The celebrity chef told the court however that she has never been a habitual drug addict or abuser.
Nigella gave evidence about the incident in the summer in which Mr Saatchi was pictured with his hand around her throat outside Scott's restaurant in London.
She said her ex-husband grabbed her by the throat when she made a comment about wanting grandchildren after seeing a young child go past.
"I'm the only person you should be concerned with, I'm the only person that should give you pleasure," she alleges her husband told her.
Nigella Lawson also told the court that she has "never been a habitual drug addict or abuser" but said she had taken cocaine on six occasions when her late husband John Diamond was suffering from cancer.
"The idea that I'm a drug addict or a habitual user of cocaine is ridiculous. I don't have a drug problem, I have a life problem."
Her late husband used the drug when he discovered he was suffering from the disease and the TV cook said she had joined him on several occasions.
Ms Lawson has also admitted smoking cannabis, starting "relatively recently" but said she has now given up.
The defence lawyer asked whether she had ever smoked the drug in front of her children and she said, "Yes, I'm afraid I did," according to Sky News.
She also said she had taken cocaine once in July 2010, when a friend offered her the drug. "I was having a very, very difficult time, I was being subjugated to intimate terrorism by Mr Saatchi," she said.
The TV cook and author said her former husband Charles Saatchi was using the case to destroy her name by "spreading false allegations of drug use".
Earlier today she told the court: “To say my relationship with Saatchi is not good would be...,” she tailed off.
“He said if I did not go back to him he would destroy me.”
She added; "I am glad to answer allegations that have come after a long summer of bullying and abuse. I felt it was my civic duty to come to court. It is difficult for me and difficult for my children.
“I have been put on trial here and in the worlds press," she said.
Nigella referred to her former husband as 'Mr Saatchi' throughout her evidence.
When cross examined after lunch, she was asked about payments to Annabel's, a London club. Anthony Metzer QC, cross-examining, says there have been card payments of over £1,300 per day to the club. Nigella explained:
"Mr Saatchi likes to drink wine, and he likes to drink expensive wine."
When asked was Saatchi a traditional family man, she replied, “No, he didn’t like to take part in family life, that’s not very traditional.”
She also said Saatchi had a temper.
“My independence matters to me, I provide for my children,” she added, saying this used to irritate her former husband.
The TV cook was quizzed about individual payments by other PAs. She denies they were for the PAs' personal use, saying they were authorised to pay for wine and clothes for Mr Saatchi and herself.
When asked about expenditure by her assistant and whether she approved £7916. She told the court it was for her birthday party.
The judge has had to interject several times to avoid certain lines of questioning.
The 53-year-old is giving evidence in the trial of two of her former personal assistants.
She is a prosecution witness in the trial of Italian sisters Elisabetta and Francesca Grillo.
The pair are accused of abusing their positions by using credit cards loaned to them by Ms Lawson and her former husband Charles Saatchi to spend more than £685,000 on themselves.
Ms Lawson, 53, wearing a long dark coat, was greeted by dozens of photographers and television crews waiting outside Isleworth Crown Court in west London as she arrived this morning.
Prosecutors in the trial claim the Grillo sisters lived the ''high life'', spending the money on designer clothes and handbags from Louis Vuitton, Christian Dior and Vivienne Westwood.
Elisabetta, 41, sometimes referred to in court as Lisa, and co-defendant Francesca, 35, both of Kensington Gardens Square, Bayswater, west London, deny committing fraud, which is said to have taken place between January 2008 and last December.
On Friday, as Mr Saatchi gave evidence, jurors listened intently as details of the breakdown of the multi-millionaire and Ms Lawson's 10-year marriage were played out in the courtroom, taking centre stage over the allegations against the defendants.
The Saatchi Gallery owner said it was a ''terrible, terrible mistake'' that a private email he sent to Ms Lawson, referring to her as ''Higella'', and claiming she had been off her head on drugs, has been made public.
''I'm utterly bereft that this private email to Nigella has come back to haunt us both," he said.
Mr Saatchi, who went through a high-profile divorce from the food writer earlier this year, told the court: ''I adore Nigella now. I absolutely adore Nigella and I'm broken-hearted to have lost her. I wanted her to be happy.''
Mr Saatchi, 70, looked exasperated as the now-infamous incident outside Scott's restaurant in Mayfair, central London, where he was photographed holding Ms Lawson by the throat, was brought up at least twice during cross-examination.
Anthony Metzer QC, representing Elisabetta, asked whether it was during an argument about her taking drugs.
''I accepted a caution for assault,'' he said.
''I was not gripping, strangling or throttling her. I was holding her head by the neck to make her focus, can we be clear?
''Was it about her drug use? No.''
Asked by Mr Metzer to explain what he meant in the email he sent Ms Lawson on October 10, in which he said he could ''only laugh at your sorry depravity'', Mr Saatchi said: ''I was very upset. I wasn't laughing, I was broken-hearted.''
Jurors heard the email went on: ''Of course now the Grillos will get off on the basis that you ... were so off your heads on drugs that you allowed the sisters to spend whatever they liked and yes I believe every word the Grillos have said, who after all only stole money.
''But I'm sure it was all great fun and now everything is perfect - bravo, you have become a celebrity hostess on a global TV game show. And you got the Pass you desired, free to heartily enjoy all the drugs you want, forever. Classy.''
Questioned about the drug-taking allegations, Mr Saatchi told the court: ''It was hearsay. I personally have absolutely no knowledge that Nigella has ever taken a drug ever.
''I don't like drugs at all and I didn't like reading what the Grillos said was the culture in my house.''
During intense questioning from Mr Metzer later on, Mr Saatchi said: ''Are you asking me whether I think that Nigella truly was off her head?
''Not for a second. Over this whole period she was writing books very successfully.
''I have never, never seen any evidence of Nigella taking any drug whatsoever.''
Mr Saatchi described the ''Higella'' reference as a ''silly pun''.
Gordon Rayner, Claire Carter and Theo Merz