“It's a really interesting area of research, but it's also very diverse. We're learning as we go along how much detail we need to get into,” she says.
Here, Morse shares more about dairy’s risks and benefits and explains the link between dairy and cancer.
Dairy may affect cancer types differently
Some studies show that consuming dairy products may lead to increased cancer risk, while other studies show that dairy may promote cancer prevention.
“We have some evidence that shows a stronger correlation with dairy consumption and prostate cancer development,” Morse says.
Morse says one possible reason consuming dairy may increase prostate cancer risk is because dairy increases circulating levels of IGF-1, a hormone known to promote prostate cancer growth.
“Dairy consumption increases insulin growth factor release in the body, and there is a correlation with increased insulin growth factor levels in prostate cancer, so that might be one mechanism,” she says.
Morse says other research shows dairy may help prevent the development of breast and colorectal cancers.
She says these protective benefits could be linked to the high amounts of calcium and vitamin D in dairy.
“We know that keeping vitamin D levels adequate is protective in terms of cancer prevention and survival,” she says.
Further research on dairy and cancer risk is needed
Morse believes there is still more research to do on dairy and cancer risk.
"These variations in the research really need to be investigated further and the mechanisms understood a little bit better,” she says.
Morse says the many different types of dairy products make it challenging to research dairy and cancer risk.
"Dairy is a pretty broad definition. It includes everything from milk, butter, cheese, ghee – which is used commonly in more South Asian cooking – as well as fermented culture products like yogurts and kefir, and even powdered condensed milk,” she says.
Morse says it is important that future studies identify what types of dairy products participants are consuming and where that dairy comes from.
Dairy affects people in different ways
Dairy can affect people differently. For example, Morse says some people don’t have the enzyme that allows them to digest lactose, the type of sugar in dairy. This might make them feel sick when they eat or drink dairy.
Morse also notes that for others, dairy is an inflammatory food that can cause bloating, cramping, diarrhea, nausea, joint pain or mood changes.
“There are some proinflammatory foods that we are learning contribute to systemic inflammation. We know that inflammation contributes to cancer, so we're trying from all angles to reduce inflammation, and through diet, that’s one of the most powerful ways you can do that,” she says.
If dairy causes inflammation for you, Morse recommends reducing the amount of dairy in your diet or choosing fermented dairy options like kefir or yogurt to help with digestion and support the gut microbiome.
If you tolerate dairy well, consuming it in moderation can provide benefits. These benefits include high protein, calcium, vitamin B and fat-soluble vitamins such as A, D, E and K, says Morse.
“Everybody is so different that it's kind of a personalized approach, but small quantities of high-quality dairy products such as fermented yogurt or cheese can be beneficial to your health,” she says.
Consuming dairy in moderation can be part of a healthy diet
When there is seemingly conflicting messaging, it can be hard to know how to proceed.
Morse encourages those who are worried about dairy’s link to cancer to follow the American Institute of Cancer Research (AICR) dietary guidelines for cancer prevention until more research on the subject has been completed.
MD Anderson recommends following a plant-based diet. Ideally, two-thirds of what you eat will be plants like vegetables, whole grains, beans and plant-based protein. The other third may be lean protein such as chicken or fish, as well as dairy products.
“We know that minimizing animal products in your eating pattern is the most beneficial in terms of cancer prevention, also cancer recurrence and survival and cardiovascular health,” Morse says.
However, that doesn’t mean you have to cut out dairy completely.
"There's a healthy way that you can incorporate dairy into your eating pattern. That’s going to be in moderation with a good quality product, being mindful of the amount of fat that you're taking in,” Morse says.
Cancer patients can talk to their doctor to determine if it is safe to consume dairy.
“I like to help patients achieve an eating pattern that fits with their culture and what they're used to while optimizing their chances at success with their cancer treatment and feeling well,” Morse says. “It’s very patient-dependent.”
Select dairy products without additives
There are several shopping tips you can use to get the most health benefits from your dairy.
If it is within your budget, Morse recommends selecting an organic product as it will be less likely to contain pesticides, antibiotics or added hormones.
She says grass-fed cow milk has a healthier omega-3 to omega-6 ratio.
“Generally, dairy coming from a grass-fed animal is going to be more nutrient-dense because that animal is eating phytonutrients,” she says.
Selecting a milk percentage can be tricky. While Morse notes there is a link between high amounts of saturated fat and cancer, milk fat also offers benefits such as increased vitamin absorption and helping us feel full.
Finally, look for products without added sugar, sweeteners or colors.
In addition to eating these products in moderation, Morse recommends switching up your dairy sources throughout the week.
“One day, maybe your dairy source would be yogurt, the next day maybe it would be a cheese,” Morse says. “Getting a variety is important, too.”