A new study suggests women may reduce their risk for breast cancer by having a diet rich in fruits and vegetables: researchers found women whose blood carried higher levels of carotenoids, nutrient compounds found in fruits and vegetables, had a lower risk of developing the disease.
The findings suggest the link is strongest for ER negative (ER-) breast cancers, which tend to be more aggressive, have a poorer prognosis and fewer prevention and treatment options. ER negative means the cancer is not driven by estrogen.
Lead author A. Heather Eliassen, of the Channing Laboratory in the Department of Medicine at Brigham & Women’s Hospital and Harvard Medical School, and colleagues, write about their findings in a paper published online on 6 December in the Journal of the National Cancer Institute.
Previous studies have linked carotenoids with reduced risk for breast cancer, but with mixed results depending on which specific carotenoid compound they looked at.
The authors analyzed data pooled from studies covering a total of 7,000 women (3,055 with breast cancer and 3,956 matched controls), and looked for links between breast cancer and total levels of circulating carotenoids, as well as individual ones.
The data came from 8 cohort studies that between them covered 80% of the data published around the world from prospective studies of blood carotenoids and breast cancer.
The researchers found a statistically significant inverse association between breast cancer risk and circulating levels of total and individual carotenoids.
“This comprehensive prospective analysis suggests women with higher circulating levels of alpha-carotene, beta-carotene, lutein+zeaxanthin, lycopene, and total carotenoids may be at reduced risk of breast cancer.”
They found no statistically significant link for beta-cryptoxanthin.
The authors note they found the strongest links were for ER negative breast cancers, and there was also some evidence that carotenoids may slow the growth of ER positive cancers too, but warn it’s possible the effect is obscured by hormone-related associations that drown out the other risk factors.
Nevertheless, they conclude:
“A diet high in carotenoid-rich fruits and vegetables offers many health benefits, including a possible reduced risk of breast cancer.”
Carotenoids in the Diet
Carotenoids are yellow, orange, and red pigments found in plants. The types the researchers looked at in this study are the ones most common in North American diets, namely alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein, zeaxanthin, and lycopene.
Alpha-carotene and beta-carotene are provitamin A carotenoids, meaning they can be converted in the body to vitamin A.
Orange and yellow vegetables like carrots and winter squash, are rich sources of alpha- and beta-carotene. Spinach is also a rich source of beta-carotene, although the chlorophyll in the leaves hides the yellow-orange pigment. Sweet potato and kale (a leaf vegetable from the cabbage family) also have high amounts of beta-carotene.
Dark green leafy vegetables like spinach, kale and turnip greens have the highest amounts of lutein and zeaxanthin, which although are separate compounds, studies often group them together.
Tomatoes are a rich source of lycopene, the carotenoid that also gives pink grapefruit, watermelon, and guava their red color.
Some Fat Required to Digest Carotenoids
There is evidence that for the body to absorb carotenoids from fruits and vegetables, they should be eaten with some fat.
A study by food scientists published mid-2012 in the journal Molecular Nutrition & Food Research suggests you won’t get much benefit from a salad without the right type and amount of salad dressing.
They concluded that the bioavailabilty of carotenoids is affected by the type and amount of fat consumed at the same time.
While not advocating a high-fat diet, lead author Mario Ferruzzi notes:
“Overall, pairing with fat matters. You can absorb significant amounts of carotenoids with saturated or polyunsaturated fats at low levels, but you would see more carotenoid absorption as you increase the amounts of those fats on a salad.”
A tomato-rich diet may reduce breast cancer risk, study shows
It has long been known that postmenopausal women are at a higher risk of developing breast cancer. But now, new research suggests that adopting a diet rich in tomatoes may reduce this risk. This is according to a study published in the Journal of Clinical Endocrinology and Metabolism.
According to the National Cancer Institute, women in the US have a 12.4% risk of developing breast cancer at some point in their lives. This risk increases with age, with women over the age of 50 having a 1 in 42 chance of developing the disease.
According to the study researchers, led by Adana Llanos of Rutgers University, postmenopausal women increase their risk of breast cancer further as their body mass index (BMI) climbs. But this latest study suggests that this risk may be reduced simply by adopting a different diet.
To reach their findings, the investigators analyzed 70 postmenopausal women for a period of 20 weeks.
For the first 10 weeks, the women were required to follow a tomato-rich diet. This involved consuming a minimum of 25 mg of lycopene each day. Lycopene is an antioxidant found in tomatoes and other fruits and vegetables.
For the remaining 10 weeks, the women followed a soy-rich diet. This required them to consume at least 40 g of soy protein daily.
All women were asked to refrain from eating any soy or tomato products 2 weeks prior to each diet.
Tomato-rich diet increases adiponectin levels
Postmenopausal women showed a 9% increase in levels of adiponectin – a fat and blood sugar regulating hormone – after following a tomato-rich diet for 10 weeks, lowering their risk of breast cancer.
Results of the study revealed that when the women followed the tomato-rich diet, they showed a 9% increase in their levels of adiponectin. This is a hormone that plays a part in the regulation of fat and blood sugar levels.
The researchers note that this effect was more prominent for women who had a lower BMI.
Llanos says the advantages of eating a high amount of tomatoes and tomato-based products are clearly evident in their findings, even if consumption is only for a short period.
“Eating fruits and vegetables, which are rich in essential nutrients, vitamins, minerals and phytochemicals such as lycopene, conveys significant benefits.
Based on this data, we believe regular consumption of at least the daily recommended servings of fruits and vegetables would promote breast cancer prevention in an at-risk population.”
Llanos points out that their findings also emphasize the importance of obesity prevention, since a tomato-rich diet had a bigger impact on adiponectin levels for women who maintained a healthy body weight.
Tomatoes have also been linked to other health benefits. Last year, Medical News Today reported on a study suggesting that eating lots of tomatoes may reduce the risk of stroke, while other research has suggested that eating a combination of soy and tomato foods may help prevent prostate cancer.
Diet and exercise: cancer benefits in huge study of women’s health
In a large study of women’s health, postmenopausal women who followed a healthy lifestyle were at a third lower risk of death, including a 20% smaller chance of dying from cancer, than women who did not follow guidance on diet, weight, physical activity, and alcohol intake.
“While it is well recognized that tobacco cessation is the lead behavioral change to reduce cancer risk,” the authors write, they analyzed the effect of other cancer prevention recommendations.
The researchers used data gathered by the observational study in the women’s health initiative of the US National Institutes of Health, which was launched in 1992 with a $140 million, 15-year contract: “the largest coordinated study of women’s health ever undertaken.”
Cynthia Thomson PhD and her colleagues analyzed data from 65,838 postmenopausal women age between 50 and 79 years.
The participants were enrolled in the women’s health initiative between 1993 and 1998 at 40 clinical centers across the country, and the team’s analysis represents the “largest study of postmenopausal women in the US.”
A large study of women’s health found that women aged between 50 and 79 who adhered to lifestyle recommendations, such as regular exercise, had a 22% lower risk of breast cancerand a 52% lower risk ofcolorectal cancer.
Those women who adhered most to lifestyle recommendations had a 22% lower risk for breast cancer and a 52% lower risk for colorectal cancer, compared with women who did not closely follow guidance.
The recommendations being followed were the American Cancer Society (ACS) guidelines on nutrition and physical activity, which have four central planks:
- “Achieve and maintain a healthy weight throughout life”
- “Be physically active”
- “Eat a healthy diet, with an emphasis on plant foods”
- “If you drink alcohol, limit your intake.”
Dr. Thomson, professor of public health at the Mel and Enid Zuckerman College of Public Health at the University of Arizona in Tucson, says:
“The message is simple and clear: If you want to reduce your risk for cancer, even later in life, eat a healthy diet, be active daily, avoid or limit alcohol, and don’t smoke.”
“Our results support the ACS guidelines for cancer prevention,” Thomson adds, but she calls for more support for other factors that can reduce the risks further, “because diet and activity alone do not account for the majority of risk.”
Ratings for women’s response to advice
The researchers scored women’s adherence to the lifestyle advice on cancer prevention.
Zeroes were given for “behaviors least consistent with the recommendations” and scores of one or two were given for healthy lifestyle actions, adding these up to a maximum level of compliance represented by a total score of eight.
Most of the women in the study had final scores between three and six. Fewer than 1% of the women scored eight after following all of the recommended lifestyle choices.
Analysis of almost 9,000 cancers
Data on the women were collected over an average of 8.3 years, a period that witnessed the diagnosis of 8,632 cancers and 2,356 cancer-related deaths.
The women whose lifestyles were rated the healthiest (a score of seven or eight) showed a lower risk of overall cancer compared with those given low scores (from zero to two).
This included a reduction by a fifth in their risk for breast cancer, and by half for colorectal cancer.
The healthier lifestyles were also associated with a lower risk of death from other causes not related to cancer.
The authors note that guidelines for healthy lifestyle in the prevention of cancer have been based on evidence from few such prospectively identified associations.
The researchers’ conclusions are drawn from the women’s health initiative, which was a study designed at the outset to track future health changes over time.
Such prospective studies result in comparisons that are controlled and more reliable than can be drawn retrospectively, by looking back on data that was not collected for the purpose.
Lifestyle effect was greater in some groups of women
The analysis found an even lower incidence of cancers and lower overall death rate among women from certain ethnic groups as a result of the lifestyle measures, and the paper calls for more research into this difference.
Dr. Thomson says:
“We found that the association was stronger for Asian, African-American, and Hispanic women, compared with non-Hispanic white women.
It is possible that different ethnic groups may have differential disease course with varied response to environmental and/or behavioral exposures.”
Other research into lifestyle changes
The cancer-protective effect of exercise was the subject of other recent research, published in October 2013, which found that postmenopausal women could derive benefit from relatively modest activity, with walking tied to lower risk for breast cancer.
For women who already have cancer, exercise may have other benefits – older breast cancer survivors benefit from exercise programs, concluded research published on December 9, 2013.
Meanwhile, with respect for dietary lifestyle choices, news regularly appears of research into nutrition and cancer prevention. Recent headlines in this area include:
- A tomato-rich diet may reduce breast cancer risk, study shows
- High-fat diets in puberty linked to breast cancer
- Meat, smoking have strongest links to cancer incidence rates
And these headlines remind us that lifestyle changes may not always be easy to make: