Medical Examiner

Your Health This Week

How travel can spread TB and how flour can help prevent stroke.

This week, Dr. Sydney Spiesel discusses the link between travel and epidemics, the benefits of fortifying flour with iron and folic acid, and the latest good news about coffee.

Travel and epidemics

Air travel can spread disease

Risk: The problem with the story of Andrew Speaker, the young lawyer with a rare and exceptionally dangerous strain of tuberculosis who flew to Greece and Rome to get married and go on his honeymoon, isn’t the risk that a fellow passenger might have actually come down with the disease. That risk, in fact, is quite low. Speaker has not been coughing and even his sputum, studied in a lab, contained very few of the deadly bacteria. (Also, his new wife remains disease-free.)

History: Still, stories like this remind us how bad it could be if a patient traveled across the world in a much more infectious condition or while carrying a more contagious disease. Airplanes and trains and buses, after all, are giant mosquitoes carrying illness from one continent to another. And in the past, disasters have been averted, but sometimes just barely.

Travelingdiseases: In 1947, a traveler took a bus from Mexico City to New York City. He arrived and was hospitalized with a condition called “hemorrhagic bronchitis.” Shortly after he died, other patients in the hospital developed smallpox and the traveler’s true diagnosis became clear. In the next three weeks, more than a half-million New Yorkers were vaccinated against smallpox and a potential public-health disaster was prevented.

And more: Though other potential sources have been suggested, West Nile disease may well have been brought to the United States in 1999 by a stowaway airline traveler—an infected mosquito from Europe or the Middle East. In 2003, SARS was carried by airline passengers from Hong Kong to Canada, leading to small but deadly local outbreaks. Lassa fever first came to the United States via an ambulance plane carrying an infected patient from West Africa. Tuberculosis, measles, and mumps have also traveled by plane.

Conclusion: It’s also possible that that the annual winter outbreak of influenza is the result of airline passengers carrying and distributing the flu virus. After air travel fell in the wake of 9/11, the annual flu outbreak occurred later in the season in the United States and Europe than it had in the previous 30 years. Speaker’s story reminds us how vigilant (and lucky) we need to be to prevent a major epidemic.

Fortifying flour with iron and folic acid

History: The addition of small amounts of vitamins and minerals to food to prevent deficiencies is one of the great triumphs of modern public health. Iodine was first added to salt in 1924 to prevent goiters, the enlarged thyroid glands seen in children who have no access to iodine-rich seafood. Next came milk fortified with vitamin D, which enhanced calcium absorption and helped prevent rickets. By the late 1930s, iron and various B vitamins (in synthetic or dried yeast form) were added to white flour to prevent beriberi, pellagra, and anemia. And in 1998, the flour additives grew to include folic acid, which helps prevent the birth defect spina bifida.

Problem: These fortifications are in use today throughout the world, though not as widely as they should be. In particular, while iron is added to flour in 49 countries, only 15 percent of the flour milled worldwide is iron-fortified. And even that is often not as effective at preventing anemia as it ought to be. The reason, it turns out, is simple.

New research: Iron is usually added to flour in the form of tiny metallic particles. A recent paper by Pauline Andang’o of the Kenya Medical Research Institute in Nairobi and her colleagues shows that this preparation works for preventing anemia when used with white flour, but not with whole-grain or corn flours, important staples in most of the developing world. The problem is that phytic acid salts, phosphorous-containing organic materials present in many plant tissues, bind the iron and prevent its absorption.

Solution: Andang’o and her team added iron to milled flour in a slightly different form: by binding it to EDTA, a chelating agent. They found that in corn flour, this iron fortification significantly helped prevent anemia and iron deficiency in children. By contrast, the standard form of iron did almost nothing to satisfy children’s nutritional needs. Because anemia saps children’s energy and decreases their ability to learn, changing to this new form of fortification would likely have a significant effect in countries with iron-poor diets.

Bonus benefit: Meanwhile, another new study highlighted a side benefit of adding folic acid to flour. Along with protecting against spina bifida, folic acid reduces the amino acid homocysteine, which at high levels is associated with cardiovascular disease, including atherosclerosis, coronary artery disease, and blood clots in deep veins. So do folic acid supplements decrease the risk of stroke?

Finding: Xiaobin Wang and colleagues at Northwestern University School of Medicine put together eight separate studies done by other researchers in which, all told, more than 16,000 patients were randomly chosen to receive or not receive a folic acid supplement. The treated and untreated groups were compared for risk of developing a stroke. The analysis showed an 18 percent reduction in the rate of stroke in the patients who got the folic acid. As might be expected, the effect was less pronounced in countries that mandate folic acid supplements, presumably because in those places both the control and experimental groups were already getting enough folic acid.

Conclusion: These two studies add to the evidence supporting the fortification of food with nutritionally necessary minerals and vitamins. The folic acid research also reinforces an older observation: The level of stroke dropped in the United States and Canada after folic acid fortification began there, while holding steady in England and Wales, which did not mandate the supplementation.

More good news for coffee

Roasted coffee beans

New research: Last year, I noted strong evidence from Finland that drinking coffee helps prevent the development of diabetes. And now there are more data to support my coffee quaffing. Hyon Choi, Walter Willett, and Gary Curhan of the University of British Columbia and Harvard Medical School have just compared the coffee-drinking habits of almost 50,000 health professionals, studying them over 12 years. The researchers found that the more coffee you drink the less likely you are to develop gout.

Conclusion: Interestingly, caffeine is not the important factor here. Decaf coffee is still fairly effective, but caffeinated tea isn’t, really. So, the gout-preventing effect must be caused by some other coffee ingredient. Mmmm. I think I’ll have another cup.