU) No 432/2012). Dose is where it gets interesting. Published analyses put EPA at 4 to 5% of dried phytoplankton, so a half-teaspoon, about a gram, works out at roughly 40 to 50mg.
That sits well below the 250mg the heart claim needs. So phytoplankton is better understood as a contribution to your omega-3 intake than a single-spoon route to the authorised dose. If 250mg is the target, check the EPA figure on your own pack, and treat a dedicated algal oil as the higher-dose route.
Vitamins and minerals in marine phytoplankton
On vitamins, you get a spread: C, E, several B vitamins and the provitamin-A pigment beta-carotene. The minerals run to iron, magnesium, calcium, potassium and phosphorus. Iron is the one I would single out, the mineral the body uses to build red blood cells, and published analyses show phytoplankton carries it in amounts that actually count. As always, your own pack has the real figure.
A word on B12
If you are vegan, slow down here, because some labels oversell this one. Algae, phytoplankton included, contain B12-like compounds, but a lot of it is pseudo-B12 (pseudocobalamin), which the human body cannot use the way it uses true cobalamin. It can appear on a label as B12 while doing very little for your actual B12 status.
So do not rely on it for B12. If you are plant-based, get your B12 from a verified supplement and let any in the phytoplankton be a bonus. Turn a pack over at the till and the panel might list B12 in micrograms, but that number is what sits in the powder, not what your body can extract from it. With pseudo-B12, the two are not the same figure.
Trace elements
There are trace elements too, zinc chief among them, with smaller amounts of others like selenium showing up in published analyses. The body only needs these in tiny quantities, but they pull their weight: zinc alone is involved in a long list of enzyme reactions.
One distinction worth drawing, because it trips people up: iodine concentrates in macroalgae like seaweed and kelp, not in marine microalgae such as phytoplankton. Grown on purified water with no added iodine, the powder carries next to none. That matters if you have a thyroid condition or already take iodine, since seaweed products can deliver far more than you would expect, while phytoplankton will not shift your levels either way.
The plant pigments in phytoplankton (phytonutrients)
The deep green colour comes from phytoplankton’s pigments, and they are part of what makes it interesting beyond the basic macros and minerals.
Chlorophyll
Chlorophyll is the pigment that runs photosynthesis, and its molecule looks strikingly like haemoglobin, give or take a magnesium centre where blood has iron. That resemblance gets stretched into a claim that green foods build the blood. They do not. The chlorophyll you eat is not converted into haemoglobin, so enjoy the chemistry trivia and ignore the liquid-blood sales pitch.
Carotenoids
Carotenoids give a lot of natural colour, and phytoplankton has several: beta-carotene, astaxanthin and zeaxanthin. They act as antioxidants, and zeaxanthin is one of the pigments the eye concentrates in the macula. The evidence is promising rather than settled, so file it as a nice extra rather than a reason to buy.
Phycobiliproteins
Phycobiliproteins are water-soluble pigments in some algae, phycocyanin being the famous one. In laboratory studies they show antioxidant activity and effects on inflammation markers. Interesting, but lab activity is a starting point, not proof of a benefit in people, and I would be wary of any product that spins these early findings into firm health promises.
So what does this actually mean for you?
Even without the superlatives, the picture holds up well. The main reason to take marine phytoplankton is its EPA omega-3 in an easily absorbed, plant-based form, with a broad supporting cast of vitamins, minerals and antioxidant pigments behind it. For anyone who does not eat fish, that is a useful profile to have in the cupboard.
What it is not is a B12 fix, or a cure for anything. I would buy it for the omega-3 and the breadth of nutrients, check the EPA figure on the pack, and treat everything else as a bonus rather than the reason. If that sounds like what you are after, you can compare the powders in our shop.
References
- Chacón-Lee T L & González-Mariño G E (2010), “Microalgae for healthy foods: possibilities and challenges”, Comprehensive Reviews in Food Science and Food Safety, 9(6), 655-675.
- Guedes A C, Amaro H M & Malcata F X (2011), “Microalgae as sources of carotenoids”, Marine Drugs, 9(4), 625-644.
- Watanabe F et al (2014), “Vitamin B12-containing plant food sources for vegetarians”, Nutrients, 6(5), 1861-1873.
- EFSA / Commission Regulation (EU) No 432/2012, authorised health claims (EPA and DHA, heart function).
How we present this, and what counts as proof
The nutrient figures here are ingredient-level facts from published analyses of marine phytoplankton, not one branded tub, and amounts vary by species and producer. The authorised nutrient-function claims referenced (EPA and DHA for heart function at 250mg; iron for red blood cell formation) apply only where a serving supplies a meaningful amount, so check your own pack. The B12, chlorophyll, carotenoid and phycobiliprotein passages reflect mixed or preliminary evidence, flagged as such. For how we weigh evidence and disclose our interests, see our editorial policy. General information, not medical advice. Last reviewed: June 2026.
Cara Hayes is an experienced natural health practitioner with a Masters in Clinical Nutrition & Dietetics from the University of Sydney. She has been writing for Plankton for Health since 2019 and contributes widely to many well-known health publications.