Converting a meal from our plates into the nutrients our bodies need is an elaborate procedure. First we produce enzymes that break down the food so our cells can use it, then hormones travel throughout our system, regulating activities within the cells. This process is called metabolism. Given that the production of all chemicals in our bodies are determined by our genes and our genes can go awry, it’s not surprising that our metabolism can be thrown off track. Many of these genetic disorders are referred to as inborn (or inherited) errors of metabolism (IEMs).
The list of these disorders, or just the ones we know about, is quite long and includes common ones such as type 1 diabetes and phenylketonuria (PKU), and more obscure conditions such as Zellweger syndrome.
We have so many cells doing different jobs in our bodies that it stands to reason that there are myriad manifestations of these disorders. Most of them result in an accumulation of a certain chemical that would otherwise be processed or broken down. The accumulation causes dysfunction in the cell and the type of cell affected determines the manifestation of the disease.
Treatment of IEMs is typically difficult. Even when the specific defect is well understood and reversing its effects may not be possible—yet. Typically, only the symptoms can be treated and even then with limited success.
Sometimes the treatment involves working around the problem, such as avoiding foods that contain substances the affected person cannot metabolize. For example, PKU is a problem with the breakdown of phenylalanine, which is a particularly ubiquitous amino acid (proteins are long strings of amino acids). So, people with PKU are instructed to avoid high-protein foods and most artificial sweeteners.
by Thomas Chappell, MD
