The journalist said that at times he felt uncomfortable interviewing "vulnerable" people for his Extreme Love programme and wondered whether it was right for him to be "let loose among the mentally ill".
"Several months on from the decision to make these shows, I look back to see that in important respects they are not so different from ones I've made investigating weird worlds and strange pastimes," he wrote in The Telegraph.
"They too involve acts that cut to the core of what it means to be human: the meaning of love and loyalty; the duties and limits of parenthood and marriage; the nature of identity."
He added: "For me, making these films has been an adventure, a revelation, occasionally a strain, more often a pleasure. I'm as proud of these shows as I am of anything I've ever done."
Louis Theroux: Extreme Love airs tonight (April 19) at 9pm on BBC Two.
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