Daily consumption of yogurt may boost the immune function in people with weakened defense systems, suggests a new study from Spain.
People with the eating disorder anorexia nervosa are known to have a compromised immune system, due to the poor diet and erroneous eating habits.
According to new findings published in the European Journal of Nutrition, daily consumption of a yogurt containing Lactobacillus bulgaricus and Streptococcus thermophilus during a re-feeding program may boost the immune system of anorexics.
Researchers from the Department of Metabolism and Nutrition at the Instituto del Frio (CSIC) report that the immune boosting benefits of the dairy product were not observed when milk was fed in place of yogurt, an observation that points to the influence of the bacterial strains in the yogurt.
“The findings suggest that the inclusion of yogurt in the refeeding therapy of AN patients may exert positive effects on the immunological markers related to the nutritional status of these patients,” wrote the researchers, led by Esther Nova.
Conventional, not ‘probiotic’, yogurt
The researchers note that conventional yogurt exclusively fermented by L. bulgaricus and S. thermophilus is the most consumed in the world. However, “relatively few studies have looked into the effects of this conventional yogurt, without any additional Lactobacillus or Bifidobacteria strains, on the immune system in humans”, they added.
The new study involved 30 anorexic and 33 health adolescents. The anorexic adolescents were randomly assigned to receive either the yogurt or semi-skimmed milk as part of their refeeding diet, while the health adolescents were also assigned to receive either the yogurt or the milk for 10 weeks.
The researchers looked at the ratio of CD4+ lymphocytes to CD8+ lymphocytes, a well established diagnostic measure of immune system functioning. Lymphocytes are white blood cells that play a key role in immune response, while CD4+ and CD8+ refer to the presence of certain receptors on the surface of the cells.
A low ratio of CD4+ to CD8+ is indicative of a suppressed immune system.
According to the findings published in the EJN, anorexics receiving the milk displayed a decrease in the CD4+/CD8+ ratio, indicating a weakening of their immune system after 10 weeks. On the other hand, those consuming the yogurt did not display this decline.
The researchers also reported a significant increase in levels of a molecule called interferon-gamma or IFN-gamma, an important marker of adaptive and innate immunity, in both yogurt-consuming groups (anorexic and healthy adolescents.
“Yogurt seems to be a good alternative to prevent the decrease observed in the CD4+/CD8+ ratio in anorexia nervosa patients, which means that yogurt could be a healthy food choice to include in the refeeding therapy of these patients,” they wrote.
Source: European Journal of Nutrition
Volume 45, Number 4, 225-233, DOI: 10.1007/s00394-006-0589-8
“Effects of a nutritional intervention with yogurt on lymphocyte subsets and cytokine production capacity in anorexia nervosa patients”
Authors: E. Nova, O. Toro, P. Varela, I. Lopez-Vidriero, G. Morande, A. Marcos