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Eating onions and garlic every day ‘reduces a woman’s risk of breast cancer by 67%’

Eating raw onion and garlic every day may reduce a woman’s risk of breast cancer, research suggests.

Scientists analysed the dietary habits of more than 600 women in Puerto Rico, where rates of the disease have skyrocketed over the past few decades.

They found those who ate more than one serving of the onion- and garlic-based condiment sofrito a day were 67 per cent less likely to develop breast cancer. 

However, consuming onions and garlic in a different form did not have the same benefits, the scientists found.

Eating raw onion and garlic every day may reduce a woman’s risk of breast cancer (stock)

Sofrito recipes vary but it typically consists of raw onions and garlic, alongside tomatoes, peppers and coriander.

Eating onions and garlic raw may be key, with past studies suggesting their cancer-fighting antioxidants are destroyed when heated.  

The study was carried out by the University of Buffalo (UB) and the University of Puerto Rico. 

One in eight women in the US and UK will develop breast cancer at some point in her life, statistics show. Men can also get the disease.

In Puerto Rico, the incidence of the disease rose from 18 cases per 100,000 women in the 1960s to 50 per 100,000 in the 1990s, the scientists wrote in the journal Nutrition and Cancer. 

Although on the rise in Puerto Rico, breast cancer is still more common in the US. For every 100,000 American women, 127.5 develop the disease every year, National Cancer Institute statistics show.

‘There is very little research on breast cancer in Puerto Rico,’ study author Dr Jo Freudenheim, from UB, said. 

‘This study was… to help us understand why rates there are lower than in the rest of the US.

‘And why rates there are continuing to increase while they are decreasing in the rest of the United States.’ 

Studies have suggested eating lots of onions and garlic reduces a person’s risk of lung, prostate and stomach cancer. 

However, little was known about how the staple ingredients affect a woman’s breast cancer odds.

To find out more, the scientists analysed women who took part in The Atabey Study of Breast Cancer in Puerto Rico between November 2008 and June 2014.

Of the participants, 314 had battled the disease, while 346 controls had never had malignant tumours, aside from some cases of non-melanoma skin cancer.

All the women, aged 30-to-79, completed a food questionnaire that asked about their onion and garlic consumption over the past year. 

It also specifically asked about how often they eat sofrito, which is widely used in Puerto-Rican cuisine. 

Results revealed while there was a ‘trend toward lower breast cancer risk’ with increased onion and garlic consumption, it was not statistically significant.

However, the women who consumed sofrito every day were found to be significantly less at risk.

Onions and garlic are members of the allium plant family, along with leeks and chives.  

Animal and cell studies in the laboratory have shown exposure to the allium compounds dialyl disulfide and S-allylmercaptocysteine prevents cells dividing uncontrollably.

Quercetin, an antioxidant in onions, suppresses a mutant protein in breast cancer, past studies show. And allicin, a compound in garlic, inhibits uncontrolled cell division.

However, these antioxidants are ‘substantially reduced upon heating at 100°C (212°F) for 40-to-60 minutes’, the scientists wrote. 

And just one minute of microwaving garlic ‘blocks its ability to inhibit a known carcinogen in rat mammary cell DNA’, they added.

The scientists stress, however, their study was small, with just 12 of the participants never eating onion, garlic or sofrito.

With recipes of the condiment varying, it is also not possible to quantity how much onion or garlic should be consumed to reap the benefits. 

The sauce is also made up of other vegetables and fresh produce, which may together work to reduce a woman’s breast cancer risk. 


Breast cancer is one of the most common cancers in the world. Each year in the UK there are more than 55,000 new cases, and the disease claims the lives of 11,500 women. In the US, it strikes 266,000 each year and kills 40,000. But what causes it and how can it be treated?

What is breast cancer?

Breast cancer develops from a cancerous cell which develops in the lining of a duct or lobule in one of the breasts.

When the breast cancer has spread into surrounding breast tissue it is called an ‘invasive’ breast cancer. Some people are diagnosed with ‘carcinoma in situ’, where no cancer cells have grown beyond the duct or lobule.

Most cases develop in women over the age of 50 but younger women are sometimes affected. Breast cancer can develop in men though this is rare.

The cancerous cells are graded from stage one, which means a slow growth, up to stage four, which is the most aggressive.

What causes breast cancer?

A cancerous tumour starts from one abnormal cell. The exact reason why a cell becomes cancerous is unclear. It is thought that something damages or alters certain genes in the cell. This makes the cell abnormal and multiply ‘out of control’.

Although breast cancer can develop for no apparent reason, there are some risk factors that can increase the chance of developing breast cancer, such as genetics.

What are the symptoms of breast cancer?

The usual first symptom is a painless lump in the breast, although most breast lumps are not cancerous and are fluid filled cysts, which are benign. 

The first place that breast cancer usually spreads to is the lymph nodes in the armpit. If this occurs you will develop a swelling or lump in an armpit.

How is breast cancer diagnosed?

  • Initial assessment: A doctor examines the breasts and armpits. They may do tests such as a mammography, a special x-ray of the breast tissue which can indicate the possibility of tumours.
  • Biopsy: A biopsy is when a small sample of tissue is removed from a part of the body. The sample is then examined under the microscope to look for abnormal cells. The sample can confirm or rule out cancer.

If you are confirmed to have breast cancer, further tests may be needed to assess if it has spread. For example, blood tests, an ultrasound scan of the liver or a chest x-ray.

How is breast cancer treated?

Treatment options which may be considered include surgery, chemotherapy, radiotherapy and hormone treatment. Often a combination of two or more of these treatments are used.

  • Surgery: Breast-conserving surgery or the removal of the affected breast depending on the size of the tumour.
  • Radiotherapy: A treatment which uses high energy beams of radiation focussed on cancerous tissue. This kills cancer cells, or stops cancer cells from multiplying. It is mainly used in addition to surgery.
  • Chemotherapy: A treatment of cancer by using anti-cancer drugs which kill cancer cells, or stop them from multiplying
  • Hormone treatments: Some types of breast cancer are affected by the ‘female’ hormone oestrogen, which can stimulate the cancer cells to divide and multiply. Treatments which reduce the level of these hormones, or prevent them from working, are commonly used in people with breast cancer.

How successful is treatment?

The outlook is best in those who are diagnosed when the cancer is still small, and has not spread. Surgical removal of a tumour in an early stage may then give a good chance of cure.

The routine mammography offered to women between the ages of 50 and 70 mean more breast cancers are being diagnosed and treated at an early stage.

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