I have a good friend who owns an independent vitamins shop, and I talk to him off and on about health issues... He is so knowledgeable, like a walking encyclopedia - you ask him about one thing, he pulls all these articles and studies out from around his counter, it's amazing!
One of the main issues in the UK at Winter time and in other cloudy areas, is that we don't get enough Vitamin D (usually from the sun)... Vitamin D is essential to healthy immune system functioning, so recommended to take a daily supplement, 2000 IU or even 4000 IU tablets.
Also, we don't get enough B6 or B12, which are precursors to useful body functions. Many of us are deficient in a number of vitamins and minerals (including Chromium, Selenium etc.) as our soil has been totally depleted of micronutrients due to intensive farming & GM (they knew about this more than 80 years ago, but did nothing!!!)
Be careful of the cheap Cod Liver Oil tablets, they'll have high levels of mercury in (Fish farms etc), and will harm you in the long run...
Carlson cod liver oil from Norway is one of the best.
Plus, Grapefruit Seed Extract (tablets or drops in juice) - Google Nutribiotic, is good to keep the flus away...
Hope this helps
