Just wondering...How do you know that it is a natural one instead of a synthetic one ?

i have heard a lots of ppl saying taking synthetic health supplements can do harm to our health instead of enriching our body, is it true?

I take:

Cod Liver oil
Fruits
Vegetables, fishes
Plenty of plain water( water is a nutrient)


ever heard of INTRA Lifestyles? anyone taking it at the moment?
I do hear from people around me that it does good to your health. made up from a few hundreds of herbs that essentially make a good supplement/detoxifier and suitable to consumed by everyone, INTRA has been very well established ...
http://www.lifestyles.net/my-en/pr_intra.php

i am not promoting the product, but i wish to know more.

I have been taking cod liver oil for the past 2 months and it helps a lots in treating my sinuses!=)