Thursday, October 22, 2020

A few more things about dietetics

In a previous post I questioned that dietetics is a science, because it seems to follow quite often what can be considered alternatives of fashion, and I gave some examples. In this article I’m going to add a few more, along with a general consideration.
  • The expiration date of yogurts. A few years ago, there were several books published and speeches made, asserting that yogurt should never be eaten just one day after its expiration date. Of course, no expired food should ever be used to help poor people. However, any quality expert knows that expiration dates always include a safety margin that can sometimes be quite long (days, weeks, or even months). Therefore, some kinds of very recently expired food are probably within that safety margin and can be eaten without problems. Not to mention the fact that there are products (such as yogurts) that don’t need an expiration date, as their substance is not spoiled, even though it may lose nutritional or flavor properties. This is why lately, in this type of products, there is no longer talk of an expiration date, but of a preferred consumption date.
  • The favorable or unfavorable effects of drinking a little wine with meals. First, it was considered proven that drinking half a glass of wine with each meal (a part of the Mediterranean diet) is good to avoid heart problems. This favorable effect was later considered applicable only to males over 50. Later there was another study that asserts that alcohol consumption is always unfavorable, because it can increase the risk of cancer. I suppose studies will continue to be carried out and results published. I don’t know to what extent the current situation can be considered final. However, a recent analysis of dietary advices on TV newscasts, says the following: One of the mantras cited by [the TV] is that drinking one or two glasses of wine a day is beneficial. But nothing is further from reality: moderate and healthy alcohol consumption is a great myth that does not prevent cardiovascular problems and, in fact, can increase the risk of diseases such as cancer. It is curious, for the link they provide to support what they say just mentions that the benefit of alcohol consumption on cardiovascular health likely has been overstated, and in relation to cancer, points out that excessive use of alcohol should be prevented, a quite ambiguous phrase.
  • The harmful or harmless effects of food additives. The same analysis cited in the previous point assures that [the TV] speaks poorly of additives in its newscasts, despite their being safe substances that help improve the appearance or texture of [foods] and preserve them better. We know that there are many controls on food additives, but it’s also true that companies sometimes abuse, introducing a large number of colorants, preservatives, flavors, sweeteners, emulsifiers, thickeners, stabilizers, acidifiers and antioxidants, whose usefulness could be debatable. The more so, since other companies put for sale the same products without additives or with a minimum of additives, thus attracting public attention, so as to induce them to buy them. In fact, there is a flourishing market for these products.
I am not saying that these things are wrong. They may all be correct. What I am saying is that it is risky to take as final things that history shows us can change abruptly overnight.
Part of the problem may be that provisional scientific results are sometimes presented as final. We know that the application of statistics to medicine often poses considerable difficulties, not always well resolved. Most of these studies are based on the analysis of a certain number of specific cases, which are compared with an equivalent number of control cases, and then statistical criteria are applied, but they aren’t always well justified. I have seen supposedly scientific news, not just in the mass media, but in professional magazines, saying things similar to the following:
Such disease was treated with such medication in 20 patients; 20 others were given a placebo. Three died in the first group; four in the second. Therefore, this medication reduces the mortality of this disease by 25%.
Mathematically the result may be correct, but its statistical significance is null.
The same post in Spanish
Thematic Thread on Linguistics and Medicine: Previous Next
Manuel Alfonseca

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