Essential Fats, Human Biology & the Truth About DHA
Is it possible to thrive on plant-based omega-3s? And what does our biology really tell us about the kind of fat we need?
We’ve been taught for decades that the omega-3 fatty acids EPA and DHA are best sourced from fish, and that those on plant-based diets are inherently at risk of deficiency. But emerging evidence is challenging that belief — and prompting a deeper look at how our bodies actually use fats, and what kind of diet supports long-term wellness.
What Are Essential Fats, Really?
Essential fatty acids (EFAs) are types of fat that the body cannot produce on its own — we have to obtain them from food. The two essential fats are:
Alpha-linolenic acid (ALA) – an omega-3 found in flax, chia, hemp, walnuts, and Ahiflower®
Linoleic acid (LA) – an omega-6 found in seeds, nuts, and whole plant foods
From ALA, the body can synthesise longer-chain omega-3s like EPA and DHA — the same ones commonly found in fish. This has led many to assume that plant-based diets are inherently deficient. However, new research tells a more nuanced story.
Blood Tests Don’t Tell the Full Story
Much of the concern about vegan or vegetarian omega-3 intake has come from blood testing. When plant-based eaters show lower blood levels of DHA, it's often assumed their brain and body are missing out.
But that’s not always true.
Newer research using isotope tracing shows that the body can biosynthesise ALA into DHA and deliver it to where it’s most needed — such as the brain — even if blood levels appear modest. What matters more is how the body functions, not just what shows up as measured in the blood.
In fact, supplementing with high-dose DHA can sometimes have unintended consequences, including raising LDL cholesterol and increasing the risk of atrial fibrillation in susceptible individuals.
Your Body Knows What It’s Doing
The body isn’t passive in all this — it adjusts based on need. When DHA intake from food is low, the body tends to increase its own production. Research shows that people on vegan diets often have more efficient conversion rates than those who consume fish, suggesting that the body adapts intelligently to different diets.
Several factors influence how well this conversion happens:
Omega-6 to omega-3 ratio in the diet
Genetic factors, especially FADS1 and FADS2 gene variations
Life stage, such as pregnancy, when DHA demand (and conversion) naturally rises
Overall nutrition, including vitamin B12 and other methylation cofactors and zinc
For people with low conversion ability, a plant-based fat called stearidonic acid (SDA) offers a more efficient path. SDA skips the slowest step in the conversion pathway and rapidly becomes EPA. Ahiflower is the richest known natural plant source of SDA, and clinical trials suggest it performs as well — or even better — than fish oil for many clinical outcomes.
Brain Health, B12, and Methylation
One common concern is brain health — particularly for those who are pregnant, ageing, or neurodivergent. However, plant-based populations do not show higher rates of neurodegenerative disease when their B12 status is adequate.
This is an important detail: it’s not just about having DHA, but being able to use it. The body needs healthy methylation — a cellular process that relies on B12, folate, and B6 — to get DHA across the blood-brain barrier. Even those consuming fish oil may struggle to utilise it effectively if B12 is low.
Lifestyle Still Matters Most
There’s no supplement that can override the effects of lifestyle. Studies show that people who eat more plant foods, fibre, and polyphenols tend to experience:
Better blood lipid profiles
Lower inflammation
Slower rates of cognitive decline
Enhanced omega-3 metabolism
This may explain why vegans and vegetarians, despite lower DHA intake, often have better heart and brain health outcomes than the general population. In some studies, the benefits attributed to fish may stem more from overall lifestyle than the fish itself.
Rethinking What’s “Essential”
When we look at the broader picture — including human evolution, metabolic pathways, and ecological impact — a new understanding emerges:
The only fats we biologically must consume are ALA and LA — both found in plants
EPA and DHA can be made by the body when needed, especially when overall health and nutrition are optimised
Most healthy adults are estimated to require only 2.4–3.8mg/day of DHA for maintaining healthy brain tissue — an amount the body can easily produce
Excess DHA may not be beneficial, and in some cases may be counterproductive
SDA from Ahiflower provides a highly efficient, sustainable source of long-chain omega-3s without relying on fish or algae
Rather than assuming deficiency and reaching for high-dose supplements, we can begin with a more respectful premise: that the human body is adaptive, intelligent, and responsive when given the right inputs.
These include:
Whole food sources of ALA and SDA
A balanced omega-6 to omega-3 ratio
Sufficient B12, folate, and B6
A lifestyle that reduces inflammation and supports methylation
Ahiflower supplementation for those who want an extra omega-3 and GLA boost
Final Reflection
The conversation around DHA has been shaped more by industry messaging and outdated testing than by current evidence. It’s time we trusted our bodies a little more, and our marketing a little less.
A well-designed plant-based diet, supported by smart naturopathic principles, appears not only sufficient for essential fat intake — it may, in fact, be optimal.