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Changes in dietary habits after migration and consequences for health: a focus on South Asians in Europe
Gerd Holmboe-Ottesen,Margareta Wandel
Food & Nutrition Research , 2012, DOI: 10.3402/fnr.v56i0.18891
Abstract: Background: Immigrants from low-income countries comprise an increasing proportion of the population in Europe. Higher prevalence of obesity and nutrition related diseases, such as type 2 diabetes (T2D) and cardiovascular disease (CVD) is found in some immigrant groups, especially in South Asians. Aim: To review dietary changes after migration and discuss the implication for health and prevention among immigrants from low-income countries to Europe, with a special focus on South Asians. Method: Systematic searches in PubMed were performed to identify relevant high quality review articles and primary research papers. The searches were limited to major immigrant groups in Europe, including those from South Asia (India, Pakistan, Bangladesh, Sri Lanka). Articles in English from 1990 and onwards from Europe were included. For health implications, recent review articles and studies of particular relevance to dietary changes among South Asian migrants in Europe were chosen. Results: Most studies report on dietary changes and health consequences in South Asians. The picture of dietary change is complex, depending on a variety of factors related to country of origin, urban/rural residence, socio-economic and cultural factors and situation in host country. However, the main dietary trend after migration is a substantial increase in energy and fat intake, a reduction in carbohydrates and a switch from whole grains and pulses to more refined sources of carbohydrates, resulting in a low intake of fiber. The data also indicate an increase in intake of meat and dairy foods. Some groups have also reduced their vegetable intake. The findings suggest that these dietary changes may all have contributed to higher risk of obesity, T2D and CVD. Implications for prevention: A first priority in prevention should be adoption of a low-energy density – high fiber diet, rich in whole grains and grain products, as well as fruits, vegetables and pulses. Furthermore, avoidance of energy dense and hyperprocessed foods is an important preventive measure.
Body weight, weight perceptions and food intake patterns. A cross-sectional study among male recruits in the Norwegian National Guard
Solveig Uglem, Tonje H Stea, Wenche Fr？lich, Margareta Wandel
BMC Public Health , 2011, DOI: 10.1186/1471-2458-11-343
Abstract: Data were collected with a 4-day food diary among 578 male recruits (age 18-26, mean 19.7) in the Norwegian National Guard (response rate 78%), in addition to a questionnaire, including questions about health and weight perceptions, and food frequency when still living at home. Weight and height were objectively measured. Food patterns were explored with principal component analysis, based on the diary data. A multivariate linear regression analysis determined the association between BMI and food patterns, and attitudes to health and slenderness, adjusting for smoking, physical activity and phase of data collection.Twenty eight percent of the recruits were overweight/obese (BMI > 25 kg/m2). Two-thirds meant that it is important for them to be slender, and these recruits reported more of both light (p = 0.025) and hard (p = 0.016) physical activity than the others. It was a positive association between the recruits' food frequency at home, and the amount of intake in the military camp for several food items. A principal component analysis identified three distinct food patterns, loading on 1) plant foods, 2) fast food/soft drinks, 3) milk/cereals. Those who stated that it is important for them to be slender, or to have good health, did not have significantly different food intake patterns than the others. BMI was inversely related to scores on the plant food pattern, and positive attitudes to slenderness.The majority of the recruits find it important to be slender. This orientation had a bearing on their physical activity pattern, but less on the food intake pattern. The data also indicate that subjects with high intakes of plant foods were less likely to have a high BMI than others. It is important to raise awareness of healthy eating in young men.Young men are among the population groups that are most difficult to reach with health and nutrition information. They are also among the groups with the lowest intake of fruits and vegetables [1,2]. This is alarming since
Secondary Accceleration of Cosmic Rays by Supernova Shocks
Amri Wandel
Physics , 1997,
Abstract: In the common model supernova shock-acceleration of cosmic rays there are two open questions: 1. where does the high energy cosmic rays below the knee (10$^4-10^6$ Gev) come from, and 2. are cosmic ray accelerated only at their origin or contineuosly during their residence in the Galaxy. We show that $10^15$ eV light nuclei are probably accelerted by associations of supernovae. The ratio of the spectra of secondary to primary cosmic rays would be affected by repeated acceleration (also called reacceleration or secondary acceleration) in the ISM during their propagation in the galaxy. The observed secondary and primary CR spectra are used to constrain the amount of such reacceleration by supernova remnants (SNR). Two cases are considered: weak shocks ($13$) of relatively young remnants. It is shown that weak shocks produce more reacceleration than what is permitted in the framework of the standard leaky box (SLB) model, making it inconsistent with dispersed acceleration that should be produced by SNR. If the SLB is modified to allow a moderate amount of RA by week shocks, the RA produced by old SNRs agrees with the rate required to fit the secondary-to primaray cosmic-ray data, making a self consistent picture. Significant reacceleration by strong shocks of young SNRs should lead to flattening of the secondary-to primaray ratio at high energies, near 1TeV/nucleon.
Spectral Dependence of the Broad Emission-Line Region in AGN
Amri Wandel
Physics , 1997,
Abstract: We derive a theoretical relation between $R_{BLR}$, the size of the broad-emission-line region of active galactic nuclei, and the observed soft X-ray luminosity and spectrum. We show that in addition to the well known $R_{BLR}\sim L^{1/2}$ scaling, $R_{BLR}$ should depend also on the soft X-ray spectral slope and derive the expected relation between $R_{BLR}$ and the X-ray luminosity and spectral index. Applying this relation to calculate a predicted BLR radius for ten AGN with reverberation data, we show that including the dependence on the spectrum improves the agreement between the calculated BLR radius and the radius independently determined from reverberation mapping. Similarly, we evaluate an expression for the line width, and show that including the dependence on the spectrum significantly improves the agreement between the calculated BLR velocity dispersion and the observed FWHM of the H$\beta$ line.
The Black Hole to Bulge Mass Relation in Active Galactic Nuclei
Amri Wandel
Physics , 1999, DOI: 10.1086/312106
Abstract: The masses of the central black holes in Active Galactic Nuclei (AGNs) can be estimated using the broad emission-lines as a probe of the virial mass. Using reverberation mapping to determine the size of the Broad Line Region (BLR) and the width of the variable component of the line profile H$\beta$ line it is possible to find quite accurate virial mass estimates for AGNs with adequate data. Compiling a sample of AGNs with reliable central masses and bulge magnitudes we find an average black-hole-to-bulge mass ratio of 0.0003, a factor of 20 less than the value found for normal galaxies and for bright quasars. This lower ratio is more consistent with the back hole mass density predicted from quasar light, and is similar to the central black hole/bulge mass ratio in our Galaxy. We argue that the black hole/bulge mass ratio actually has a significantly larger range than indicated by mssive black holes detected in normal galaxies (using stellar dynamics) and in bright quasars, which may be biased towards large black holes. We derive a scenario of black hole growth that explains the observed distribution.
The Mass-Luminosity Relation in AGN
Amri Wandel
Physics , 1998,
Abstract: Probably the most fundamental characteristic of the quasar-AGN power house, the mass of the central black hole, is the least well known. I review the three main classes of mass estimation methods---broad emission-line kinematics, X-ray variability and accretion-disk modeling, and the masses they give in terms of the Eddington ratio, $L/L_{\rm Edd}$. The broad emission lines are probably the best probe of the central mass. They provide mass estimates that suggest a narrow spread for the Eddington ratio - 1--2 orders of magnitude over more than six orders of magnitude in continuum luminosity, possibly indicating a universal $M/L$ ratio for AGN. However, other methods give a larger spread and possibly a luminosity- dependent Eddington ratio. Potential sources of errors and bias are discussed.
Spectral Dependence of the Broad Emission-Line Region in AGN
Amri Wandel
Physics , 1998,
Abstract: We derive a theoretical relation between $R_{BLR}$, the size of the broad-emission-line region of active galactic nuclei, and the observed soft X-ray luminosity and spectrum. We show that in addition to the well known $R_{BLR}\sim L^{1/2}$ scaling, $R_{BLR}$ should depend also on the spectral shape and derive the expected relation between $R_{BLR}$ and the X-ray luminosity and spectral index. Applying this relation to calculate a predicted BLR radius for ten AGN with reverberational data, we show that including the dependence on the spectrum improves the agreement between the calculated BLR radius and the radius independently determined from reverberation mapping. Similarly, we evaluate an expression for the line width, and show that including the dependence on the spectrum significantly improves the agreement between the calculated BLR velocity dispersion and the observed FWHM of the H$\beta$ line.
On the BH-galaxy relation of AGN and Narrow Line Seyfert 1 Galaxies
Amri Wandel
Physics , 2011,
Abstract: Massive black holes (BHs) are detected in the centers of many nearby galaxies are linearly correlated with the luminosity of the host bulge (spheroid), the black hole mass being about 0.1% of the stellar mass. In active galaxies, the BH mass is best measured by the reverberation mapping (light echo) technique. We and others have shown that in AGNs the BH mass follows the same relation with the luminosity of the host galaxy as in ordinary (inactive) galaxies, with the exception of narrow line AGNs which apparently have significantly lower values of the BH/bulge mass (or BH/bulge luminosity) ratio. The BH/bulge ratio is also found to be strongly correlated with the velocity dispersion of the broad line-emitting gas in the active nucleus. However, in the BH-stellar velocity relation the difference between broad- and narrow-line AGNs (in particular NLS1s) seems to be less obvious. We review the subject adding recent updates and suggestions.
On the abundance of extraterrestrial life after the Kepler mission
Amri Wandel
Physics , 2014, DOI: 10.1017/S1473550414000767
Abstract: The data recently accumulated by the Kepler mission have demonstrated that small planets are quite common and that a significant fraction of all stars may have an Earth-like planet within their Habitable Zone. These results are combined with a Drake-equation formalism to derive the space density of biotic planets as a function of the relatively modest uncertainty in the astronomical data and of the (yet unknown) probability for the evolution of biotic life, Fb. I suggest that Fb may be estimated by future spectral observations of exoplanet biomarkers. If Fb is in the range 0.001 -- 1 then a biotic planet may be expected within 10 -- 100 light years from Earth. Extending the biotic results to advanced life I derive expressions for the distance to putative civilizations in terms of two additional Drake parameters - the probability for evolution of a civilization, Fc, and its average longevity. For instance, assuming optimistic probability values (Fb Fc 1) and a broadcasting longevity of a few thousand years, the likely distance to the nearest civilizations detectable by SETI is of the order of a few thousand light years. The probability of detecting intelligent signals with present and future radio telescopes is calculated as a function of the Drake parameters. Finally, I describe how the detection of intelligent signals would constrain the Drake parameters.
Relations between Massive Black Holes in AGN and their Host Galaxies
Amri Wandel
Physics , 2003,
Abstract: Massive black holes detected in the centers of many nearby galaxies are linearly correlated with the luminosity of the host bulge, the black hole mass being about 0.1% of the bulge mass. An even stronger relation exists between the BH mass (Mbh) and the stellar velocity dispersion in the host bulge. We show that massive BHs of AGNs (measured by reverberation mapping) and their bulge luminosity (measured by using a bulge/disk decomposition) follow the same relations as ordinary (inactive) galaxies, with the exeption of narrow line AGN which apparently have significantly lower BH/bulge ratios. Narrow line AGNs seem to be outstanding also in the Mbh-velocity dispersion relation: the few Seyfert galaxies with measured velocity dispersion seem to indicate that narrow line Seyfert 1 galaxies have a smaller BH mass/velocity dispersion ratio than quiescent galaxies and broad line Syferts. Estimating the velocity dispersion for from the bulge luminosity with the Faber-Jackson relation more than doubles the sample and supports these results.
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