naturopathydigest.com -- Critical Research

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Critical Research

Critical Research is a regular feature in Naturopathy Digest. Each month, we provide abstracts from studies published in the top peer-reviewed journals; each abstract includes the complete citation and an online link to the journal. Whenever possible, this link directs you to a page where you can order the full text of the study, if desired.

Combining fish-oil supplements with regular aerobic exercise improves body composition and cardiovascular disease risk factors.

AM Hill, JD Buckley, KJ Murphy, PR Howe

Background: Regular exercise and consuming long-chain n-3 fatty acids (FAs) from fish or fish oil can independently improve cardiovascular and metabolic health, but combining these lifestyle modifications may be more effective than either treatment alone.

Objective: We examined the individual and combined effects of n-3 FA supplements and regular exercise on body composition and cardiovascular health.

Design: Overweight volunteers [body mass index (BMI; in kg/m(2)): >25] with high blood pressure, cholesterol, or triacylglycerols were randomly assigned to one of the following interventions: fish oil (FO), FO and exercise (FOX), sunflower oil (SO; control), or SO and exercise (SOX). Subjects consumed 6 g tuna FO/d ( approximately 1.9 g n-3 FA) or 6 g SO/d. The exercise groups walked 3 d/wk for 45 min at 75% age-predicted maximal heart rate. Plasma lipids, blood pressure, and arterial function were assessed at 0, 6, and 12 wk. Body composition was assessed by dual-energy X-ray absorptiometry at 0 and 12 wk only.

Results: FO supplementation lowered triacylglycerols, increased HDL cholesterol, and improved endothelium-dependent arterial vasodilation (P < 0.05). Exercise improved arterial compliance (P < 0.05). Both fish oil and exercise independently reduced body fat (P < 0.05).

Conclusions: FO supplements and regular exercise both reduce body fat and improve cardiovascular and metabolic health. Increasing intake of n-3 FAs could be a useful adjunct to exercise programs aimed at improving body composition and decreasing cardiovascular disease risk.

Source: Am J Clin Nutr. May 2007;85(5):1267-1274.

Running is rewarding and antidepressive.

S Brené, A Bjørnebekk, E Aberg, et al.

Natural behaviors such as eating, drinking, reproduction and exercise activate brain reward pathways and consequently the individual engages in these behaviors to receive the reward. However, drugs of abuse are even more potent in activating the reward pathways. Rewarding behaviors and addictive drugs also affect other parts of the brain not directly involved in the mediation of reward. For instance, running increases neurogenesis in hippocampus and is beneficial as an antidepressant in a genetic animal model of depression and in depressed humans. Here we discuss and compare neurochemical and functional changes in the brain after addictive drugs and exercise with a focus on brain reward pathways and hippocampus.

Source: Physiol Behav. May 21, 2007 [Epub ahead of print].

The effects of a topical treatment derived from black raspberries on UVB-activated neutrophil activity and carcinogenesis.

FJ. Duncan, Sam Shin, Jason Martin, et al.

Immunosuppressed individuals such as cancer patients and transplant recipients are more likely to develop and die from squamous cell carcinomas (SCC) than the general population. To help alter these alarming statistics, we have developed a topical, post-sun exposure treatment derived from black raspberries. In a series of studies using an established model of UVB-induced skin cancer, we determined the effects the black raspberry extract (BRE) on acute and chronic UVB exposure. To assess the effect on acute UVB exposure, female SKH-1 hairless mice were exposed to one minimal erythemal dose of UVB (experimentally determined to be 2240 J/m2). Immediately after UVB exposure mice were treated with either vehicle or 500 ug of the BRE (all mice were paired with appropriate non-UVB controls). Mice were sacrificed 48 hours later and edema, myeloperoxidase (MPO) activity and neutrophil infiltration were assessed as parameters of cutaneous inflammation. Topical BRE significantly reduced both skin edema (p<0.001) and MPO activity (p=0.03) compared to controls. Since MPO is primarily produced by activated neutrophils and is routinely used in our lab as an indicator of neutrophil activation, we then determined the level of skin neutrophil infiltration. However, histological analysis of Ly6G+ cells in BRE-treated skin indicated that the number of infiltrating neutrophils was unchanged compared to vehicle treated animals. We then determined whether neutrophil chemoattractants were reduced in BRE-treated skin using ELISA. BRE reduced the levels of the neutrophil chemoattractant KC (CXCL1), (p<0.02), although the levels of MIP-2 (CXCL2) were unchanged. Taken together, these data show that topical BRE application after UVB exposure significantly reduced UVB-induced inflammation. Since chronic inflammation substantially contributes to tumor development, we then hypothesized that BRE could reduce UVB-induced carcinogenesis. To test this, we exposed female SKH-1 hairless mice to one MED of UVB thrice weekly for twenty-five weeks. Again, mice were topically treated with either vehicle or 500 mg BRE immediately after exposure, and were paired with appropriate non-UVB controls. Tumor number and size (length and width) were recorded beginning in week 11. BRE treatment significantly reduced tumor size, area and number (p<0.003, p<0.004 and p=0.05). When tumors were blindly graded by a board-certified veterinary pathologist, BRE treatment slightly retarded tumor progression. These results show that BRE is able to significantly reduce both UVB-induced inflammation and carcinogenesis and may have potential to reduce tumor progression. Thus, we consider BRE to have excellent potential as an effective skin cancer preventive agent.

Source: AACR Annual Meeting, April 14-18, 2007 in Los Angeles.

Calcium plus vitamin D supplementation and the risk of postmenopausal weight gain.

B Caan, M Neuhouser, A Aragaki, et al.

Background: Obesity in the United States has increased significantly during the past several decades. The role of calcium in the maintenance of a healthy body weight remains controversial.

Methods: A randomized, double-blinded, placebo-controlled trial was performed with 36 282 postmenopausal women, aged 50 to 79 years, who were already enrolled in the dietary modification and/or hormone therapy arms of the Women's Health Initiative clinical trial. Women were randomized at their first or second annual visit to receive a dose of 1000 mg of elemental calcium plus 400 IU of cholecalciferol (vitamin D) or placebo daily. Change in body weight was ascertained annually for an average of 7 years.

Results: Women receiving calcium plus cholecalciferol supplements vs women receiving placebo had a minimal but consistent favorable difference in weight change (mean difference, -0.13 kg; 95% confidence interval, -0.21 to -0.05; P = .001). After 3 years of follow-up, women with daily calcium intakes less than 1200 mg at baseline who were randomized to supplements were 11% less likely to experience small weight gains (1-3 kg) and 11% less likely to gain more moderate amounts of weight (>3 kg) (P for interaction for baseline calcium intake = .008).

Conclusion: Calcium plus cholecalciferol supplementation has a small effect on the prevention of weight gain, which was observed primarily in women who reported inadequate calcium intakes.

Source: Arch Intern Med. May 14, 2007;167(9):893-902.

Effects of dietary calcium compared with calcium supplements on estrogen metabolism and bone mineral density.

N Napoli, J Thompson, R Civitelli, RC Armamento-Villareal

Background: High calcium intake has been associated with both high bone mineral density (BMD) and high urinary estrogen metabolites. However, the role of dietary calcium and calcium supplements on estrogen metabolism and BMD remains unknown.

Objective: The objective was to investigate the importance of the source of calcium intake on estrogen metabolism and BMD.

Design: The average total daily calcium intake from supplements and diet, urinary estrogen metabolites, and spine and proximal femur BMD were studied in 168 healthy postmenopausal white women.

Results: Women who obtained calcium primarily from the diet or from both the diet and supplements had significantly (P=0.03) lower ratios of nonestrogenic to estrogenic metabolites (2-hydroxyestrone 1/16 alpha-hydroxyestrone) than did those who obtained calcium primarily from supplements. Adjusted BMD z scores were significantly greater in the subjects who obtained calcium primarily from the diet or from both the diet and supplements than in those who obtained calcium primarily from calcium supplements at the spine (P=0.012), femoral neck (P=0.02), total femur (P=0.003), and intertrochanter (P=0.005). This difference was evident especially in those who obtained calcium primarily from the diet, whose total calcium intake was lower than that in those who obtained calcium primarily from supplements.

Conclusion: Calcium from dietary sources is associated with a shift in estrogen metabolism toward the active 16 alpha-hydroxyl metabolic pathway and with greater BMD and thus may produce more favorable effects in bone health in postmenopausal women than will calcium from supplements.

Source: Am J Clin Nutr. May 2007;85(5):1428-33.

Relationship between pediatric obesity and otitis media with effusion.

Jong Bin Kim, Dong Choon Park, Chang Il Cha, Seung Geun Yeo

Objective: To investigate the relationship between pediatric otitis media with effusion and obesity, as determined by body mass index (BMI) (calculated as weight in kilograms divided by height in meters squared) and serum triglyceride (TG) and total cholesterol (TC) concentrations.

Design: A prospective, nonrandomized, case-control study.

Setting: University-affiliated hospital.

Subjects: The experimental group comprised 155 children aged 2 to 7 years, who received unilateral or bilateral ventilation tube insertion for the treatment of otitis media with effusion. The control group comprised 118 children with no history of otitis media with effusion, who underwent operations for conditions other than ear diseases. Based on BMI and serum TG and TC concentrations, we divided the experimental group into 2 subgroups, those who were and were not obese.

Main Outcome Measures: We determined the difference between the experimental and control groups in BMI and serum TG and TC concentrations and the difference between the obese and nonobese subgroups in frequency of ventilation tube insertion.

Results: Mean ± SD BMI (22.0 ± 3.4 vs 16.3 ± 2.4) (P = .01) and mean ± SD TC level (195.0 ± 31.0 mg/dL vs 159.3 ± 26.9 mg/dL [5.05 ± 0.80 mmol/L vs 4.13 ± 0.70 mmol/L]) (P = .04), but not mean serum TG level (109.4 ± 40.4 mg/dL vs 90.0 ± 52.3 mg/dL [1.24 ± 0.46 mmol/L vs 1.02 ± 0.59 mmol/L]) (P = .13), were significantly higher in the experimental group than in the control group. Frequency of ventilation tube insertion, however, did not differ significantly between the obese and nonobese subgroups, whether divided by BMI (P = .10) or serum TG (P = .12) or TC (P = .07) concentration.

Conclusion: Childhood obesity may be associated with the occurrence of otitis media with effusion.

Source: Arch Otolaryngol Head Neck Surg. April 2007;133(4):379-382.

Probiotics for prevention of necrotizing enterocolitis in preterm neonates with very low birthweight: a systematic review of randomized controlled trials.

G Deshpande, S Rao, S Patole

Background: Results of recent clinical trials suggest that probiotic supplementation reduces the risk of necrotising enterocolitis in preterm neonates. We aimed to systematically review randomized controlled trials evaluating efficacy and safety of any probiotic supplementation (started within first 10 days, duration > or =7 days) in preventing stage 2 or greater necrotising enterocolitis in preterm neonates (gestation <33 weeks) with very low birthweight (<1500 g).

Methods: We followed the standard search strategy of the Cochrane Neonatal Review Group. We searched the Cochrane Central Register of Controlled Trials (CENTRAL), Medline, Embase, CINAHL databases, and proceedings of the Pediatric Academic Society meetings (from 1980) and Pediatric Gastroenterology conferences (from 1980) in November, 2006.

Results: Seven of 12 randomized controlled trials retrieved (n=1393) were eligible for inclusion in the analysis. Meta-analysis using a fixed effects model estimated a lower risk of necrotising enterocolitis (relative risk 0.36, 95% CI 0.20-0.65) in the probiotic group than in controls. Risk of sepsis did not differ significantly between groups (0.94, 0.74-1.20). Risk of death was reduced in the probiotic group (0.47, 0.30-0.73). The time to full feeds was significantly shorter in the probiotic group (weighted mean difference -2.74 days, 95% CI -4.98 to -0.51) than in controls.

Conclusion: Probiotics might reduce the risk of necrotising enterocolitis in preterm neonates with less than 33 weeks' gestation. However, the short-term and long-term safety of probiotics needs to be assessed in large trials. Unanswered questions include the dose, duration, and type of probiotic agents (species, strain, single or combined, live or killed) used for supplementation.

Source: Lancet. May 12, 2007;369(9573):1614-20.

Fiber and magnesium intake and incidence of type 2 diabetes: a prospective study and meta-analysis.

MB Schulze, M Schulz, C Heidemann, et al.

Background: Prospective studies on fiber and magnesium intake and risk of type 2 diabetes mellitus were inconsistent. We examined associations between fiber and magnesium intake and risk of type 2 diabetes and summarized existing prospective studies by meta-analysis.

Methods: We conducted a prospective cohort study of 9702 men and 15 365 women aged 35 to 65 years who were observed for incident diabetes from 1994 to 2005. Dietary intake of fiber and magnesium were measured with a validated food-frequency questionnaire. We estimated the relative risk (RR) by means of Cox proportional hazards analysis. We searched PubMed through May 2006 for prospective cohort studies of fiber and magnesium intake and risk of type 2 diabetes. We identified 9 cohort studies of fiber and 8 studies of magnesium intake and calculated summary RRs by means of a random-effects model.

Results: During 176 117 person-years of follow-up, we observed 844 incident cases of type 2 diabetes in the European Prospective Investigation Into Cancer and Nutrition-Potsdam. Higher cereal fiber intake was inversely associated with diabetes risk (RR for extreme quintiles, 0.72 [95% confidence interval [CI], 0.56-0.93]), while fruit fiber (0.89 [95% CI, 0.70-1.13]) and vegetable fiber (0.93 [95% CI, 0.74-1.17]) were not significantly associated. Meta-analyses showed a reduced diabetes risk with higher cereal fiber intake (RR for extreme categories, 0.67 [95% CI, 0.62-0.72]), but no significant associations for fruit (0.96 [95% CI, 0.88-1.04]) and vegetable fiber (1.04 [95% CI, 0.94-1.15]). Magnesium intake was not related to diabetes risk in the European Prospective Investigation Into Cancer and Nutrition-Potsdam (RR for extreme quintiles, 0.99 [95% CI, 0.78-1.26]); however, meta-analysis showed a significant inverse association (RR for extreme categories, 0.77 [95% CI, 0.72-0.84]).

Conclusion: Higher cereal fiber and magnesium intakes may decrease diabetes risk.

Source: Arch Intern Med. May 14, 2007;167(9):956-65.

Consumption of fluid skim milk promotes greater muscle protein accretion after resistance exercise than does consumption of an isonitrogenous and isoenergetic soy-protein beverage.

SB Wilkinson, MA Tarnopolsky, MJ Macdonald, et al.

Background: Resistance exercise leads to net muscle protein accretion through a synergistic interaction of exercise and feeding. Proteins from different sources may differ in their ability to support muscle protein accretion because of different patterns of postprandial hyperaminoacidemia.

Objective: We examined the effect of consuming isonitrogenous, isoenergetic, and macronutrient-matched soy or milk beverages (18 g protein, 750 kJ) on protein kinetics and net muscle protein balance after resistance exercise in healthy young men. Our hypothesis was that soy ingestion would result in larger but transient hyperaminoacidemia compared with milk and that milk would promote a greater net balance because of lower but prolonged hyperaminoacidemia.

Design: Arterial-venous amino acid balance and muscle fractional synthesis rates were measured in young men who consumed fluid milk or a soy-protein beverage in a crossover design after a bout of resistance exercise.

Results: Ingestion of both soy and milk resulted in a positive net protein balance. Analysis of area under the net balance curves indicated an overall greater net balance after milk ingestion (P < 0.05). The fractional synthesis rate in muscle was also greater after milk consumption (0.10 +/- 0.01%/h) than after soy consumption (0.07 +/- 0.01%/h; P = 0.05).

Conclusions: Milk-based proteins promote muscle protein accretion to a greater extent than do soy-based proteins when consumed after resistance exercise. The consumption of either milk or soy protein with resistance training promotes muscle mass maintenance and gains, but chronic consumption of milk proteins after resistance exercise likely supports a more rapid lean mass accrual.

Source: Am J Clin Nutr. April 2007 Apr;85(4):1031-40.