Now, the topic of todays talk isnutrition specifically, vitamins andminerals. Ill be dealing first with some of the most commonmisconceptionsabout them. Then Im going to talk about whatvitaminsthere are, where they come from, and thequantitieswe need. Well have some time at the end of the talk for any questions you may have.
Well, vitamins are known to the general public in fact, the public knows more about them than it does about certain other keyaspectsof nutrition. One reason for this is that vitamins have been in the public eye for quite a while at least since the middle of the20th century, when their importance first became widelyrecognized. This awareness does mean that the public knows how important vitamins are even if it doesnt mean that we all eat a healthy diet all the time. However, a problem does arise that isassociatedwith this, which is the number of oldwives talesabout vitamins. Usually these fallacies are not dangerous, but they do lead to anunnecessarilyhigh intake of vitamin supplements. For example, it is widely held that high doses of vitamin C will cure colds and flu. Id like to hit this one on the head there is noevidencethat any vitamin can cure anything! No, Im afraid youll just have to let time sort out your cold. And of course, the body cant store vitamin C, so those tablets you take are just anexpensivewaste of time.
Another common belief with no evidence is the idea that vitamin A helps you see in the dark. Actually, there is some truth in this one, because vitamin A is necessary for goodvision. But in the dark, in real darkness, nobody can see. And of course, taking too much vitamin A can actually be bad for you. But perhaps the mostmisleadingidea, heavily promoted by certain companies, is that vitamins will make youintelligent. Now, while a healthy diet isessentialif you are to make the most of your intelligence, there is no evidence whatsoever that vitaminsupplementscan make the slightest bit of difference. [Pause for 3 seconds].
So what can vitamins do? Or, perhaps moreaccurately, why do we need them? Well, the answer is that we need them for all sorts of reasons.
Vitamin A, for example, also calledretinol, is essential for good eyesight, especially at night, and to help us fight offinfectionand illness. We get it from liver, butter,egg yolksand milk.
Vitamin D, as is well known, is used to build strong teeth andbones, but it also helps usabsorbcalcium. Vitamin D is mainly formed in the skin through the action ofsunlight. How much you need depends on different factors such as age and health.
Vitamin E,tocopherol, is less well-known, but is necessary in maintaining a healthybalanceof fats in the body. We need 10-12 mg every day, and although some people takesupplements, you can normally get what you need from a balanced diet.
The B complex includes vitamins BI,thiamine, B2, riboflavine, B6, pyridoxine and B12,cyano cobalamin. It performs many functions, including allowing our bodies to metabolise carbohydrates, forming healthy tissue, and perhaps most importantly, forming red blood cells to preventpernicious anemia. We need varying amounts of the B complex, and while most of us can get enough from awell-balanceddiet, vegetarians may find themselves deficient in B12, which is only found in anynoticeablequantity in meat, especially liver.
Finally, vitamin C is the one everyone knows.ascorbicacid, as its also known, helps fight infection, which perhaps accounts for the myth about preventing colds. It also helps protect againstscurvy. We need 30 mg a day, and can only really get this amount from eating plenty of citrus fruit and fresh vegetables. Now, in a moment Ill be moving on to talk about how we can plan a diet which willsupplyall our vitamin needs. But before that. Id like to look at some of the recentadvancesin our knowledge of the ways vitamindeficienciescan affect us