【Brain Health Ingredient Series 5】 Docosahexaenoic Acid (DHA): The “Neural Gold” for Building the Brain

1. What is Docosahexaenoic Acid (DHA)?

Docosahexaenoic acid (DHA) is an omega-3 polyunsaturated fatty acid [1] that the human body cannot synthesize on its own, and thus must be obtained from dietary sources. It is classified as an 'essential fatty acid.' DHA constitutes about 20% of the brain’s gray matter and approximately 50% of the retina, making it a critical nutrient for brain function and visual health from fetal development through adulthood [2]. Natural sources include deep-sea fish such as salmon and tuna, as well as microalgae, and it is a key component in infant formula.

2.Basic Characteristics

（Image source: Food Research Association）

DHA is a light yellow to orange oily liquid that is soluble in most organic solvents but poorly soluble in water. It is sensitive to heat, oxygen, and light, and prone to oxidative degradation [3]. As a lipid-soluble compound, DHA must be consumed with dietary fats for optimal absorption (30–50%) [14]. It can cross both the blood–brain barrier and the retinal barrier, where it preferentially accumulates in the hippocampus (the memory center) and retinal photoreceptor cells [4,21]. The main production methods include fish oil extraction and microbial fermentation.

3. Functional Effects: From Metabolic Regulation to Cognitive Protection

Image source：Bie Nana. Neuroprotective Effects of Docosahexaenoic Acid and Its Mechanism Research [D]. Tianjin University of Science and Technology, 2022.

• Delays Cognitive Decline in the Elderly: DHA enhances neuronal membrane fluidity and increases the secretion of soluble amyloid precursor protein-alpha (sAPPα) [7,19], modulating secretase activity to reduce the formation and aggregation of β-amyloid (Aβ). These effects lower the risk of Alzheimer’s disease [7,19]and improve symptoms such as memory loss and slower response times in the elderly [24].

• Inhibits Oxidative Stress and Inflammation to Protect Neuronal Cells [23]: DHA is metabolized into protectins and resolvins, which not only mitigate inflammation [5,17] but also exert neuroprotective effects [6,20] by inhibiting the expression [8] and release of adhesion molecules and inflammatory mediators.

4. Regulatory Status: A Globally Recognized Essential Nutrient

• China: In March 2010, the Ministry of Health officially approved DHA algal oil (from Schizochytrium and other microalgae) as a new food resource (Announcement No. 3, 2010), with a recommended intake of ≤300 mg/day (as pure DHA). In 2023, DHA algal oil was listed in the 'Health Food Raw Material Catalogue – Nutrient Supplements (2023 Edition).

• United States: The FDA has granted both GRAS and NDIN certifications for DHA, allowing its use in various foods. Recommended intake is 300 mg/day for pregnant women and 1 g/day for older adults.

• European Union: DHA algal oil derived from Schizochytrium sp. is authorized as a novel food for use in both infant and general food products. The established safe upper limit for adults is 3 g/day.

• Australia & New Zealand: In 2017, FSANZ approved DHA algal oil from Schizochytrium sp. for use in infant formula.

• Japan: Foods containing microalgae-derived DHA are classified directly as processed foods.

• World Health Organization (WHO): Recommends 20 mg/kg DHA per day for infants and a combined daily intake of 200–500 mg EPA + DHA for adults to help prevent chronic diseases.

5. Clinical Research Support: The “Golden Nutrient” for Brain Development

•  A double-blind, randomized, placebo-controlled study involving 102 healthy middle school students was conducted over 30 days. The experimental group received daily DHA algal oil softgels, while the control group received placebos without DHA. Cognitive assessments—including memory scales, recall tests, and blood DHA levels—showed that the DHA group exhibited significant improvements in short-term memory retention, information recall, and attention, indicating notable short-term cognitive benefits.

•  A double-blind clinical trial by the University of Gothenburg, Sweden, demonstrated [22] that daily supplementation with 1.8 g of DHA for 24 months in older adults with mild cognitive impairment resulted in a 19% improvement in memory test performance and a 40% slower rate of hippocampal volume loss, suggesting substantial neuroprotective effects.

•  A meta-analysis covering 15 randomized controlled trials (RCTs) confirmed that [24], among healthy adults aged 18–90 years, whether or not they had mild memory complaints, daily DHA supplementation averaging over 580 mg led to significant enhancement of episodic memory performance.

•  A longitudinal cohort study of 1,490 dementia-free adults aged 65 and above [10], with a median follow-up of 7.2 years, found that individuals with higher blood DHA levels had a 49% lower risk of developing Alzheimer’s disease and a 44% lower risk of all-cause dementia.

6. Safety Profile: Long-Term Use without Adverse Effects

•  Acute toxicity studies have shown that even a single dose far exceeding the recommended level (up to 10 g) caused no adverse reactions such as nausea or diarrhea.

•  Long-term studies (3 g/day for 5 years) demonstrated no abnormalities in liver, kidney, or coagulation function, and no dependence.

• In special populations—pregnant or lactating women, and infants—DHA supplementation within the recommended range is not only safe but also beneficial for fetal and infant development [11,12]. Mild gastrointestinal discomfort (e.g., bloating) may occur in a small number of individuals and can be alleviated by taking DHA with meals.

7. Recommended Intake

• Infants (0–3 years): Obtain DHA through breast milk (with maternal DHA supplementation), formula, or algal oil DHA. Recommended 100 mg/day.

• Children and adolescents (4–17 years): 250–500 mg/day, achievable through deep-sea fish consumption (2–3 times weekly, 100 g per serving) or algal/fish oil supplements.

• Adults: 250–1000 mg/day; for individuals engaged in intensive mental work, 1000–2000 mg/day. Algal DHA is recommended for its higher purity and absence of fishy odor.

• Elderly: 1000–2000 mg/day, divided into two doses with meals. Co-supplementation with vitamin E is advised to prevent DHA oxidation and improve absorption.

8. Precautions

•  When choosing fish oil-based DHA, pay attention to 'purity' and 'heavy metal content.' Always prefer products tested by third-party laboratories to avoid contamination.

•  Algal DHA and fish-derived DHA provide equivalent benefits, with the former being ideal for vegetarians or individuals allergic to fish.

• DHA supplements should not replace natural dietary sources—regular consumption of deep-sea fish and nuts rich in omega-3 fatty acids remains important.

•  If mild diarrhea occurs after supplementation, reducing the dose or taking DHA with meals usually alleviates the issue.