Nutrition Updates


  • KE D'Anci


Temple JL, Bulkley AM, Badawy RL, Krause N, McCann S, and Epstein LH. Differential effects of daily snack food intake on the reinforcing value of food in obese and nonobese women. Am J Clin Nutr. 2009;90:304–313.

Management and treatment of obesity currently has limited success. Some estimates suggest that less than 10% of individuals who attempt significant weight loss using lifestyle changes are successful at maintaining that loss for more than 3–5 years. One possible reason for this failure to maintain weight loss could be related to the nature of many weight-reducing diets. Namely, traditional diets restrict calories and particularly restrict highly palatable, preferred snack foods. Such restriction is hypothesized to increase feelings of deprivation and increase the likelihood of relapse to prior eating habits. When examined from a behavioral perspective, the reinforcing value of a preferred food can change dependent upon its relative scarcity or availability. Highly preferred foods that are available with high frequency may lead to reinforcer satiety or monotony, which would reduce the relative reinforcing properties of the food. In contrast, withholding of a highly preferred food would lead to an increased reinforcing value of the food and an increased desire to consume the food. In lean individuals, this pattern is seen, where daily presentation of a food leads to monotony and thus decreased drive to eat that food. However, it is proposed that obese individuals are less sensitive to monotony, and may not show the same pattern of reduced reinforcement when presented with highly preferred foods. Temple et al. evaluated the effects of daily snack food presentation on food reinforcement and liking in obese and nonobese women.

Obese (n= 27) and nonobese (n= 31) women were screened for their personal highly preferred snack food (e.g., potato chips, popcorn, ice cream, brownies, etc). During the first portion of the study (weeks 1 and 2), participants were trained in using a food reinforcement task, an operant procedure with which they could earn points towards obtaining their preferred food. Food points were earned on a progressive variable ratio scale, whereby the number of responses increases incrementally throughout the testing session. The greater the number of responses a person is willing to make, the greater the reinforcing value of the target (here, food). For the last 2 weeks of the study, women were assigned to snack conditions of 0-, 100-, and 300-kcal snacks. Those in the 0-kcal condition did not receive snacks. Participants in the 100- and 300-kcal conditions were given 14 portions of their preferred snack and were instructed to consume one snack per day. The food-reinforcement task was administered again after the daily snack phase. For all women, ratings for liking the preferred food decreased after daily snacking, and decreases were most significant in the 300-kcal condition. Laboratory responding for the preferred food decreased in nonobese women. For women who were obese, however, responding for the preferred food increased. These observations suggest that the reinforcing properties of the preferred food increased after daily snacking even though self-reported liking for that food was decreased in obese women. These data support the notion that individuals who are obese are relatively insensitive to food-related monotony and suggest that diets which promote daily snacking on a particular food would not be beneficial in obese individuals.

Comment: Dr. Bray outlines some considerations in ‘real world’ daily food intake, including whether a meal is eaten at a fast-food restaurant, quality of the food, and to what degree daily kcal intake derives from caloric soft drinks. Based on the study by Temple et al., food intake in the obese may not be affected by monotony, independent of actual liking of a food, and much remains to be learned regarding behavioral change and eating behaviors. He suggests that noncaloric strategies, such as encouraging water intake, might be useful in weight control.

Comment: Bray GA. Can we reduce snack food intake? Am J Clin Nutr. 2009;90:251–252.


Rodondi A, Ammann P, Ghilardi-Beuret S, and Rizzoli R. Zinc increases the effects of essential amino acids-whey protein supplements in frail elderly. J Nutr Health Aging. 2009;13:491–497.

Malnutrition and inadequate protein intake contribute to loss of bone mass in the elderly. In particular, low-protein diets are associated with increased bone resorption, decreased bone formation, and reduced IGF-1. Supplementation with dietary protein, using amino acid supplements, increases IGF-1 and reduces the rate of bone loss. In addition to protein, dietary zinc is important in IGF-1 production, and zinc supplementation increases circulating levels of IGF-1. The objective of the study reported by Rodondi et al. was to determine whether provision of zinc in combination with amino acid supplements would further improve levels of IGF-1 and biochemical markers of bone health in frail elderly.

Fifty-two hospitalized elders were randomly assigned to receive 20 g/d oral protein supplement (15 g whey protein and 5 g essential amino acids with 550 mg calcium), the protein supplement with an additional 30 mg/d zinc, or nothing. Primary outcome measures included clinical status, activities of daily living, serum IGF-1, osteocalcin, serum bone resorption markers (CrossLaps), and serum zinc levels. Determinations were made at baseline, 1, 2, and 4 weeks of supplementation. Both groups receiving protein supplementation showed increased serum IGF-1, and the increase was accelerated in the group receiving zinc supplementation. Over the 4 weeks of the trial, osteocalcin increased in both of the protein-supplemented groups but it was not further affected by zinc. Across the study, the marker for bone resorption increased in the control condition and remained unchanged in the protein-only supplemented condition, but it was significantly reduced in the protein and zinc-supplemented condition. The decrease in CrossLaps was evident after 1 week of protein and zinc supplementation. Activities of daily living, which give an indication of physical performance, were improved following protein supplementation relative to no supplementation. Zinc supplementation in conjunction with protein further improved activities-of-daily-living scores in individuals with low baseline levels of serum albumin. This was a small study, with no true placebo control; as such, the findings should be interpreted with these caveats in mind. However, the ability of zinc supplementation to accelerate the positive effects of protein supplementation on physical functioning and markers of bone health will be of significance in the care management of frail elders.


Ivanovic DM, Rodríguez Mdel P, Pérez HT, Alvear JA, Almagià AF, Toro TD, Urrutia MS, Cruz AL, and Ivanovic RM. Impact of nutritional status at the onset of elementary school on academic aptitude test achievement at the end of high school in a multicausal approach. Br J Nutr. 2009;102:142–154.

While it is generally understood that poor nutritional status in childhood can have long-reaching implications with respect to cognitive development, relatively few long-term studies have directly examined the impact of nutritional status on academic achievement. The relationships among socioeconomic status, academic achievement, and intelligence have been well characterized. Children living in conditions with low parental income, poor housing conditions, and low parental educations typically fare worse in measures of academic achievement such as completion of high school and aptitude testing. Anthropometrics are a commonly used measure of nutritional status in large population studies, and measures such as head circumference and weight- and height-for-age are used as a proxy of past nutrition. Head circumference, in particular, is a useful measure in determining learning and intelligence, and it constitutes one of the more sensitive indicators of undernutrition from an early age. In the present long-term analysis, Ivanovic et al. describe the relationship between early nutritional status, as characterized using anthropometric measures, and academic achievement at the end of secondary school.

Chilean children (N= 813) were enrolled into the study at the beginning of first grade (age ∼6.5 years) and were followed for up to 12 years (final age ∼18.0 years). Baseline measures were taken on weight, height, head circumference, triceps skin fold, and arm circumference. Measures were standardized and compared to normed data, allowing children to be categorized into undernourished, well-nourished, and overnourished as well as having normal head circumference, microcephaly, and macrocephaly. Other baseline measures included intellectual ability, as measured using Raven's Progressive Matrices Test, scholastic achievement (verbal and non-verbal), and familial socioeconomic factors. Outcome measures included performance on the academic aptitude test, which is the admissions test for university in Chile, and level of school completed. Follow-up data were available for 632 of the original 813 children as follows: ∼43% of children graduated from high school, ∼25% had delays in schooling, and ∼9% had dropped out of school. Of the subpopulation of children who graduated, 260 took the academic aptitude test. The remainder of the data analysis reported is related to the 260 children who took the academic aptitude test. Unsurprisingly, scholastic achievement in first grade was the single greatest predictor of success in the academic aptitude test. Maternal schooling and intellectual ability were the next greatest predictors. Finally, head-circumference-for-age was significantly associated with performance on the academic aptitude test. One important consideration when evaluating these data is that only ∼3% of children who took the academic aptitude test were classified as undernourished. The present data, while comprehensive in the many factors affecting academic achievement, would be more compelling if data on the other children who did not take or were not eligible to take the academic aptitude test were also presented.


Pooya S, Jalali MD, Jazayery AD, Saedisomeolia A, Eshraghian MR, and Toorang F. The efficacy of omega-3 fatty acid supplementation on plasma homocysteine and malondialdehyde levels of type 2 diabetic patients. Nutr Metab Cardiovasc Dis. 2009 doi: 10.1016/j.numecd.2009.04.002

Diabetic patients are at increased risk for the development of cardiovascular disease, decreased quality of life, and increased risk of mortality. Individuals with diabetes typically have elevated levels of homocysteine, a risk factor for cardiovascular diseases. Elevated levels of malondialdehyde (MDA) are reflective of lipid peroxidation, and are increased in individuals with diabetes. Omega-3 fatty acid intake is associated with reduced risk for cardiovascular disease and some data show that intake of omega-3 fatty acids is associated with reduced levels of C-reactive protein, suggesting an anti-inflammatory effect, and reduced levels of homocysteine. In the present study, Pooya et al. describe the ability of omega-3 fatty acid supplementation to reduce risk factors associated with cardiovascular disease in patients with type 2 diabetes. Participants (N= 81; aged 45–85 years) with type 2 diabetes were randomized into either the supplement (2714 mg/d omega-3 fatty acid) or placebo condition and were followed for 2 months. The supplement contained the following components: 1548 mg/d EPA; 828 mg/d DHA; and 338 mg/d “other” omega-3 fatty acids. Blood samples were collected at baseline and at 2 months of treatment. Primary outcome measures included total cholesterol, HbA1c, C-reactive protein, MDA, homocysteine, and fasting blood sugar. Following 2 months of omega-3 fatty acid supplementation, there were no differences between the treatment and control groups for fasting blood glucose levels, cholesterol measures, C-reactive protein levels, or MDA levels. Homocysteine and HbA1c levels were significantly reduced following 2 months of supplementation with omega-3 fatty acids relative to placebo. The reduction of homocysteine from ∼14.4 µmol/L to ∼11.3 µmol/L in 2 months represents a significant decrease; however, in the absence of reduction in other cardiovascular risk factors it is not clear if this reduction represents a meaningful reduction in total risk. Reduction of homocysteine alone has not been shown to produce benefits in a number of clinical trials evaluating homocysteine lowering and incidence of cardiovascular disease. Supplementation with omega-3 fatty acids also reduced HbA1c relative to controls, suggesting a modest benefit in glycemic control, although, as fasting blood glucose levels were not reduced, this interpretation must be approached with caution. Markers for inflammation and for oxidative stress were not modified by omega-3 fatty acid supplementation. Based on the present data, relatively short-term omega-3 fatty acid supplementation modestly improves some risk factors for cardiovascular disease, but the long term effects remain to be elucidated.