What Is Bioavailability?
Bioavailability is the proportion of a nutrient that your body can absorb and use after you consume it. A nutrient listed on a label does not guarantee your body will use all of it. The chemical form, the food matrix, your individual physiology, and what else you eat alongside it all affect how much actually reaches your bloodstream and tissues.
This concept matters for algae supplements in several specific ways. Chlorella requires broken-cell-wall processing because the intact cellulose wall blocks nutrient absorption. We covered the fermented vs regular distinction in our chlorella hub. Omega-3 bioavailability varies with the chemical form: triglyceride-bound, ethyl ester, or phospholipid-bound omega-3 are absorbed at different rates. We explained what to check on labels in our omega-3 label guide.
What Affects Bioavailability in Supplements
- Chemical form (omega-3): Ethyl ester omega-3 is only 40 to 48 per cent as bioavailable as triglyceride-form in human studies; a significant gap, not a marginal one
- Cell wall processing (algae): Intact chlorella cell walls are made of cellulose that human digestive enzymes cannot break down; broken-cell-wall or fermented chlorella is required for meaningful nutrient access
- Fat intake timing: Carotenoids (including violaxanthin and chlorophyll precursors in phytoplankton) show near-zero absorption without dietary fat; 3 to 5 grams of fat in a meal is sufficient to make the difference
- Mineral form: Non-haem iron from algae absorbs less efficiently than haem iron; pairing with vitamin C at the same meal meaningfully improves uptake
- Individual variation: Genetics, gut microbiome, age, and concurrent medications all affect absorption; the same dose produces different blood levels in different people
Why Bioavailability Claims Deserve Scrutiny
You will see supplement brands claim "superior bioavailability" without specifying what they are comparing against, at what dose, or in which population. A meaningful bioavailability claim should reference a specific study comparing two forms of the same nutrient in human subjects, not just an in vitro absorption test.
When you see bioavailability used as a marketing differentiator, check whether the claim is backed by published human data or is extrapolated from laboratory conditions that do not reflect your digestive system.
For your daily choices, the most practical bioavailability factors are the ones you can control: taking fat-soluble nutrients with food, choosing broken-cell-wall chlorella over whole-cell, and pairing plant-based iron sources with vitamin C. These steps often matter more than the differences between competing product formats.
What our research found
When we compared absorption evidence across omega-3 formats and algae processing methods while developing our product formulations, three findings shaped what we specify on our labels and how we advise customers on timing.
The omega-3 form difference is not marginal. In the West et al. 2021 randomised crossover trial, ethyl ester omega-3 delivered around 73 per cent of the plasma EPA+DHA response achieved by triglyceride-form supplements; a meaningful gap when trying to reach the 250 mg daily intake associated with EFSA cardiovascular health outcomes.
Published crossover trials comparing phospholipid-bound omega-3 (krill oil) against ethyl ester supplements have reported 2.7- to 5.0-fold higher plasma concentrations for the phospholipid form.
To be fair to ethyl esters: they are the cheapest form to manufacture at high EPA/DHA potency, which is why most pharmaceutical-grade fish oil prescriptions use this form. The bioavailability gap is real, but the format is not a scam; it is a cost-access trade-off.
Without fat in your meal, carotenoid absorption is essentially zero. One study found no measurable carotenoid uptake when vegetables were eaten with fat-free dressing. As little as 3 to 5 grams of fat is enough to enable uptake. Whole-cell phytoplankton retains the full nutrient matrix that oil extraction removes, including phospholipids, pigments, and trace minerals. That is a genuine compositional advantage over algae oil capsules.
The fat-timing issue only affects the fat-soluble fraction. But if you are taking whole-cell phytoplankton specifically for violaxanthin or chlorophyll, an empty stomach is a poor choice.
When we specified fermentation for our Chlorella, cell wall integrity was the deciding variable. We reviewed published data comparing mechanical milling against fermentation-based processing and found that mechanical disruption produces inconsistent cell wall breakdown across batches. Fermentation achieves more complete and uniform disruption.
That consistency was what we required before putting a nutrient claim on the label. You cannot claim the chlorophyll and protein content is bioavailable if a proportion of cells arrive at the gut intact.
Sources
- West AL et al. Pharmacokinetics of Supplemental Omega-3 Fatty Acids Esterified in Monoglycerides, Ethyl Esters, or Triglycerides in Adults in a Randomized Crossover Trial. Journal of Nutrition. 2021;151(5):1111–1118. PubMed
- Watanabe F et al. Characterization and bioavailability of vitamin B12-compounds from edible algae. Journal of Nutritional Science and Vitaminology. 2002;48(5):325–331. PubMed
Cara Hayes, MSc Nutrition and Dietetics (University of Sydney), writes all content in the Phytality Knowledge Centre. Read our editorial policy.
This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Consult your GP or other healthcare professional before starting any supplement.
Methodology and Disclosure
Phytality manufactures algae supplements where bioavailability is a relevant quality variable. We have a commercial interest in bioavailability being understood by consumers. Absorption factors described reflect established nutrition and pharmacology science. EFSA cardiovascular intake thresholds (250 mg EPA+DHA daily) are referenced for context; no specific authorised health claim text is quoted or made in this article.
Last reviewed: March 2026
