Sn-2 DHA Algal Oil Powder Fortified Infant Formula: Comparison With Human Milk And Advantage Analysis

Docosahexaenoic acid (DHA), a core member of the omega-3 long-chain polyunsaturated fatty acid family, is a key structural component of phospholipids in the cerebral cortex and retina of infants. It plays an irreplaceable role in neurodevelopment, visual maturation, and cognitive function establishment. As the primary nutritional alternative for infants when breastfeeding is insufficient, infant formula needs to not only meet the content requirement of DHA, but also approximate human milk in molecular structure and digestion-absorption patterns to achieve genuine nutritional equivalence.

Traditional infant formulas mostly supplement DHA with regular fish oil or algal oil, where the positional distribution of DHA on the triglyceride backbone differs significantly from that in human milk, resulting in low digestion and absorption efficiency. High sn-2 DHA algal oil powder, which optimizes the molecular distribution of DHA via structured lipid technology and is processed into powder form through microencapsulation, has become an important raw material for the human milk-like upgrading of infant formula. Among them, the sn-2 DHA algal oil series independently developed by Hubei Xinhe Biological Technology Co., Ltd. (Xinhe Biotech) achieves human milk-like simulation of DHA positional distribution through oriented enzymatic interesterification technology. Verified by the State Key Laboratory of Food Science and Resources of Nanchang University through systematic in vitro digestion, cell model and animal experiments, it demonstrates remarkable advantages in bioavailability and functional activity, providing a high-quality raw material solution for the nutritional upgrading of the infant formula industry.

I. Structural Characteristics and Physiological Value of DHA in Human Milk

1. Forms and Positional Distribution of DHA in Human Milk

Human milk is the gold standard for DHA nutrition in infants, with appropriate DHA content as well as unique molecular structural features. Specialized test data shows that the total DHA content in human milk is approximately 0.098 mg/mL, of which over 98% is bound to milk fat in the form of triglycerides, only a small amount exists in the form of phospholipids, and the proportion of free DHA is extremely low.

In terms of the positional distribution of fatty acids in triglycerides, human milk shows high structural specificity: DHA at the sn-2 position of triglycerides accounts for 56.25% of total triglyceride-bound DHA, meaning more than half of DHA is concentrated at the middle position of the glycerol backbone, while saturated fatty acids dominate the sn-1 and sn-3 positions. This distribution pattern is a nutritionally optimized result of long-term human evolution, and is highly compatible with the immature digestive system of infants.

2. Digestive Physiological Basis of sn-2 DHA

Human pancreatic lipase has strict sn-1,3 positional specificity: it only hydrolyzes the ester bonds at both ends of triglycerides and has no hydrolytic activity on the ester bond at the middle sn-2 position. Therefore, after intestinal digestion of dietary triglycerides, fatty acids at the sn-1 and sn-3 positions are released as free fatty acids, while fatty acids at the sn-2 position remain intact in the form of 2-monoglyceride (MAG).

Free DHA molecules have strong polarity and are prone to oxidation; they need to be re-esterified in the intestine before absorption, with a long metabolic pathway and low bioavailability. In contrast, 2-monoglyceride DHA (MAG-DHA) can directly enter the lymphatic circulation through the transport channels of intestinal epithelial cells without additional metabolic conversion, resulting in significantly higher absorption efficiency. This is the core structural mechanism why the bioavailability of DHA in human milk is much higher than that in regular infant formula.

II. Structural Defects and Absorption Shortcomings of DHA in Commercial Infant Formulas

1. DHA Structure in Traditional Infant Formulas Deviates Severely from Human Milk

Limited by raw material properties, DHA in commercial infant formulas is generally randomly distributed across the three positions of triglycerides, with an extremely low proportion at the sn-2 position. Tests on three mainstream commercial infant formulas show that DHA at the sn-2 position of triglycerides only accounts for 7.59% to 13.33% of total triglyceride-bound DHA, less than one quarter of the level in human milk, and the vast majority of DHA is distributed at the easily hydrolyzed sn-1 and sn-3 positions.

Although the total DHA content of most infant formulas is close to or even higher than that of human milk, the difference in structural distribution directly leads to the gap in nutritional efficacy. Currently, China's National Food Safety Standard: Infant Formula Food (GB 10765-2021) only specifies the addition range of DHA (3.6 mg to 9.6 mg per 100 kJ), and has not yet put forward requirements for the positional distribution of fatty acids, which is an important reason for the widespread phenomenon of "valuing content over structure" in the industry.

2. Significant Gap in Digestion and Absorption Efficiency Compared with Human Milk

Verified by an in vitro digestion model simulating the gastrointestinal tract of infants, the DHA digestion and absorption efficiency of commercial infant formulas differs by an order of magnitude from that of human milk:

The bioaccessibility of DHA in human milk reaches 63.09% ± 2.90%, meaning more than 60% of DHA can enter the micellar phase for intestinal absorption;

The DHA bioaccessibility of the three commercial formulas is only 16.50% to 17.25%, less than one third of that in human milk.

In terms of the composition of digestion products, 63.62% of DHA in human milk exists in the form of MAG-DHA after digestion, which is the main form for intestinal absorption. In contrast, the proportion of MAG-DHA in digested commercial formulas is extremely low, and most DHA is in free form. This not only leads to low absorption efficiency, but also makes DHA prone to oxidative inactivation in the intestine, and may even increase the gastrointestinal metabolic burden of infants.

III. Product Performance and Core Advantages of Xinhe Biotech Sn-2 DHA Algal Oil Powder

To address the structural shortcomings of traditional DHA raw materials, Xinhe Biotech adopts oriented enzymatic interesterification technology to modify the molecular structure of DHA algal oil derived from Schizochytrium sp., directionally enrich DHA at the sn-2 position of triglycerides, and then processes it into algal oil powder through microencapsulation and spray drying, achieving triple improvements in structure, stability and absorption efficiency.

1. Molecular Structure Highly Close to Human Milk, Leading sn-2 Proportion in the Industry

The positional distribution test of Xinhe's algal oil series conducted by the Nanchang University laboratory shows that the sn-2 DHA proportion varies significantly among different grade products, and the high-specification products are highly close to the level of human milk:

For regular commercial algal oil, DHA at the sn-2 position accounts for only 2.98% to 6.01% of total triglyceride-bound DHA, at the same level as that in traditional infant formulas;

For Xinhe Biotech's regular winterized algal oil, the sn-2 DHA proportion is 9.81%, slightly better than common commercial products;

For Xinhe Biotech's basic-grade sn-2 winterized algal oil, the sn-2 DHA proportion can reach 34.23%, far exceeding similar raw materials on the market;

For different batches of Xinhe Biotech's high-specification sn-2 winterized algal oil, the sn-2 DHA proportion can reach up to 50.48%, highly close to the 56.25% level in human milk, making it one of the DHA algal oil raw materials with the best structural simulation degree in China.

This structural feature fundamentally solves the problem that the digestion mode of traditional DHA raw materials is inconsistent with human milk, laying a molecular foundation for infant formula to achieve "human milk-like DHA nutrition".

2. Microencapsulated Powder Technology, Fully Compatible with Infant Formula Production

Xinhe Biotech processes high sn-2 DHA algal oil into uniform powder through microencapsulation coating and spray drying, perfectly matching the production and storage requirements of infant formula:

Excellent shelf stability: Food-grade milk-derived wall materials form a dense microcapsule structure, isolating DHA from contact with oxygen, light and moisture, and greatly delaying oxidative rancidity of DHA. Under conventional storage conditions, the DHA retention rate during shelf life is significantly higher than that of liquid oil, which can ensure stable nutritional activity of infant formula within the 2-year shelf life without rancid odor.

Strong processing compatibility: The powder particle size is highly matched with the formula matrix, with high uniformity in dry blending, and no risks of oil floating, agglomeration or delamination. It can be directly applied to dry, wet and dry-blending production processes of infant formula, with low processing loss and good batch consistency.

Pleasant sensory performance: With the dual effects of deodorization process and microencapsulation taste masking, the product has no inherent fishy odor of algal oil. It does not affect the original flavor of infant formula when added, with a light taste, and is more acceptable to infants.

3. Digestion and Absorption Efficiency Close to Human Milk Level

Based on the in vitro infant gastrointestinal digestion model and Caco-2 intestinal epithelial cell model, the Nanchang University laboratory systematically verified the absorption efficiency of Xinhe Biotech's product series. The results show that its digestion and absorption performance is significantly better than that of regular algal oil and highly close to human milk:

Remarkably high bioaccessibility: The DHA bioaccessibility of Xinhe Biotech's high sn-2 batch algal oil reaches 58.86% ± 1.95%, which is 2 to 3 times that of regular commercial algal oil and more than 3.5 times that of commercial infant formula. There is no significant difference from the 63.09% level of human milk, achieving the design goal of "structural simulation leading to absorption equivalence".

Digestion product composition matching human milk: After digestion, the proportion of MAG-DHA in the product is highly similar to that in human milk, and the proportion of free DHA is greatly reduced, which fully conforms to the digestive physiological pattern of infants and reduces the intestinal metabolic burden.

Higher intestinal epithelial transport efficiency: Experiments on the Caco-2 cell monolayer model show that the apparent permeability coefficient (Papp) of DHA is significantly positively correlated with the sn-2 proportion. The transport efficiency of Xinhe Biotech's algal oil series follows the order: high sn-2 batch > basic-grade sn-2 winterized oil > regular winterized oil > regular commercial algal oil, which directly proves that the high sn-2 structure can significantly improve the intestinal absorption efficiency of DHA.

IV. Functional Value of Xinhe Biotech Sn-2 DHA Algal Oil: Evidence-Based Evidence from Animal Experiments

To further verify the in vivo functional activity of the product, the Nanchang University laboratory conducted animal experiments with gradient control groups using Xinhe Biotech's DHA algal oil with different sn-2 contents as test raw materials, verifying the functional advantages from the dimensions of neurodevelopment, brain accumulation and gut microbiota.

1. More Efficient Brain Accumulation to Support Neurocognitive Development

Existing randomized controlled studies have confirmed that DHA supplementation in early life has a positive effect on psychomotor development and visual development of infants. Animal experiments further confirm that under the premise of exactly the same total DHA intake, the higher the sn-2 proportion of dietary DHA, the more significant the benefit to brain development:

Higher brain DHA accumulation: The total DHA content in the brain of mice in the high sn-2 DHA group (corresponding to Xinhe Biotech's high-specification sn-2 algal oil) reaches 1.809 mg/g brain tissue, significantly higher than 1.112 mg/g in the low sn-2 group. Among them, the contents of active forms that can efficiently cross the blood-brain barrier, such as lysophosphatidylcholine DHA (LPC-DHA), non-esterified DHA (NE-DHA) and lysophosphatidylethanolamine DHA (LPE-DHA), increase significantly with the rise of sn-2 proportion.

Synchronous activation of transport pathways: High sn-2 DHA can significantly upregulate the expression of MFSD2A, a key transporter protein at the blood-brain barrier (1.40 times that of the control group), and simultaneously increase the levels of fatty acid transporter proteins in the brain such as FABP5, FATP1 and ACSL6, promoting DHA entry and utilization in the brain from the molecular pathway level.

Better cognitive performance: The Morris water maze test shows that mice in the high sn-2 DHA group have shorter escape latency, longer stay in the target quadrant after platform removal, and more times crossing the original platform position, with significantly better spatial learning and memory ability than the regular DHA group. The open field test also shows that mice in the high sn-2 group have higher exploration desire and activity level.

More complete neural structure development: Mice in the high sn-2 DHA group have more complete morphology and denser structure of neurons in the hippocampus; the number of neurons in the CA1, CA3 and DG regions increases by 1.31 to 1.57 times compared with the control group. Meanwhile, the expression of key synaptic development proteins such as brain-derived neurotrophic factor (BDNF), synaptophysin (SYN) and postsynaptic density protein 95 (PSD-95) in the hippocampus is significantly increased, providing a solid structural basis for cognitive development.

2. Regulating Gut Microbiota to Exert Gut-Brain Axis Synergistic Benefits

The nutritional effect of DHA is not limited to the brain; it can also indirectly affect neurodevelopment through the gut-brain axis. Experimental data shows that Xinhe's high sn-2 DHA can significantly optimize the gut microbiota of model animals:

It increases the alpha diversity of gut microbiota and reduces the Firmicutes/Bacteroidetes (F/B) ratio, improving the structure of gut microecology;

It significantly increases the contents of short-chain fatty acids (SCFAs) such as acetic acid, propionic acid and isobutyric acid in the intestine, and the n-butyric acid content in the high sn-2 group is significantly higher than that in the control group. As core signaling molecules of the gut-brain axis, SCFAs can affect central nervous system development through the circulatory system, while maintaining intestinal barrier function and reducing the risk of intestinal discomfort in infants.

3. Good Edible Safety

A 4-week animal feeding experiment shows that Xinhe's DHA algal oil with different sn-2 proportions has no significant effect on the body weight gain and average daily food intake of mice, and the growth and development indexes of all groups are consistent, proving that high sn-2 DHA algal oil has good edible safety and will not increase the metabolic burden of infants.

The human milk-like upgrading of infant formula is deepening from "content matching" to "structure and function matching". Xinhe Biotech's sn-2 DHA algal oil powder breaks through the structural limitations of traditional DHA raw materials, highly simulates human milk in the positional distribution of triglycerides, and achieves a stable powder form combined with microencapsulation technology. It is significantly superior to regular DHA raw materials in terms of digestion and absorption efficiency, brain development benefits and intestinal health regulation, serving as a core solution for the nutritional upgrading of infant formula.

In line with the recommendations in the Expert Consensus on DHA Supplementation for Pregnant/Lactating Women and Infants in China, sn-2 structured DHA raw materials further improve the nutritional utilization efficiency of DHA and better fit the physiological needs of infants. In the future, with the development of more clinical studies and the improvement of industry standards, sn-2 structured DHA raw materials will promote the infant formula industry to shift from "quantity addition" to "quality optimization", and ultimately provide infants with nutrition support closer to human milk.

References

[1] State Key Laboratory of Food Science and Resources, Nanchang University. Final Report on Bioavailability and Functional Evaluation of High sn-2 DHA Algal Oil [R]. 2024.

[2] Birch E E, Garfield S, Hoffman D R, et al. A randomized controlled trial of early dietary supply of long-chain polyunsaturated fatty acids and mental development in term infants [J]. Developmental Medicine & Child Neurology, 2000, 42(3): 174-181.

[3] Expert Group on DHA Supplementation for Pregnant/Lactating Women and Infants in China. Expert consensus on DHA supplementation for pregnant/lactating women and infants in China [J]. Chinese Journal of Reproductive Health, 2015, 26(2): 99-103.