This is the first study to show such a strong link between dairy products and breast cancer.
One ice cream or yoghurt a day could hinder the survival of women with breast cancer, scientists say.
Those with the disease who eat a single portion daily of a product containing full-fat milk could be 50 per cent more likely to die.
US scientists suspect this is because milk and other dairy foods contain the hormone oestrogen, which encourages tumour growth.
There is already some evidence that diet plays a role in improving the chances of surviving cancer and preventing it returning. But this is the first study to show such a strong link between dairy products and breast cancer.
Around one in eight women will develop breast cancer at some point in their lives and there are around 50,000 new cases a year.
Although survival chances are far better than other forms of the illness it still leads to 11,800 deaths annually.
Scientists from the Kaiser Permanente research centre in California looked at the records of 1,500 women diagnosed with breast cancer between 1997 and 2000.
They had all completed questionnaires on how often they consumed dairy products, the sizes of portions and what specifically they ate.
The most common were ice cream, yogurts, cheese, full-fat lattes and hot chocolates.
The scientists found that those who ate just one portion of one of these products a day were 50 per cent more likely to die from the illness within 12 years.
They point out that most milk consumed in Britain and the U.S. comes from pregnant cows and is rich in the hormone oestrogen.
This is known to trigger tumour growth and there are particularly high levels in full-fat dairy foods.
In fact women who ate one portion of full-fat dairy a day were 64 per cent more likely to die from any cause - not just breast cancer.
Dr Bette Caan, who led the research said: 'High-fat dairy is generally not recommended as part of a healthy diet.
'Switching to low-fat dairy is an easy thing to modify.'
Many women who have just been diagnosed with breast cancer ask their doctor whether they should change their diet.
But so far there is just too little research on the subject for them to give any specific advice.
Susan Kutner, chair Kaiser Permanente Northern California Regional Breast Care Task Force, said: 'Women have been clamouring for this type of information.
'They're asking us, 'Tell me what I should eat?' With this information, we can be more specific about recommending low-fat dairy products.'
Sally Greenbrook, Senior Policy Officer at Breakthrough Breast Cancer, said: 'This study specifically looks at women who have already been diagnosed with breast cancer and how low or high fat dairy products may affect them.
'Any women who have had breast cancer and are concerned about their diet should discuss this with their doctors.
'For a number of health reasons it's advisable that all women should follow a healthy balanced diet. It helps you to maintain a healthy weight which, together with good practices such as lower alcohol intake and regular physical activity, can help to reduce your breast cancer risk and improve overall well-being.
'There are many risk factors for breast cancer, not just diet.'
There is no evidence of a link between hormone replacement therapy and breast cancer, research published in the British Medical Journal suggests.
The study at the University of Cape Town Medical School looked at HRT use and the incidence of breast cancer in 11 countries. It found that the benefits of the drug in alleviating menopause symptoms outweigh any possible risks.
Most people believe that animals should not be harmed unnecessarily, but the consumption of animal products forces animals into a life of misery and an untimely death.
By choosing a compassionate diet and not taking part in their suffering, we can prevent thousands of animals from being harmed and killed on our behalf. Each of us can make influencing decisions, that can literally save lives.
Learn more: www.bit.ly/changeinyourhands