Do I need to Avoid Dairy After Prostate Cancer?

By Meredy Birdi, Oncology Dietitian and Nutritional Therapist

“Should I avoid dairy after prostate cancer?”

If you’ve been looking into diet and prostate cancer, you may have come across information suggesting that milk or dairy foods might increase risk - in articles, online discussions, or scientific papers.

It’s easy to see how this can leave you wondering whether dairy is something you should avoid.

To make sense of this, it helps to look at the overall body of evidence rather than focusing on individual studies.

Why this question comes up

Dairy appears so often in conversations about prostate cancer because individual studies occasionally report ‘associations’ between dairy intake and prostate cancer outcomes.

These findings can circulate quickly and, when taken out of context, can sound more certain than they are.

What the studies on dairy and prostate cancer are looking at

Not all studies are examining the same question.

Some studies follow people in the general population to see whether certain dietary patterns are linked with developing prostate cancer or with prostate cancer mortality over time. Other studies focus specifically on men who have already been diagnosed, examining outcomes such as recurrence, disease progression, or prostate cancer-specific mortality.

These are different questions, and they can lead to different types of findings. It’s important to be clear about who is being studied and what outcome is being measured.

Most research in this area is observational

When it comes to diet and prostate cancer, most of the research we have is observational.

In observational research, scientists follow large groups of people over time. Participants report what they typically eat, and researchers track health outcomes. These studies are useful because they help identify potential patterns between diet and disease.

However, observational studies also have important limitations.

Dietary intake is usually measured using tools such as food frequency questionnaires, where people report how often they eat certain foods. This relies on memory and estimation, so it’s never perfectly precise. People may under or over-estimate what they eat, and the way questions are interpreted can vary from person to person.

Sometimes dietary information is only collected once at the beginning of a study, even though participants may be followed for many years. People’s diets can change over time, so that single snapshot may not reflect what someone is eating later on. 

Another important challenge is something called confounding factors. People who eat certain foods often differ in other ways too - for example in body weight, physical activity, smoking, alcohol intake, or overall diet. Researchers try to adjust for these differences, but it’s impossible to account for everything perfectly.

For these reasons, observational studies are good at identifying patterns and associations, but they cannot prove that a particular food directly caused a health outcome.

Association does not mean cause

When two things appear together in research, it doesn’t necessarily mean one caused the other.

A simple example to help illustrate this is that when people are carrying umbrellas, their feet are often wet. Umbrellas and wet feet appear together. But umbrellas do not cause wet feet. The rain is the underlying factor explaining both.

Nutrition research can work in a similar way, where two things may occur together without one directly causing the other.

Why scientists look for patterns across many studies

Because of these limitations, scientists do not rely on single studies. Instead, they look for consistent signals across multiple studies and populations.

If a dietary factor has a strong effect, we expect to see similar findings across different studies. When results are inconsistent, it suggests that any possible effect that might exist is likely to be small or may be influenced by other factors.

Another factor scientists consider is the population being studied. Dietary patterns, portion sizes and food production practices can vary between countries and cultures, so findings from one population do not always translate perfectly to another.

For this reason, studies from different populations are considered together, rather than relying too heavily on findings from a single setting.

What the research shows about dairy and prostate cancer

When researchers examine the overall body of evidence, the findings on dairy and prostate cancer are inconsistent and don’t show a clear pattern.

Some studies have suggested a possible association between higher intake of whole milk and prostate cancer outcomes. However, this pattern is not seen consistently across other dairy foods such as yoghurt or cheese, nor across overall dairy intake.

If dairy itself were a strong causal factor, we would expect to see similar signals appearing across multiple dairy foods. That is not what the research shows. 

Organisations such as the World Cancer Research Fund (WCRF) and the American Institute for Cancer Research (AICR) review the totality of the evidence across all types of studies to provide evidence-based guidance.

In their assessments, the evidence linking higher intakes of calcium with prostate cancer risk is classified as “limited - suggestive.” 

Their guidance focuses on overall dietary patterns, with moderate dairy intake able to fit within a healthy diet.

Another question that sometimes comes up is whether calcium itself, rather than dairy foods specifically, might play a role.

What about calcium?

Researchers have explored whether higher calcium intake, rather than dairy foods themselves, could influence prostate cancer biology. Some of this research considers calcium from both food and supplements.

One proposed explanation is that higher calcium intake may affect vitamin D metabolism, although the exact mechanisms remain uncertain.

However, the overall evidence is not strong or consistent.

Calcium is also an important nutrient for bone health, particularly for men receiving prostate cancer treatments such as androgen deprivation therapy.

Biological pathways such as insulin-like growth factor (IGF-1) have also been explored, but these are not fully understood and do not change the overall picture that the evidence remains limited and inconsistent.

Putting risk statistics into perspective

When people read research papers directly or explore resources such as PubMed (a large database of scientific studies), they sometimes come across risk statistics that sound quite scary.

A paper may report a 40-50% increase in risk, which understandably sounds worrying. However, these figures usually refer to something called relative risk, rather than the actual number of people affected.

To give a simple example, imagine that out of 1000 men, 4 develop a particular outcome. A reported 50% increase in relative risk would not mean 50% more people overall. It would mean that the number increases from 4 men to around 6 men out of 1000.

So whilst the percentage sounds large, the real-world difference in numbers may still be quite small. This is why researchers interpret risk statistics alongside the underlying numbers, and why it’s helpful to keep that perspective when reading headlines or individual studies.

What seems to matter most for long-term health after prostate cancer?

When we step back and look at the overall body of evidence, what we see is that outcomes after a prostate cancer diagnosis are influenced far more by overall dietary pattern and lifestyle than by any single food.

The factors that appear to have the greatest influence include:

• Maintaining a healthy body weight

• Regular physical activity

• A plant-rich diet that provides plenty of fibre

• Supporting overall cardiometabolic health – for example by not having large amounts of refined sugar or saturated fat, and maintaining healthy muscle mass through diet and activity

What about dairy after prostate cancer?

When the research is considered as a whole, dairy foods do not need to be avoided.

For people who have a good appetite and are maintaining their weight, a balanced approach might look like:

• Including dairy in moderate amounts

• Choosing lower-fat milk such as semi-skimmed rather than large amounts of whole milk

• For people who particularly enjoy whole milk, keeping it as an occasional choice rather than a regular habit can be a sensible compromise

However, if you are struggling with appetite, experiencing weight loss, or finding it difficult to eat during treatment, the priorities can be different. In those situations, ensuring adequate nutrition and maintaining weight are important, and higher-energy foods may be helpful. Seeking personalised advice from a cancer dietitian or nutrition professional can help ensure your nutritional needs are properly supported.

If you choose to reduce or avoid dairy, that’s absolutely fine, and it is possible to meet your nutritional needs in other ways. This is here to help if you’re including dairy but feeling unsure about it.

Key takeaways on dairy and prostate cancer

The research around dairy and prostate cancer can feel worrying or confusing when individual studies are viewed in isolation. When you step back and look at the evidence as a whole, and in context, it helps to put things into proportion.

Current evidence does not show that dairy foods are a major driver of prostate cancer outcomes and does not support the need to remove dairy from the diet.

What appears to matter far more is the overall pattern of diet and lifestyle - including maintaining a healthy body weight, staying physically active, and following a balanced, plant-rich dietary pattern.

Frequently asked questions

Should men with prostate cancer avoid dairy?

No, you don’t have to. Current evidence does not show that dairy foods are a major driver of prostate cancer outcomes.

Dairy foods do not need to be avoided entirely and moderate amounts can fit comfortably within an overall healthy dietary pattern.

Some studies have raised questions about higher intakes of whole milk, so this might be something to have in moderation rather than in large amounts.

Does drinking milk increase prostate cancer risk?

When the overall body of evidence is considered, there isn't a clear or consistent link between dairy intake and prostate cancer risk.

Expert reviews describe the evidence linking higher intakes of calcium and dairy foods with prostate cancer risk as “limited - suggestive,” meaning the findings are not strong or consistent enough to support firm conclusions.

Some individual observational studies have raised questions about higher whole milk intake, but this is not seen consistently across all studies or across all dairy foods.

As with many areas of nutrition, this is not an all-or-nothing decision. What appears to matter far more is the overall pattern of diet and lifestyle - including maintaining a healthy body weight, staying physically active, and following a balanced, plant-rich diet.

Does the type of dairy you choose matter?

Yes - from an overall health perspective, it’s fair to say that not all dairy foods are the same.

Think about both what that food is contributing to your diet and how often it’s part of your usual pattern of eating. For example, foods like natural yoghurt or kefir can add protein and beneficial bacteria and may be something you choose to include more regularly. There’s also space for things like good quality cheese across the week.

At the same time, dairy that comes as part of foods that are higher in sugar or saturated fat - for example milkshakes or more heavily processed options - is usually something to have more occasionally, rather than relying on it day to day as a main source of nutrition.

This isn’t about avoiding certain foods altogether, but about how often they’re included and the overall balance of the diet.

Some fermented dairy foods, such as yoghurt and kefir, may also be associated with more favourable cardiometabolic outcomes in broader nutrition research.

As with many areas of nutrition, the overall pattern of the diet matters more than any single food.

References and further reading

• World Cancer Research Fund. https://www.wcrf.org/preventing-cancer/cancer-types/prostate-cancer/

• American Institute for Cancer Research. https://www.aicr.org/cancer-survival/cancer/prostate-cancer/

• Langlais CS, et al. https://link.springer.com/article/10.1007/s11912-021-01017-xCurr Oncol Rep. 2021 Mar 10;23(3):37. doi: 10.1007/s11912-021-01017-x. PMID: 33689041

This blog is for general information only and is not a substitute for individual medical or dietetic advice.