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Test on Fish Oil Supplements Revealed Omega-3 Fatty Acid Content Varied Greatly Among Samples Harmful Contaminants Detected in All Samples with 4 Exceeding EU Limits Industry Urged to Promptly Improve

  • 2022.11.15

Despite their hectic lifestyle, many Hong Kong people are health-conscious enough to consume supplements made from fish oil. These products promote their richness in omega-3 fatty acids, such as DHA and EPA, claiming to help provide essential nutrients for the body. However, according to the Consumer Council’s test on 25 samples of fish oil supplements, the detected DHA and EPA content per capsule were found to vary by 13 times and 50 times amongst the 23 capsule form samples respectively, whereas the fill content weight per capsule (i.e. excluding the soft gel capsule) does not necessarily correlate with the respective nutrient content. Besides, the percentage of saturated fatty acids (SFAs) and trans fatty acids (TFAs) varied considerably across samples, with the SFAs percentage ranging from 1.7% to 35.4%, and the TFAs percentage ranging from 0.4% to 8.7%. As both SFAs and TFAs could increase the levels of bad cholesterols in the body, consumers are reminded to select carefully. The detected DHA or EPA amounts of 3 samples were lower than their labelled values by over 70% and 30% respectively. The Council has passed the relevant information to the Centre for Food Safety (CFS) for follow-up.

A point of concern was that all samples were detected with different types of contaminants. 24 samples were detected with the contaminant 3-MCPD, of which 3 had a detected level that exceeded the upper limit of the EU standard. 14 samples were detected with the genotoxic carcinogen glycidol, of which 1 sample had detected levels of glycidol and 3-MCPD which both exceeded the EU’s upper limit whereas the same sample’s detected levels of the antioxidant butylated hydroxytoluene (BHT) also exceeded the requirements of the Hong Kong regulations. Besides, 6 samples were detected with polycyclic aromatic hydrocarbons (PAHs), with the detected levels in 1 sample exceeding the EU’s upper limit. According to the test results, some samples had higher contents of bad fatty acids and contaminants that exceeded the limit, not only going against the consumer’s wish for better health, but on the contrary increasing the health risks for long-term consumption. The Council urges traders to improve their product formulas and quality, so as to safeguard consumers’ health. 

The Council sourced 25 samples of fish oil supplements from major retail outlets, with 23 samples in the form of soft gel capsules, of which 5 samples did not state the suitable age range of their intended users, while amongst the other samples, according to the claims on their labelling, 4 were suitable for adults, 6 were suitable for adults and children, 6 were suitable for babies and children, and 2 were specifically for pregnant or breastfeeding women, or those planning to conceive. The capsule-type samples ranged from $0.24 to $9.5 per capsule, a price difference of over 38 times. The 2 remaining samples were liquid formulas, priced at $0.23 and $3.4 per millilitre respectively, a difference of almost 14 times. 

13-time and 50-time Differences in DHA and EPA Content Per Capsule

According to a study by the European Food Safety Authority (EFSA) on the health claims of DHA and EPA, these nutrients are recognised as useful for maintaining essential functions such as normal blood pressure, blood lipid levels, cardiovascular functions, heart health, and blood circulation, etc. Fish oil products generally tout the benefits of being “rich” or “highly concentrated” in omega-3 fatty acids, usually labelled as containing omega-3 fatty acids such as DHA and EPA. When purchasing such products, consumers might expect the nutrient content per capsule to be more or less similar, yet according to the test results, the DHA contents of the 23 soft gel capsule samples ranged from 30.9mg to 444.8mg per capsule, a difference of over 13 times. Based on per 100g, for the sample with the greatest discrepancy between the actual and labelled DHA content, it claimed to have a DHA content of 60.6g on its nutrition label, yet the test results revealed it only contained 10.3g DHA, which was 83% lower than the labelled value. Another sample from the same brand had detected DHA contents 73.2% lower than the labelled value. For another type of fatty acid EPA, within the soft gel capsule samples, the detected amount ranged from 12.3mg to 631.4mg per capsule, varying over 50 times. Amongst this, the detected EPA level of 1 sample was 31.7% lower than its labelled value. While it was labelled as containing 180mg of EPA per 3 capsules, only 123mg per 3 capsules was detected in the test. 

No Definite Correlation Between the DHA and EPA Contents and the Capsule Fill Weight

The Council reminds consumers that the weight of the capsule’s fill content does not necessarily bear correlation with its DHA and EPA content. Amongst the 23 samples of soft gel capsules, the fill content of each capsule weighed 0.3g to 1.5g after deducting the capsule itself. The detected DHA content ranged from 30.9mg to 444.8mg per capsule across the samples, while the detected EPA content ranged from 12.3mg to 631.4mg per capsule. The sample with the highest fill weight (1.5g) was detected with a total DHA and EPA content of 412.5mg per capsule, whereas that for the sample with the lowest fill weight (0.3g) was 225.9mg, thus consumers should pay heed to the ingredients and daily dosage on the labelling to calculate the nutrient intake. Based on the total detected DHA and EPA content per capsule, the Council compared the average price per 100mg content. While the average unit price amongst all samples was $1.60, that for the cheapest sample was only $0.17, a difference of over 37 times compared with the highest-priced sample which cost $6.52. In light of this, consumers should choose prudently. 

Huge Disparity in “Bad Fatty Acids” Amongst Samples; Select with Care

SFAs could increase the level of bad cholesterols in the body, while excessive intake over a prolonged period could increase the risks of cardiovascular diseases. The SFAs percentage also varied significantly amongst samples, with the lowest being 1.7% and the highest being 35.4%. Similarly, TFAs could increase the bad cholesterols level and even lower the level of good cholesterols, posing even greater health risks than SFAs. The detected TFAs percentage also recorded a huge variance ranging from 0.4% to 8.7%. As many consumers purchase fish oil supplements hoping to take in healthy polyunsaturated fatty acids (PUFAs) such as DHA and EPA, it would be unsatisfactory if the product had a higher percentage of TFAs and SFAs.  

All Samples Dedicated for Pregnant Women or Children Detected with Carcinogenic Contaminants

PAHs might be produced in the process of heating, baking and smoking food. Benzo[a]pyrene (B[a]P), one of the more common types of PAHs found in fat-containing foods cooked at high temperatures, is classified as a genotoxic carcinogen and intake should be avoided as far as practicable. 6 of the tested samples were detected with PAHs, of which 2 were found with B[a]P at detected levels of 1.4μg/kg and 12.7μg/kg respectively. This included 1 sample of fish oil capsules for pregnant women with a detected B[a]P level that exceeded the upper limit of EU regulations by over 5 times, while its total detected levels of 4 types of PAHs also reached 54.0μg/kg, exceeding the upper limit of 10.0μg/kg set out in EU regulations.

During the 160°C high-temperature deodorisation process of oils, 3-MCPD esters (3-MCPDE) might be formed. Excessive consumption of 3-MCPD over a prolonged period would adversely affect the kidney functions, central nervous system, and male reproductive system of experimental animals. Except for 1 sample dedicated for pregnant women, all samples were detected with 3-MCPD, of which the detected amounts in 3 samples exceeded the EU’s upper limit. However, taking the sample with the highest detected amount for instance, when making reference to the Tolerable Daily Intake (TDI) set by the Joint Food and Agriculture Organization/World Health Organization (WHO) Expert Committee on Food Additives (JECFA) and EFSA, it would require a daily consumption of 15 capsules and 8 capsules respectively in order to exceed the recommended TDI. As long as consumers consume the supplements according to the recommended serving size, it should not result in excessive 3-MCPD intake. On the other hand, glycidyl esters (GE) might be formed during the deodorisation process of oils at over 200°C. Upon hydrolysation in the gastrointestinal tract, GE would release the genotoxic carcinogen glycidol. Glycidol was found in 14 samples, of which 1 sample had detected levels of glycidol and 3-MCPD which both exceeded the upper limits stipulated by the EU. Since these contaminants might exist in various types of foods, such as cooking oil and biscuits, consumers should nurture healthy eating habits to avoid excessive intake of such contaminants. 

Besides, close to 90% (22) of the samples were detected with the persistent organic pollutants (POPs) dioxins, dioxin-like polychlorinated biphenyls, or non-dioxin-like polychlorinated biphenyls. Although the detected amounts did not exceed the upper limit set by the EU, POPs, which are released through the manufacturing process, are an agent classified as carcinogenic to humans and could persistently exist in the environment, eventually accumulating in the human body through the food chain. In the test, 1 sample of fish oil capsules for pregnant women had the highest detected levels of dioxins and dioxin-like polychlorinated biphenyls, whereas the sample with the highest detected levels of non-dioxin-like polychlorinated biphenyls was a sample of fish oil capsules for children. Consumers should pay extra heed before purchase.

Some food manufacturers might add antioxidants in foods with high fat and oil contents so as to slow down the rancidification process resulting from oxidation. While the current test included 9 types of antioxidants, 1 sample was detected with 430.6mg/kg BHT, higher than the permitted level of 200mg/kg set out in the Preservatives in Food Regulation.

Fish Oil Supplements Also Contain Vitamins but Prolonged Excessive Intake Might Pose Health Risks

     Despite the health benefits of the supplements’ nutrient contents to the body, it does not mean the more, the better. The detected vitamin A content of 3 samples and the detected vitamin D content of 4 samples were higher than the labelled values. Out of these, the detected amounts of vitamin A for 1 sample for babies not only exceeded the claims by 25%, its detected vitamin D content was even higher than claimed by 3.3 times, far exceeding the tolerance limit of 80%.

The Council reminds consumers that while vitamin A boasts various benefits including the prevention of certain eye diseases, and maintaining the health of the respiratory tract, intestines, hair, nails and skin, excessive intake over a prolonged period could lead to poisoning or various health issues, such as liver damage, hair loss, impairment of the central nervous system, and even foetal deformation. On the other hand, vitamin D, which is usually formed by the human body through sun exposure, could assist general body functions such as normal growth of bones, nerve conduction, etc. However, prolonged intake of a high dosage of vitamin D supplement could easily lead to hypercalcemia, and might cause arrhythmia and other issues. Although the vitamin A and D contents per fish oil capsule may not be high, inaccurate labelling information on the product’s nutrient content not only affects the fundamental consumer right to have accurate information, but could also be harmful to individuals concerned with their nutrient intake.

     The Council reminds consumers that omega-3 fatty acids could be absorbed through regular diet, such as by consuming seafood. Consumers should seek the advice of medical professionals on the necessity of consuming additional supplements, while paying heed to the following recommendations:

General Adults

  • According to the recommendations of the American Heart Association, adults should consume fish at least twice a week, especially species with a higher fat ratio, in order to ensure a sufficient omega-3 fatty acid intake. The CFS recommends that better options would include salmon, skipjack tuna, false halibut, barramundi, black bonito, mangrove red snapper, etc. Vegetarians could consume algae oil supplements as a source of DHA;
  • Individuals with hyperlipidemia should consult professional medical advice if they need to supplement a higher dosage of omega-3 fatty acids. As omega-3 could suppress platelet activity, individuals with a prescription of warfarin or other anticoagulants should avoid ingesting fish oil products of high dosages;

Pregnant or Breastfeeding Women

  • As seafood might be a source of neurotoxins such as mercury, pregnant or breastfeeding women should select various types of seafood with a higher DHA and lower mercury content with 8 to 12 ounces as the recommended intake amount;
  • The Hong Kong Medical Association points out that according to medical literature, consumption of omega-3 during pregnancy might reduce the chance of premature birth, while also lowering the risks of perinatal mortality, hospital care for newborns, and low birthweight;


  • As long as children maintain a balanced diet to ensure sufficient nutrient intake, they might not need extra omega-3 supplements.


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