Seminars in Oncology Nursing
Volume 28, Issue 1 , Pages 75-84, February 2012

Nutrition in Complementary and Alternative Medicine

  • Suzanne Dixon

      Affiliations

    • Corresponding Author InformationAddress correspondence to Suzanne Dixon, MPH, MS, RD, 1904 SE Ladd Ave, Portland, OR 97214.

Article Outline

Objectives

To review the prevalence of nutrition-related complementary and alternative medicine (CAM) used by patients with cancer, to discuss nutrition issues commonly raised by cancer survivors, and to describe how the oncology health care practitioner can best address these issues.

Data Sources

Journal articles, texts, and personal oncology nutrition clinical experience.

Conclusion

The interest in and use of special diets and nutrition-related CAM is prevalent in oncology patients. While some nutrition interventions may offer benefit, not all are without risk.

Implications for Nursing Practice

Every patient must be assessed for the use of special diets and nutrition-related CAM, any use must be documented, and the person counseled about the pros and cons of these approaches.

Key Words: Nutrition, dietary supplements, herbs, vitamins, antioxidants

 

INDIVIDUALS diagnosed with cancer seek out and use nutrition-related complementary and alternative medicine (CAM), including dietary supplements, herbs, vitamins, minerals, and special diets at a significant rate. Considering all forms of CAM in use today, dietary supplements are of most concern for individuals because they have the highest likelihood of interacting with cancer therapies. Dietary supplements are products taken by mouth that contain a dietary ingredient intended to supplement the diet. They may include vitamins, minerals, herbs, or other botanicals, amino acids, and substances such as enzymes, organ tissues, glandular extracts, and metabolites. Dietary supplements can be extracts or concentrates, and may be found in forms such as tablets, capsules, softgels, gelcaps, liquids, or powders.1

In one of the earliest systematic surveys of the literature on this topic, Ernst and Cassileth2 found that use of all types of CAM ranged from 7% to 64%. A more recent comprehensive survey notes that CAM use is increasing in oncology patients, and reported that an estimated 26% to 81% of all cancer patients are using vitamins, minerals, or a multivitamin.3 In one study of cancer patients during treatment, the use of all CAM modalities combined was 91%.4 It is important to note that between 14% and 32% of cancer survivors report initiate dietary supplement use after diagnosis.3 Conversely, this means that up to 86% of these individuals were using supplements before diagnosis. This fact is critical because dietary supplement use may not stop at diagnosis. If these products are a normal part of an individual's everyday routine, it may not be apparent that this information should be shared with the oncology provider. Indeed, the comprehensive literature survey on dietary supplement use in cancer patients found up to 68% of oncology physicians reported they were unaware of supplement use among their patients.3 These figures suggest that individuals with a long-standing history of using dietary supplements or other nutrition-related CAM modalities may be less likely to report this to oncology health care providers.

Also of interest is that many cancer patients elect to use dietary supplements regardless of explicit prohibitions against such use. A 2004 Mayo Clinic survey on CAM use found that among 108 patients with advanced malignancies who were enrolled in phase I chemotherapy trials, 88% used at least one type of CAM, with 93% of those using pharmacologically active CAM, including combination vitamin and mineral products, individual nutrients such as vitamins C and E, green tea preparations, the herb Echinacea, and a mixed herbal product called essiac,5 which is typically comprised of the herbs burdock root, slippery elm bark, sheep sorrel, and turkey rhubarb root, and may include other herbs as well. Nearly all phase I chemotherapy clinical trials prohibit dietary supplement use, per the study protocol. Yet as this survey demonstrates, nutrition-related CAM use in cancer patients, even those on clinical trials, remains high.

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Interest in Nutrition and Diet Improvement Among Cancer Survivors 

As with nutrition-related CAM, interest in and use of special diets is significant among cancer survivors both during and after treatment. One study indicated that 57% of 978 breast and prostate cancer survivors surveyed wanted programs to help them implement cancer risk reduction habits, beginning at diagnosis, or within 6 months of diagnosis.6 A survey of 227 long-term breast cancer survivors, on average 12 years from initial cancer diagnosis, found that half reported making positive changes to exercise or diet habits. Twenty-five percent reported making positive changes in both diet and exercise.7

A review of research on health behavior change in survivors of lung, bladder, and head and neck cancer found that between 53% and 81% of smokers quit or attempted to quit smoking after diagnosis. The review also noted that common health-related behavior changes made by patients after cancer diagnosis included abstaining from alcohol, increasing physical activity levels, consuming more fruits and vegetables, cutting back on salt intake, and following a low-fat diet.8

Despite the high interest in improving diet and other health-related behaviors post-cancer diagnosis, many cancer survivors struggle to meet healthy eating goals. A survey of more than 9,000 cancer survivors found that <20% were meeting the basic 5-A-Day recommendation to consume a minimum of five fruit and vegetable servings per day for good health. While up to 92% of survivors were meeting the recommendation to avoid tobacco, fewer than half were meeting physical activity recommendations, and only 5% of those surveyed were meeting all three lifestyle recommendations on diet, exercise, and tobacco.9 Data suggest that positive changes in health-related behaviors correlates with younger age, greater education, breast cancer diagnosis, longer time since diagnosis, comorbidities, vitality, fear of recurrence, and spiritual well-being.10

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Why Do Cancer Survivors Focus on Special Diets and Nutrition-Related CAM? 

Many of the reasons why individuals diagnosed with cancer turn to nutrition are self-evident; they want to have a sense of control and are seeking hope for a healthy future. Beyond these reasons, formal surveys have identified other important factors that may be associated with use of nutrition interventions during cancer treatment. Demographic factors, including gender, ethnicity, and education level, are most consistently associated with dietary supplement use during cancer care, with female gender, white ethnicity, and higher education levels predicting higher likelihood of supplement use.3, 11, 12 Results are equivocal regarding the effect of age on dietary supplement use among cancer survivors, with some data suggesting younger patients are more likely to use dietary supplements,13, 14 and other studies finding older age to be predictive of dietary supplement use.11, 12, 14 Cancer patients using dietary supplements tend to have a lower body mass index and to engage in more regular physical activity.12

In a survey of 827 participants in the American Cancer Society's longitudinal Study of Cancer Survivors, reasons given by patients themselves for using dietary supplements during cancer care include, “something they could do to help themselves,” “to boost their immune system,” and “to give them more energy.”15

The literature provides insight into some of the demographic factors and reasons given by patients to explain cancer survivors' interest in nutritional interventions. These insights can guide clinical care, but it is important not to lose sight of one important fact. Regardless of why a person indicates he or she is taking dietary supplements or following a special diet during cancer care, the most important reason to any patient for using these approaches is that the person believes it will help. For the busy oncology nurse with concerns about nutrient-drug and herb-drug interactions, it is easy to lose sight of this fact and to respond to the information that a patient is taking CAM products or following a special diet with cynicism. However, this may erect barriers to effective communication and safe and accurate care. Among the best ways to respond to patients when they divulge this information is to commend the person on engagement with the cancer care process, acknowledge that interest in nutritional self-care demonstrates a commitment to being an important part of one's own cancer care, and to iterate you would like to work with the person to ensure that whatever self-care routine they chose, it is safe in conjunction with conventional cancer treatments. This opens a dialogue and increases the likelihood of full disclosure on the part of the patient. Once supplement use or adherence to a special diet is disclosed, documenting this information for easy access by all health care team members will improve the likelihood of early identification of potential problems. A patient may elect to continue using nutrition-related CAM or follow a restrictive diet during cancer treatment, despite being advised against it. In this situation, it is important to document what the patient is doing, be non-judgmental, and maintain an open dialogue with the patient. When patients indicate they are using, or interested in using, dietary supplements and special diets, a framework to evaluate their choices is helpful. Michaud et al16 have provided six key concepts to apply regarding use of dietary supplements in patients with cancer, as detailed in Table 1.

Table 1. Six Questions to Ask as a Starting Point for Evaluating Safety of Nutrition-Related CAM

•Is the supplement an antioxidant?

•Does the supplement have anticoagulant or procoagulant properties?

•Does the supplement have immunosuppressive or immunomodulating properties?

•Does the supplement have hormonal properties?

•Is use of the supplement associated with known safety issues?

•Does the supplement have any known or theoretical drug interactions?

In addition to these considerations, an algorithm for evaluating special diets and dietary supplements for safety and efficacy has been developed. This algorithm can be view in the online version of this article at www.seminarsoncologynursing.com. This algorithm is designed to aid communication with the patient in a way that fosters collaborative decision-making for the best patient care outcomes. Most patients are receptive to altering choices about nutrition and dietary supplement use when given rational, clear explanations as to why a choice is not safe or effective. This is preferable to advising against use without providing the patient objective rationale for this advice.

In addition to the importance of nutrition safety and efficacy, issues of patient hope and expectation must not be overlooked. As health care practitioners we are familiar with the concept of the placebo effect; hope, faith, and expectation are believed to drive this phenomenon. Less well known is the nocebo effect, which appears to operate in two potential ways. First, nocebo effect is a term used to describe a phenomenon in which people report a negative side effect from a treatment, despite the fact that the treatment itself is a placebo and contains no pharmacologically active constituents. It is speculated that disclosing information about potential side effects can contribute to producing adverse effects.17, 18 The second form of the nocebo effect, which is most relevant to the discussion of nutrition in cancer care, posits that the efficacy of a pharmacologically active intervention can be reduced when that intervention is delivered with a negative message about potential efficacy.19, 20, 21, 22 Thus, when a special diet or nutrition-related CAM use is disclosed, telling the patient that these approaches are a “waste of time,” “always unsafe,” “must be avoided,” or “a waste of money,” may decrease the patient's faith and hope for the future. If we are to adhere to the Western medical paradigm of “first do no harm,” we must acknowledge that universal discouragement of nutritional modalities may be harmful for the patient and may decrease the likelihood of positive outcomes. Because the majority of individuals with cancer will use dietary supplements and have an interest in improving diet, health care practitioners need to understand the importance of safety, efficacy, and the nocebo effect to provide knowledge-based advice on this topic.

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Special Diets, Nutrition Myths, and Patient Fears 

Any dietitian or other health care practitioner who routinely counsels cancer patients regarding diet and nutrition will encounter interest in special diets as well as fear of common cancer nutrition myths. Unfortunately, available information and well-intended health “experts” are ready to advise patients regarding which foods fight cancer, what the patient ate that contributed to his or her disease, and which foods “fuel cancer growth.” Indeed, more than two decades ago, Dwyer23 reported that the phenomenon of cancer nutrition myths was common (Table 2), illustrating the enduring nature of many misunderstandings about the links between diet and cancer. Today, many patients still have misconceptions and questions about nutrition and cancer (Table 3).

Table 2. Common Cancer Nutrition Myths Reported in 1986
Data from Dwyer.23

•Following the cancer prevention dietary guidelines guarantees protection against cancer.

•If the victim had eaten differently, the cancer never would have developed.

•Cancer prevention dietary guidelines are appropriate in the nutritional support of all cancer patients.

•Cancer patients can rely on their appetites to know when and how much to eat.

•Special diets can cure cancer.

•All cancer anorexia can be treated by following the proper diet.

Table 3. Commonly Asked Questions About Cancer Nutrition Myths in 2011

•Does sugar feed cancer?

•Do soy foods contain estrogen, making them unsafe for women with a history of estrogen receptor-positive breast cancer?

•Do pesticides in food cause cancer?

•Must all food be organic to be healthy?

•Do dairy foods cause cancer?

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Addressing Cancer Nutrition Myths 

When guiding patients through a plethora of information and misinformation regarding diet as a cause of cancer and the role of diet in maintaining health post-diagnosis, it is essential to acknowledge our own biases and susceptibility to nutrition myths. Scope of practice and what any individual health care practitioner can be expected to know should not be forgotten. For example, a dietitian would not have the most recent data regarding chemotherapy protocols, new targeted therapies, and dosing regimens at his or her fingertips, and a physician or nurse cannot be expected to be knowledgeable about the numerous studies published yearly on diet and cancer. Thus, for a patient who is confused about nutrition issues or who is struggling to reconcile belief in a nutrition myth with common sense and consumer literature, it may be necessary to provide an appropriate referral. However, familiarity with four common nutrition issues discussed in Table 3 can help nurses provide expert and reassuring counsel to cancer patients and their families.

Does Sugar Feed Cancer? 

The notion that dietary sugar will spur tumor growth is confusing and, in the experience of the author, can lead many cancer patients to remove carbohydrates, including healthy foods such as fruit and whole grains from their diet. To assist the patient in understanding this issue, it helps to use simple terms about the different kinds of carbohydrates and how they affect cellular energy use. First, simple sugar (glucose) fuels all cells in our bodies, including cancer cells. Based on this, it may seem obvious that eliminating sugar and carbohydrates from the diet will starve cancer cells of fuel. Unfortunately, most cancer cells are adaptable, and will readily switch to using protein and fats for fuel in the absence of glucose.24, 25 This means that sugar itself is not the most important issue, from a physiologic standpoint.

Rather, research suggesting that excess dietary sugar increases cancer risk and promotes cancer cell growth points to growth hormones, including insulin and insulin-like growth factor, as the true culprits in this phenomenon.26 In other words, dietary sugar does not necessarily “feed” tumors any more than it feeds all cells in the body, but high intake of simple sugar increases the production of growth hormones. In turn, the increase in growth hormone levels may promote cancer cell growth. Fortunately, protein, fat, and fiber greatly blunt the insulin response to dietary sugar. This means that eliminating all sugar is not necessary, but eating a balanced diet that does not contain excessive amounts of simple sugar is the goal. Thus, individuals should eat a healthy diet and be provided with nutritional guidelines by the health care provider that focus on the benefits of complex carbohydrates over simple, and choosing snacks and meals that contain a mix of protein, fat, fiber, and carbohydrates.

There is one exception to this approach on counseling patients concerned about sugar feeding their cancer. Although all other body cell types readily use fatty acids and ketones as fuel, brain cells have an absolute need for glucose to function properly. Brain cancer cells also may share this property.27 Unlike other tumor types, for brain tumors, particularly glioblastoma and astrocytoma, limiting or completely avoiding carbohydrates to create ketosis may be a viable therapeutic option. However, maintenance of a true ketogenic diet is challenging, as only a few grams of carbohydrate, inadvertently eaten, can stop ketosis. Most patients are unable to maintain a ketogenic diet without significant nutrition counseling and support. If a patient (eg, a brain tumor patient) expresses interest in trying a ketogenic diet, referral to a registered dietitian is essential.

Are Soy Foods Dangerous for Women With a History of Hormone-Sensitive Cancers? 

The idea that soy foods contain estrogen likely arises from the term “phytoestrogens,” which is used to describe a class of nutrients in soy called isoflavones. Unfortunately, this term suggests that “estrogenic activity” of soy food nutrients is the only, or the most important, aspect of these foods. Most of the anti-cancer properties attributed to soy are unrelated to so-called “estrogenic” effects. These include inhibition of angiogenesis through actions on the vascular endothelial growth factor (VEGF) and epidermal growth factor pathways, induction of G2/M cell cycle phase arrest through increased expression of P21, inhibition of tyrosine kinases, binding and activation of peroxisome proliferator regulators, upregulation of natural killer cell function, inhibition of endogenous steroid biosynthesis, and antioxidant actions.28, 29, 30

Three large-scale, well-designed epidemiologic studies31, 32, 33 report no adverse effects of soy food consumption on breast cancer prognosis. These studies represented different ethnic/cultural groups (two from the United States [US] and one from China) and examined various types of soy food consumption, with the results strongly supporting that clinicians no longer need to advise against soy for female breast cancer survivors.31 In addition, the three studies concurred that soy consumption may be protective against breast cancer recurrence.31, 32, 33 Table 4 summarizes the findings from these three population-based studies.

Table 4. Summary of Three Epidemiologic Studies on Soy and Breast Cancer Recurrence Risk
StudynFollow-upSoy intake associated with reduced risk of recurrenceMagnitude of risk reduction, lowest vs. highest intake
WHEL313,0887 years>16.3 mg isoflavones per day∗54%‡
LACE321,9546.3 years≥ 1.4 mg daidzein per day†60%
Kang et al335245 years> 43.2 mg total isoflavones per day33%§

∗16.3 mg of isoflavones = two servings of Kashi ‘GoLean’ cereal or a 3-ounce serving of silken tofu.

†Daidzein is one of two main soy isoflavones; the other is genistein. Highest soy consumers at an average of 1.4 mg daidzein per day = 5-6 servings of Kashi ‘GoLean’ cereal or six to seven 3-ounce servings of silken tofu.

‡Not statistically significant.

§Reduced risk among postmenopausal women; no positive or negative association with recurrence risk in premenopausal women.

Recent human studies examining the potential physiologic effects of soy foods on breast tissue provide additional reassurance that these foods likely are safe for women with a history of breast cancer. Among 96 women studied in a randomized, crossover design, two servings of soy foods daily, which provided 50 mg total isoflavones per day, did not affect nipple aspirate fluid (NAF) estrogen levels.34 In a similarly designed crossover trial, volume of NAF, a possible indicator of breast cancer risk, did not significantly increase over a period of 6 months in women fed a high soy (two servings per day) diet.35 All women, regardless of the group (high or low soy) to which they were initially assigned, produced similar NAF volumes at the start of the study. Both groups of women produced less NAF, an indicator of decreased breast cancer risk, during the first 3 months on a high soy diet; both groups' NAF volume returned to baseline by the month 6 on a high soy diet.

A recently published meta-analysis of four studies on breast cancer recurrence and 14 studies on breast cancer incidence considered the question of soy consumption and breast cancer risk.36 Higher soy intake was associated with a modest (24%) reduction in breast cancer risk overall, though this protective effect was observed only in Asian populations. Among Western populations, soy intake did not significantly change breast cancer risk. Among all populations, women with the highest reported intake of soy isoflavones were 16% less likely to experience a breast cancer recurrence compared with women with the lowest isoflavone intake.

A consideration of preclinical data on soy and breast cancer risk demonstrate a mixed picture.37 Some studies suggest isolated soy isoflavones, in particular genistein (the isoflavone for which the most data are available) can increase breast cancer cell growth in certain cell and animal models. Other studies support a protective effect of soy compounds against breast tumor development and growth in vitro and in vivo. A comprehensive review of the cell, animal, and human literature also notes the ability of the isoflavone genistein to stimulate the growth of mammary tumors in ovariectomized athymic nude mice implanted with estrogen-sensitive breast cancer cells. However, the findings from clinical studies in which breast biopsies taken before and after isoflavone consumption do not support a strong pro-growth effect of these compounds on breast cells.38

Evidence for soy-based dietary supplements is lacking, and women should avoid soy dietary supplements because of their potential high concentration of isoflavones. However, current data strongly support that whole soy foods as part of a balanced diet are safe, and possibly beneficial, for women with a history of breast cancer. While soy is safe and may be beneficial for breast cancer survivors, superimposing soy foods onto the high-fat, low-fiber, processed-food diet typical of most Americans is unlikely to be helpful. For women who remain concerned about soy-based ingredients in processed foods, a solution is to focus on the unprocessed, whole foods that do not contain these ingredients.

What about Pesticides in Produce? Must all Vegetables and Fruit be Organic? 

Organic food is the fastest growing sector in the marketplace, but this growth is weighted toward processed organic foods. It is critical to educate individuals that organic junk food is still processed and not as healthy as eating whole foods. In blind taste tests, consumers consistently rated foods labeled organic as tasting better and having fewer calories and less fat than conventionally labeled foods, even when tasting the identical product in a blind taste test.39 Once patients understand this natural tendency to view organic foods as healthier (eg, the “health halo”), they can better understand how, why, and when choosing organic foods may be a good option.

To assist patients in their understanding of the potential of pesticides to induce cancer, context must be considered and explained. It is true that occupational exposures to pesticides and other agricultural chemicals, such as what occurs during manufacture, transport, and application, can increase cancer risk.40, 41, 42 However, the trace amounts of pesticides found on produce have not yet been linked with increased cancer risk: people who eat more produce, even non-organic conventional products, tend to have lower cancer risk. This association between plant foods and cancer risk was examined extensively in “Food, Nutrition, Physical Activity and the Prevention of Cancer: a Global Perspective,” first published in 1997 and updated and re-released in 2008. Twenty-one cancer experts were assembled to evaluate results from over 7,000 studies related to cancer and diet, physical activity, and weight management.43 This landmark report supports the concept that the majority of produce consumed in nearly all countries is not organic, yet eating these foods is associated with lower cancer risk, suggesting the benefits of eating plant foods outweighs the harm of pesticide residues found in these foods.

However, there are other reasons beyond personal health that people eat organic food. For example, many individuals support a system of agriculture that does not contribute additional pesticides to the environmental load of these compounds; individuals may believe in the importance of protecting others (farmers and migrant workers) from the threat of occupational pesticide exposure, and many people believe that as evidence accumulates, organic food will be shown to provide additional health benefits over conventional produce. Consider also that the majority of studies comparing health and environmental costs and benefits of organic and conventional produce are relatively recent, and with time, it may be proven that pesticide residues in food do harm human health. The message for patients should be that organic food is an excellent choice, but if obtaining organic vegetables and fruit becomes a barrier to consumption, priorities should be reconsidered. The ideal choice is to consume as many whole plant foods, especially colorful vegetables and fruit, as possible.

Does Dairy Cause Cancer? 

The relationship between dairy and cancer is complicated. For certain tumor types, dairy may contribute to increased cancer risk,44 while for others data supports that dairy is protective against cancer development.45 In addition to the importance of tumor type, an important consideration when helping patients sort through the conflicting data on dairy and cancer is that this is one of the most politicized foods in the US. Pro-dairy groups, such as the National Milk Producers Federation, indicate that dairy foods are absolutely necessary for good health. Pro-vegan groups, such as the Physicians Committee for Responsible Medicine, report that dairy is very bad for health and is a primary cause of many diseases, including cancer. In reality, dairy is not absolutely necessary for good health.46 Neither is dairy, when consumed in moderate amounts as part of a healthy diet, the main cause of most cancers.47 Table 5 presents some of the commonly cited reasons for and against adult dairy consumption.

Table 5. Commonly Cited Reasons for and Against Dairy Consumption
Anti-dairy consumptionPro-dairy consumption
Natural and artificial dairy hormones may promote cancer cell growthDairy is a good source of calcium and potassium
Adult humans do not need nutrition provided by another species' “baby food”Dairy is a good source of vitamin D
There are plenty of other dietary sources of calciumDairy is a good source of protein
Lactose intolerance is common; we are not “designed” to drink milk into adulthoodIt is a convenient way for many to obtain calcium, potassium, vitamin D, and protein
Our diets are protein-rich; we do not need additional dairy protein for good healthMany people enjoy the taste of dairy
We can obtain vitamin D from the sun, other foods, and dietary supplementsDairy may protect against some chronic diseases, including some cancers
Data equivocal on dairy's role in preventing osteoporosis; not needed for bone healthControlled trials report low-fat dairy can help in the management of hypertension

Regarding cancer risk, dairy appears to have variable effects, depending upon tumor type, quantity, and possibly type (low fat vs. high fat) of dairy consumed. A recent meta-analysis of 18 high-quality cohort studies involving 1,063,471 participants and 24,187 breast cancer cases found a 15% reduction in overall breast cancer risk in women with the highest total dairy intake compared with those who had the lowest dairy intake.45 Low-fat dairy appeared to be slightly more protective than high-fat dairy, and the effect was more pronounced in pre- versus postmenopausal women. These data suggest that if there is an effect of dairy on breast cancer risk, it is a small protective effect. Many health experts believe this protective effect is because of the vitamin D and calcium in dairy. A 4-year, double-blind, randomized placebo-controlled trial conducted in 1,179 healthy, postmenopausal women found that a daily supplement providing 1,400 to 1,500 mg calcium plus 1,100 IU vitamin D3 significantly reduced cancer risk in this group.48 If a person wishes to avoid dairy foods, dietary supplements or other food sources of calcium and vitamin D to achieve the potential cancer protective effects of these nutrients are reasonable choices.

None of the studies included in the meta-analysis assessed organic versus conventionally produced milk or milk produced with or without bovine somatotropin (bST, BST, bovine growth hormone, or BGH). Organic milk accounts for approximately 3% to 5% of all milk consumption in the US, but likely accounted for less in the past, when these studies were originally conducted, so the effects of choosing organic dairy cannot be assessed. While many patients have concerns about the “pro-growth” effects of hormones (natural and synthetic) that are found in milk or used to produce it, data do not support that these substances increase breast cancer risk. Colon cancer is another tumor type for which dairy consumption appears to offer some protective effect. A recent meta-analysis of 60 epidemiologic studies that included 26,335 colorectal cancer cases found a 22% reduction in colon cancer risk among those consuming the most milk, and a 16% reduction in colon cancer risk among those consuming the most total dairy products. No effects of dairy consumption on rectal cancer risk were evident.49 Although one clinical trial did not reveal a protective effect with supplemental calcium and vitamin D,49 other randomized, double-blind, placebo-controlled trials of calcium and vitamin D supplements support that the potential protective effect of dairy against colon cancer development is mediated through calcium and vitamin D.50, 51, 52, 53, 54

If a person wishes to avoid dairy foods, dietary supplements or other food sources of calcium and vitamin D are reasonable choices to achieve the potential colon cancer protective effects. The issue of organic versus conventionally produced milk or milk produced with or without BGH remains unresolved for colon cancer as well. Avoidance of dairy products produced with growth hormones is not supported by available data at this point, nor is it proven with complete confidence to be completely safe. Informed patient choices to consume or not consume dairy, and the type of dairy chosen, should be supported and encouraged.

Dairy and risk of prostate cancer is less clear, but numerous observational studies suggest that high dairy and/or calcium intake may be associated with a modestly increased risk of prostate cancer.44, 55, 56, 57, 58, 59 Observational data support that calcium intake significantly above the 1,000 mg/day recommended intake for adult men, in the range of 1,200 to 1,500 mg per day, is associated with increased prostate cancer risk.58, 59 However, clinical trials and prospectively collected data have produced conflicting results, with one large trial showing no increased prostate cancer risk in men who took 1,200 mg of calcium daily for 10 years,60 and another trial suggesting that high dietary calcium intake increases risk of low-grade prostate cancer and significantly decreases the risk of developing high-grade prostate tumors.61 The conflicting results of these investigations suggest that work remains to be done to elucidate the potential associations between dairy foods, calcium intake, and prostate cancer risk.

Despite the lack of consensus, it is prudent to counsel men concerned about or with a history of prostate cancer to consume no more than the recommended intake of 1,000 mg of calcium per day from all sources, and to consume no more than one to two dairy servings daily. As with breast and colon cancer, the issue of conventional versus organic and dairy produced with or without BGH remains unresolved. The precautionary principle applies here as well, and avoidance of dairy produced with growth hormone is a reasonable choice. Consideration of the varying state laws regarding the use of BGH in dairy production may need to be made.

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Conclusion 

The literature points to an increasing awareness of the issue of dietary supplement use and interest in nutrition and special diets among individuals with cancer. Unfortunately, this awareness is not always translated into action in the clinic. Given the vast number of cancer patients who use nutrition-related CAM and succumb to nutrition myths that may result in poor dietary choices, failing to address this issue can result in sub-optimal care. Thus, every patient must be assessed for the use of nutrition-related CAM and their dietary strategies. Patient choices must be documented, and each person must be counseled about the pros and cons of these approaches.

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Supplementary Data 

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References 

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Suzanne Dixon, MPH, MS, RD: Consultant/Owner, The Health Geek, LLC, Portland, OR.

PII: S0749-2081(11)00101-X

doi:10.1016/j.soncn.2011.11.008

Seminars in Oncology Nursing
Volume 28, Issue 1 , Pages 75-84, February 2012

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