Clinical focus Omega-3 polyunsaturated fatty acids and vegetarian diets egetarians have a lower overall risk of common Summary chronic diseases, possibly due to a lower saturated Vfat and cholesterol intake than non-vegetarians.1 • While intakes of the omega-3 fatty acid ␣-linolenic acid However, vegetarians (and those who eat minimal (ALA) are similar in vegetarians and non-vegetarians, amounts of oily fish) may be at a disadvantage where intakes of eicosapentaenoic acid (EPA) and intake of essential fatty acids (EFAs) is concerned, and this docosahexaenoic acid (DHA) are low in vegetarians could potentially counteract some health benefits of the and virtually absent in vegans. vegetarian diet. In this article, we review EFA intake and • Plasma, blood and tissue levels of EPA and DHA are status of vegetarians and consider whether current intakes lower in vegetarians than in non-vegetarians, although in this population are sufficient to achieve and maintain the clinical significance of this is unknown. Vegetarians optimal health. We also explore the potential benefits of do not exhibit clinical signs of DHA deficiency, but adding supplemental sources of docosahexaenoic acid further research is required to ascertain whether levels (DHA) and eicosapentaenoic acid (EPA) derived from observed in vegetarians are sufficient to support microalgae, and make practical suggestions for optimising optimal health. EFA status in vegetarians. • ALA is endogenously converted to EPA and DHA, but Angela V Saunders the process is slow and inefficient and is affected by BS(Dietetics), genetics, sex, age and dietary composition. MA(Ldshp&Mgmt–HS), Functional and biological aspects of EFAs APD, Vegetarians can take practical steps to optimise Senior Dietitian, conversion of ALA to EPA and DHA, including reducing Science and Advocacy1 Fats in foods and the body contain saturated, intake of linoleic acid. Brenda C Davis monounsaturated and polyunsaturated fatty acids HBASc(Human • There are no official separate recommendations for Nutrition), RD, (PUFAs), the latter comprising omega-6 (n-6) and omega- intake of fatty acids by vegetarians. However, we Consulting Dietitian,2 3 (n-3) families. There are two EFAs: linoleic acid (LA), the and Lead Dietitian3 suggest that vegetarians double the current adequate parent of the n-6 fatty acid family; and ␣-linolenic acid Manohar L Garg intake of ALA if no direct sources of EPA and DHA are PhD, MND, MSc, (ALA), the parent of the n-3 fatty acid family. EFAs cannot consumed. Professor and Director, Nutraceuticals be synthesised by the body and therefore must be supplied • Vegetarians with increased needs or reduced Research Group4 by the diet. LA and ALA can be converted by enzymes into conversion ability may receive some advantage from long-chain PUFAs.2 LA is a precursor of arachidonic acid DHA and EPA supplements derived from microalgae. 1 Corporate Nutrition, (AA), and ALA is a precursor of EPA, DHA and A supplement of 200–300 mg/day of DHA and EPA is Sanitarium Health docosapentaenoic acid (DPA), with stearidonic acid (SDA) suggested for those with increased needs, such as and Wellbeing, Berkeley Vale, NSW. an intermediate in the pathway. The long-chain PUFAs are pregnant and lactating women, and those with MJA Open ISSN: 0025-729X 4 June 2012 1 2 22-26 reduced conversion ability, such as older people or 2 Kelowna, not technically “essential” because they can be produced British Columbia,©MJA Canada. Open 2012 www.mja.com.au those who have chronic disease (eg, diabetes). endogenously, but they can become essential if insufficient 3 Diabetes Wellness ClinicalCenter, Majuro, Focus precursor is available for their production. Marshall Islands. AA and EPA act as substrates for eicosanoids gene expression. DHA is particularly abundant in the 4 School of Biomedical cerebral cortex, retina, testes and semen.2,6,7 Sciences and Pharmacy, (prostaglandins, thromboxanes, leukotrienes and University of Newcastle, prostacyclins) that regulate inflammation, platelet LA and ALA share the same pathway and enzymes for Newcastle, NSW. aggregation and blood clotting, blood vessel contraction conversion to long-chain PUFAs. An excess of LA, angela.saunders@ and dilation, muscle contraction and relaxation, immune common in Western diets, can suppress conversion of ALA sanitarium.com.au responses and regulation of hormone secretion. to EPA and DHA and increase production of AA. This in Eicosanoids from n-3 PUFA (3-series) have opposing MJA Open 2012; 1 Suppl 2: 22–26 effects to those from n-6 PUFA (2-series). Eicosanoids doi: 10.5694/mjao11.11507 from AA are very potent and overproduction is associated with increased risk of disease (heart disease, cancer, diabetes, osteoporosis, and immune and Abbreviations inflammatory disorders).2-4 Eicosanoids from AA arachidonic acid AI adequate intake EPA are less potent and have anti-inflammatory ALA ␣-linolenic acid properties that assist in preventing coronary DHA docosahexaenoic acid heart disease, hypertension, autoimmune DPA docosapentaenoic acid diseases, arthritis and several cancers.2-4 EFA essential fatty acid EPA eicosapentaenoic acid Extremely powerful mediators called protectins LA linoleic acid (derived from DHA) and resolvins (derived n-3 omega-3 from DHA and EPA) help protect against and n-6 omega-6 resolve inflammation.5 Long-chain n-3 PUFAs PUFA polyunsaturated fatty acid also favourably affect cell membranes, SDA stearidonic acid enhancing intracellular signalling processes and 22 MJA Open 1 Suppl 2 · 4 June 2012 Clinical focus turn can have significant adverse consequences for 1 Dietary sources of omega-3 and omega-6 2,8,9 health. The balance of LA and ALA can be even more polyunsaturated fatty acids precarious in vegetarian diets, as vegetarians largely rely on conversion for the production of long-chain n-3 PUFAs Omega-3 polyunsaturated fatty acids and their metabolites.10,11 Other dietary factors associated ␣-linolenic acid (ALA) with reduced conversion are trans fatty acids and excesses Chia seed, chia oil of alcohol and caffeine. Nutritional inadequacies such as Flaxseed, flaxseed oil Canola oil protein deficiency or lack of vitamin and mineral cofactors, Walnut, walnut oil especially zinc, magnesium, niacin, pyridoxine and vitamin Hempseed, hempseed oil* C, can diminish the activity of conversion enzymes.12 Non- Soybean, soybean oil dietary factors that negatively affect conversion are Wheatgerm, wheatgerm oil Green leafy vegetables genetics, sex (young males convert less efficiently than Stearidonic acid (SDA) young females), advancing age, chronic disease (eg, Echium oil diabetes, metabolic syndrome, hypertension and Blackcurrant oil hyperlipidaemia) and smoking.12,13 Genetically modified soybean oil† Genetically modified canola oil† Dietary sources of PUFAs Eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and docosapentaenoic acid (DPA) Microalgae (plant DHA and EPA), not blue-green algae The n-3 PUFAs ALA and SDA originate from land plants, Fish and other seafood, particularly oily fish whereas EPA, DHA and DPA that occur in fish or other Meat (from grass-fed animals) seafood originate from marine plants (eg, microalgae). The Eggs n-6 fatty acid LA originates from land plants, and AA Breast milk Sea vegetables originates from animal-based foods. Box 1 shows important dietary sources of PUFAs. Omega-6 polyunsaturated fatty acids Linoleic acid (LA) EFA intake and status of vegetarians Safflower seed, safflower oil Sunflower seed, sunflower oil Sesame seed, sesame seed oil While ALA intakes are similar among vegetarians, vegans Walnut, walnut oil‡ and non-vegetarians, LA intakes tend to be somewhat higher Corn kernel, corn oil among vegetarians and vegans.14-18 In one study, vegetarians Wheatgerm, wheatgerm oil‡ ‡ and vegans averaged 19.4 g/day of LA and 1.34 g/day of ALA Soybean, soybean oil compared with 13.1g/day of LA and 1.43 g/day of ALA for Arachidonic acid 17 Poultry and red meats meat eaters. These findings are consistent with other Eggs 19 research studies. By excluding fish and other seafood, Milk intakes of EPA and DHA are low in vegetarian diets and * Not currently available in Australia as a food. † Regular soybean and canola virtually absent in the vegan diet. oils are not sources of SDA. ‡ Walnuts, wheatgerm and soybeans are sources Plasma, blood and tissue concentrations of EPA and of both ALA and LA. ◆ DHA are about 30% lower in vegetarians and 40%–50% lower in vegans than in non-vegetarians.6,14,17,20 A large 0.5% as ALA.25 The World Health Organization prospective study in the United Kingdom (196 meat- recommends that 5%–8% of calories consumed be from 26 eaters, 231 vegetarians and 232 vegans) reported no n-6 PUFA and 1%–2% from n-3 PUFA. Health change in long-chain n-3 PUFA status in vegetarians and authorities worldwide recommend daily intakes ranging 27-29 vegans over time (< 1 year to > 20 years), suggesting that from 250 to 550 mg/day for EPA and DHA. In endogenous synthesis of EPA and DHA from ALA was Australia, adequate intakes (AIs) for ALA have been set at sufficient to keep levels stable over many years.6 1.3 g/day for men and 0.8 g/day for women, and AIs for It is unknown whether the lower DHA levels reported in long-chain n-3 PUFAs are 160 mg/day for men and 90 mg/ vegetarian and vegan populations have adverse day for women (115 mg/day during pregnancy, and 30 consequences for health,19 although increased platelet 145 mg/day during lactation) (Box 2). aggregation has been reported and is thought to be linked Suggested