Green light for soy

New nutrition advice for breast cancer sufferers

We almost all know of someone who has been diagnosed with breast cancer. It is one of the most common causes of cancer related death in women. The incidence is growing, with data from the Australian Institute of Health and Welfare (2010) indicating 1 in 9 women will be diagnosed with breast cancer before the age of 85, and projections to 2015 suggesting the number of new breast cancer cases among women is likely to be 22% higher than in 2006. Early test tube studies conducted in the laboratory caused some concern that soy could promote breast tumour growth. A new study has added to the growing body of evidence that soy foods, like tofu and soy milk, have no adverse affects on breast cancer prognosis.

Most of the earlier studies investigating soy foods and breast cancer examined isoflavones; an antioxidant component found in legumes such as soy beans, in isolation in a test tube and found that they may enhance the growth of breast cancer cells. Based on this early evidence and along with the potential for isoflavones to interfere with the effectiveness of Tamoxifen – a drug that has been used treat breast cancer for over 30 years, some medical professionals treating women with breast cancer advised them to limit their consumption of soy foods. Two recent epidemiological studies conducted with breast cancer survivors have suggested that soy intake does not affect breast cancer prognosis and may even reduce recurrence. New data from the Women’s Healthy Eating and Living study (WHEL), with a larger number of participants further supports the existing research, suggesting there are no adverse affects of soy foods on breast cancer prognosis.

A secondary analysis of data from the WHEL study was used for this paper. The WHEL was a randomised controlled trial of a high fibre and high fruit and vegetable intervention in over 3,000 early stage breast cancer survivors in the USA. The participants aged from 18 - 70 years, recently surviving breast cancer, were recruited for the dietary intervention with an average follow up of 7.3 years from the time of enrolment. Soy intake measured by milligrams of isoflavones, (not total soy protein) was measured post diagnosis by the Arizona semi quantitative Food Frequency Questionnaire which included specific soy items and an option to include other soy foods not on the list.

The women in the highest quintile of isoflavone intake (16.3mg/day) had a 54% reduced risk of death compared with the lowest quintle of intake, (effectively non-soy consumers, 0-0.7mg/day) however this was not statistically significant. The highest quintile of isoflavone intake consumed on average the equivalent to around 1 cup of soy milk or approximately 3 ounces (85g) of tofu each day - which is not particularly high and probably reflects a similar amount to common levels of intakes in western consumers who eat soy. Younger women, Asians and those with a college degree or higher were most likely to be in the highest quartile.

Isoflavone intake was unrelated to the risk of a second breast cancer event, and for overall mortality, risk of death tended to be lower as isoflavone intake increased. Although the interaction between Tamoxifen use and mortality was not statistically significant, the observed effect toward lower mortality with increased soy seemed stronger in women who used Tamoxifen.

This study is now the third epidemiological study that shows lack of harm from soy consumption, and provides sufficient evidence that women with breast cancer no longer need to be advised to avoid soy products .

References:

• Soy Food Consumption and Breast Cancer Prognosis. Caan BJ, Natarajan L, Parker B, Gold EB, Thomson C, Newman V, Rock CL, Pu M, Al-Delaimy W, Pierce P. Cancer Epidemiology, Biomarkers & Prevention 2011;20(5):854-8.

• National breast and ovarian cancer centre - www.nbocc.org.au

Fibre helps protect against colorectal cancer

New World Cancer Research Fund Report supports dietary fibre for protection against colorectal cancer

 

The number of new cancer cases in Australia is rising each year. Data from 2007 (AIHW) indicates that bowel cancer (also known as colorectal cancer) is the second most common cancer in Australia and the second largest cause of cancer deaths in Australia, killing almost 80 people a week (Bowel Cancer Australia).

 

Rates of colorectal cancer increase with industrialisation and urbanisation and are generally more prevalent in high income countries, but now becoming increasingly more common in middle and low income countries. Somewhat more common in men than in women, colorectal cancer is fatal in just under half of all cases, however if detected early, it is actually one of the most curable cancers, with food and nutrition having an important role in its prevention and cause.

 

A new update to the Food, Nutrition, Physical Activity, and the Prevention of Colorectal Cancer Report by the World Cancer Research Fund (WCRF) and the American Institute for Cancer Research (AICR) as part of the Continuous Update Project (CUP) has just been published, including an additional 263 new articles from cohort studies and randomised controlled trials. The CUP provides a comprehensive and up-to-date systematic review of scientific developments on the relationship between diet, physical activity, obesity and cancer, with the panel consisting of leading scientists in these fields.

 

In this new report, the CUP panel agreed that the evidence for a protective effect from foods that contain dietary fibre had strengthened from probable in the previously completed Secondary Expert Report (SER) and therefore the evidence has been upgraded to ‘convincing’. This is highest level of evidence set by the WCRF and AICR, which identifies a causal relationship between a particular aspect of food, nutrition, physical activity or body composition, and cancer.

 

Twelve new papers were included in the review that investigated total dietary fibre and fibre from cereals, wholegrains, legumes, fruit and vegetables. The new report found that 13 of the 18 studies showed a decreased risk for colorectal cancer with increased intake of total dietary fibre.

 

The new meta-analyses showed a 10 per cent decreased risk for colorectal cancer and 11 per cent decreased risk for colon cancer with an increase in dietary fibre of 10g/day, which is a slightly better risk reduction than the 2007 report. The updated meta-analyses for rectal cancer, trended in the direction of decreased risk, but did not reach statistical significance.

 

Likewise, the updated reviews for sources of fibre and colorectal cancer showed a 10 per cent decreased risk for cereal fibre, but estimates for other sources of fibre were in the direction of decreased risk, but again did not reach statistical significance.

 

With 3 servings of wholegrains per day there was a 21 per cent decreased risk for colorectal cancer and 16 per cent decreased risk for colon cancer. There was also convincing evidence that physical activity protects against colon cancer. It is interesting to note the review concluded there is probable evidence that consumption of garlic, milk, and calcium may also protect from colorectal cancer.

 

The way in which fibre helps reduce the risk of colorectal cancer is due to several effects in the gastrointestinal tract, but the precise mechanism is still yet to be fully understood. Fibre dilutes faecal content, decreases transit time and increases stool weight whilst healthy gut bacteria from a wide range of dietary carbohydrates that reach the colon produce fermentation products, particularly short-chain fatty acids such as butyrate which helps to maintain healthy colon cells. Fibre intake is strongly correlated with intake of folate, however, adjusting for this does not often affect the risk reduction attributed to fibre.

 

The latest evidence from the WCRF review report also shows that consumption of red meat and processed meat, ethanol from alcoholic drinks (by men and probably by women), as well as body fatness and abdominal fatness, the factors that lead to greater adult attained height, or its consequences are convincing or probable causes of colorectal cancer.

 

Australian healthy eating guidelines recommend we eat at least 4 serves of core grain-based foods a day such as breads, breakfast cereals, rice, pasta and noodles, preferably wholegrain. One serve is equal to 2 slices of bread, approx 1 cup of breakfast cereal, 1 cup of cooked rice/noodles/pasta/oats. Don’t forget legumes are also a great source of fibre. Aim for at least 2 serves per week, 4 serves or more is even better for improved health outcomes. One serve is equal to half a cup of cooked dried beans, lentils, chickpeas etc.

 

References:

WCRF/AICR World Cancer Research Fund / American Institute for Cancer Research.Continuous Update Project Interim Report Summary.Food, Nutrition, Physical Activity, and the Prevention of Colorectal Cancer. 2011

http://www.aihw.gov.au/

http://www.bowelcanceraustralia.org/