Indulge me as I digress from writing about health this week to write about an important scientific breakthrough.

People have been altering the living things around us as long as we have been around.  We domesticated wild wolves into tame dogs and kept them for protection and as pets.  Eventually humans began to farm, and raise livestock.  We then began selecting the best animals to breed for the next generation, and we selected seeds from the best plants to sow.  Generation after generation, we changed the animals and plants that we had domesticated by allowing only those with characteristics we valued to reproduce.  We had no idea what made wheat grain larger or why some sheep grew more wool, we just knew that these traits are inherited, and by breeding the right specimens we could get more of what we wanted.  Through this simple repetitive selective breeding all human crops and domesticated livestock eventually became unrecognizable from their wild origins.  The wheat we eat today has about as much resemblance to pre-human wheat as my neighbor’s yippy dachshund has to a wolf.

So millennia before any people were rigorously studying living things (engaged in what we now call biology) people were progressively modifying many animal and plant species.  In 1859 Charles Darwin published “On the Origin of Species” his landmark work which argued that just as people select the pet cats and tomatoes and carrots that form the next generation, nature selects the survivors of every species to reproduce.  He proposed that it is this selection by nature (i.e. natural selection) that explains how all species change over time and how new species arise from older forms.

At about the same time Gregor Mendel showed that inheritance follows certain predictable patterns.  The offspring are not simply a blend of the traits of the parents.  Rather the parents’ traits are somehow transmitted in distinct indivisible packages (now called genes) which are inherited and expressed according to simple rules he described.

In the 1940s and 50s the molecule carrying genetic information was found to be deoxyribonucleic acid, DNA.  And in 1953 James Watson and Francis Crick discovered the shape of the DNA molecule – the double spiral staircase – that allowed it to serve as a molecular information storehouse.

Since then the fields of molecular biology and genetic engineering have exploded, with the development of techniques to identify, isolate and sequence genes.  In 1977 the entire set of genes (genome) of a virus was sequenced, meaning its entire DNA code was deduced.  Since then the genomes of many species, including humans, have been sequenced.  Genes have been inserted into crops to make them more resistant to disease and the molecular mechanisms of some genetic diseases have been discovered.

(By the way, those who object to genetically modified organisms in their food should not eat any crops at all since all modern crops have been modified through human selection since prehistory.  Genetic modification is just a finer tool for continuing the work of millennia.  Now that I think about it, these critics should also only keep wild tigers and wolves for pets.)

This week another threshold has been crossed.  Investigators synthesized an entire genome from scratch, inserted it into cells that had their original DNA removed, and formed cells that reproduced and expressed their new synthetic genes.  The effort took 15 years.  The achievement has no immediate practical uses.  It was simply a demonstration of the technologies required for such a feat.  Potential practical uses are myriad, but are likely far off in the future.  Their discovery was published in the journal Science and has received much press attention.

Though we have much more to learn, the pace of discovery is accelerating.

Learn more:

Wall Street Journal article:  Scientists Create Synthetic Organism

Science article:  Creation of a Bacterial Cell Controlled by a Chemically Synthesized Genome

The Ancestor’s Tale by Richard Dawkins is a fascinating tour through the history of life on Earth.

A lot of people who believe they have food allergies don’t.  What’s worse, a lot of people who were told by their doctor they have food allergies don’t.

An article in the current issue of the Journal of the American Medical Association tried to review the existing literature on food allergies to standardize how food allergies are diagnosed.  What the study found was an inconsistent jumble of unreliable test results and methods.

First, to clear up some of the confusion, we have to understand the difference between food allergy and food intolerance. A food allergy is a reproducible adverse reaction to a specific food that is mediated by a specific antibody that your body makes.  It usually results in a rash or difficulty breathing and can be life-threatening.  The article estimates that more than 1% or 2% of the population (but less than 10%) have true food allergies.

Food intolerance is any other adverse effect from food.  Lactose intolerance, for example, is the inability to digest lactose, the carbohydrate in dairy products.  It leads to abdominal discomfort and diarrhea whenever dairy foods are ingested.  It is not an allergy.  Neither is acid reflux, which can be exacerbated by certain foods, or gustatory rhinitis, in which spicy foods cause a runny nose.  These are all food intolerances.  So if you get heartburn every time you eat mint, you’re not allergic.  You just have acid reflux that is exacerbated by mint.

But we doctors are a more important source of the confusion.  Unfortunately, there is no easy way to accurately test for food allergies.  The most common tests are skin prick tests, in which small amounts of the food proteins are injected into the skin, and blood tests which look for antibodies to certain food proteins.  The problem with both tests is that they are very inaccurate and yield many false positives – the tests can be abnormal even when the person is not allergic.  So based on these tests many patients have been incorrectly told that they have a food allergy.

The most accurate way to diagnose a food allergy is a food challenge – a patient is given the test food in a disguised form so that she doesn’t know if it is the suspected allergen or a placebo.  Then the patient is observed.  This is accurate but impractical.  The patient must be under observation for a prolonged time in a facility that is equipped to handle a potentially life-threatening allergic reaction.

So the current state of the field is disorganized.  There is no standardized accepted way to accurately test for food allergies, and without that foundation, no way to study them.  The authors conclude

“There is voluminous literature related to food allergy, but high-quality studies are few. Prime needs for advancement of the field are uniformity in the criteria for what constitutes a food allergy and a set of evidence-based guidelines on which to make this diagnosis.”

Learn more:

Los Angeles Times Booster Shots:  With food allergies, much is said but little is known, conclude researchers

New York Times article:  Doubt Is Cast on Many Reports of Food Allergies

Journal of the American Medical Association article:  Diagnosing and Managing Common Food Allergies

Tangential miscellany:

An article in the current issue of Annals of Internal Medicine reviews the experience of the Israeli Field Hospital that responded to the Haiti earthquake. The field hospital had 121 medical staff and 109 support personnel. They arrived 89 hours after the earthquake with a mobile hospital that had operating rooms, intensive care units, equipment for radiology and laboratory testing, and medications. In 10 days they triaged 1,111 patients, hospitalized 737 of them and performed 244 surgeries – an impressive demonstration of logistical, medical and humanitarian preparedness.

Annals of Internal Medicine article:  Early Disaster Response in Haiti: The Israeli Field Hospital Experience