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 — 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’s 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’s meant by body mass index and offer some helpful strategies for trimming calories.
Diet and prostate cancer
Chan JM, Gann PH, Giovannucci EL. Role of Diet in Prostate Cancer Development and Progression. Journal of Clinical Oncology 2005;23:8152–60. PMID: 16278466.
Chan JM, Holick CN, Leitzmann MF, et al. Diet After Diagnosis and the Risk of Prostate Cancer Progression, Recurrence, and Death (United States). Cancer Causes and Control 2006;17:199–208. PMID: 16425098.
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’s 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’s 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’ll have less room for meat. They’ll gain more beneficial nutrients and decrease the intake of potentially detrimental things, like fat, that are a concern, especially with prostate cancer.*
|*Note: See “Diet and prostate cancer,” above.|
Does that mean men concerned about prostate health should not eat meat? Or just that they need to eat it in moderation?
KENNEDY: We’re not saying, “Don’t ever eat red meat.” We don’t advocate eliminating any food group altogether.*
|*Note: See “Few absolute truths” at the end of this article.|
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’s a lot; for others, that’s not very much at all. So we’re not asking people to eliminate red meat, but to eat less of it. We’re also asking people to eat other types of protein that are lower in fat and don’t carry the inherent risks that red meat does — 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.
The case for fish
Augustsson K, Michaud DS, Rimm EB, et al. A Prospective Study of Intake of Fish and Marine Fatty Acids and Prostate Cancer. Cancer Epidemiology, Biomarkers, and Prevention 2003;12:64–67. PMID:12540506.
Aren’t 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.
|*Note: To learn more about fats, see “What makes fats saturated, unsaturated, or trans fats?” below.|
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’re 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’s 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.*
|*Note: See “The case for fish,” above.|
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’s another reason why men concerned about prostate cancer should pay attention to the type of fats they choose to eat.
Figure 1: It’s all in the label
Use the Nutrition Facts label to help you select foods that are lowest in saturated fat and trans fat. Trans fat doesn’t have a % Daily Value, but consume as little as possible. The % Daily Value for total fat includes all kinds of fats. Note that unsaturated fats do not have to be listed on the label.
The information on the Nutrition Facts label is based on one serving, but many packages contain two or more. If you eat two servings instead of one, you double the calories, nutrients, and % Daily Values you consume.
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.*
|*Note: See Figure 1.|
KENNEDY: That’s right. You’d have to read the ingredients, speak with your dietitian, or do a little research to find out about those fats.
McMANUS: There’s 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.
What makes fats saturated, unsaturated, or trans fats?
Fats are like an extended family because they share similar traits. All fats share a similar chemical “backbone,” which is a chain of carbon atoms bonded to hydrogen atoms. But the length of that backbone, the way that the atoms bind to each other, and the number of hydrogen atoms can vary, yielding different types of fats.
In a saturated fat, the carbon atoms are linked to each other with single bonds, which enables the maximum number of hydrogen atoms to attach to the chain. At room temperature, saturated fats are solid — cooled bacon drippings, for example.
Some of the carbon atoms in monounsaturated and polyunsaturated fats form double bonds, reducing the number of hydrogen atoms the chain can hold. Monounsaturated fats have one double bond and two fewer hydrogen atoms. Polyunsaturated fats have two or more double bonds and hold even fewer hydrogen atoms. Unsaturated fats are liquid at room temperature.
About a century ago, food chemists discovered that they could solidify polyunsaturated vegetable oil by heating it in the presence of hydrogen. The process, called hydrogenation, gives the carbon atoms more hydrogen atoms to hold, changing the molecular structure to look more like that of a saturated fat. The result: trans fats. Trans fats are found not only in solid foods like margarine, but also in foods that contain partially hydrogenated oil. Some cooking oils are partially hydrogenated to keep them from becoming rancid during storage. Trans fats have no known health benefits. In fact, they raise LDL (bad) cholesterol, lower HDL (good) cholesterol, and raise the risk of heart disease.
Really? Many patients have told us that they’ve 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’s 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’t 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.
|*Note: See “Flaxseed studies,” below.|
Does the method of cooking make any difference?
KENNEDY: Absolutely. We encourage people to bake or broil. If you’re grilling, it’s 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’re 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’s 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.
Basch E, Bent S, Collins J, et al. Flax and Flaxseed Oil: A Review by the Natural Standard Research Collaboration. Journal of the Society for Integrative Oncology 2007;5:92–105. PMID: 17761128.
Brouwer IA, Katan MB, Zock PL. Dietary Alpha-Linolenic Acid is Associated With Reduced Risk of Fatal Coronary Heart Disease, but Increased Prostate Cancer Risk: A Meta-Analysis. The Journal of Nutrition 2004;134:919–22. PMID: 15051847.
Demark-Wahnefried W, Robertson CN, Walther PJ, et al. Pilot Study to Explore Effects of Low-Fat, Flaxseed-Supplemented Diet on Proliferation of Benign Prostate Epithelium and Prostate-Specific Antigen. Urology 2004;63:900–04. PMID: 15134976.
Demark-Wahnefried W, Price DT, Polascik TJ, et al. Pilot Study of Dietary Fat Restriction and Flaxseed Supplementation in Men With Prostate Cancer Before Surgery: Exploring the Effects on Hormonal Levels, Prostate-Specific Antigen, and Histopathologic Features. Urology 2001;58:47–52. PMID: 11445478.
No more charred hot dogs on the Fourth of July?
KENNEDY: No. That’s probably your most offensive food right there. That’s a double whammy — burned and processed meat.
But broiling and baking are totally fine?
KENNEDY: Yes. And grilling is okay as long as you’re not burning the meat. And if you’re grilling vegetables or tofu, it’s not a problem. We have this concern about carcinogens only with animal proteins. You can grill vegetables and tofu all you want; you’re not going to form carcinogens.
Baron JA, Beach M, Wallace K, et al. Risk of Prostate Cancer in a Randomized Clinical Trial of Calcium Supplementation. Cancer Epidemiology, Biomarkers, and Prevention 2005;14:586–89. PMID: 15767334.
Giovannucci E, Rimm EB, Wolk A, et al. Calcium and Fructose Intake in Relation to Risk of Prostate Cancer. Cancer Research 1998;58:442–47. PMID: 9458087.
Prostate cancer patients often cut calcium out of their diet. Doesn’t that put them at risk for osteoporosis? What’s the correct line of thinking here?
McMANUS: This is a very controversial issue because the research doesn’t give us any clear answers.
KENNEDY: First, I should say that calcium and prostate cancer are distinct issues. We can’t extrapolate those data to women or other groups of people. Second, we can obtain calcium from dairy products, but it’s 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.*
|*Note: See “Calcium studies.”|
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’s 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’t 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’t 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’re avoiding calcium, do you think that they mean they’re 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’t 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.
|*Note: To learn more, see “What D does.”|
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’s 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.
What D does
Vitamin D helps the body absorb calcium and phosphorus, which are essential for strong bones. It also tells the kidneys to hang on to these minerals. And at least in test tubes, vitamin D blocks the growth and reproduction of various cancer cells, including those that attack the breast, ovaries, prostate, and colon.
Current nutritional guidelines recommend 200 international units (IU) of vitamin D a day for people ages 50 and younger; 400 IU for people 51 to 70; and 600 IU for people 71 and older. However, because there is some evidence that we need more vitamin D than is currently recommended, some experts suggest getting as much as 800 to 1,000 IU per day.
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.
|*Note: To calculate your body mass index, see “BMI explained.”|
That’s just the number of men who are obese? That doesn’t include men who are simply overweight?
McMANUS: No, not overweight. That’s the number of men who are obese.
KENNEDY: I think that there’s a big disconnect in the general public between what’s considered overweight and what’s 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’s why many people who meet the clinical criteria for obesity actually see themselves as simply overweight. The numbers are really staggering, but I don’t think we’re 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’t 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’t 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.
|*Note: Distribution of body fat makes a difference, too. See “Waistline woes.”|
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’t regulated by the FDA.
On the plus side, there’s a lot of research showing that behavior change — independent of weight loss — 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’s 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’re looking at this as an endurance event. We’re looking at our health over the long term, so we need to use long-term approaches — healthy, balanced eating and moderate amounts of physical activity consistently over time. That’s 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.
Body mass index (BMI) is a measure of body fat that accounts for a person’s weight and height. It does not measure body fat directly, but research has shown that it correlates to direct measures of body fat such as underwater weighing and dual energy x-ray absorptiometry, which uses two types of x-rays to estimate body fat. Free and easy to determine, BMI designates an ideal body weight for a given height. You can calculate your BMI with any of these methods:
|Height||Weight in pounds|
|SOURCE: National Heart, Lung, and Blood Institute, National Institutes of Health.|
|Once you know your BMI, check the table below to see your weight classification. A recent study found that a patient’s BMI at the time of prostate cancer diagnosis was an independent risk factor for death related to prostate cancer. Men with a BMI of 25 or greater were almost twice as likely to die from locally advanced prostate cancer as men with a normal BMI at the time of diagnosis.|
|40.0 and above||Morbidly obese|
I’m sure you’ve 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’s 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’s no statistically significant weight-loss advantage.* In fact, there can be considerable disadvantages because you’re missing a lot of critical nutrients.
|*Note: See “Weight loss and low-carb diets.”|
The U.S. Departments of Agriculture and Health and Human Services recommend healthy eating patterns that are fairly broad in terms of the body’s 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 — carbohydrates, for example — is not a helpful approach either in terms of weight loss or overall health.
Whether you carry body fat around your abdomen or your hips — that is, whether your shape mimics an apple or a pear — can affect your health. A National Institutes of Health panel concluded that a man with a BMI over 25 and a waist size of 40 inches or more (apple shape) has a higher risk for diabetes, hypertension, and cardiovascular disease than a man of the same weight whose fat is centered further south (pear shape). Even if your weight remains stable, an expanding middle may be a sign of trouble ahead.
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’s important for weight management.
McMANUS: Planning ahead is critical. Healthy meals don’t just happen; you have to make them happen. We’d 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’t drink your calories. Some people still drink a lot of sugary beverages — 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 entrée 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.
Weight loss and low-carb diets
Foster GD, Wyatt HR, Hill JO, et al. A Randomized Trial of a Low-Carbohydrate Diet for Obesity. The New England Journal of Medicine 2003;348:2082–90. PMID: 12761365.
Stern L, Igbal N, Seshadri P, et al. The Effects of Low-Carbohydrate Versus Conventional Weight Loss Diets in Severely Obese Adults: One-Year Follow-Up of a Randomized Trial. Annals of Internal Medicine 2004;140:778–85. PMID: 15148064.
What about alcohol consumption?
KENNEDY: There’s 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’t clearly show a set number of drinks below which there’s no increased risk. That’s 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’t tell teetotalers to start drinking. When people ask us about alcohol and cancer prevention or treatment, we say to drink in moderation. That’s defined as no more than two drinks a day for men and no more than one drink a day for women.
Nutrition on the Web
American Cancer Society
Visitors can search for information on healthy eating to prevent cancer as well as what to eat before, during, and after cancer treatment.
Dana-Farber Cancer Institute, Nutrition Services
Dietitians explain how to develop a healthy meal plan, review current research, and offer nutritious recipes.
Harvard Medical School’s Consumer Health Information Service
Harvard Medical School faculty write about health and review nutrition information.
Harvard School of Public Health Nutrition Source
Maintained by the school’s Department of Nutrition, this Web site offers general nutrition information and helps visitors interpret the latest research and diet news.
National Cancer Institute’s “Nutrition in Cancer Care”
This Web site explains the importance of healthy eating for cancer patients and offers suggestions for getting enough protein, vitamins, and minerals when the side effects of treatment interfere with appetite.
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’t. 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’s not to say that patients can’t be followed on a regular basis close to home. But if they are at a large academic medical center that offers nutrition counseling, it’s 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.
|*Note: See “Nutrition on the Web” for a list of informative sites.|
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’ll be more likely to succeed.
Few absolute truths
A commentary by David Rosenthal, M.D.
Dr. Rosenthal is a professor of medicine at Harvard Medical School and director of the Harvard University Health Service. He is also the medical director of the Leonard P. Zakim Center for Integrative Therapies at Dana-Farber Cancer Institute, which seeks to integrate complementary therapies with conventional cancer treatments. A member of the editorial board of Perspectives on Prostate Disease, Dr. Rosenthal comments on nutrition and prostate health.
When it comes to diet and nutrition, consumers’ skepticism is certainly justified. After all, research seems to contradict itself with surprising regularity. One day we’re told that a high-fiber diet can prevent colon cancer, only to hear about a study that came to the opposite conclusion. One day coffee should be avoided, but the next morning, your cup of java is preventing Parkinson’s disease, diabetes, and colon cancer. So what can you believe about diet and prostate health?
Unfortunately, as Professor and Doctor of Public Health Walter Willett reminds me, we don’t have any absolute truths in this area. The irony, says Willett, chairman of the Department of Nutrition at the Harvard School of Public Health, is that until about 10 to 15 years ago, most participants in scientific studies were men, yet data on diet and prostate health are relatively scarce, especially compared with what we know about diet and breast cancer in women.
Why? When researchers launched some of the world’s largest studies, nutrition wasn’t the focus. For example, in 1982, the Physicians’ Health Study began as a trial of aspirin and beta carotene for the prevention of heart disease and cancer. Initially, researchers collected only a limited amount of information on participants’ diets. But the study has evolved since then, with physicians regularly completing detailed questionnaires on dietary habits and lifestyle.
As we await solid evidence from ongoing trials, physicians, dietitians, and researchers are making educated guesses about what’s best for patients based on what we do know. That’s why some doctors recommend eliminating red meat from the diet, replacing it with fish and other foods high in protein and iron, for example.
My recommendation to patients: Avoid the things we know are unhealthy, such as saturated fat and trans fat. Substitute fruits and vegetables for high-calorie foods with limited nutritional value. And eat a variety of foods in moderation.