Countless times when we were young we were told "eat your greens, they’ve got vitamins in", or eagerly chobbled down that tasty little haliborange tablet. But just what are vitamins, and what do they do for us? What happens if we don’t get enough, and can we have too much of a good thing?
In short, vitamins are chemical compounds which are required for essential metabolic reactions to take place in the body. In these reactions, vitamins can either be participants (the raw materials involved in the reaction) or a catalyst (something that speeds up a chemical reaction, without being altered itself). Vitamins generally cannot be made by your body – hence the need to eat food containing them, although there are two exceptions to this.
Until the last 30 or so years, vitamins could only be obtained by eating food that contains them. Each food source contains different ratios of vitamins, so it’s important to eat a wide-ranged and balanced diet to get all the vitamins you need. Because fruit and vegetables available vary with the seasons, it’s important to alter your diet accordingly to maintain that correct balance of necessary vitamins throughout the year.
There is a good argument for taking vitamin tablets – however, these should only be taken as a supplement to your diet, and only when necessary. Plus – can anyone honestly say it’s more fun swallowing a tablet with a glass of water than biting into a nice juicy orange? Didn’t think so!
Not all vitamins come from our diets though – as mentioned, there are two exceptions, Vitamin K, which is produced by bacteria in our intestines, and Vitamin D, which is formed in the skin following exposure to natural sunlight.
How long have we known about vitamins? Well, for a very long time, although it wasn’t always known that vitamins were the cause or cure of certain illnesses. One of the most well known cases is scurvy, a disease that used to be fatal, where collagen (a component of connective tissue) is not formed properly. Symptoms included poor healing of cuts and open wounds, bleeding of the gums and severe pain. A Scottish doctor named James Lind discovered that feeding people citrus foods helped prevent scurvy, which we now know is due to the Vitamin C present in the fruit. The Royal Navy at the time took this information and fed its’ sailors lemons and limes (hence the nickname “Limeys” for British people). It was at the start of the last century, around 1905, that vitamins were finally defined and named.
So what are the common vitamins? Vitamin A, B, C, D, E, and K are the most well known. There are skipped letters because many chemical compounds initially identified as vitamins were later reclassified as fatty acids or were chemically very similar and grouped under the Vitamin B “complex” of vitamins (more on that later), such as Riboflavin, which used to be Vitamin G but is now Vitamin B2.
So, let’s move on and look at the most common vitamins that we can get from our diet.
Vitamin A, otherwise known as Retinol, is important in vision and bone growth. As a child you may have been told to eat your carrots so you can see in the dark – Vitamin A is required for the production of a visual pigment called rhodopsin, which is used in low light levels. While eating more carrots probably won’t help you see in the dark any better, not getting enough Vitamin A can make you go blind, as happens too much in the developing world.
Vitamin A is also important for epithelial cells that line your throat, stomach, nose etc, to function correctly, which helps fight against infection. It is also used in maintaining parts of the immune system such as white blood cells, and in formation of red blood cells, and also bone development.
Where can we get Vitamin A from? There are several fruit and vegetables that contain chemicals known as provitamins, which are precursors to vitamins – that is, the body absorbs them, and converts them into the active vitamin. Fruit and vegetables containing yellow, orange and dark green pigments (carotenoids) are good, which the most commonly known beta-carotene, which can be found in large amounts in carrots. These are taken up by the body and turned into Vitamin A.
Vitamin B is not just one vitamin, but a “complex” of many different but related vitamins. This is because it was once thought to be a single vitamin, and it wasn’t until relatively recent chemical research that we realised the truth. Some of the more well known ones in this group are riboflavin and thiamine. These vitamins, in varying amounts, are responsible for breakdown of carbohydrates, fats and proteins (basically metabolism of your food), and maintenance of skin, hair, mouth and eyes amongst other things.
Because B vitamins are a relatively large group, where we can get them from our food varies, and is too detailed to go into for each vitamin in this article. In general however, B vitamins are found in potatoes, chilli peppers, bananas and green vegetables.
Vitamin C is a biggie - otherwise known as ascorbic acid, is needed to produce collagen in connective tissue, in skin, mucous membranes, bones and teeth. It's also needed for production of certain hormones, and chemicals required in energy transfer processes in cells, all in all a pretty busy vitamin!
The body cannot store vitamin C, so it is required constantly fresh in the diet. Deficiency of vitamin C causes a disease called scurvy, which has a number of symptoms including easy bruising, bleeding, poor immunity against disease, and loose teeth amongst other things. If not treated (by the intake of vitamin C), scurvy is eventually fatal.
The amount of vitamin C required in the diet can vary, depending on the state of the body itself - for example, people under stress or pregnant women require a diet with slightly more Vitamin C in than others. Vitamin C can also help against some diseases, such as decreasing the duration and harshness of colds (unfortunately it doesn't stop you getting them!); it can also help prevent lead poisoning by removing the heavy metal from the body before it can be properly absorbed and stored in tissue. There is also some evidence to show that vitamin C can be used to fight certain types of cancer.
So, how much vitamin C do we need to take to stay healthy? Well, the suggested recommended daily intake is around 40-100mg (milligrams) a day, although when trying to fight off a cold, it can be increased up to 5g/day. However, the more you take in, the more chance of side effects, and the side effects of overdosing on vitamin C includes diarrhea, which can take effect anywhere between 5 to 25 grams per day dosage. There are no long term ill effects of this; it's simply inconvenient and unpleasant! Additionally, if large doses are taken on an empty stomach, acid indigestion (heartburn) can occur, which again is harmless but unpleasant.
Citrus fruits, such as oranges, lemons, and grapefruit are a good source of Vitamin C and one of the most convenient, although chilli peppers have a higher concentration, but are not necessarily as pleasant to eat! Potatoes, broccoli, sprouts, cauliflower, and spinach are good vegetable based sources of Vitamin C, while tomatoes, papaya, cantaloupe melons, kiwifruit and strawberries are good fruit sources. There are no real fixed values for how much you can get from fruit or vegetables though, since it can vary based on the variety, soil condition, growing climate, storage conditions, and preparation, with fresh produce containing the most. Cooking as usual destroys vitamin C content, since it is water soluble and leeches into the water while cooking.
For some example figures, there are approximately 190mg of Vitamin C per 100 grams of red pepper, 90mg per 100 grams of Kiwifruit or Broccoli, 50mg per 100 grams of orange, 30mg per 100 grams of passion flower, and 10mg per 100 grams of tomato.
Vitamin D is important for maintaining a strong and healthy skeletal system, your bones! It controls the levels of calcium and phosphorus in the blood by regulating the intake from the digestive system. It also regulates the growth of skin cells. Rickets is the main disease caused by Vitamin D deficiency, and its main symptoms are muscle weakness and fragile bones; osteoporosis is another condition. Vitamin D is typically obtained from fortified milk products such as milk or cheese, and some fish, and it is also naturally formed in the skin after exposure to sunlight - no fruit and veg though, so moving on…
Vitamin E's main role is in helping skin healing and the healing of scars after major injuries such as burns. For this reason, it's used in many skin lotions and creams. One of the best sources for Vitamin E is vegetable oils, including sunflower oil and olive oil, although nuts and sunflower seeds are good sources too. Leafy green vegetables such as cabbage or spinach are a good vegetable based source.
It's believed that Vitamin E has a protective effect against cancer, by preventing the damaging effect of free radicals, and it also blocks the formation of some carcinogens, and also enhances the immune system. However, none of this has been definitively proven in clinical trials as of yet. There is some encouraging evidence however that Vitamin E can protect against Alzheimer's (a wasting of the brain), and Parkinson's Disease (a disease of the nervous system that results in loss of nerve and muscle control).
Vitamin K is responsible for regulating some chemical processes in the body, including clotting of blood and bone formation. It is produced naturally in the intestine by certain bacteria, and is not taken in from any fruit or vegetables.
As already mentioned, you can top up your diet with Vitamin supplements and pills; for example, if you're trying to treat a cold early, you're not going to be able to eat enough foods to supply you with the required level of Vitamin C, so supplements would be necessary. Generally however, it's more fun to eat them as fresh as possible.
Can you overdose on vitamins? Well we already discussed the downside to taking too much Vitamin C. Put simply, there's a greater chance of under-dosing on vitamins than over-dosing, and you won't be risking death by having a few too many, you just may end up with a few unpleasant but non-serious symptoms!
It's amazing that something so small, and in such small amounts as vitamins are required can have such intense effects on the body, and can be varied to affect as many bodily processes as you can think of, but vitamins can. Even more curious is the fact that they don't get used up as raw materials during reactions, but excreted afterwards instead, almost as though they're there along for the ride. Vitamins are just one more thing that you can get from fresh fruit and vegetables.