Publications about vitamins, you see them over and over. However the conclusions are usually more or less the same. People with a healthy diet claim that we don't need supplements, people from the industry will claim we need them, the government will probably not say anything about them but they will try to stimulate a healthy diet. To make a long story short, my opinion is: The majority of people do not have a healthy diet if you look at all vitamins. Changing to healthy diet would be the best for health, however not changing at all will not increase your health, since taking a supplement is hardly any effort, I think taking a supplement for that vitamins you lack in your diet is a good thing to do.
A recent article from the Guardian concludes with the following user guide:
Vitamin A (retinol)
Helps keep skin healthy, enhances immunity and helps you see in dim light. But all you need is 0.7mg a day if you are a man and 0.6mg if you are a woman, according to the Food Standards Agency (FSA), which says you can get all you need from foods such as cheese, eggs, oily fish, milk and yoghurt. Liver, another source, is not recommended for pregnant women. More than 1.5mg of per day may make your bones more brittle and prone to fracture as you age.
We need around 40mg a day and it is not stored in the body because it is water soluble - but we should get enough from a normal diet. It is in a wide variety of fruit and vegetables and protects cells and helps the body absorb iron. Taking less than 1000mg in supplements is unlikely to do harm, says the FSA, but large amounts can cause diarrhoea and flatulence.
Turns into vitamin A in the body. You should get all you need from a varied diet, in particular from yellow and green leafy vegetables such as spinach, carrots and red peppers; and yellow fruit such as mangos, melons and apricots. Too much beta-carotene can increase the chances of smokers developing lung cancer and subsequent mesotheliomas. The FSA recommends taking no more than 7mg a day in supplements.
Protects cell membranes. It is fat soluble, so the body will store it and you do not need a dose every day. It is found in plant oils, nuts and seeds and wheatgerm in cereals. The FSA advises that taking too much supplementary vitamin E is not a good idea, but less than 540mg a day is "unlikely to cause any harm".
The tiny amounts we need should be easily obtained from meat, nuts, bread, fish or eggs. It has an important role in the immune system, in thyroid hormone metabolism, reproduction and prevention of damage to cells and tissues. Too much can lead to loss of skin, hair and nails, but ingesting less than 0.35mg a day will do no harm.