i dont know if its true but ive heard that cla was present in a much higher level in beef years ago but modern farming practices of not only hormones to grow the cattle fast and the use of chemical fertilzers to grow their hay and grazing land has caused the levels of cla in beef to decline over the years , but i personally feel that a lot of us take in such large quanities of beef that we make up for this . on the other hand for those who prefer chicken , fish , etc. the addition of a good cla [ tonalin ] is benificial , i dont follow the mainstream when it comes to supplements , i take in little or no supplements when im bulking/eating anything i want but i really go all out with supplements when im running a calorie deficit