Here's a gutsy, nutritional, low sunlight kind of blog post to suit our post-holiday season.  First the gutsy bit.  Irritable bowel syndrome (IBS) - with its characteristic symptoms of abdominal pain, altered bowel habit, and possibly bloating - is very common, affecting about 15% of the population.  Ford et al systematically reviewed all research on treating IBS with fibre, antispasmodics, or peppermint oil.  Fibre was some use, but only in the form of ispaghula (UK Fybogel, Isogel).  The antispasmodics otilonium and hysocine (UK Buscopan) seemed also to be of help.  But what attracted me to the study was the finding that most helpful of the three treatments seemed to be the old-fashioned remedy of taking peppermint oil. 

I've also included a couple of studies on the New-Year-resolution-relevant subject of weight loss - or more importantly, maintaining weight loss.  The Marinilli et al study shows that although very low-calorie diets were initially most successful, those who used a self-guided approach " ... maintained their initial weight losses with the greatest success."  Wing et al looked at the importance of psychological and behavioural factors in maintaining large weight losses.  They concluded "Future programs should focus on maintaining physical activity, dietary restraints, and frequent self-weighing and should include stronger components to modify psychological parameters."

Finally I return to the bee-in-my-bonnet subject of vitamin D.  I've posted before on this issue, and here are three more papers.  Norman's freely-viewable full text editorial not only makes the point that current recommendations on intake levels are probably too low, but then goes on to highlight very helpfully that besides the well-known actions on bone, " ... over the past decade, new evidence has shown that there are 5 additional physiologic systems in which the vitamin D receptor and its cognate steroid hormone, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], generate biological responses. These are the immune, pancreas, heart-cardiovascular, muscle, and brain systems; the control of the cell cycle and thus of the disease process of cancer is also involved."  Looker et al highlight the paradox that, in the face of this mounting evidence for the very broad benefits of higher vitamin D intake, in fact levels of vitamin D seem to be falling in the US population.  Cashman and colleagues then estimate that "Vitamin D intakes required to maintain serum 25(OH)D concentrations of >37.5, >50, and >80 nmol/L in 97.5% of the sample were 19.9, 28.0, and 41.1 µg/d, respectively."  Getting our blood levels up to 80 to 100 nmol/L seems sensible - suggesting the 41.1 µg/d dose i.e. over 1,600 i.u. of vitamin D per day.

Ford, A. C., N. J. Talley, et al. (2008). "Effect of fibre, antispasmodics, and peppermint oil in the treatment of irritable bowel syndrome: systematic review and meta-analysis." BMJ 337(nov13_2): a2313-.  [Free Full Text]    
Objective To determine the effect of fibre, antispasmodics, and peppermint oil in the treatment of irritable bowel syndrome. Design Systematic review and meta-analysis of randomised controlled trials. Data sources Medline, Embase, and the Cochrane controlled trials register up to April 2008. Review methods Randomised controlled trials comparing fibre, antispasmodics, and peppermint oil with placebo or no treatment in adults with irritable bowel syndrome were eligible for inclusion. The minimum duration of therapy considered was one week, and studies had to report either a global assessment of cure or improvement in symptoms, or cure of or improvement in abdominal pain, after treatment. A random effects model was used to pool data on symptoms, and the effect of therapy compared with placebo or no treatment was reported as the relative risk (95% confidence interval) of symptoms persisting. Results 12 studies compared fibre with placebo or no treatment in 591 patients (relative risk of persistent symptoms 0.87, 95% confidence interval 0.76 to 1.00). This effect was limited to ispaghula (0.78, 0.63 to 0.96). Twenty two trials compared antispasmodics with placebo in 1778 patients (0.68, 0.57 to 0.81). Various antispasmodics were studied, but otilonium (four trials, 435 patients, relative risk of persistent symptoms 0.55, 0.31 to 0.97) and hyoscine (three trials, 426 patients, 0.63, 0.51 to 0.78) showed consistent evidence of efficacy. Four trials compared peppermint oil with placebo in 392 patients (0.43, 0.32 to 0.59). Conclusion Fibre, antispasmodics, and peppermint oil were all more effective than placebo in the treatment of irritable bowel syndrome.

Marinilli Pinto, A., A. A. Gorin, et al. (2008). "Successful weight-loss maintenance in relation to method of weight loss." Obesity (Silver Spring) 16(11): 2456-61.   [PubMed] 
This study examined the relation between method of weight loss and long-term maintenance among successful weight losers enrolled in a weight-loss maintenance trial. Participants were 186 adults (mean age = 51.6 +/- 10.7 years, mean BMI = 28.6 +/- 4.7 kg/m(2)) enrolled in the STOP Regain trial who had lost at least 10% of their body weight in the past 2 years using a very low-calorie diet (VLCD; n = 24), commercial program (n = 95), or self-guided approach (n = 67). Participants were randomized to a weight-maintenance intervention delivered face to face or over the internet or to a newsletter control condition, and followed for 18 months. At study entry, individuals who had used a VLCD had achieved a weight loss of 24% of their maximum weight within the past 2 years compared to 17% achieved by those who had used a commercial program or self-guided approach (P < 0.001). However, individuals who had used a VLCD regained significantly more weight than the other two groups and by 6 months, there were no significant differences in overall percent weight loss (i.e., initial weight loss and maintenance) between VLCD, commercial, and self-guided methods. In contrast, individuals who had used a self-guided approach maintained their weight losses from baseline through 18 months. The large initial weight losses achieved by individuals who had used a VLCD were not maintained over time, whereas individuals who had used a self-guided approach maintained their initial weight losses with the greatest success. The generalizability of these findings is limited by the sizeable weight losses achieved by study participants.

Wing, R. R., G. Papandonatos, et al. (2008). "Maintaining large weight losses: the role of behavioral and psychological factors." J Consult Clin Psychol 76(6): 1015-21. [PubMed] 
Few studies have examined predictors of weight regain after significant weight losses. This prospective study examined behavioral and psychological predictors of weight regain in 261 successful weight losers who completed an 18-month trial of weight regain prevention that compared a control condition with self-regulation interventions delivered face-to-face or via the Internet. Linear mixed effect models were used to examine behavioral and psychological predictors of weight regain, both as main effects and as interactions with treatment group. Decreases in physical activity were related to weight regain across all 3 groups, and increased frequency of self-weighing was equally protective in the 2 intervention groups but not in the control group. Increases in depressive symptoms, disinhibition, and hunger were also related to weight regain in all groups. Although the impact of changes in restraint was greatest in the Internet group and weakest in the face-to-face group, the latter was the only group with increases in restraint over time and consequent decreases in magnitude of weight regain. Future programs should focus on maintaining physical activity, dietary restraints, and frequent self-weighing and should include stronger components to modify psychological parameters.

Norman, A. W. (2008). "A vitamin D nutritional cornucopia: new insights concerning the serum 25-hydroxyvitamin D status of the US population." Am J Clin Nutr 88(6): 1455-1456.  [Free Full Text]  
This freely viewable full text editorial comments:  The current adequate intake allowance of vitamin D, recommended in 1997, is considered by many scientists to be too low and to be focused only on vitamin D's actions on calcium and bone issues. However, over the past decade, new evidence has shown that there are 5 additional physiologic systems in which the vitamin D receptor and its cognate steroid hormone, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], generate biological responses. These are the immune, pancreas, heart-cardiovascular, muscle, and brain systems; the control of the cell cycle and thus of the disease process of cancer is also involved. Acting through the vitamin D receptor, the steroid hormone 1,25(OH)2D can produce a wide array of favorable biological effects that collectively are projected to contribute to the improvement of human health.

Looker, A. C., C. M. Pfeiffer, et al. (2008). "Serum 25-hydroxyvitamin D status of the US population: 1988-1994 compared with 2000-2004." Am J Clin Nutr 88(6): 1519-1527.  [Abstract/Full Text] 
Background: Changes in serum 25-hydroxyvitamin D [25(OH)D] concentrations in the US population have not been described. Objective: We used data from the National Health and Nutrition Examination Surveys (NHANES) to compare serum 25(OH)D concentrations in the US population in 2000-2004 with those in 1988-1994 and to identify contributing factors. Design: Serum 25(OH)D was measured with a radioimmunoassay kit in 20 289 participants in NHANES 2000-2004 and in 18 158 participants in NHANES III (1988-1994). Body mass index (BMI) was calculated from measured height and weight. Milk intake and sun protection were assessed by questionnaire. Assay differences were assessed by re-analyzing 150 stored serum specimens from NHANES III with the current assay. Results: Age-adjusted mean serum 25(OH)D concentrations were 5-20 nmol/L lower in NHANES 2000-2004 than in NHANES III. After adjustment for assay shifts, age-adjusted means in NHANES 2000-2004 remained significantly lower (by 5-9 nmol/L) in most males, but not in most females. In a study subsample, adjustment for the confounding effects of assay differences changed mean serum 25(OH)D concentrations by {approx}10 nmol/L, and adjustment for changes in the factors likely related to real changes in vitamin D status (ie, BMI, milk intake, and sun protection) changed mean serum 25(OH)D concentrations by 1-1.6 nmol/L. Conclusions: Overall, mean serum 25(OH)D was lower in 2000-2004 than 1988-1994. Assay changes unrelated to changes in vitamin D status accounted for much of the difference in most population groups. In an adult subgroup, combined changes in BMI, milk intake, and sun protection appeared to contribute to a real decline in vitamin D status.

Cashman, K. D., T. R. Hill, et al. (2008). "Estimation of the dietary requirement for vitamin D in healthy adults." Am J Clin Nutr 88(6): 1535-1542.  [Abstract/Full Text] 
Background: Knowledge gaps have contributed to considerable variation among international dietary recommendations for vitamin D.  Objective: We aimed to establish the distribution of dietary vitamin D required to maintain serum 25-hydroxyvitamin D [25(OH)D] concentrations above several proposed cutoffs (ie, 25, 37.5, 50, and 80 nmol/L) during wintertime after adjustment for the effect of summer sunshine exposure and diet.  Design: A randomized, placebo-controlled, double-blind 22-wk intervention study was conducted in men and women aged 20-40 y (n = 238) by using different supplemental doses (0, 5, 10, and 15 µg/d) of vitamin D3 throughout the winter. Serum 25(OH)D concentrations were measured by using enzyme-linked immunoassay at baseline (October 2006) and endpoint (March 2007).  Results: There were clear dose-related increments (P < 0.0001) in serum 25(OH)D with increasing supplemental vitamin D3. The slope of the relation between vitamin D intake and serum 25(OH)D was 1.96 nmol•L-1•µg-1 intake. The vitamin D intake that maintained serum 25(OH)D concentrations of >25 nmol/L in 97.5% of the sample was 8.7 µg/d. This intake ranged from 7.2 µg/d in those who enjoyed sunshine exposure, 8.8 µg/d in those who sometimes had sun exposure, and 12.3 µg/d in those who avoided sunshine. Vitamin D intakes required to maintain serum 25(OH)D concentrations of >37.5, >50, and >80 nmol/L in 97.5% of the sample were 19.9, 28.0, and 41.1 µg/d, respectively.  Conclusion: The range of vitamin D intakes required to ensure maintenance of wintertime vitamin D status [as defined by incremental cutoffs of serum 25(OH)D] in the vast majority (>97.5%) of 20-40-y-old adults, considering a variety of sun exposure preferences, is between 7.2 and 41.1 µg/d.