Here’s How the Mediterranean Diet May Reduce Your Breast Cancer Risk

Like your gut, the breast has a microbiome, and a new study shows it can be directly influenced by what you eat.

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A few simple dietary changes can go a long way. Getty Images

Breast glands have a microbiome.

And, like the gut microbiome, it can be affected by diet, according to researchers at Wake Forest School of Medicine in North Carolina.

“Microbiome” refers to a variety of living organisms, such as bacteria and fungi, that populate our bodies. This ecosystem is essential to good health.

“We were surprised that diet directly influenced microbiome outside of the intestinal tract in sites such as the mammary gland,” the study’s lead author, Katherine Cook, PhD, said in a press release.

The researchers say that shifting the breast microbiome through diet may reduce the risk of developing breast cancer.

The scientists used female monkeys to see how diet affects breast tissue. They fed one group a high-fat Western diet and another group a Mediterranean diet, which is plant based.

After 2 1/2 years, which is about the same as 8 years for humans, the two groups had significant differences in bacteria in their breast tissue.

The Mediterranean diet group had 10 times more mammary gland Lactobacillus. These bacteria have been shown to slow growth in breast tumors. Also, cancerous breast tumors have lower Lactobacillus abundance than noncancerous breast tumors.

The Mediterranean diet group also had more bile acid metabolites, which the researchers say may reduce the risk of breast cancer.

Study authors acknowledge the research is still in the early stages.

Because microbiomes vary according to where a person lives, they say future studies will involve primates from different regions.

Other studies are also underway to see if fish oil or probiotic supplements can affect microbiomes in mammary glands.

Details of the research are published in Cell Reports.

Dr. Janie Grumley is a breast surgical oncologist, director of the Margie Petersen Breast Center at Providence Saint John’s Health Center, and associate professor of surgery at John Wayne Cancer Institute in California.

“I love these studies because they help encourage patients to be aware of diet,” she told Healthline.

But breast cancer prevention isn’t that simple.

Women in the United States have a 1 in 8 lifetime risk of developing breast cancer.

Some breast cancer risk factors, such as genetics and age, are beyond a person’s control.

“Studies are really important, but you have to be careful how you interpret the conclusions. It’s not one thing, but a combination of things. Age is a huge factor for breast cancer,” said Grumley.

And breast cancer isn’t a single disease.

“What makes cancer research so interesting and challenging is that you’re trying to attack a very wide range of diseases. There are many different kinds of breast cancer,” she explained.

And many things can affect development of breast cancer.

“Diet may be one small portion of that. I don’t want patients to think if they adopt a diet like this they won’t get breast cancer. You can adopt these diet habits and it may reduce risk, but that doesn’t mean you don’t have to screen or you’ll never have breast cancer,” cautioned Grumley.

She tells her patients to keep things simple.

“A healthy diet, exercise, and moderate alcohol intake are all factors we have control of to reduce the risk of breast cancer,” said Grumley.

She added, “Weight control is important. We know that obese women are at higher risk.”

Grumley advises patients to get their nutrients through a healthy, natural diet. When you do that, large amounts of vitamin supplements aren’t necessary.

She also emphasizes the need for moderation in how much you eat.

“We can pick apart these diets, but I sometimes wonder if what’s wrong is volume. If you sit down for a meal in Europe, they don’t give ginormous portions and expect you to eat it all. Here, what they serve you can feed a family of four,” said Grumley. “And if olive oil is good, you shouldn’t just pour it on everything or eat a jar of olives.”

Moderation is key, both for general health and for lowering the risk of breast cancer.

Grumley said her patients work with a nutritionist.

“It’s really enlightening to have a patient do a food diary to see how much they’re eating. Keeping track helps them reflect and realize maybe they could be doing better,” she said.

Samantha Lyles, an Illinois-based registered dietitian, told Healthline, “The Mediterranean diet is more focused on plants and whole grains.”

“Contrast that with the Western diet, which is full of white breads, refined grains, and processed and prepackaged foods,” she continued.

Whenever possible, choose fresh over processed foods, she advises.

“When you’re trying to decide if something is plant based or processed, ask if it looks like something you would find in nature. You won’t find Fruit Loops sitting in a field,” explained Lyles.

A few simple dietary changes can go a long way.

“For example, instead of a prepackaged breakfast bar, have a nut mix. Look for foods that don’t have added sodium and sugar,” she said.

Lyles also recommends substituting high-starch foods like corn and potatoes with other vegetables.

“Fresh is best. But if you have to, frozen or canned vegetables are OK.”

The typical Western diet includes a lot of fatty red meat, which can contribute to inflammation. The Mediterranean diet limits red meat in favor of more fish and poultry.

“The Mediterranean diet contains more omega-3 fatty acids, which are anti-inflammatory. Consuming fish such as salmon, plus nuts and healthy oils, lowers your risk of cancer and other illnesses,” said Lyles.

“Think about how much red meat and pork you consume in a week. Keep it down to once or twice a week and have chicken and fish more often,” she suggested.

“Less red meat and dairy can help lower cholesterol, triglycerides, and blood pressure. Also, the Mediterranean diet is typically lower in salt and sodium than the Western diet. That helps control blood pressure.”

Lyles suggests replacing white bread with whole-wheat bread. But that can be tricky.

“It’s important to know that wheat bread and honey wheat bread are not the same as whole-grain wheat bread. They’re just white bread in disguise. Look for 100 percent whole wheat, not enriched flour,” she said.

Eating out can make things even trickier.

But you can still make a few healthier tweaks.

“When ordering salad in a restaurant, choose oil- and vinegar-based dressings rather than creamy ones, like ranch. Olive oil has healthy fats and is a huge component of the Mediterranean diet. It helps control inflammation. And look for options other than potatoes. Instead of fries, ask for a side salad or see if you can substitute a fresh vegetable or fruit,” she explained.

Lyles said the typical American diet is filled with processed and prepackaged foods meant to make our lives easier — but they’re not good for overall health. So, every time you swap these things out for fresh vegetables or fruit, it’s a step in the right direction.

“Everything else will fall into place from there,” she said.

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