According to researchers, only the best sperm that have the highest chance of succeeding in fertilization will survive the production process without a tag.

A small protein called ubiquitin marks abnormal sperm cells, including cells that have two heads, two tails or are otherwise misshaped. This recycling tag on the sperm cell tells the body which cells need to be broken back down into amino acids. This provides evidence that there is an active removal process or marking of defective sperm during the epididymal passage.

Fertilization is, in a way, a numbers game, said Peter Sutovsky, associate professor of animal sciences, clinical obstetrics and gynecology in the MU College of Agriculture, Food and Natural Resources. You need a certain number of normal sperm cells to reach the egg. If too many are tagged with ubiquitin, there may be not enough to fertilize an egg.

This study suggests that the male reproductive system must be able to evaluate and control the quality of the sperm to insure an optimal chance of fertilization. High levels of ubiquitin in the sperm can indicate low-sperm count or infertility. This process of quality control has been found in both humans and other mammals including bulls, boars and rats.

In many cases, the cells that are tagged with ubiquitin are obviously abnormal with two tails or two heads, but many of them look like they don't have defects, Sutovsky said. Oftentimes, these cells may look normal but lack proteins that are important to fertility.

Once sperm cells are tagged as defective, it is unlikely that the process can be reversed. Sutovsky stresses the importance of a healthy lifestyle to reduce the likelihood of abnormal sperm cells. He suggests avoiding exposure to toxic chemicals, abstaining from smoking and maintaining a healthy diet. He suggests people who work with toxins on a daily basis should minimize their exposure by wearing protective clothing and respirators.

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Professor Caroline Fall, of the MRC Epidemiology Resource Centre in Southampton one of the authors who predominantly looks at nutrition in India said: Children who are undernourished in the first 2 years of life and who put on weight rapidly later in childhood and in adolescence are at high risk of chronic diseases related to nutrition. It would appear their metabolism, which is largely set during early development, is particularly ill-equipped for coping with times of plenty they may experience later in life. Having said that, rapid height gain in the first 2 years of life is not associated with adverse health consequences in later life.

Professor Fall is spearheading a large-scale intervention trial in Mumbai looking at the impact of better diet on mother and offspring by recruiting young women before they become pregnant and providing them with a daily dietary supplement (in the form of a samosa) high in micronutritients. The trial is still in early stages, but it is hoped it will provide evidence for what intervention may work to address the problem of poor maternal and child nutrition in India.

The damage suffered as a result of mother and child under-nutrition leads to permanent physical and mental impairment, and also harms future generations. Populations who are severely affected by stunting and the negative health and life impacts of under-nutrition in early life will be less able to grasp opportunities to climb out of poverty. We simply must find ways of addressing these problems, concluded Professor Fall.

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