Recipe for Analyzing Trace Nutrients in the U.S
(Services daily intake of one 25-to-30-year-old male)
With a Teflon knife, cut away samples of 201 cooked foods. Blend together in a food processor fit with a titanium blade. Pulse a few times, then add "cocktail" -- a conglomeration of beer, juice and other commonly consumed beverages. Mix until smooth. Freeze-dry, bombard with nuclear radiation and analyze for 24 trace nutrients. Repeat similar procedure for diets of 10 other countries to help formulate diet recommendations and health policy.
This one-of-a-kind recipe is the groundwork for a first-of-its-kind international research project. Coordinated jointly by the National Bureau of Standards, the Food and Drug Administration, the U.S. Department of Agriculture and the Austria-based International Atomic Energy Agency (IAEA), a facsimile of this "research recipe," will be repeated in laboratories all over the world.
Trace nutrients, recognized more commonly as lead, zinc, iron, calcium, chromium or selenium, are the most elusive of nutritional elements. On the one hand, they are crucial for the proper functioning of the body. On the other, they are required in such small amounts that they are often difficult to measure. In addition, trace element deficiencies in humans don't occur overnight -- and marginal deficiencies are very hard to detect.
Up until now, very little accurate or consistent information has existed about the trace nutrient status of other countries, explained Venkatesh Iyengar, principal investigator for the U.S. portion of the project, who works out of the National Bureau of Standards in Gaithersburg.
But such findings could prove illuminating, particularly for Third World countries. Already, identifications of trace element deficiencies have led to food and supplement fortification. Salt fortified with iodine helped rectify goiter in this country, according to trace-nutrient expert Walter Mertz, director of the USDA's Beltsville Human Nutrition Research Center. And a selenium-deficient diet among a localized population of Chinese children was identified as the cause of a fatal heart disease called keshan, Mertz said.
Iyengar and the other scientists on the project have established a standardized, quality-controlled method for analyzing the elements. Collection procedures may vary since food habits are different on the weekends in western countries (thus, a collection for seven days would be required), whereas in many developing countries, food habits are less varied.
Besides from the United States, food samples will be taken from Thailand, Turkey, Brazil, China, Italy, Spain, Sudan, Sweden, Canada and Iran.
Several of the countries have been broken into two or three study groups in order to track diverse food habits due to geography or social class. For instance, the diets of Italians have been divided into 1) general population, industrial area, 2) general population, mountainous area and 3) general population, area with high intake of seafood. The Sudanese diet has been divided into the urban, lower middle class and the suburban lower class. Other countries are studying possible risk groups such as children and pregnant women.
The NBS lab has already done preliminary analysis of the samples of the U.S. and Turkish diets, although much of the information still needs to be verified, according to Rolf Zeisler, project leader for the program. "Early indications," however, show that the two samples are quite different, Zeisler said. Interestingly, the samples indicate that the Turkish diet is about three times as high in sodium chloride (salt) as the American diet, noted Zeisler.
On a bookshelf in Iyengar's office sit two little vials -- the U.S. and Turkish diets reduced to a powdery mass. The American "diet," a concentrate of the 201 foods, is a mustard color and has a sweet smell. The Turkish diet is a whiter, finer powder. Even by looking at them, you can tell the dietary differences, noted Iyengar. The American powder is more clumpy, possibly an indication of the higher fat content. The whiter color of the Turkish diet indicates a higher cereal and vegetable diet, Iyengar said.
The process to powder, which turns common table food into a scientific tool, involves a lengthy and rather unusual set of procedures with industrial-size Robot Coupes, vaporous specimen banks and "clean" rooms where scientists work under ultra-sterilized conditions.
At NBS headquarters, it all starts in a freezer stocked with zip-locked plastic bags. It looks like anyone's somewhat sloppy freezer, except these bags are filled with coded food samples (139: Scalloped potatoes; 070: macaroni).
Sent from the FDA field office in Kansas City, the samples are from the agency's Total Diet Study, an annual program which involves the purchase of selected foods in grocery stores across the United States and analysis for essential minerals, toxic elements, pesticides, industrial chemicals and radionuclides.
(TDS also analyzes for trace nutrients, but only for about half of the elements that will be analyzed in the joint research program. Scientists involved will also analyze the foods mixed together, not separately, as TDS researchers do, a technique that makes a project of this size more manageable, said Zeisler. While the mixed-foods method will still turn on "warning lights," Zeisler said, it does have its disadvantages since it limits the ability to recognize which foods or food groups are contributing to trace nutrient deficiencies or excesses.)
The foods have already been prepared via TDS specifications. For each food, there are recipe instructions meant to mirror typical American preparation methods. (Pork chop, pan cooked with added fat: Melt hydrogenated vegetable fat in pan about 1/4 inch . Brown chops on both sides medium-well done . Discard bone and excess fat.)
From there, the food enters the "dust-free clean room," a lab with bright white cabinets, filtered air and protective shields around the work tables that look like giant salad bar sneeze guards.
Nothing must get into the food other than what's already in it, Iyengar explained. That's why the clean room is equipped with "kitchen equipment" made out of either Teflon or titanium, two materials that limit the possible contamination of the samples.
But before the food can enter the room, the scientists must don their clean room garb: long white lab coats, booties for over the shoes, hats that fully cover the hair and goggle-like plastic glasses. Work is performed with clear disposable gloves, a safeguard against contamination caused by sweat.
Iyengar demonstrates the recipe technique: Foods are transported via a Teflon scooper and weighed on a little scale. The array of foods spans from corn flakes to a bright orange sample of spaghetti with canned tomato sauce, to a seaweed look-alike sample of canned spinach, to coffee cake and fried chicken. On the same table, there is "Cocktail A" and "Cocktail B," huge mason jars filled with an unappetizing conglomeration of beverages such as whiskey, beer, coffee, Coke, tea and juice. Few of the foods look anything like their original state.
The foods are then placed in the Robot Coupe food processor with the titanium blade, a special model, according to John Henkel, spokesman for NBS.
Iyengar pulses the concoction, 15 seconds at a time, and soon it begins to resemble something that even a bad chef couldn't whip up.
After that, the food is freeze-dried and readied for neutron activation analysis, a technique that irradiates the food with neutrons to produce radioactive isotopes. The now-radioactive food samples allow the scientists to determine the trace elements.
Some of the freeze-dried samples are saved and stored in liquid nitrogen, in what NBS calls its Environmental Specimen Bank. In a room adjoining the clean room, three huge tanks are filled with cylinders containing the food samples, as well as 500 human livers and a batch of marine mussels and oysters -- materials saved for contaminant analysis for other projects. The preserved food, a kind of library archive, will allow the scientists to compare it with future findings, and to track trace nutrient trends.
As for the results of the joint project, Zeisler estimated that a full international comparison should be out in about two years. Groups such as the World Health Organization and the National Institutes of Health should be among the groups interested in the resulting scientific data base, said Iyengar. And from there, the link with health problems and nutritional inadequacies will hopefully set the stage for intervention to improve the health of target populations, Iyengar said.