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Two registered dietitians from Harvard-affiliated hospitals share their thoughts on calcium, fats, and shedding excess weight

More and more evidence links obesity to an increased risk of prostate cancer and, especially, to a poorer outcome for men with the disease. Of course, staying lean will not provide immunity from prostate cancer or other prostate conditions, but it should help. And a lifestyle that includes a healthy diet and regular exercise will also go a long way to reducing the risk of heart attack, stroke, high blood pressure, and diabetes 鈥� as well as obesity and its undesirable consequences.

In part 1 of this two-part series, dietitians from two Harvard-affiliated hospitals explained the benefits of eating a diet rich in fruits, vegetables, and whole grains. They were

• Stacy Kennedy, M.P.H., R.D., L.D.N., senior clinical nutritionist at Dana-Farber Cancer Institute. She is most interested in weight management, physical activity, integrative therapies, and plant-based diets.
• Kathy McManus, M.S., R.D., L.D.N., director of the Department of Nutrition at Brigham and Women鈥檚 Hospital. She has been a co-investigator on a number of obesity research trials, presented her research in national and international forums, and written numerous publications and book chapters.

Here, they continue the conversation and make recommendations for the consumption of fats, meat, and dairy products. They also explain what鈥檚 meant by body mass index and offer some helpful strategies for trimming calories.

Get the skinny on fats

Studies have shown a link between the consumption of red and processed meats and the development of prostate cancer. Has the connection been explained?

KENNEDY: There are a few theories and hypotheses. Fat content in these foods is one broad category that鈥檚 being examined. Researchers are also looking at components of the fat that are particular to animal proteins like red meat. For example, fat-soluble nutrients, androgens, and pesticides may affect the progression of prostate cancer or encourage cancer cell growth. Processed and cured meats tend to contain heterocyclic amines and other cancer-causing substances that come from the processing of the meat. It鈥檚 kind of hard to get around that.

One of the reasons we encourage men to eat more fruits and vegetables is to decrease their consumption of red meat, which includes beef, pork, lamb, and goat, and other fatty foods. If people eat more fruits and vegetables, they鈥檒l have less room for meat. They鈥檒l gain more beneficial nutrients and decrease the intake of potentially detrimental things, like fat, that are a concern, especially with prostate cancer.*

Does that mean men concerned about prostate health should not eat meat? Or just that they need to eat it in moderation?

KENNEDY: We鈥檙e not saying, 鈥淒on鈥檛 ever eat red meat.鈥� We don鈥檛 advocate eliminating any food group altogether.*

The American Cancer Society recommends that people strive for one or two servings of red meat a week at the most. A serving is about 4 to 6 ounces. For some people, that鈥檚 a lot; for others, that鈥檚 not very much at all. So we鈥檙e not asking people to eliminate red meat, but to eat less of it. We鈥檙e also asking people to eat other types of protein that are lower in fat and don鈥檛 carry the inherent risks that red meat does 鈥� things like white meat poultry and vegetarian sources of protein, such as soy foods, nuts, and seeds. Those are healthier choices.

McMANUS: The recommendation from the World Cancer Research Fund is that people should consume no more 300 grams, or 11 ounces, of cooked red meat per week, and very little, if any, of that should be processed meat. Again, not eliminating it, but moving along the path to a more plant-based diet for better overall health. Certainly from the cardiovascular disease standpoint, we do know that data support eating less red meat and more fish and poultry, which can decrease risk.

Aren鈥檛 some types of fats considered healthy?

McMANUS: The healthy fats are monounsaturated and polyunsaturated fats.* Foods with monounsaturated fats include olive oil, canola oil, most nuts, peanut butter, and avocados. There are two types of polyunsaturated fats: omega-3 fatty acids and omega-6 fatty acids. Omega-3s come mainly from fatty fish like salmon, sardines, herring, and anchovies, but there are plant-based sources, including walnuts and flaxseed. Omega-6s come mainly from nuts, seeds, and the oils derived from them: corn, sunflower, safflower, and soy oils.

All of these unsaturated fats can certainly decrease the risk of heart disease when substituted for unhealthy fats, which are trans fats and saturated fats. Trans fats are man-made fats formed when a liquid oil is solidified, or partially hydrogenated. They鈥檙e found in margarines, fried foods, fast foods, bakery products like pies and cookies, and packaged savory snacks. Saturated fats are mostly solid at room temperature. Major sources include red meat, cheese, butter, whole milk, dairy products, ice cream, and cream.

There鈥檚 evidence that omega-3s may lower the risk of prostate cancer. The Health Professionals Follow-up Study tracked more than 47,000 men over 12 years. Researchers found that the men who reported eating fish more than three times a week had a 44% lower risk of metastatic prostate cancer than those men who ate fish less than twice a month.*

KENNEDY: I think one of the other reasons why the higher-fat meats are so detrimental for men with prostate cancer is that research has shown that they can act as pro-oxidants, the opposite of antioxidants. Pro-oxidants are compounds that seem to promote more cancer growth. I think that鈥檚 another reason why men concerned about prostate cancer should pay attention to the type of fats they choose to eat.

Are fats broken out by type on the nutrition label?

McMANUS: The only fats that must be broken out on the nutrition label are total fat, trans fat, and saturated fat. Most food labels do not show the amount of monounsaturated fat or polyunsaturated fat, or the omega-3s versus the omega-6s.*

KENNEDY: That鈥檚 right. You鈥檇 have to read the ingredients, speak with your dietitian, or do a little research to find out about those fats.

McMANUS: There鈥檚 another type of omega-3 that I should mention called alpha-linolenic acid. One research study indicated that alpha-linolenic acid, especially in very concentrated sources such as flaxseed oil, may actually increase the risk of prostate cancer.

Really? Many patients have told us that they鈥檝e added flaxseed to their diet.

KENNEDY: Adding ground flaxseed is different. We encourage them to add ground flaxseed. It has the consistency of wheat germ and contains protein, fiber, and other nutrients. However, flaxseed oil is a very highly concentrated source of alpha-linolenic acid. But to be honest, there鈥檚 been research showing that flaxseed oil both inhibits and promotes prostate cancer cell growth.* So the research has been inconclusive. In the meantime, the take-home message for patients is that they can add ground flaxseed to cereal, yogurt, or oatmeal, but that they shouldn鈥檛 take flaxseed oil capsules or use flaxseed oil as sources of omega-3. Rather, they should choose the kinds of fish that we discussed earlier.

Does the method of cooking make any difference?

KENNEDY: Absolutely. We encourage people to bake or broil. If you鈥檙e grilling, it鈥檚 very important to avoid charring or burning any animal protein. If you burn chicken or red meat, it creates carcinogenic, or cancer-causing, substances that raise your overall cancer risk, not just your prostate cancer risk. Also, when you鈥檙e grilling higher-fat meats, other compounds that can be carcinogenic are formed from the high heat interacting with the fat. The same is true with frying. Most people know that frying is unhealthy because fried foods have a lot of fat. But it鈥檚 also unhealthy because when you heat oil to such a high temperature, the shape of the molecules that compose the oil changes. That changed shape can promote cancer.

No more charred hot dogs on the Fourth of July?

KENNEDY: No. That鈥檚 probably your most offensive food right there. That鈥檚 a double whammy 鈥� burned and processed meat.

But broiling and baking are totally fine?

KENNEDY: Yes. And grilling is okay as long as you鈥檙e not burning the meat. And if you鈥檙e grilling vegetables or tofu, it鈥檚 not a problem. We have this concern about carcinogens only with animal proteins. You can grill vegetables and tofu all you want; you鈥檙e not going to form carcinogens.

Prostate cancer patients often cut calcium out of their diet. Doesn鈥檛 that put them at risk for osteoporosis? What鈥檚 the correct line of thinking here?

McMANUS: This is a very controversial issue because the research doesn鈥檛 give us any clear answers.

KENNEDY: First, I should say that calcium and prostate cancer are distinct issues. We can鈥檛 extrapolate those data to women or other groups of people. Second, we can obtain calcium from dairy products, but it鈥檚 in other foods, too. I think the concern is that some research has shown an increased risk of prostate cancer in men who took calcium supplements and had a high dietary intake of calcium.*

McMANUS: In that study, the men with an increased risk of prostate cancer had a calcium intake greater than 2,000 milligrams from both supplements and foods. That鈥檚 a lot of calcium!

KENNEDY: More recent studies are not showing that connection. But it does remain controversial. Some people believe that consuming a lot of milk and other dairy products will contribute to prostate cancer and other diseases; others think that it will help prevent fractures. But we don鈥檛 have enough evidence yet to know for sure.

The No. 1 thing men can do to maintain strong bones is exercise. Physical activity, especially resistance exercise, is extremely important for maintaining strong bones. So is vitamin D, independent of calcium. So those are two things that are very safe and actually can help to decrease your cancer risk, as well as maintain your bones.

McMANUS: I agree.

KENNEDY: I encourage men to meet the recommended daily allowance for calcium through their diet. I do not recommend that men take calcium supplements unless their doctor advises it. Depending on their age, men should consume between 1,000 and 1,200 milligrams of calcium a day through diet. An 8-ounce cup of whole milk contains 276 milligrams of calcium; an 8-ounce cup of plain, nonfat yogurt has about 450 milligrams.

McMANUS: Men really should be aware that more is not better, particularly in this instance. They shouldn鈥檛 go anywhere near 2,000 milligrams. Calcium has been controversial for 10 years now, especially in relation to the recommended Daily Value and what the data show. I think that in the next revision of the nutrition guidelines, the recommended amount of calcium is probably going to go down a little bit. The data do not support the prevention of fractures, which is one of the reasons why people were hyped about calcium.

When people say they鈥檙e avoiding calcium, do you think that they mean they鈥檙e avoiding dairy products?

KENNEDY: Maybe. A lot of cancer patients ask about dairy products, not just patients with prostate cancer. But we want to be very individualized in our recommendations. And remember, the amount in that study was 2,000 milligrams, which is a lot. You would have to be getting a fair amount of calcium in your diet and taking a supplement to get that much.

McMANUS: I think the other big thing that people are missing is the importance of vitamin D.* We don鈥檛 want to focus just on calcium and miss the importance of vitamin D, strength training, and all of those other things that contribute to good health and strong bones.

Patients can ask their oncologist or primary care physician to check their blood level of vitamin D to determine if they need a supplement. There鈥檚 more than one test; the one patients should have is called the 25-hydroxyvitamin D, or calcidiol, test. It measures total vitamin D from diet, supplements, and sun exposure. The total number should be above 32 ng/ml, and research suggests that levels of 40 or 50 ng/ml may be even better for cancer prevention. If the test shows that a man needs a supplement, he can talk with his doctor or a dietitian to determine how much he should take.

Trim the calories

Studies have shown that obese men are more likely to die of prostate cancer than slimmer men. How should men go about trying to reduce their weight? Might diet pills be an option?

McMANUS: Obesity, which is defined as having a body mass index of 30 or greater, is definitely a growing problem.* I just got the most recent data from the Centers for Disease Control and Prevention and the National Center for Health Statistics. They show that about 34% of adults in the United States are obese, which is about 72 million people. About 33% of all men fall into that category. And about 40% of men between the ages of 40 and 59 are obese.

That鈥檚 just the number of men who are obese? That doesn鈥檛 include men who are simply overweight?

McMANUS: No, not overweight. That鈥檚 the number of men who are obese.

KENNEDY: I think that there鈥檚 a big disconnect in the general public between what鈥檚 considered overweight and what鈥檚 obese. Because such a significant proportion of the population is overweight or obese, it dilutes our visual understanding of weight.

McMANUS: Yes, absolutely.

KENNEDY: All the portion sizes are getting bigger. All the clothes are getting bigger. All the seats are getting bigger. That鈥檚 why many people who meet the clinical criteria for obesity actually see themselves as simply overweight. The numbers are really staggering, but I don鈥檛 think we鈥檙e recognizing the significance and prevalence of the problem.

McMANUS: Obesity rates have dramatically increased in the last 25 years. There was a significant increase in the prevalence of obesity among men between 1999 and 2006; we didn鈥檛 see this in women. But I think the good news is that there was no significant change in obesity prevalence between 2003 and 2004 or between 2005 and 2006, so the numbers might be leveling off.

Obviously, our recommendation is to reach and maintain a healthy body weight.* But we recognize that not everybody is going to get down to an ideal weight. Even losing modest amounts of weight has been shown to improve risk factors for chronic diseases. A 10% decrease in body weight can lower blood pressure, blood glucose, and cholesterol. A healthy, balanced diet and daily exercise can help men achieve that goal. We don鈥檛 usually recommend any kind of over-the-counter diet pills. But if a man still needs help after vigorous efforts in the right direction, he should seek the advice of a dietitian or his physician.

KENNEDY: Some over-the-counter weight-loss aids are of particular concern. Many of them work in a way that may be cancer-promoting, yet they fly below the radar because dietary supplements aren鈥檛 regulated by the FDA.

On the plus side, there鈥檚 a lot of research showing that behavior change 鈥� independent of weight loss 鈥� can be advantageous in lowering your risk of cancer or its progression. Walking has been shown across the board to be one of the best forms of physical activity. It can help strengthen the immune system. It has its own way of helping to fight against cancer recurrence. And it can help you to lose weight. So walking is by itself a very effective form of physical activity that鈥檚 inexpensive and relatively easy to do. Exercise does not have to be aggressive, just like our approach to eating does not have to be drastic. Even getting in small bouts of activity during your day has been shown to be beneficial. Three 10-minute walks can be just as effective as one 30-minute walk.

Slow and steady wins the race. We鈥檙e looking at this as an endurance event. We鈥檙e looking at our health over the long term, so we need to use long-term approaches 鈥� healthy, balanced eating and moderate amounts of physical activity consistently over time. That鈥檚 where gaining additional support from your care team, from your friends and family, a counselor, or another member of your medical team can really help. They can help you implement and stick with the healthy behavior changes.

I鈥檓 sure you鈥檝e talked with many people who, eager to lose weight, have cut carbohydrates out of their diet and replaced them with more protein. Does that strategy work?

McMANUS: Let me say that there should be a balance of carbohydrates, protein, and fat. There鈥檚 no evidence to suggest that drastically cutting carbohydrates in favor of protein is a healthy strategy for men concerned about prostate health. Or for that matter, to help men lose weight in the long term. Short-term studies, meaning six months or less, have shown a greater weight loss with this kind of approach. But when you look out beyond six months to a year, there鈥檚 no statistically significant weight-loss advantage.* In fact, there can be considerable disadvantages because you鈥檙e missing a lot of critical nutrients.

The U.S. Departments of Agriculture and Health and Human Services recommend healthy eating patterns that are fairly broad in terms of the body鈥檚 daily energy and nutrition needs to minimize risk for chronic disease. They say that 45% to 65% of calories should come from carbohydrates, 10% to 35% from protein, and 20% to 35% from fat. So there are lots of healthy eating patterns we can look to for chronic disease prevention. And we really do talk in terms of eating patterns, not diets. Restricting whole categories of food 鈥� carbohydrates, for example 鈥� is not a helpful approach either in terms of weight loss or overall health.

What other suggestions do you have for weight loss?

McMANUS: Limit sedentary habits, such as watching television. Even starting with that can be a positive step in the right direction.

KENNEDY: Qigong, which combines movements with meditation and controlled breathing, as well as yoga and other types of exercise, might be helpful. Not only is the mind-body connection beneficial for stress reduction, but it can help decrease cancer risk. And it鈥檚 important for weight management.

McMANUS: Planning ahead is critical. Healthy meals don鈥檛 just happen; you have to make them happen. We鈥檇 like to see people eat smaller meals, perhaps three smaller meals and two snacks, spread throughout the day. Eating breakfast can be helpful as far as managing your weight. And don鈥檛 drink your calories. Some people still drink a lot of sugary beverages 鈥� a can of Pepsi here, a glass of lemonade there. Those things are just loaded with sugar. Cutting back on sugary beverages is a simple way to manage weight and reduce calories. Plan the week, plan your lunches. Maybe take lunch to work a couple of days a week versus eating out all the time. Share an entr茅e instead of ordering your own. You can also reduce calorie intake by watching portion sizes. Try to cover half of your plate with vegetables, a quarter of your plate with healthy carbohydrates like quinoa (a South American grain), brown rice, or whole-wheat pasta, and a quarter of your plate with lean protein, such as fish or poultry. Another idea is to prepare just a little less food. There are a number of different strategies that men can use to get started on healthy eating and managing their weight.

What about alcohol consumption?

KENNEDY: There鈥檚 really not a lot of conclusive information about whether alcohol increases or decreases the risk of prostate cancer. So again, we recommend moderation.

McMANUS: For cancer, alcohol consumption is a bit controversial because the evidence doesn鈥檛 clearly show a set number of drinks below which there鈥檚 no increased risk. That鈥檚 particularly true with breast cancer. For other chronic diseases, the benefits of alcohol are clearer. For example, data clearly show that alcohol helps prevent cardiovascular disease, though we certainly don鈥檛 tell teetotalers to start drinking. When people ask us about alcohol and cancer prevention or treatment, we say to drink in moderation. That鈥檚 defined as no more than two drinks a day for men and no more than one drink a day for women.

Ask for help

Can anyone see a dietitian? Or do people need to be in treatment for cancer or another condition before they can make an appointment?

McMANUS: We have an outpatient nutrition service, and we see patients for disease prevention, either as part of their treatment or after treatment. Patients typically need some kind of referral. Some insurance companies cover our services, some don鈥檛. We recommend that people check with their insurance company first.

Can people access nutrition services at their local community hospital? Or do they need to go to an academic medical center to see a dietitian?

KENNEDY: Community hospitals certainly offer nutrition services, and many community hospitals have affiliations with larger academic medical centers. You can find oncology nutritionists outside an academic medical center, but many patients go to cancer centers and large hospitals because of the volume.

McMANUS: Oncology nutrition is a real specialty. The depth and breadth of what we have here in Boston may not be available in other areas.

KENNEDY: That鈥檚 not to say that patients can鈥檛 be followed on a regular basis close to home. But if they are at a large academic medical center that offers nutrition counseling, it鈥檚 a good thing to take advantage of.

What other sources of information do you recommend to patients?

KENNEDY: Dana-Farber has a great Web site that lists lots of books and other resources.* We post healthy recipes every month, and people can write to us with questions.

Any parting comments for our readers?

McMANUS: Start with small steps. Making too many changes at once can be difficult. Make one change and stick with it for a while. Then take another step. You鈥檒l be more likely to succeed.