UNA DIETA ADECUADA, ACTIVIDAD FÍSICA Y CUIDADO DE LA MICROBIOTA INTESTINAL, PIEZAS CLAVE PARA UN SISTEMA INMUNITARIO FUERTE EN EL NIÑO

  “La nutrición es un componente determinante en el desarrollo y el mantenimiento de la respuesta inmune. Pero no es una relación sencilla ya que influyen también otros factores”, asegura el doctor José Manuel Moreno Villares, coordinador del Comité de Nutrición y Lactancia Materna de la Asociación Española de Pediatría (AEP). “El éxito de esta relación pasa por la participación, en distinto grado, de los nutrientes que están contenidos en los alimentos, pero también de la microbiota intestinal y de otros elementos presentes tanto en la luz intestinal como en la propia pared del aparato digestivo”, asegura el doctor en el transcurso de su intervención “Influencia de la alimentación en la inmunidad” enmarcada en la iniciativa de la AEP ‘Jueves con la Ciencia’.

Entre las funciones de la microbiota intestinal cabe destacar que favorece la digestión fermentando los alimentos no digeribles y favoreciendo la absorción de los nutrientes (aminoácidos, azúcares, vitaminas, etcétera) a través de las células del intestino. Además, actúa como barrera contra los microbios y toxinas, y contribuye en el desarrollo del sistema inmunitario intestinal y a un correcto funcionamiento y mantenimiento de la mucosa que protege el intestino. “La presencia de algunos desequilibrios en la alimentación puede dar lugar a alteraciones en la inmunidad, que pueden manifestarse como aumento en el riesgo de infecciones o en reacciones alérgicas”, asegura el doctor Moreno Villares.

Influencia de la alimentación en la capacidad inmune en la infancia

El bebé ya recibe influencias de la alimentación de la madre cuando está en el útero

materno y contribuye a preparar su sistema inmune. Después del nacimiento el tipo de alimentación contribuye a la maduración de ese sistema inmune. “En los primeros meses de vida la lactancia materna es el alimento más completo que puede ofrecerse al bebé”, explica el doctor Moreno. La lactancia natural  protege frente al riesgo de infecciones, no solo en la etapa de lactante sino también en la infancia. “No sabemos si este efecto se debe a determinados nutrientes presentes en la leche materna o a la interacción de ellos entre sí”, asegura este experto. Algunos de esos nutrientes (HMOs, probióticos, etcétera) se han ido incorporando a las fórmulas infantiles con el objetivo de intentar imitar los beneficiosos efectos de la leche materna.

Más allá del periodo de lactancia exclusiva se produce una progresiva incorporación de alimentos a su dieta, que va  acompañado de una correcta maduración del sistema inmune. “La buena relación entre ambos actores es la que da lugar a mayor riesgo o mayor protección frente a enfermedades, fundamentalmente infecciosas, autoinmunes o alérgicas”, explica el coordinador del Comité de Nutrición.

Esa relación entre inmunidad y nutrición se ve claramente en la desnutrición, en la que el riesgo de infecciones es más elevado. La mitad de los niños menores de cinco años que fallecen en el mundo lo hacen como consecuencia de la desnutrición y las infecciones relacionadas con la misma. “Pero también la obesidad se asocia a mayor riesgo de infección”, matiza el experto. La mejor prevención para la obesidad del adulto es prevenir la obesidad en el niño. “La edad para intervenir es preferiblemente antes de los 5 años”, indica el doctor Moreno Villares.

Algunos nutrientes tienen un mayor efecto sobre la función inmune, como el zinc o la vitamina D. “Se debe garantizar que los niños con niveles bajos de vitamina D reciben las cantidades adecuadas y tienen una exposición solar mínima todos los días para garantizar su síntesis en la piel”, asegura.

Nutrición frente a la COVID-19

En cuanto a la infección por COVID-19, no parece haber un patrón de alimentación determinado que modifique el curso de la enfermedad. “El consejo nutricional es el mismo antes, durante y después de la pandemia: dieta variada y ajustada a las necesidades, basada fundamentalmente en

Stubborn gut bacteria offer insights into yo-yo dieting

Previously obese dieters may struggle to keep weight off because of poor gut bacteria diversity, according to a new study presented today at the European Congress of Endocrinology.

For every cell that makes up the body, there are ten bacteria living on and in it – which means the diversity of bacterial species we have in our system (known as the microbiome) has a huge impact on our health.

Recent studies show that the gut microbiome plays an important role in regulating digestion and energy metabolism, and that obese people have gut bacteria that are better able to extract energy from food. Any surplus energy is converted in the body to fat. As most dieters struggle to keep off the weight they originally lost, manipulating the gut microbiome could be the key to helping stave off obesity and diabetes.

In this study, German researchers from University Hospital Schleswig Holstein in Kiel put eighteen obese adults on a diet of just 800 calories per day for a three month period and tracked how much weight they lost, their sensitivity to insulin, as well as both the activity and diversity of their gut bacteria using stool samples. They then tracked the same factors after putting the dieters on a weight maintenance diet for a further three months. The researchers then compared the results to thirteen obese (control group) and thirteen lean adults who followed their regular diets throughout.

Compared to the control or lean group, they found that the obese dieters had a (beneficially) altered microbiome diversity and metabolism at the end of their three month dieting, but this was not sustained during the three-month weight maintenance phase, despite losing an average of 20kg overall and having improved insulin sensitivity at the end of the six month period.

One of the limitations of the study is that the medications patients may have been taking was not accounted for, which could have an impact on gut bacteria diversity and metabolism.

“Anti-obesity campaigns often recommend low calorie diet programs such as the one we offered here”, said lead author of the study Professor Dr. Matthias Laudes. “However, our work shows that this is not making enough of a long-term change in obese people’s gut bacteria, which may explain why so many of them put weight back on”.

“We want to know why the gut microbiome is resistant to maintaining change after dieting,” he continued. “In the future we will look at the potential of using prebiotics during weight maintenance, or even the potential of faecal transplantation from a healthy gut to that of an obese patient”.

Injection of appetite gene may offer a more effective alternative to dieting

Increasing the amount of appetite hormone, leptin, in the brain causes long-term weight loss without the bone weakening which is a common side effect of weight loss by dieting, according to a study published today in theJournal of Endocrinology.

Leptin, known as the appetite-suppressing hormone, is produced by fat cells in the body and sends a signal to the brain that tells us when to stop eating. Obese people often become desensitised to their leptin hormone signals and over eat as a result.

Conventional weight loss methods such as dieting lead to weight loss that is often difficult to maintain and can lead to weakening of bones and osteoporosis equivalent to significant aging. Because osteoporosis is a major public health issue associated with decreased quality of life and increased mortality, there is a strong incentive to develop weight loss strategies that preserve bone strength.

Researchers at the Oregon State University and the University of Florida in the USA have found that injecting the gene that codes for leptin into the brains of adult female rats causes them to lose weight and maintain lower body weight. The researchers also looked at the structure of bones from rats that lost weight as a result of leptin gene-therapy and compared them to bones of normal rats that gained weight; they found that the gene-therapy rats did not lose bone mass.

Dr Urszula Iwaniec who conducted the study said, “Unfortunately, dieting, exercise and weight loss drugs have limited long-term success in controlling weight and can result in detrimental side effects such as weakening of the bones. In this study we show that leptin gene-therapy causes effective long-term weight loss while maintaining bone mass” 

“Although the results are promising, additional research will be required to determine whether leptin gene therapy is practical for use in humans.”

Obesity is a major public health issue across the world. In the UK it is predicted that in 2015 obesity will cost the NHS £27 billion and in the US the annual cost of obesity exceeds $147 billion. These expenses are projected to increase over the years with 1/3 of the US adult population now being affected by obesity.

“Novel approaches like leptin gene-therapy for treating obesity are needed to address this public health crisis”, said Dr Iwaniec.

More exercise, eating less fat and weight loss programs are in, popular diets are out

Contrary to popular perception, a large proportion of obese Americans can and do lose weight, say researchers at Beth Israel Deaconess Medical Center. What's more, they say, the old tried and true methods of eating less fat and exercising are some of the most effective paths to weight loss success. The research results appear in the April 10 online issue of the American Journal of Preventive Medicine.

"This is great news because studies have shown that even a 5 percent reduction in weight can lead to improved health," says lead author Jacinda M. Nicklas, MD, MPH, MA, a clinical research fellow at Beth Israel Deaconess Medical Center and Harvard Medical School. "With more than a third of Americans now obese and fifty to seventy percent of them trying to lose weight, this is important because the health risks associated with carrying that extra weight are substantial."
Nicklas and colleagues analyzed data from more than 4,000 obese individuals culled from the 2001-2006 National Health and Nutrition Examination Survey conducted by the Centers for Disease Control and Prevention to assess the health and nutritional status of adults in the United States.
Individuals included in the study were over 20 years of age with a body mass index of 30 or more 12 months prior to the interview.
Of those surveyed, 2,523 individuals reported trying to lose weight. Forty percent of these said they experienced weight loss of 5 percent or greater, and another 20 percent lost 10 percent or more.
"Those who exercised more and ate less fat were significantly more likely to lose weight," say the authors. "Additionally we found a correlation between joining weight loss programs and greater reported weight loss, which may speak to the importance of structure in a weight loss regimen" says Nicklas. And while those who used prescription weight loss medications also reported weight loss success, this represented only a small number of study participants.
In contrast, the authors found that, "self-reported use of popular diets, liquid diets, nonprescription weight loss pills and diet foods/products were not associated with weight loss."
"It's very encouraging to find that the most of the weight loss methods associated with success are accessible and inexpensive," says senior author Christina Wee, MD, MPH who conducts research on obesity and health disparities as the Co-Director of Research in BIDMC's Division of General Medicine and Primary Care. "There are lots of fad diets out there as well as expensive over-the-counter medications that have not necessarily been proven to be effective, and it is important that Americans discuss product claims with their doctor before trying such products."
This study did not look at the long-term impact of these interventions on an individual's ability to keep the weight off. The authors suggest that future research is needed to identify and address barriers to maintaining weight loss.

**Source: Beth Israel Deaconess Medical Center