By giving volunteers doses of the vitamin that have been made harmlessly radioactive, they can trace the radioactivity and follow vitamin C as it moves through the body, thereby establishing the patterns of bodily processing, storage, uptake by the blood, and elimination. These patterns become the basis for establishing healthful vitamin C levels in an overall set of dietary standards, the recommended dietary allowances promulgated by government health authorities. In the United States these standards are based on measurements of the daily quantity sufficient to prevent scurvy, to replenish amounts chemically processed by the body in 24 hours, and to maintain an adequate reserve against the unlikely circumstance of an extended lapse in normal vitamin C intake.
The recommendations vary slightly from country to country, primarily because different countries use slightly different criteria for measurement. In West Germany, for example, the daily recommendation for adults is 75 milligrams in “food as purchased.” The United Kingdom stipulates a minimum—30 milligrams per day for adults. In Denmark, Finland, East Germany, Japan and Czechoslovakia, the recommendations for adults are 45, 30, 70, 50 and 50 milligrams per day, respectively.
In the United States the suggested amount, called a recommended dietary allowance, or RDA, for healthy teenagers and adults is 60 milligrams, for young children 45 milligrams, for infants 35 milligrams. Pregnant women, particularly those in the second and third trimesters, need an extra 20 milligrams a day. Nursing mothers need as much as 40 additional milligrams daily, virtually all of which is passed on to the suckling infant, Labels on processed foods generally express vitamin content as a percentage of the RDA contained.
Anyone eating a moderately well-balanced diet will more than meet the RDA for vitamin C. A single eight-ounce glass of fresh, canned or frozen orange juice, for example, provides approximately 120 milligrams of vitamin C, 20 per cent more than the RDA for nursing mothers and twice as much as the average adult needs. In addition to citrus fruits, fresh fruits of many sorts are rich in vitamin C, as are such fresh vegetables as broccoli, brussels sprouts, turnips, and red and green peppers. (Albert Szent-Gyorgyi delightedly noted that the vitamin he discovered was richly provided by the distinctive seasoning of his native Hungary: paprika.)
Even cooked vegetables and fruits—whether fresh, frozen or canned—will supply significant amounts of vitamin C if they are heated briefly, at moderate temperatures and for immediate consumption. Frozen and canned vegetables and fruits, if picked at peak maturity and properly processed with little delay, may actually retain more vitamin C than fresh counterparts that have been stored poorly or for long periods.
Although health authorities around the world are in general if not perfect agreement on optimum amounts of vitamin C, Linus Pauling has disputed the consensus, contending that the present RDAs are too low to help the body fight colds. The obvious way to find out if he is right is to test his thesis: Give experimental groups large doses of the vitamin and see if they catch fewer colds than other people. This has been done, The results are controversial, as such tests are maddeningly subject to error. The challenge is to design a study so flawless that even the most biased opponent can repeat it with his own staff and subjects and get the same results.
The more that researchers learn about the complexities of colds, the harder it is for them to create such unchallengeable tests. If one group of volunteers gets measured doses of vitamin C and a second, control, group takes doses of a substance known to be innocuous—a placebo—the two groups must be virtually identical in age distribution, male- female ratio, general state of health, past experience of colds, general diet, smoking habits, stress levels, family composition and work environment.
As the test proceeds, the dropout rates of the two groups must remain substantially the same. The sample size and the duration of the test must be great enough to rule out chance variations that have nothing to do with the effect of the vitamin or the placebo.
For example, if the group includes hundreds of individuals, the impact of one person’s cold on the total test results will be far less likely to tilt scores one way or the other than the impact of such an event in a group of just 10 people. Another essential for a reputable test is a safeguard against psychologically induced error, for medical experimenters and their subjects are very vulnerable to self-deception. Subjects and test administrators alike must be kept completely in the dark about who is and who is not receiving the active drug. This technique, known as a double-blind study, is never more necessary than in investigating colds and flu.
Evaluation of respiratory infections depends on slippery data—the subjective views of the sufferer and the investigator, who must record what are at best inexact and unquantifiable symptoms. For some test subjects, the psychosomatic effect of knowing they are getting vitamin C rather than a placebo will be enough to make them feel better.
Similarly, subjects who learn that they have only a placebo to ward off infection may in some way become more susceptible to sickness or at least tend subconsciously to give more importance to the symptoms they do experience. The test administrator, who may well begin his research with an unacknowledged bias for or against the test substance, may subconsciously permit that bias to get in the way of a fair evaluation, too.
In a classic double-blind test a system of coded numbers, known only to a third party, matches volunteers and medications, keeping everyone on an equally infirm footing. Further, great care is taken to make the placebo and the medication similar in size, color and taste, so that no one involved has any basis for identifying the substance until after the results are tabulated. One experiment with vitamin C ran into problems because -of a simple error that was discovered only after the experiment ended: The researchers tested the sharply acid vitamin against a bland-tasting placebo. When they later asked the subjects if they were able to guess which they had been administered, several said they were. (Those subjects were eliminated from the results, which, thus corrected, indicated no special value for the vitamin.)
Finally, a proper test should include a reasonable certainty of compliance on the part of subjects. Many “open” tests depend on unsupervised volunteers, who have to remember to take a prescribed dose two or three times a day, week after week, and to keep accurate records of their experiences. More reliable on this score are trials administered in a “closed” situation such as a school, a prison or a common place of employment, where supervisory personnel can oversee the administration of substances, the general diet and the reporting of illness. However, a closed environment introduces errors of its own. The special nature of the situation raises doubts about the relevance of participants’ reactions to those of the general population.
The complexities of modem drug testing and the potential for misinterpretation that lurks in all tests make it clear that seeing should not always be believing when it comes tojudging the efficacy of vitamin C. Persuasive though Aunt Millie’s unfailing success with vitamin C or mustard plaster may be, her miracles could derive from any number of circum stances, including hyperactive cilia, a super immune system or a natural bent for looking on the bright side, none of which owe anything to vitamins or the bracing sting of mustard.