We learn how molecular sequencing helped test and eventually prove the endosymbiont hypothesis for the origin of mitochondria and chloroplasts; these eukaryotic organelles are now known to have evolved from once free-living bacteria. And we learn that although molecular phylogenetics provided the means with which to build a universal tree of life that includes microbes, it also provided the data that ultimately led us to question the precise nature of the tree. From the late s onwards, with dozens and eventually thousands of complete genome sequences in hand, biologists began to realize that the horizontal exchange of genes between distantly related organisms is an important evolutionary force.
Quammen also reminds us that, as early as , medical microbiologist Tsutomu Watanabe and colleagues provided evidence for horizontal gene transfer as a mediator of antibiotic resistance in bacteria. Current evidence suggests that this is also true for at least some macroorganisms such as plants. The tree of life is tangled, some branches hopelessly so. It brims with revelations from dozens of interviews with key players in their native habitats: the late Lynn Margulis, US champion of endosymbiotic theory; former Woese Lab members George Fox, Mitchell Sogin and Linda Bonen; and the environmental-DNA-sequencing legend and three-domains defender Norman Pace.
Some of the stories are laugh-out-loud funny. Their friendship survived. Other tales are shockingly intimate. I was surprised, for instance, to learn that Woese believed in a deity. We see the fiercely determined young scientist struggling to collect the data that he intuited would be important, and the brooding, combative mid-career professor fighting to have his beloved archaea and three-domains tree accepted by the scientific community.
Finally, there is the jaded, curmudgeonly legend wracked by a Darwin complex. None of the accolades showered on Woese seemed to matter he and many others clearly felt he deserved a Nobel prize, but he never got one. Above all, Quammen reminds us that science is an imperfect, highly social activity.
It happens in labs — but also in hallways and airports, over pizza or coffee. And as with any other human endeavour, egos and reputations play a huge part.
Friendships are forged, broken and mended over perceived or actual slights in the literature or at conferences. The actual data matter less often than we would like to admit. On this thorny question, Quammen is clear: among practising scientists, opinions differ greatly. And it is here that our twenty-first-century science connects back to the centuries-old struggle to classify and make sense of the world around us. Higher gestational age, older maternal age and longer maternal education were study-wide associated with greater use of vitamin D supplements.
Most of the infants received vitamin D supplements during the first 6 months of life in the European countries, whereas in Canada only half and in the USA and Australia very few were given supplementation. Some developed countries 1 — 4 have reported a resurgence of vitamin D deficiency and rickets in children and infants, in spite of national recommendations for vitamin D supplementation in infancy. The content of vitamin D in breast milk is very low 5 , 6 and thus exclusively breast-fed children have greater risk of developing vitamin D deficiency than children receiving infant formula 7.
Adequacy of prenatal vitamin D transfer depends on maternal vitamin D stores, which have been shown to be inadequate in many countries 8.
Natural food sources of vitamin D are few, the most common being egg yolk and fish 9. Vitamin D fortification of foods has become common in various countries. Typical fortified food items are milk, margarine, juices and breakfast cereals Also, infant formulas are fortified with vitamin D. Recommendations given for the use of vitamin D supplements during infancy are currently quite uniform in different countries 11 — 13 , while compliance with these recommendations varies widely 14 — There is a lack of internationally comparable data on vitamin D supplement use.
The TRIGR prospective nutrition questionnaires provide a unique opportunity to compare information on vitamin D supplement use in different countries. Through that study we aimed to determine how vitamin D supplements were used in infancy in the TRIGR countries and to assess adherence with national recommendations. Further, we assessed how infant feeding, sociodemographic and perinatal factors, region and maternal T1D were related to the use of vitamin D supplements.
Newborn infants with a biological first-degree relative affected by T1D as defined by the WHO were invited into the study. The families were recruited when the mother was in late pregnancy gestational age 35 weeks or more or immediately after the delivery. Human leucocyte antigen HLA genotyping was performed from cord blood or from a blood sample obtained before the age of 8 d.
Infants with increased HLA-conferred susceptibility to T1D were eligible to participate in the study. Of these, were born to women with diabetes and to unaffected women. The study was conducted according to the guidelines laid down in the Declaration of Helsinki.
The ethical committee of each site approved the study and signed consent was obtained from the parents or legal guardians of the infant. Breast-feeding was encouraged. Those infants who had received any infant formula other than Nutramigen prior to randomization were excluded. Finally, families having any other reasons e. Study formulas were enriched with vitamin D. Information on infant feeding was acquired from the family through standardized dietary interviews. Data on vitamin D supplement use were collected with a validated 18 FFQ at several time points during the first year of life.
The content of vitamin D in the supplements was not inquired and therefore the amount of supplemental vitamin D could not be calculated. In the present study, vitamin D supplementation refers to the use of vitamin D as supplements and does not include the intake of vitamin D from infant formulas or other foods. Mothers were interviewed by a study nurse or dietitian by telephone when the child was 2 weeks, 1 month, 2 months, 4 months and 5 months old, and at study centre visits at the ages of 3 and 6 months.
The use of vitamin D supplements was divided into two categories: i any use and ii daily use. The use of vitamin D supplements was recorded at each dietary interview. The associations of sociodemographic and perinatal factors with the use of vitamin D supplements at 6 months of age were analysed using univariate and multivariate logistic regression analyses. Vitamin D supplementation from 2 weeks to 6 months of age varied significantly by region Table 1.
Most of the infants who received vitamin D supplements were given them daily. There were no significant differences in the vitamin D supplementation of infants between mothers with and without T1D see online supplementary material, Supplemental Table 1. When vitamin D supplement use was examined in relation to exclusive breast-feeding, differences between those exclusively breast-fed up to at least 5 months and the others were notable only for Canada, with exclusively breast-fed infants receiving more supplementation than the other infants Table 2.
Maternal T1D, caesarean section and living in Central Europe II, Southern Europe and Canada were associated with less frequent use of vitamin D supplements, whereas higher gestational age was associated with more frequent use of vitamin D supplements at the age of 6 months in univariate analysis Table 3. When all the factors associated with the use of vitamin D supplementation at 6 months of age were considered simultaneously in a multivariate analysis, higher gestational age, older maternal age and longer maternal education were associated with more frequent use of vitamin D supplements Table 3.
The USA and Australia were not included in the analysis as the use of vitamin D supplements in those regions was very low. The use of vitamin D supplements was extremely rare in the USA and Australia, where very few infants received any supplementation during the first 6 months of life. Higher gestational age and maternal age and longer education were associated with more frequent use of vitamin D supplements.
Maternal T1D was not associated with vitamin D supplement use. Considerable difference in supplementation by breast-feeding status was only seen in Canada, where exclusively breast-fed infants received more supplementation.
The present study provides valuable comparative information about vitamin D supplement use in infancy from fifteen countries on three continents. The information on vitamin D supplementation was acquired by an FFQ which was validated against two 48 h recall interviews In the validation study, the agreement of the two methods for vitamin D supplementation was shown to be moderate. Limitations of the present study are that we did not assess either the dosage of vitamin D supplementation nor vitamin D intake from food. Nor had we an opportunity to measure vitamin D from the peripheral circulation.
We were not able to collect data regarding vitamin D supplement use after the age of 6 months. The generalizability of the findings is limited because the study subjects represent a select group of children as they have an increased HLA-conferred susceptibility to T1D as well as a family member affected by T1D. The use of vitamin D supplements may be more frequent in the present risk group since vitamin D intake has been associated with decreased risk of T1D With the exception of Australia, the overall recommended amounts of supplementation are now very similar during the first year of life in these countries and also the differences in the recommended age at introduction and end of supplementation are minor.
In the current study, the majority of the European children received vitamin D supplements. The lack of vitamin D recommendations for the general population in Australia is reflected in the results of the present study and it is likely that the children participating in TRIGR did not belong to those specific groups for whom supplementation has been recommended. In most TRIGR regions, there were no significant differences in vitamin D supplementation between infants exclusively breast-fed for at least 5 months and those who were not.
Canada was an exception in this respect; supplement use was more common in the exclusively breast-fed group. None of the formula-fed infants had been supplemented with vitamin D.
Some sociodemographic factors have been associated with the use of vitamin D supplements. Mothers who are younger have been reported to be less likely to give vitamin D supplements to their infants 16 , 38 ; this was also seen in our study. Having more than one child in the family may be associated with less use of vitamin D supplements 16 , Higher maternal education was associated with more frequent use of vitamin D supplements in the current study as has been reported before 40 , Vitamin D is particularly important for the skeleton because it is needed for Ca absorption from the intestine.
In the present study, vitamin D supplementation refers to the use of vitamin D as supplements and does not include the intake of vitamin D from infant formulas or other foods. For over 18's only Sensitivity analyses To independently compare early postnatal transfer with controls, and ongoing non-tertiary neonatal care with controls, we conducted matched pairwise rather than matched triplet analyses. When women at risk of extremely preterm delivery present at non-tertiary hospitals, transfer to a tertiary hospital can occur either before delivery prenatal or in utero transfer or after delivery following stabilisation of the infant in the non-tertiary hospital postnatal transfer. Arthur Mitchell. The Submissive Bride. College education was a cornerstone of the state committed to supporting and sustaining the social welfare of its citizens, ensuring better quality of life, greater contributions to social security because of presumably higher lifetime earnings, and the lower likelihood of needing unemployment benefits.
Insufficient vitamin D intake causes rickets in children and osteomalacia in adults. Vitamin D supplementation in infancy has also been associated with reduced risk of T1D There is also some evidence that vitamin D deficiency is associated with increased risk of cardiovascular and autoimmune diseases in adults and lower respiratory infections in children The main natural source of vitamin D is the synthesis in the skin induced by UV radiation from the sun 9.
With minimal sun exposure, for example at northern latitudes, or due to protective clothing or sunscreen, other sources of vitamin D are required. Because the intake of vitamin D from food is inadequate for most infants, supplementation is necessary. It is clear that new protocols and strategies are needed in some regions to ensure that families get enough information on the importance of adequate vitamin D intake, especially in infancy and childhood.