22nd September 2017, Volume 130 Number 1462

Michele Eickstaedt, Kathryn L Beck, Cathryn A Conlon

Adequate dietary intakes of long chain polyunsaturated fatty acids (LCPUFAs) are required during pregnancy to support both the mother and foetus.1,2 Omega-3 (n-3) PUFAs include alpha-linolenic acid (ALA: 18:3n-3) and the LCPUFAs docosahexaenoic acid (DHA: 22:6n-3), eicosapentaenoic acid (EPA: 20:5n-3) and docosapentaenoic acid (DPA: 22:5n-3). Omega-6 (n-6) PUFAs include linoleic acid (LA: 18:2n-6) and the LCPUFA arachidonic acid (AA: 20:4n-6). Both ALA and LA are unable to be synthesised by the human body, so must be obtained from the diet.3 These essential fatty acids (EFA) are required for the synthesis of LC-PUFAs, which are important for normal growth, development and physiological functions in the foetus.4 DHA is critical during the time when the neural tube closes5 and throughout pregnancy as it accumulates in the foetal brain and retinal tissues.6 The amount of DHA accumulated by the foetus occurs mainly in the third trimester of pregnancy,7 and is influenced by the maternal diet.8

It is important that women meet recommendations for LC-PUFA intakes, in particular DHA, to ensure a healthy pregnancy and optimal foetal development.2 In New Zealand and Australia, the National Health and Medical Research Council (NHMRC) have set adequate intakes (AIs) of 115mg/d for combined DHA, DPA and EPA for pregnant women, with a suggested dietary target (SDT) of 430mg/d for women.9 Several international organisations recommend pregnant women should aim to achieve at least 200mg of DHA per day,10,11 with recommended intakes for combined DHA plus EPA set at 300mg/d.11

Fish and seafood are rich sources of n-3 LC-PUFAs.11 However, during pregnancy women may decrease their intakes of fish and seafood due to concerns regarding food safety and foetotoxic effects of environmental contaminants such as mercury.12 Although including fish and seafood in the diet may contribute substantially to meeting DHA recommendations, many pregnant women assume that avoiding fish and seafood is a safer option.12 In New Zealand, fish and seafood are a relatively available food source, however, there is limited information regarding n-3 and n-6 PUFA intakes in pregnant women. The aim of this study was to determine dietary intakes and sources of n-3 and n-6 PUFAs in pregnant women living in New Zealand, and whether dietary recommendations are being met.

Methods

Participants and study design

This cross-sectional study recruited women aged over 16 years old, in their third trimester of pregnancy (≥28weeks’ gestation) from all regions in New Zealand. There were no exclusion criteria. A sample size of 450 pregnant women was determined as appropriate to determine the mean value of DHA to within ±20mg based on a 5% significance level. Participants were recruited using convenience and snowball sampling techniques, which included the distribution of informative material (eg, email invitations, flyers and posters) to district health boards and health professionals caring for pregnant women. Community strategies included targeting workplaces, press releases and social networking media. Pregnant women were invited to take part in this anonymous study by accessing a link to an online survey. The survey gathered information on participants’ socio-demographic characteristics, medical history, health during pregnancy and dietary intake. Eligibility was confirmed at the start of the online survey, and all participants then provided consent. This project was reviewed and approved by the Massey University Human Ethics Committee (MUHEC): Northern, Application 14/027.

Assessment of dietary polyunsaturated fatty acids

Dietary assessment was conducted using a validated New Zealand semi-quantitative PUFA FFQ (NZ-PUFA FFQ).13 The NZ-PUFA FFQ is a reasonably short (~15 minutes) self-administered online tool designed and validated to capture the usual intake of PUFAs in healthy adults in New Zealand. Thirty-six New Zealand-specific items that provide ≥0.1g PUFA/100g are included and are grouped as meats, sausage/delicatessen meats, fish/seafood, eggs, fats/oils/spreads, vegetables, breads, cereals, nuts, desserts, takeaway foods and PUFA containing supplements. The NZ-PUFA FFQ calculates respondents’ intakes of each individual PUFA (LA, ALA, AA, EPA, DPA and DHA) based on New Zealand food composition data. Average PUFA intakes are calculated in grams (g) per day according to the selection of predefined portion sizes and frequency intakes available for each item in the FFQ, with the frequency intakes ranging from ‘never’ to ‘daily intakes’ over the past three months. The FFQ also takes into account infrequent use of PUFA supplements, such as once or twice per week. In addition, open-ended questions are available to allow the identification of items not included in the FFQ, such as specific brands and types of foods, n-3 fortified products and PUFA supplements. Further information regarding the development and validation of the NZ-PUFA FFQ and the food composition database used are described elsewhere.13

To determine the contribution of different foods to the total intake and individual PUFAs, main food sources resulting from the FFQ responses were combined into nine main food groups according to their similarities in nutritional composition. These food groups included delicatessen meats and sausages, takeaway foods, snacks and desserts, milk, fish and seafood, vegetables, meat, poultry and eggs, fats and oils, nuts and seeds, and cereals.

Statistical analysis

Variables were tested for normality using the Shapiro-Wilk and Kolmogorov-Smirnov tests as well as visual inspection of normality plots. Descriptive statistics for participants’ characteristics are presented using mean ± SD or median (25th, 75th percentiles) for continuous data and frequency summary statistics for categorical data. Participants were divided into subgroups for statistical analysis, according to consumption of n-3 supplements. Frequency tests were performed to determine the proportion of participants meeting the recommended intakes for PUFAs and the contributions of food sources to total and individual PUFA intakes. In addition, the Chi-square test and odds ratio were used to determine the likelihood of achieving recommended DHA intakes during pregnancy. A P value of <0.05 was considered statistically significant. All statistical analysis was performed using SPSS statistical software package for Windows (version 21.0, IBM Incorporation, New York, USA).

Results

Characteristics of participants

The characteristics of the 596 participants who completed the study are shown in Table 1. The majority of women (37.4%) were from the largest urban city in New Zealand (Auckland), were of New Zealand European ethnicity (74.3%) and were between 28 and 32 weeks gestation (50.8%). Most had planned their pregnancy (75.9%) and were pregnant for the first time (37.2%).

Table 1: Participant characteristics.

Characteristics

N=596

Age (Years)a

 

31 [28, 35]

Ethnicity n (%)b

New Zealand European

Māori

Pacific Island

Other

442 (74.3)

56 (9.4)

20 (3.4)

77 (12.9)

Country of birth n (%)

New Zealand

Other

460 (77.2)

136 (22.8)

Length of time in New Zealand n (%)c

 

Less than 5 years

5–9 years

10–19 years

20 years plus

27 (20.1)

35 (26.1)

42 (31.3)

30 (22.4)

Highest educational level n (%)

 

Primary school

Secondary school

University degree

Postgraduate degree

Prefer not to answer

Other

None

3 (0.5)

157 (26.3)

268 (45.0)

120 (20.1)

13 (2.2)

31 (5.2)

4 (0.7)

Gestational age n (%)

 

Between 28–32 weeks

Between 33–37 weeks

Between 38–40 weeks

40 weeks and over

303 (50.8)

214 (35.9)

65 (10.9)

14 (2.3)

Current pregnancy planned n (%)d

Yes

No

448 (75.9)

142 (24.1)

Number of pregnancies including current pregnancy n (%)d

 

1

2

3

4 or more

222 (37.2)

180 (30.5)

104 (17.6)

84 (14.3)

aMedian [25th, 75th percentile]; bMissing data for two participants; cn = 134 (missing data for two participants); dMissing data for six participants. 

Most of the participants followed an omnivorous diet (96.1%). The majority of participants (75.3%) reported excluding higher risk foods from their diets during pregnancy, including fish and seafood (19%).

Dietary intakes of PUFAs

The median [25th, 75th percentile] and mean ± SD dietary intakes of total and individual PUFAs for the study population and by n-3 supplement use are shown in Table 2. The data, particularly for the n-3 LC-PUFAs intakes, is skewed, with visually large differences between the mean and median values. Thus, results are reported using medians [25th, 75th percentile].

Table 2: Polyunsaturated fatty acid intakes compared to international dietary recommendations for fatty acids.

 

International dietary recommendations (mg/d)

Daily intakes (mg/d)

Mean (SD)

Daily intakes (mg/d)

Median [25th, 75th percentile]

n (%) meeting reference values

 

All participants (n=596)

ALA

NHMRC9

 

AI - 1,000

 

1,620 (1,130)

 

1,300 [790, 2,120]

 

383 (64.3)

DHA

Perinatal Lipid Intake Working Group10 FAO & WHO11

 

200

 

200 (250)

 

110 [50, 250]

 

184 (30.9)

Total n-3 LC-PUFA (EPA+DPA+DHA)

NHMRC

 

 

 

AI - 115a

SDT - 430

UL - 3,000

 

 

410 (530)

 

 

 

 

220 [120, 520]

 

 

 

457 (76.7)

178 (29.9)

591(99.2)

Total EPA+DHA

FAO & WHO

 

300

 

360 (510)

 

180 [90, 460]

 

208 (34.9)

LA

NHMRC

 

AI - 10,000

 

13,240 (6,890)

 

11,580 [8,840, 15,760]

 

384 (64.4)

AA

FAO & WHO

 

UL - 800

 

90 (50)

 

90 [60, 110]

 

596 (100)

 

Participants taking n-3 supplements (n=117)

ALA

NHMRC

 

AI - 1,000

 

1,570 (1,110)

 

1,260 [770, 2,130]

 

71 (60.7)

DHA

Perinatal Lipid Intake Working Group FAO & WHO

 

200

 

430 (310)

 

370 [210, 530]

 

93 (79.5)

Total n-3 LC-PUFA

(EPA+DPA+DHA)

NHMRC

 

 

 

 

AI - 115

SDT - 430

UL - 3,000

 

 

920 (700)

 

 

 

770 [480, 1,140]

 

 

 

116 (99.1)

95 (81.2)

114 (97.4)

Total EPA + DHA

FAO & WHO

 

300

 

870 (680)

 

680 [440, 1,090]

 

105 (89.7)

LA

NHMRC

 

AI - 10,000

 

14,450 (6,800)

 

13,040 [9,900, 17,880]

 

88 (75.2)

AA

FAO & WHO

 

UL - 800

 

90 (50)

 

90 [70, 120]

 

117 (100)

 

Participants not taking n-3 supplements (n=479)

ALA

NHMRC

 

AI - 1,000

 

1,630 (1,130)

 

1,310 [810, 2,130]

 

312 (65.1)

DHA

Perinatal Lipid Intake Working Group FAO & WHO

 

200

 

140 (200)

 

90 [50, 160]

 

91 (19.0)

Total n-3 LC-PUFA

(EPA+DPA+DHA)

NHMRC

 

 

 

AI - 115

SDT - 430

UL - 3,000

 

 

280 (380)

 

 

 

 

180 [100, 300]

 

 

 

 

341 (71.2)

83 (17.3)

477 (99.6)

Total EPA + DHA

FAO & WHO

 

300

 

230 (340)

 

140 [70, 240]

 

103 (21.5)

LA

NHMRC

 

AI - 10,000

 

12,940 (6,880)

 

11,330 [8,650, 15,290]

 

296 (61.8)

AA

FAO & WHO

 

UL - 800

 

90 (40)

 

90 [60, 110]

 

479 (100) 

aAI for pregnant women aged 19–50 years.
AI, adequate intake; AA, arachidonic acid; ALA, alpha-linolenic acid; DHA, docosahexaenoic acid; EPA, eicosapentaenoic acid; LA, linoleic acid; PUFA, polyunsaturated fatty acid; SDT, suggested dietary target; UL, upper limit.
Definitions of Nutrient Reference Values.9
Adequate intake—the average daily nutrient level based on observed or experimentally-determined approximations or estimated of nutrient intake by a group (or groups) of apparently healthy people that are assumed to be adequate.
Upper level of intake—the highest average daily nutrient intake level likely to pose no adverse health effects to almost all individuals in the general population. As intake increases above the UL, the potential risk of adverse effects increases.
Suggested dietary target—a daily average intake from food and beverages for certain nutrients that may help in prevention of chronic disease. 

Intakes of omega-3 PUFAs

The majority of the pregnant women were meeting the National Health and Medical Research Council (NHMRC) Nutrient Reference Values (NRVs) for ALA (64.3%). Although most women (76.7%) met the NHMRC NRV for combined DHA/EPA/DPA intakes (115mg/d), only one-third of the whole group were meeting the NHMRC SDT of 430mg/day (29.9%), and international recommendations for DHA of 200mg/day (30.9%), and for total EPA plus DHA of 300mg/day (34.9%) (Table 2). Median intakes of DHA were 110 [50, 250] mg/d. Only 117 participants (19.7%) reported taking supplements containing n-3 LC-PUFAs and the majority of these participants met the NHMRC NRVs for total and individual n-3 LC-PUFAs. Nearly 80% of participants taking n-3 supplements met DHA recommendations compared to only 19% of the participants not taking n-3 supplements. In addition, participants taking n-3 supplements were 16.5 times more likely to meet DHA recommendations compared to participants not taking supplements (P<0.001). Further statistical analysis revealed that approximately 33% of all participants had DHA intakes below 70mg/day.

The NHMRC recommend an UL of 3,000mg/d for total n-3 LC-PUFAs. Three participants taking PUFA supplements and two participants not taking PUFA supplements exceeded the upper limit.

Intakes of omega-6 PUFAs

The majority of participants were meeting the NHMRC NRV for LA (64.4%). All participants had AA intakes below the recommended UL of 800mg/d with a median intake of 90 [60, 110] mg/d (Table 2).

Food sources of PUFAs

The major food sources contributing to total polyunsaturated fatty acid intakes were fats and oils, including vegetable oils, butter, lard and margarine. This food group was the main contributor towards LA (43.2%) and ALA (55.7%) intakes. Meat, poultry and eggs were the main contributor to AA (60.0%) intakes. The main contributor to DHA intake was fish and seafood (84.8%), which included all fresh, frozen and canned fish as well as shellfish and fish paste. Fish and seafood were also the main contributor to EPA (82.1%) and DPA (46.2%) intakes. Only minor contributions (less than 4.0%) to individual PUFA intakes were observed for takeaway foods, snacks and desserts, milk, nuts and seeds, and vegetables (see Figure 1).

Figure 1: Contributions (%) of food groups to estimated mean daily intakes of individual PUFAs within study population (n=596). 

c

AA, arachidonic acid; ALA, alpha-linolenic acid; DPA, docosapentaenoic acid; LA, linoleic acid; DHA, docosahexaenoic acid; EPA, eicosapentaenoic acid; PUFA, polyunsaturated fatty acid. 

Consumption of fish, seafood and meat

A large proportion of participants indicated ‘never’ or ‘less than once per month’ for intakes of fresh/frozen fish (26.4%), canned fish (54.7%) and shellfish/seafood (82.7%). Less than 15% of participants reported consuming fresh/frozen fish (12.3%), canned fish (9.5%) and shellfish/seafood (1.5%) at least twice per week. Over half of participants reported consuming chicken (63.1%) and beef (60.8%) at least twice per week.

Discussion

The majority of pregnant women in this study were not meeting international recommendations for omega-3 polyunsaturated fatty acids including DHA intake. The FFQ was completed during the last trimester of pregnancy when eating habits are likely to be firmly established and are indicative of DHA supply to the foetus.

Intakes of omega-3 PUFAs

DHA accumulated in the brain peaks during the third trimester of pregnancy and first year of life, which corresponds with a period of rapid brain growth and development.14 Although metabolic adaptations during pregnancy may upregulate the maternal ability to convert ALA into DHA15 and there is a priority use of DHA stored in adipose tissue,16 it is not clear whether these mechanisms are adequate to meet increased foetal growth and development demands.1 Most participants (76.7%) had a higher intake than the NHMRC AI of 115mg/d for total n-3 LC-PUFAs (EPA, DHA plus DPA).9 The AI is the average nutrient level assumed to be adequate based on estimates of nutrient intakes in healthy individuals.9 However, the SDT (average nutrient intake, which may help in the prevention of chronic disease) of 430mg/d9 was met by only 29.9% of women, and the majority of pregnant women (69.1%) were not meeting international recommendations for DHA of 200mg/d.10,11 Nearly one-third (33%) had DHA intakes below 70mg/d (the amount of n-3 fatty acids (predominantly DHA) accumulated in the foetus per day during trimester three).17 Similar results were observed in Australian pregnant women (n=94), with median intakes of 75mg/d DHA with just 9% of participants meeting the daily 200mg consensus recommendation.18 Other studies in Western countries have observed similar inadequate intakes of DHA in pregnant women.19–25

Although n-3 supplements are not recommended by current nutrition guidelines for pregnant women in New Zealand,26 approximately one-fifth (n=117) of participants took n-3 supplements. These participants were 16.5 times more likely to meet DHA recommendations than participants not taking n-3 supplements. Similarly, a Canadian study in 600 pregnant women also found participants taking n-3 supplements (30%) were over 10 times more likely to meet DHA recommendations compared to participants not taking supplements.19 Three participants taking n-3 supplements exceeded the UL of 3,000mg/day.9

Intakes of omega-6 PUFAs

Total PUFA intakes comprised 86.7% n-6 PUFAs (99.3% LA and <1% AA), with most pregnant women meeting the NHMRC NRVs for n-6 PUFAs. Mean dietary intakes were 13,240±6,890mg/d of LA and 90±50mg/d of AA, which are consistent with the levels observed in pregnant women in Canada20–22 and the US.23,25 Dietary intakes of LA that exceed recommended intakes may decrease the synthesis of n-3 LC-PUFAs as well as their incorporation into tissues, because both PUFA families share the same metabolic pathway and compete for the same enzymes.27 Although AA is required for normal foetal growth and development, it is a precursor of pro-inflammatory eicosanoids, which may be unfavourable during gestation.8 Pregnant women in this study were consuming well below the upper limits for AA; however, as intakes of LA were above recommended levels, they may benefit from reducing intakes of LA, the majority of which came from fats and oils (43.2%).

Food sources of PUFAs

Despite fish and seafood being the primary source of DHA (84.8%), EPA (82.1%) and DPA (46.2%) intakes, the majority of participants were not meeting the suggested intakes of two to three 150g servings of most fish types (low mercury) per week.28 This finding is similar to that of pregnant women in other countries.21,29 This may be due to concerns regarding mercury contamination, with a decrease in fish consumption observed among pregnant women in the US following a national mercury advisory.30 The consumption of fish and seafood during pregnancy provides benefits such as the provision of other nutrients, lays the foundation for improved lifelong dietary habits and reduces the risks of toxicity that may occur with supplementation as well as providing omega-3 PUFAs.

Study strengths and limitations

The validated FFQ to assess PUFA intakes was an important strength of this study. The online structure allowed the collection of nationwide data from a large number of participants (n=596). In addition, the NZ-PUFA FFQ asked about dietary intakes over the past three months, thereby increasing the likelihood of detecting foods not typically eaten on daily basis, such as fish and seafood.

The NZ-PUFA FFQ has been validated in New Zealand adults.13 Although not validated specifically in pregnant women, findings from this study are comparable to findings from other studies using FFQs to assess PUFA intakes in pregnant women.20–25 In addition, other studies have shown that FFQs are a valid way to assess dietary intakes of DHA in pregnant women.31,32 However, FFQs are dependent on participants’ memory and interpretation of portion sizes, and have a requirement for a minimal level of literacy. Regardless of how omega-3 and omega-6 dietary intakes are assessed, analysis is dependent on the availability of an accuarate and complete food composition database.21 The majority of foods (86%) in the database considered to be major dietary contributors to n-3 LCPUFA intake were derived from New Zealand-specific analytical data.13

The use of snowballing recruitment techniques and a volunteer convenience sample may have attracted participants who were generally more health conscious and interested in their dietary intake. Therefore, it is not possible to exclude the risk of selection bias in this study and therefore findings are unlikely to be representative of all pregnant women living in New Zealand.

Conclusion

In conclusion, the majority of pregnant women in this study had low intakes of n-3 LC-PUFA including DHA and did not meet international consensus recommended intakes. The low intake of fish and seafood in this study population contributed to women not meeting these recommendations. Future research should investigate dietary intakes and biomarkers of n-3 LC-PUFAs intakes in a representative sample of pregnant women in New Zealand. Further studies and interventions should focus on ways to promote optimal intakes of long-chain omega-3 fatty acids during pregnancy. Strategies to overcome barriers to the consumption of fish and seafood during pregnancy should be explored.

Summary

Adequate dietary intakes of long chain polyunsaturated fatty acids (LCPUFAs) such as omega 3 and omega 6 are required during pregnancy to support both the mother and growing baby. An important omega 3 fatty is docasahexaenoic acid (DHA). DHA is mainly found in fish and seafood, however women may restrict their intake of fish and seafood during pregnancy due to concerns regarding food safety and foetotoxic effects of environmental contaminants such as mercury. Most of the 500-plus women in their third trimester of pregnancy who completed an online food frequency questionnaire had low intakes of omega 3 fatty acids including DHA during pregnancy. Women who are currently pregnant or planning to become pregnant should aim to eat a variety of foods from the four food groups every day, including cooked fish. There is little concern with canned tuna, canned salmon, mackerel or sardines, farmed salmon, terakihi, blue cod, hoki, john dory, monkfish, warehou, whitebait and flat fish like flounder, as the mercury levels in these fish are seen as low risk.

Abstract

Aim

To investigate dietary intakes and food sources of polyunsaturated fatty acids in New Zealand pregnant women.

Method

Women (n=596) 16 years plus in trimester three of pregnancy completed an online food frequency questionnaire validated for omega-3 and omega-6 polyunsaturated fatty acids.

Results

Estimated median [25th, 75th percentile] intakes of omega-3 polyunsaturated fatty acids were: 1,300 [790, 2,120] mg/d alpha-linolenic acid (adequate intake 1,000mg/d); 220 [120, 520] mg/d total long chain omega-3 polyunsaturated fatty acids (adequate intake 115mg/d); and 110 [50, 250] mg/d docosahexaenoic acid (recommended 200mg/d). Only 30.9% of participants consumed more than 200mg/d docosahexaenoic acid. Participants taking omega-3 supplements (19.6%) were 16.5 times more likely to meet recommendations for docosahexaenoic acid. Fish and seafood were the main contributors to docosahexaenoic acid (84.8%) intakes, yet only 21.7% of women consumed fish at least twice per week. Intakes of omega-6 polyunsaturated fatty acids were 11,580 [8,840, 15,760] mg/d linoleic acid (adequate intake 10,000mg/d) and 90 [60, 110] mg/d arachidonic acid (upper limit 800mg/d).

Conclusion

Most participants did not meet recommended intakes for docosahexaenoic acid, which may be partly due to low intakes of fish, seafood and omega-3 supplements.

Author Information

Michele Eickstaedt, Public Health Nutritionist, School of Food and Nutrition, College of Health, Massey University, Auckland; Kathryn L Beck, Senior Lecturer, School of Food and Nutrition, College of Health, Massey University, Auckland; Cathryn A Conlon, Senior Lecturer, School of Food and Nutrition, College of Health, Massey University, Auckland.

Acknowledgements

The authors thank all the volunteers who completed this study: PC Tong for helping with data handling, Owen Mugridge for developing the study website, Matt Levin, Peter Jeffery and Steve Chalmers for technical support on issues related to the online NZ-PUFA FFQ and database. 

Correspondence

Dr Kathryn Beck, School of Food and Nutrition, College of Health, Private Bag 102904, North Shore 0745, Auckland.

Correspondence Email

k.l.beck@massey.ac.nz

Competing Interests

Nil.

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