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Nutrition Bytes

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Prenatal Programming of Obesity by Fetal Malnutrition: A Role for Leptin

With the current growing epidemic of obesity in the United States [18] and broad acceptance of the idea that the prenatal period may be a critical period for programming permanent changes in metabolic processes, increasing attention in the past decades has focused on the idea that intrauterine events can program adult obesity. Animal and human studies supporting a relationship between prenatal malnutrition and postnatal obesity [14,15] have spurred research elucidating mechanisms of prenatal programming of obesity. This paper reviews evidence for the role of leptin in programming of postnatal obesity by prenatal malnutrition based on published studies in animals and humans. Though human evidence is reasonably limited by the ethics of well-controlled trials studying fetal malnutrition, sufficient animal evidence exists to support several biologically-plausible mechanisms involving programming of leptin resistance at the level of the hypothalamus. Though more research is needed to provide conclusive data regarding the role of leptin in mediating the postnatal effects of prenatal malnutrition, evidence for mechanisms of prenatal programming of obesity may have widespread implications for public health and medicine in the future.

Medicinal Marijuana: A Legitimate Appetite Stimulant?

Medicinal marijuana has been at the center of controversy for the treatment of cancer cachexia and AIDS related weight loss. Dronabinol, the oral form of marijuana, was approved for appetite stimulation, but its variability in absorption has led researchers to believe that smoked marijuana may be more effective. The discovery of endocannabinoids and their receptors has drawn attention from the research community, and as a result, marijuana’s role in appetite stimulation is clearer. Marijuana may play a critical role in the leptin pathway of appetite stimulation, and continued research in this field may lead to obesity prevention and treatment. The downfall of medicinal marijuana is its side effect profile, which includes increased risk of pulmonary malignancy, neural damaging effects, and psychosis. With more research on minimizing side effects and maximizing effectiveness, marijuana may be valuable in the treatment of appetite suppression related diseases such as cancer and AIDS.

Breast-feeding Lowers Childhood Obesity

Given the several morbid conditions associated with obesity, as well as its increasing prevalence and its difficult treatment, it is necessary that efficient preventive measures be found. Simple measures, without potential adverse effects and a low cost should be a priority. The inverse association between breast-feeding and obesity suggests a role for breast-feeding in the reduction of obesity prevalence in later life. This protective effect of breastfeeding is supported by many epidemiological studies, but literature data are still controversial. Possible explanations for how breastfeeding protects against later obesity include behavioral and hormonal mechanisms and differences in macronutrient intake.

Antitumorigenic Effects of Flaxseed and Its Lignan, Secoisolariciresinol Diglycoside (SDG)

The flax plant (Linum usitatissimum) is an annual herb. The seeds are also one of the richest dietary sources of phytoestrogens (estrogenic compounds derived from plants). Because flaxseed is the richest dietary source of lignans, it has been used to investigate the potentially anticarcinogenic effects of lignans in animal studies and some human trials. The plant lignan secoisolariciresinol diglycoside (SDG) has been suggested to be the primary effector of the antitumorigenic effects of flaxseed observed in vitro with mammary and colon carcinogenesis models. Proposed mechanisms to date for the observed inhibition of tumor growth have included estrogenic and antiestrogenic effects, anti-oxidative effects, antiproliferative and anti-aromatase effects. This review addresses some of the animal and human studies of flaxseed’s anticarcinogenic effects in breast, melanoma, and prostate cancers. The data on possible antitumorigenic effects of flaxseed in humans are inconclusive at best, however, in vitro data suggest that SDG as an anticarcinogenic agent warrants further study. Its potential mechanism of action in cancer prevention remains unclear. Flaxseed supplementation for its own sake is harmless, however, and potentially beneficial in other ways not addressed by this review.

Trimming Adolescent Obesity: Is Surgery the Answer?

The pervasiveness of obese children and adolescents in the United States has almost tripled in the past 30 years, and current conservative estimates indicate that 15.5% of children and adolescents are obese (defined as body mass index [BMI] of 95th percentile for age). Given this, it is necessary to identify whether bariatric surgery should be indicated for obese adolescents. The Roux-en-Y gastric bypass (RYGB) and adjustable gastric banding (AGB) have been used to treat morbidly obese adolescents, and this paper reviewed primary clinical studies that examined the efficacy of each procedure in this population. Multiple studies confirm that both procedures produce significant weight loss in morbidly obese adolescents. However, there is currently no definitive evidence demonstrating one procedure to be superior to the other, or either procedure being superior to non-surgical weight loss treatments. Most troubling is the fact that only one study outlined comprehensive guidelines for adolescent patient management before, during, and after surgery with provisions for nutritional and psychological counseling. Therefore, more research is needed to prove the efficacy and safety of gastric bypass surgery in morbidly obese adolescents, and currently this treatment should be reserved for the most severely obese adolescents for which all other forms of treatment have failed.

"Net Carbs": The Lowdown on Low-carb Labeling

In light of the increased popularity of low-carb dieting in the US, food manufacturers have invented new claims to make their products more appealing to consumers. Instead of touting a low total carbohydrate content, these products use the phrases “net carbs,” “effective carbs,” and “impact carbs” to reflect only the number of carbohydrates that have a significant impact on blood sugar. The theory is that only carbs that cause a rapid insulin response “count” in low-carb dieting. Measures of “net carbs” often subtract out the carbohydrates due to sugar alcohols. The scientific basis for discounting all sugar alcohol effects is questionable. It is based on the assumption that all sugar alcohols behave the same in the body, and in a way that is significantly different than other carbohydrates – an assumption that is largely untrue. The use of phrases like “net carbs” on product labels can cause confusion, resulting in important health risks to the consumer. While the FDA is responsible for regulating labeling claims, they have yet to take significant action in resolving the confusion surrounding “low-carb” claims.

Carotenoids: Nature’s Cure to Macular Degeneration?

Age related macular degeneration (AMD) is the leading cause of irreversible vision loss in the elderly populations of the US and Western World. Although the pathogenesis of AMD is still being debated, studies that show the anti-oxidant carotenoids, Lutein and Zeaxanthin may have protective affects against AMD are mounting. This article will conduct a PubMed based review of the most current literature on the protective role of carotenoids against the progression of AMD. Our search noted studies showing decreases in carotenoid density in the retina’s of AMD sufferers and the ability of nutritional supplementation to increase retinal densities in AMD and non-AMD sufferers. Recent studies have also shown improvement in other clinical measurements such as enhanced visual acuity amongst patients started on dietary supplementation with carotenoids. Our review concludes that there is epidemiological and clinical evidence suggesting that the carotenoids, Lutein and Zeaxanthin, do play a protective role against the progression of AMD however, further large randomly controlled clinical trials are needed.

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