Aldaniti, As the forum Nutritionist (are there any others on here ?) I would like to tell you what I tell patients. This is just what I have been taught and what I believe, I am sure others wil disagree with me, as usual, but maybe some of it will be useful to you.
A balanced diet is indeed best, however since the soil of our island is depleted of minerals like selenium by over farming due to small space, much of the food we get here is not as nutrient rich as it might be - and you know a lot of it is imported too. Cooking also takes vitamins and minerals out so the way you eat your food matters too. Long transport time and picking food before it is ripe means we only get a percentage of the goodness. Try to buy local food, both meat and veg. (Like your own chickens!)
Despite Gillian McKeith's best efforts to tell us that we are what we eat - we are not. We are more likely to be what we absorb and if our system is not working correctly then we do not absorb much. Krizon is right, get your blood tested, this can tell you about your liver function as well as if you need iron or are low in minerals and vitamins. NEVER ignore a bout of fatigue it could be something nasty lurking which you need medical attentuion for.
Eat some raw food, it is highest in nutrients, even a little helps. Avoid over processed food like sugar, white flour and cakes and biscuits. They are nutrient empty and you use up energy to digest them.
It is also correct that herbs like Echinachea will boost the immune system, But be careful, long term use of it can make you immune to it. Best to use during winter or when you need a boost and then take a break for a few months.
Drinking more water helps to keep our systems hydrated, and less caffiene helps our blood sugar levels, so go light on tea/coffee. Green tea contains some caffeine but also lots of phytonutrients which help to prevent colds and even cancer.
Stress depletes our energy levels and gobbles up nutrients at a fast rate. Loss of our 4 legged friends, for those who love them, is high on the scale along with moving house, changing jobs, and divorce.
You might want to look at Bach Flower Remedies to help with emotional traumas. Most people know about Rescue Remedy, but there are 38 remedies. I can advise you if you want, I am a practitioner. Rescue Remedy is useful for loss of pets, and people. It is herbal, does not harm or react with other medicines. I use it on the family and all of the animals. Very useful for sick creatures, and for major events in their lives like foaling or moving.
If you get a multi vitamin get one with minerals. Be careful where you buy, some are made in laboratoires and are chemcial replicas. It is better to take a blanced supplement than trying to get separate bottles of pills. It is easy to get an imbalanced vitamin regime and make yourself sick. Do not take too many either, as someone said on here, water soluable vitamins such as Vit C wash through your system, oil soluable such as A and D stick with us and can build up causing side effects. If you are reasonably healthy and eat well, have a normal level of stress, you should only need a multi vit/min which will ensure you get a good dose of nutrients every day. If you remember to take it!
Whatever you decide to do, remember natural solutions are never instant, it takes about 2-3 weeks for flower remedies to really help, and about 3 months for a new vitamin regime.
Hope this helps! Let me know how you get on.