Study Suggests Milk Could Increase Breast Cancer Risk

 Study Suggests Milk Could Increase Breast Cancer Risk

Veronica Hackethal, MD

February 28, 2020

Hot on the heels of a review from top nutrition scientists that cautioned against drinking cow's milk comes another study with another caution: drinking milk increases the risk of developing breast cancer, say the researchers. But this finding comes from an observational study, and there may be confounders that are not accounted for, says an expert not involved with the study.   

The latest research was based on data from the long-running larger study called Adventist Health Study-2 (AHS-2), which is looking at diet and health among Seventh Day Adventists in North America. Past results from this study have suggested that Seventh Day Adventists have longer life spans and lower rates of some cancers, perhaps because of healthier lifestyles.

The latest analysis suggests that milk raises breast cancer risk, and the more you drink the higher your risk may be. 

"Consuming as little as 1/4 to 1/3 cup of dairy milk per day was associated with an increased risk of breast cancer of 30%," first author Gary E. Fraser, MBChB, PhD, said in a press statement. Fraser is affiliated with the School of Public Health at Loma Linda University, California.

"By drinking up to 1 cup per day, the associated risk went up to 50%, and for those drinking 2 to 3 cups per day, the risk increased further to 70% to 80%," he added.

The findings were published February 25, 2020 in the International Journal of Epidemiology.

"The AHS study is provocative, but it's not enough to warrant a change in guidelines. The caution being espoused by the authors is not warranted given the observational nature of this study," commented Don Dizon, MD, director of Women's Cancers, Lifespan Cancer Institute at Brown University in Providence, Rhode Island. He was not involved with the study and was approached by Medscape Medical News for comment.

Because of its observational design, the study cannot prove that cow's milk causes breast cancer, Dizon emphasized.

"I'd want to see if the findings are replicated [by others]. Outside of a randomized trial of [cow's] milk vs no milk or even soy, and incident breast cancers, there will never be undisputable data," he said.

"Probably the biggest point [about this study] is not to overinflate the data," Dizon added.

He noted that the results were significant only for postmenopausal women, and not for premenopausal women. Moreover, analyses showed significant associations only for hormone receptor-positive cancers.

"We know that breast cancer increases in incidence with age, so this tracks with that particular trend. It suggests there may be confounders not accounted for in this study," he said.

Research so far has been inconclusive on a possible link between dairy and increased risk for breast cancer. Dairy has even been tied to decreased risk for breast cancer, according to the World Cancer Research Fund.

Study Details

The current study included 52,795 Seventh Day Adventist women from North America who did not have cancer at the start of the study. Women had a mean age of 57.1 years, and 29.7% were black. At baseline, women reported their dietary patterns for the past year using food frequency questionnaires. For 1011 women, researchers double-checked food intake with 24-hour diet questionnaires, and verified soy intake by analyzing urine levels of soy isoflavones.

Data on invasive breast cancer diagnoses came from national registries in the US and Canada. Over the course of 7.9 years, 1057 women developed invasive breast cancer. Results were adjusted for a range of factors related to breast cancer risk, including diet, lifestyle, and family history of breast cancer.

Overall, women who consumed the most calories from dairy per day had 22% increased risk for breast cancer, compared with women with the fewest calories from dairy (hazard ratio [HR], 1.22; 95% confidence interval [CI], 1.05 - 1.40, P = .008). Women who drank the most cow's milk per day had 50% increased risk for breast cancer compared with women who drank the least (HR, 1.50; 95% CI, 1.22 - 1.84, P < .001). 

Drinking full or reduced fat cow's milk did not change the findings (P for trend = .002 and P for trend < .0001, respectively).

No significant association was found between breast cancer risk and cheese or yogurt consumption (P = .35 and P = .80, respectively).

Need for Change?

US dietary guidelines are under review. A new version, which will cover pregnant women and children under age 2 for the first time, is expected later this year.

Current guidelines recommend that adults and children aged 9 and over drink three 8 oz glasses of milk per day, or equivalent portions of yogurt, cheese, and other dairy products.

"Evidence from this study suggests that people should view that recommendation with caution," Fraser said.

Milk Is Complex Topic

A top nutrition scientist agrees. Walter Willett, MD, DrPH, professor of epidemiology and nutrition at Harvard T.H. Chan School of Public Health in Boston, Massachusetts, told Medscape Medical News: "There is little scientific justification for the recommendation of 3 cups of milk per day. This new study adds a further reason for caution.” 

"This was a high-quality study conducted by experienced investigators," Willett said. Strengths of the study include the high soy intake and low consumption of foods from animal sources, factors that are hard to study in other populations.

Willett was a coauthor, along with David Ludwig, MD, PhD, also from Harvard, of the recent review published in the New England Journal of Medicine that questioned the science behind milk-drinking recommendations. An article about this review on Medscape Medical News has attracted a huge number of comments from our readers.  

Milk is a complex topic, Willett explained. As a good source of essential nutrients, especially calcium and vitamin D, cow's milk has been touted to have several health benefits, especially decreased fracture risk. But Willett said calcium recommendations have probably been overstated, and current evidence does not support high milk intake for fracture prevention.

Other benefits include improved nutrition in low-income settings, taller stature, and decreased colorectal cancer risk. But cow's milk has also been linked to increased risk for some cancers, including prostate and endometrial cancer. Many of the benefits derived from nutrients found in milk may be obtained from other sources without these risks, according to Willett.

"Given the risks and benefits, we suggest a possible range from zero to two servings per day of dairy foods, including milk, cheese, and yogurt. If intake is zero or one serving, taking a calcium/vitamin D supplement would be good to consider," he said.

However, Fraser and Willett also suggested another option: replacing cow's milk with soy milk. Analyses from the current study showed no significant association between consumption of soy and breast cancer, independent of dairy (P for trend = .22).

In addition, substituting average amounts of soy milk for cow's milk was linked to a 32% drop in risk for breast cancer among postmenopausal women (HR, 0.68; 95% CI, 0.55 - 0.85, P = .002). However, these results were not significant among premenopausal women (HR, 0.70; 95% CI, 0.36 - 1.38, P = .31).

"The suggestion that replacing some or all of [cow's] milk with soy milk may reduce risk of breast cancer is consistent with other studies supporting a benefit of soy milk for risk of breast cancer," Willett said.

"If someone does choose soy milk, picking one with minimal amounts of added sugar is desirable," he added.

Drinking Milk, or Some Related Factor?

Fraser, the lead author of the current study, said in a statement that the results provide "fairly strong evidence that either dairy milk or some other factor closely related to drinking dairy milk is a cause of breast cancer in women.”

That 'other' factor is probably complicated, but may be related to what humans have done to cows. To increase milk production, humans have bred cows to have higher levels of insulin-like growth factor, which in turn has been linked to some cancers, including breast cancer.

Sex hormones in cow's milk may also be involved. About 75% of a dairy herd is pregnant and the cows are by definition lactating. So the milk they produce may have higher levels of progestins and estrogens, which may play a role in hormone-responsive breast cancer. 

Other factors that researchers did not measure in this study, such as poverty and the income of participants, may be at play.

But to know what's really going on, all agree that more research is needed.

"The overall evidence so far has not shown a clear increase or decrease in risk of breast cancer with higher [cow's] milk intake. Thus, this topic needs further examination," Willett said.

Dairy, soy, and risk of breast cancer: those confounded milks

Gary E Fraser,  Karen Jaceldo-Siegl,  Michael Orlich,  Andrew Mashchak,  Rawiwan Sirirat,  Synnove Knutsen

International Journal of Epidemiology, dyaa007, https://doi.org/10.1093/ije/dyaa007

Published: 25 February 2020 Article history

Abstract

Background

Associations between soy, dairy intakes and breast cancer risk are inconsistent. No studies exist with large numbers of dairy consumers and soy consumers to assess mutual confounding.

Methods

The study cohort contains 52 795 North American women, initially free of cancer, followed for 7.9 years (29.7% were Black). Dietary intakes were estimated from food frequency questionnaires and, for 1011 calibration study subjects, from six structured 24-h dietary recalls. Incident invasive breast cancers were detected mainly by matching with cancer registries. Analyses used multivariable proportional hazards regression.

Results

The participants (mean age of 57.1 years) experienced 1057 new breast cancer cases during follow-up. No clear associations were found between soy products and breast cancer, independently of dairy. However, higher intakes of dairy calories and dairy milk were associated with hazard ratios (HRs) of 1.22 [95% confidence interval (CI): 1.05–1.40] and 1.50 (95% CI 1.22–1.84), respectively, comparing 90th to 10th percentiles of intakes. Full fat and reduced fat milks produced similar results. No important associations were noted with cheese and yogurt. Substituting median intakes of dairy milk users by those of soy milk consumers was associated with HR of 0.68 (95% CI: 0.55–0.85). Similar-sized associations were found among pre- and post-menopausal cases, with CIs also excluding the null in estrogen receptor (ER+, ER-), and progesterone receptor (PR+) cancers. Less biased calibrated measurement-error adjusted regressions demonstrated yet stronger, but less precise, HRs and CIs that still excluded the null.

Conclusions

Higher intakes of dairy milk were associated with greater risk of breast cancer, when adjusted for soy intake. Current guidelines for dairy milk consumption could be viewed with some caution.

6 Must Have Summer Herbs...

 This was such amazing information and so easily read and understood that I had to share it with all of you. Now, you can easily add these fabulous herbs to your diet.

6 Must Have Summer Herbs

Basil

Basil is so versatile, and its scent is divine. It is high in Vitamin A and is known to be excellent for eye health and vision, eliminating bad bacteria and viruses in the body, reducing inflammation, and promoting a healthy gut.

From pesto to caprese salads, you’ll want to have this plant front and center on your countertop. Pick its fresh leaves and sprinkle liberally in salads, sauces and even desserts for a sweet and savory contrast. 

Stinging Nettle

Stinging nettle has been used for at least 2,000 years to treat arthritis and other inflammatory diseases. It’s most famous as a hair tonic and its other benefits include regulating blood sugar, enhancing circulation, and treating gout and impotence. 

Dried stinging nettle leaves can be steeped to make a delicious herbal tea, while its fresh leaves, stems and roots can be cooked and added to soups, stir-frys, and smoothies. The leaves get their ‘sting’ from histamine and formic acid contained in their underleaf hairs. But once cooked, stinging nettle is nothing but tasty. 

Mint

Mint smells great, grows fast, and has many healing properties. It’s great for reducing flatulence, masking bad breath, relieving headaches, soothing digestion, and has a calming quality that’s good for heart health. 

Having a supply of fresh mint water or tea is a great way to keep cool. The easiest way to enjoy this lovely leaf is to place a handful of fresh mint leaves in a quart pitcher or jar, add spring or distilled water and leave it in the refrigerator overnight for a cold-brewed infusion. Sip, hot or cold throughout the day. 

Dill

Similar to mint’s attributes, a warm dill tea treats an upset stomach, is a light aromatic that freshens breath and adds a tasty zing to any dish. Another surprising benefit of dill is its high calcium content and antibacterial properties. 

Mix this feathery favorite in with your favorite tuna or chicken salad or use it to garnish grilled asparagus. 

Rosemary

Rosemary, fresh or dried, is a pungent, sturdy herb with superb health benefits. Rosemary, high in antioxidants and volatile oils, has long been used for everything such as pain relief, digestion, hair growth, and treating depression. 

One of its lesser known benefits is as a memory enhancer. Studies have shown that rosemary boosts memory and helps students recall facts if they smelled the herb while studying, and again while taking their tests. 

Use a fresh sprig of rosemary or some essential oil as an herbal cheat sheet during your exam for better recall! Also, while cooking, rosemary goes great with a variety of dishes such as soups, salads, stews, fish, and grains. 

Chives

Mild and oniony, chives are a delicious addition to many dishes. They are high in Vitamins A and K. Chives also contain allicin (similar to garlic, onions, leeks), a plant compound that is good for keeping cholesterol levels in check. 

The best way to eat chives is to snip them with scissors instead of chopping and add them to garnishes, salads, sandwiches, soups, and sauces just before serving. 

Who knew these summer herbs had so many healing properties? If you’re interested in a free online course that shows simple healthy recipes to try at home, check out Healthy Eating Tips: Easy Vegan Recipes led by certified rejuvenation chef, Kryssi Gala. 

Written by Gabi Petrylaite @ Changeyourenergy.com

GMO foods......are we going to outa real food soon????

Sugar beet industry converts to 100% GMO, disallows non-GMO option The US sugar beet industry coordinated an industry-wide conversion to genetically modified sugar beets, thus eliminating a non-GMO alternative for food manufacturers and consumers. Meanwhile, production of GM sugar beet seed is likely to contaminate organic and conventional vegetable seed production in Oregon’s Willamette Valley. Frank Morton faces a major threat to his livelihood. Morton’s business, Wild Garden Seed, which sells organic vegetable and flower seed in Philomath, Oregon, is threatened by the incursion of genetically modified sugar beets in Oregon’s Willamette Valley. The Willamette Valley is known as a center of seed production. The valley features fertile soil with ample water from irrigation. Winters are mild and wet and summers are dry, and not too hot. Seeds for specialty crops such as the Brassica family, which includes cabbages, broccoli, cauliflower, mustard seed, and canola are grown here, along with onions, spinach, beets, chicories, endives, chard, and many flowers. “It’s seed dreamland,” Morton says. Unanimous decision to go GMO The Willamette Valley is also home to all the sugar beet seed production in the United States. Two large companies, Beta Seed and West Coast Beet Seed, supply seed to sugar beet farmers in Idaho, Montana, Wyoming, Minnesota, North Dakota, and other states where the beets are grown. Harvested beets are processed by seven processing companies, the biggest being American Crystal Sugar Company, based in Moorhead, Minnesota. These processors supply beet sugar, which accounts for one-half of the US sugar production, to food and candy manufacturers, such as Mars and Hershey’s. Three years ago, these processors decided to convert the entire US sugar beet production to Roundup Ready genetically modified varieties, developed by Monsanto Company. The industry said farmers needed the GM beets for better weed control. Unanimity was necessary, Morton says. “If any one of the beet processors or a major candy company had rejected the idea of GM beets, the introduction would not have gone ahead.” Unlike corn and soybean production where non-GMO alternatives are available, the sugar beet processors did not want that option. “This was a coordinated effort to genetically modify an entire sector of the processed food industry simultaneously and without holdouts that might otherwise have provided a source of conventional beet sugar to fulfill non-GMO consumer demand,” Morton says. Stealth introduction in the Valley Field trials of the GM beets began in the Willamette Valley in 2005—quietly, Morton says. “The initial stages of GM beet seed production were carried out in secrecy for at least two years without other sugar beet seed growers having any knowledge or notification that GMOs were in the air, literally,” he says. The Oregon Department of Agriculture (ODA) did not ask for public comments nor notify anyone about the trials. “A farming technology revolution went on silently for three years, and was definitely not televised, or bragged about,” Morton says. Restricted GM canola The Willamette Valley specialty seed industry has a tradition of ensuring seed purity. Seed producers adhere to requirements for isolation distances between crops to prevent cross pollination. Vegetable seed must be 100% pure. “We take purity seriously,” Morton says. When some farmers wanted to introduce GM canola for biofuel production in the valley, the Willamette Valley Specialty Seed Association (WVSSA) worked with the ODA to restrict plantings. The Rapeseed Control Areas rules aim to protect specialty vegetable seed production from cross pollination by GM canola. At a hearing at the ODA, Morton pointed out a double standard with the restriction of GM canola and the allowance of GM sugar beets. “I remarked at the irony that one of our own (seed association) members had just converted 95% of its 2008 crop to Roundup Ready technology, but no one bothered to mention that as they bashed Roundup Ready contamination by biofuel canola,” he says. “Contamination is inevitable” Cross pollination between GM sugar beets and related plants, such as chard and table beets, is a major threat in the valley where sugar beets are the predominant crop. Morton says there are many areas where chard and sugar beet fields are “rubbing up against one another.” The two plants cross pollinate because they are the same species. Sugar beet seed producers wanted to establish a six-mile isolation distance between GM sugar beets and non-GM crops in the valley, based on research showing such a distance was necessary to keep GMO contamination down to .01%. They wanted the distance to protect themselves from potential lawsuits in case of contamination problems. Morton says such a distance would be impossible to achieve, given the size of the Willamette Valley. “They would overlap existing farms. If my closest sugar beet neighbor had six miles, it would take out all my fields,” he says. The WVSSA refused to approve the six-mile isolation, and instead lowered it to three miles, and thus increased the risk of GMO contamination to conventional and organic seed. Morton is angry. “GMO contamination is inevitable under the current situation.” A sugar beet company representative even admitted this in a meeting Morton attended. “Organic seed growers in the Willamette Valley must now test their chard and table beet seed for transgenic contamination, paying an expense on account of a technology that will destroy the value of our crop if we get positive results,” he says. “Nobody considered that Roundup Ready sugar beet in one generation might turn up as Roundup Ready salad greens in the next.” “Last step”: Lawsuit Seeing no other recourse, Morton joined a lawsuit organized by the Center for Food Safety to sue the US Department of Agriculture for failing to conduct an environmental impact statement (EIS). “USDA didn’t consider the impact on all these farms and markets to where we sell seeds. My markets have zero tolerance to GMOs,” he says. “If there is any GMO contamination, my customers won’t buy the seed. Who is going to pay for that?” Morton and the other plaintiffs hope that a judge’s ruling last year requiring USDA to conduct an EIS for Roundup Ready alfalfa will set a precedent for their case. The suit was necessary to save precious seed resources. “This was a last step to protect an industry and our businesses from introgression of genetic pollution into the Willamette Valley,” Morton says. Copyright The Organic & Non-GMO Report June 2008.