Twisting while lifting is perhaps the most dangerous movement you can make to your low back. Many times I will see people who are shocked when they reach down to grab the morning paper and 'all of a sudden" find themselves unable to stand back up and are afflicted with severe pain. I would suggest that many times the morning paper was the straw that broke the camels back, and years of prior neglect had led to that moment of truth.
The fibers of tissues in your low back primarily run up/down and left/right. This means that oblique motions, which use both planes of motion (inefficiently) can cause micro tears and stresses. While these micro-injuries may go unnoticed for many years or just considered "normal" aches and pains, the true nature of these injuries comes to fruition in the morning paper example given above.
A few tips for lifting would be- use your legs, keep the weight close, keep your elbows in, and move your feet to "square up" instead of twisting while holding weights.
Just using those simple tips above will put you ahead of 95% of people when trying to save your back.