Patricia Hewitt has said the sell-off of a service which delivers supplies to hospitals and GP surgeries is the best move for staff and the health service.
Ms Hewitt says she wants the best care for patients and best value
The health secretary spoke out as workers employed by NHS Logistics voted to strike after the government awarded a 10-year contract to German firm DHL.
Union officials say the walkout will cause "major inconvenience" and could see operations cancelled.
Ms Hewitt says the sell-off will save the NHS £1bn over 10 years.
Union officials have warned that the move could lead to hospitals quickly running out of supplies of bedpans, urinals, hand gel, latex gloves breakfast cereals, drinks and tinned vegetables.
But Ms Hewitt told BBC Radio 4's Today programme that NHS Logistics only provide about 51,000 of the 500,000 different products ordered by the NHS.
"It is quite clear with this new management we are going to save the NHS £1bn over 10 years," she said.
She pledged to protect the terms and conditions of staff and their pensions and dismissed as "absolute rubbish" suggestions it was part of a wider plan to privatise the NHS.
"The NHS has always been a mixed economy," she said.
"This is not driven by ideology. It's driven by ensuring we continue to get the best care for patients and the best value.
"The reason why NHS hospitals, NHS providers will go on providing the great majority of health services is quite simply because they are the best."
However, the plans have not gone down well with NHS Logistics workers who voted by three to one to strike.
Health service workers union Unison has yet to announce when the walkout will be, but the action could last up to three days and could see operations cancelled.
Unison leader Dave Prentis announced details of the strike at the TUC conference in Brighton.
"These are not troublemakers, not hardliners but workers who care deeply about the NHS, who want to stay part of it, who want to play their part in saving it," he said.
For the Conservatives, shadow health minister Stephen O'Brien accused Ms Hewitt of "trying to curry favour" with Chancellor Gordon Brown "in offering up a potential billion pound saving".
"Whilst we condemn the threat of strikes, which ultimately only threaten the care of NHS patients, there is no getting away from that this is a mess of the government's own making," he said.
"Instead of ramming this deal through on the sly, she should step back from starting the contract within weeks, allow proper consultation with NHS workers and suppliers, and bring her proposals before Parliament for proper scrutiny."
The last time there was a national strike in the NHS was 1988, when midwives took action.
From 1 October, DHL - best known for delivering parcels - will supply everything from stationery to bed linen and MRI scanners.
A deal reached earlier this month will see 1,700 employees from parts of NHS Logistics and the NHS Purchasing and Supply Agency transferred to the private sector.
The Department of Health said most hospitals had their own supply and delivery arrangements and most products used by the NHS would not be affected by the strike.
A spokesman said private sector involvement in the NHS was nothing new - for example, pharmacists were paid for the services they provided and hospitals had always bought services from private firms.