The composition of human breast milk changes in the first two months of life, adapting itself to the evolving needs of the growing new-born. Lipids in milk are a source of energy, essential fatty acids (FA), fat-soluble vitamins, and vital bioactive components. Information on breast milk FA of Malaysian lactating women is scarce. Based on convenience sampling, a total of 20 Malay breastfeeding women who fulfilled the inclusion criteria were recruited. Breast milk was collected three times from each subject at consecutive intervals of 2–3 weeks apart. A total of 60 breast milk samples were collected and classified into “transitional milk” (n = 8), “early milk” (n = 26) and “mature milk” (n = 26). All milk samples were air freighted to University of Groningen, Netherlands for analysis. The dominant breast milk FA were oleic acid, constituting 33% of total fatty acids, followed by palmitic acid (26%). Both these FA and the essential FA, linoleic acid (10%) and alpha-linolenic acid (0.4%), showed no significant changes from transitional to mature milk. Breast milk ratio of n-6:n-3 polyunsaturated fatty acids (PUFA) was comparatively high, exceeding 10 throughout the lactation period, suggesting a healthier balance of PUFA intake is needed in pregnancy and at postpartum.

Breast-fed infants are susceptible to vitamin D deficiency rickets. The current vitamin D ‘adequate intake’ (AI) for 0–6-month-old infants is 10 µg/d, corresponding with a human milk antirachitic activity (ARA) of 513 IU/l. We were particularly interested to see whether milk ARA of mothers with lifetime abundant sunlight exposure reaches the AI. We measured milk ARA of lactating mothers with different cultural backgrounds, living at different latitudes. Mature milk was derived from 181 lactating women in the Netherlands, Curaçao, Vietnam, Malaysia and Tanzania. Milk ARA and plasma 25-hydroxyvitamin D (25(OH)D) were analysed by liquid-chromatography-MS/MS; milk fatty acids were analysed by GC-flame ionisation detector (FID). None of the mothers reached the milk vitamin D AI. Milk ARA (n; median; range) were as follows: Netherlands (n 9; 46 IU/l; 3–51), Curaçao (n 10; 31 IU/l; 5–113), Vietnam: Halong Bay (n 20; 58 IU/l; 23–110), Phu Tho (n 22; 28 IU/l; 1–62), Tien Giang (n 20; 63 IU/l; 26–247), Ho-Chi-Minh-City (n 18; 49 IU/l; 24–116), Hanoi (n 21; 37 IU/l; 11–118), Malaysia–Kuala Lumpur (n 20; 14 IU/l; 1–46) and Tanzania-Ukerewe (n 21; 77 IU/l; 12–232) and Maasai (n 20; 88 IU/l; 43–189). We collected blood samples of these lactating women in Curaçao, Vietnam and from Tanzania–Ukerewe, and found that 33·3 % had plasma 25(OH)D levels between 80 and 249·9 nmol/l, 47·3 % between 50 and 79·9 nmol/l and 19·4 % between 25 and 49·9 nmol/l. Milk ARA correlated positively with maternal plasma 25(OH)D (range 27–132 nmol/l, r 0·40) and milk EPA+DHA (0·1–3·1 g%, r 0·20), and negatively with latitude (2°S-53°N, r −0·21). Milk ARA of mothers with lifetime abundant sunlight exposure is not even close to the vitamin D AI for 0–6-month-old infants. Our data may point at the importance of adequate fetal vitamin D stores.

Iodine and selenium are essential for thyroid hormone synthesis. Iodine and selenium interact. Pregnancy increases the maternal iodine requirement. We previously reported inadequate iodine status in pregnant Dutch women. Since little is known about their selenium intake, we investigated the iodine status and selenium intake in relation to iodine and selenium supplement use during pregnancy. Iodine status was established in 201 apparently healthy pregnant women as 24 h iodine excretion (24H-UIE; sufficient if median ≥225 µg), iodine concentration (24H-UIC; ≥150 µg/L) and iodine/creatinine ratio (24H-UICR; ≥150 µg/g). Selenium intake was calculated from 24 h selenium excretion. Iodine status in pregnancy proved insufficient (medians: 24H-UIE 185 µg; 24H-UIC 95 µg/L; 24H-UICR 141 µg/g). Only women taking 150 µg iodine/day were sufficient (median 24H-UIE 244 µg). Selenium intake was below the Estimated Average Requirement (EAR; 49 µg/day) in 53.8%, below the Recommended Dietary Allowance (RDA; 60 µg/day) in 77.4% and below the Adequate Intake (AI; 70 µg/day) in 88.7%. Combined inadequate iodine status and selenium intake <RDA was found in 61%. Women who want to become pregnant should, consistently with WHO and ETA recommendations, be advised to use a 150 µg iodine-containing supplement. Concomitant selenium supplementation should be added to this advice, at least in The Netherlands.

Pregnant and lactating women and breastfed infants are at risk of vitamin D deficiency. The supplemental vitamin D dose that optimises maternal vitamin D status and breast milk antirachitic activity (ARA) is unclear. Healthy pregnant women were randomised to 10 (n10), 35 (n11), 60 (n11) and 85 (n11) µg vitamin D₃/d from 20 gestational weeks (GW) to 4 weeks postpartum (PP). The participants also received increasing dosages of fish oil supplements and a multivitamin. Treatment allocation was not blinded. Parent vitamin D and 25-hydroxyvitamin D (25(OH)D) were measured in maternal plasma at 20 GW, 36 GW and 4 weeks PP, and in milk at 4 weeks PP. Median 25(OH)D and parent vitamin D at 20 GW were 85 (range 25–131) nmol/l and ‘not detectable (nd)’ (range nd–40) nmol/l. Both increased, seemingly dose dependent, from 20 to 36 GW and decreased from 36 GW to 4 weeks PP. In all, 35 µg vitamin D/d was needed to increase 25(OH)D to adequacy (80–249 nmol/l) in >97·5 % of participants at 36 GW, while >85 µg/d was needed to reach this criterion at 4 weeks PP. The 25(OH)D increments from 20 to 36 GW and from 20 GW to 4 weeks PP diminished with supplemental dose and related inversely to 25(OH)D at 20 GW. Milk ARA related to vitamin D₃dose, but the infant adequate intake of 513 IU/l was not reached. Vitamin D₃dosages of 35 and >85 µg/d were needed to reach adequate maternal vitamin D status at 36 GW and 4 weeks PP, respectively.