The American Institute for Cancer Research (www.aicr.org) notes a reduction in risk of cancer by 30% to 40% through following the Diet and Health Guidelines for Cancer Prevention. These guidelines can serve as appropriate advice for individuals on prevention of cancer. These guidelines are described in the following sections.

CHOOSE A DIET RICH IN A VARIETY OF PLANT-BASED FOODS

Increase intake of vitamins, minerals, and phytochemicals as naturally found in plant-based foods. This includes a variety of cruciferous vegetables (broccoli, spinach, cabbage, and Brussels sprouts), legumes, fruits, and whole grains that has long been associated with reduced cancer risk.

With a focus on a plant-based diet, sugar intake is indirectly inhibited. Avoidance of sugar-based drinks is part of the 2005 Dietary Guidelines. Following this guideline helps normalize hyperinsulinemia among persons with the metabolic syndrome and likely minimizes risk of cancer development for such individuals. This is because of the reduced production of insulin-like growth factor that occurs in the presence of hyperinsulinemia.

EAT PLENTY OF VEGETABLES AND FRUITS

Increase fiber intake by increased intake of vegetables and fruits. Insoluble fiber (generally the skin and seeds of vegetables and fruits; see Chapter 2) is believed to lower cancer risk in part because the fiber moves food through the gastrointestinal tract faster. This rapid transit of food through the intestines decreases the amount of time carcinogens are in contact with the gastrointestinal mucosa.

Other benefits of increasing vegetables and fruits is the impact on serum levels of antioxidants. High plasma levels of ascorbic acid, selenium, and carotenoids have been noted to protect against cancer. High plasma concentrations of carotene are associated both with lower mortality from all causes and with lower rates of cancer in the elderly (Buijsse and colleagues, 2005). A focus on dark-green leafy vegetables will provide vitamins A and C, folate, and magnesium. Retinoids (vitamin A) as found in dark-green leafy and orange vegetables and fruits have cancer preventative and treatment properties. Magnesium is now known to reduce inflammation, which is now being connected with cancer. Legumes and dark-green leafy vegetables are very high in magnesium content. Researchers looking at cancer risk and prevention are increasingly recognizing a multitude of factors that allow complex cellular actions. Therefore the fact that eating a variety of unprocessed foods reduces cancer risk is likely related to the complexity of nutrients found in such foods. Review of various antioxidant supplements, including glutathione (a polypeptide), melatonin, vitamin A, vitamin C, and vitamin E, found no significant evidence in outcomes of cancer treatment (Block and colleagues, 2007).

Flavonoids are partially responsible for the cancer prevention effect of common vegetables and fruits (Cherng and colleagues, 2007). The much lower risk of colon, prostate, and breast cancers in Asians may be due to the polyphenol (flavonoid) components and the higher intake of vegetables, fruits, and tea than typical Western diets provide (Kandaswami and colleagues, 2005).

Minimize salt intake to lower cancer risk, especially gastric cancer (Tsugane, 2005). Chinese-style salted fish increases the risk for nasopharyngeal cancer, particularly if eaten during childhood, and should be eaten only in moderation (Key and colleagues, 2004). The impact of salt on risk of cancer may have to do with its ability to erode the protective mucous lining of the stomach. A similar irritant effect on the pharyngeal region may also occur.

PREPARE AND STORE FOODS SAFELY

Practice safe food-handling practices, including avoidance of food pathogens that occur with spoiled foods. Aflatoxins that occur with moldy foods are known carcinogens. Avoiding excess intake of foods cooked at high temperatures, such as barbecued meats, reduces intake of harmful nitrosamines. Using tin foil on a barbecue grill reduces the exposure of foods to smoke from meat drippings on hot coals.

DO NOT USE TOBACCO IN ANY FORM

Chewing tobacco is a known risk factor for cancer of the oral cavity. Cigarette, cigar, and pipe smoking allows carcinogens to enter systemically and is related to a variety of cancers. The combination of excess alcohol intake and tobacco further increases the risk of oral and throat cancer.

Cultural Considerations

Low socioeconomic status has been linked with increased risk of cancer such as bladder, colon, and rectal cancers. Although it may be presumed this is due to lifestyle, the connection appears more complex and is not understood (Goy, Rosenberg, and King, 2008).

Fact & Fallacy

FALLACY

Drinking orange juice reduces the risk of cancer.

FACT

This is an overly simplistic statement that, when put into practice, can actually increase cancer risk in persons with insulin resistance. To help prevent the development of hyperinsulinemia, fresh fruits and vegetables are advisable. Eating an orange is preferable to drinking juice because juice is often consumed in excess amounts. One orange equates to 4 oz of juice (see Figure 1-1). A person who drinks a 12-oz serving of juice is consuming the equivalent of cup of sugar. Even though this is fructose, not sucrose, excess may promote hyperinsulinemia and cancer risk. Vegetable juices are lower in sugar content and likely will reduce cancer risk, such as with tomato juice and its lycopene content.

HOW DOES NUTRITION INCREASE OR REDUCE RISK OF SPECIFIC CANCERS?

BLADDER CANCER

The fourth leading type of cancer in men in the United States is bladder cancer, which ranks ninth in worldwide cancer incidence. Men have a greater incidence of bladder cancer than women. Cigarette smoking and chronic urinary tract infections (UTIs) are associated with an increased risk of this cancer (Murta-Nascimento and colleagues, 2007). Cranberry juice has been shown to reduce risk of UTIs. Other potential risk factors include drinking tap water with chlorination by-products or arsenic. Heavy consumption of phenacetin-containing analgesics has been shown to cause bladder cancer in humans (Jankovi and Radosavljevi, 2007). Obesity contributes modest adverse risk for bladder cancer (Koebnick and colleagues, 2008).

Factors that reduce risk of bladder cancer include intake of fruits and vegetables. Intake of B vitamins (B₂, B₆, B₁₂, and folate—see Chapter 3 for food sources) and retinol as found in deep orange and dark-green leafy vegetables are associated with a reduced risk. In particular vitamin B₆ and retinol showed the strongest evidence of risk reduction (García-Closas and colleagues, 2007). Compounds in cruciferous vegetables (broccoli, cauliflower, Brussels sprouts, and cabbage) have an anticarcinogenic effect on bladder cancer (Zhao and colleagues, 2007). Two mushroom extracts, when combined with moderate amounts of vitamin C, became highly cytotoxic, resulting in greater than 90% cell death related to bladder cancer (Konno, 2007).

BREAST CANCER

Breast cancer is the second leading cause of cancer death among U.S. women. Breast cancer can also occur in men, although rarely, and generally there is a worse prognosis because of a delay in diagnosis. Excess weight appears to contribute to risk. Postmenopausal overweight women have an increased risk, as do premenopausal women who have a high waist-to-hip ratio (greater than 0.87) (Tehard and Clavel-Chapelon, 2006). Because estrogen levels increase as a result of obesity, this is one factor behind the increased risk of breast cancer found with obesity (Suzuki and colleagues, 2006).

Evidence supports a moderate association between type 2 diabetes and the risk of breast cancer, particularly among postmenopausal women (Xue and Michels, 2007). A low level of high-density lipoprotein (HDL) cholesterol, as found with the metabolic syndrome, has recently been related to increased breast cancer risk in overweight and obese women (Furberg and colleagues, 2005). The common link with obesity, type 2 diabetes, and breast cancer appears to be insulin resistance with high insulin levels. Hyperinsulinemia has been associated with poor outcomes in breast cancer. Medical nutrition therapy that helps normalize hyperinsulinemia is important in early-stage breast cancer and for the long-term management of breast cancer survivors (Goodwin and colleagues, 2009). See Chapters 5 and 8 on managing hyperinsulinemia via low–glycemic load meals.

Traditional dietary goals have been aimed at low-fat diets to prevent breast cancer. However, in one study among postmenopausal women, a low-fat diet did not reduce breast cancer risk (Prentice and colleagues, 2006). This finding was supported by another study over a 7-year period that found a low-fat diet high in fiber did not reduce reoccurrence of breast cancer (Pierce and colleagues, 2007). On the other hand, a large prospective study found dietary fat intake was directly associated with the risk of postmenopausal breast cancer regardless of type (Thiébaut and colleagues, 2007).

The different outcomes of research related to dietary fat intake likely are due to the type of fat. A low incidence of breast cancer has been noted in the Mediterranean region, where there is a high intake of olive oil. It has been suggested that the beneficial effect of olive oil on lowering risk of breast cancer is due to the many phenolic compounds found in olive oil (Menendez and colleagues, 2007). Intake of oily fish suppresses at least one form of breast cancer. The research suggested there was suppressed tumor incidence and reduced mammary gland abnormality (Sun, Berquin, and Edwards, 2005; Yee and colleagues, 2005). This positive impact of fish oil may result, in part, from decreased inflammation as associated with cancer. See Chapters 5 and 7 on reducing inflammation with diet.

For women with the metabolic syndrome, lowering carbohydrate intake can be presumed beneficial. In fact, a high glycemic index has been associated with increased breast cancer risk, especially among those who were physically inactive or those of normal weight who had used hormone replacement therapy (Silvera and colleagues, 2005). In premenopausal women, increased risk with high glycemic load was related only to overweight and obese women, not women of normal weight (McCann and colleagues, 2007). This is likely due to women of normal weight being insulin sensitive, not insulin resistant. Among women of Italian heritage a high–glycemic load diet increases risk of breast cancer particularly in premenopausal women and those of normal weight (Sieri and colleagues, 2007). Following the Therapeutic Lifestyle Changes (TLC) diet (see Chapter 7) as advised for management of the metabolic syndrome should help reduce risk of breast cancer for women with insulin resistance. Increasing physical activity levels also is linked with lower risk of breast cancer (Bardia and colleagues, 2006). Physical activity improves insulin sensitivity.

A high intake of fruits and vegetables has been shown to significantly decrease risk of breast cancer (Fung and colleagues, 2005). It may be the dietary fiber from fruit and cereal that helps reduce breast cancer risk (Suzuki and colleagues, 2008). A high folate intake, as found in high amounts in legumes and greens, from diet or supplements is associated with a lower incidence of postmenopausal breast cancer (Ericson and colleagues, 2007).

Alcohol consumption, even in moderation, is associated with breast cancer risk, and the risk was found to be greatest in women with lower total folate intake (Stolzenberg-Solomon and colleagues, 2006). The usual recommendation is for women at risk of breast cancer to avoid all alcohol. However, among women with folate intake higher than 350 mcg no association between the alcohol intake and the breast cancer incidence rate was found (Tjonneland and colleagues, 2006). Thus women who want to and can keep alcohol intake within moderate amounts should increase folate intake, especially if known to have a high risk for breast cancer. Folate is found in dark-green leafy vegetables, legumes, whole grains, milk, and fish.

A traditional Asian type of diet of vegetable and soybean products is found with lower breast cancer among Chinese women, whereas a Western type of diet increases breast cancer risk among those who are menopausal (Cui and colleagues, 2007). Phytoestrogens, as found in soy, are a group of plant-derived substances that are similar to estradiol. Because a decreased risk of breast cancer has been recognized in women from Asian countries, phytoestrogens have been implicated as the beneficial factor. Early exposure to soy products in childhood or early adolescence is suggested to be protective. This same benefit has not been shown among breast cancer survivors. The phytoestrogen genistein as may be found in supplemental form interferes with the effects of tamoxifen to reduce breast cancer cell growth (Duffy, Perez, and Partridge, 2007). Soy supplements containing the active ingredients found in soy are generally discouraged. Green tea polyphenols have been linked with reduced cancer risk, including breast cancer (Thangapazham and colleagues, 2007).

Teaching Pearl

In one study only about one third of women with breast cancer received dietary advice from their physicians. However, over one half stated they would like more information. Diet changes made by the women included less sugar intake, less saturated and trans fats, and reduced alcohol while increasing monounsaturated fats, high-fiber foods, and low-fat dairy products (Landers and colleagues, 2008). Higher intakes of total calcium and vitamin D reduce risk for premenopausal women. However, the benefit was not seen among postmenopausal women (Lin and colleagues, 2007). The health care professional can ask if advice on diet is desired, and at least general guidelines can be promoted. For specific medical nutrition therapy, a referral to a registered dietitian is advised.

COLORECTAL CANCER

The incidence of colon cancer in industrialized countries has increased since the early 1970s and has followed the increased rate of obesity and diabetes. Cancer of the colon and rectum continues to be a major cause of death and illness in persons over 50 years of age and is related to the metabolic syndrome.

High waist circumference is an independent risk factor for colorectal adenoma (Kim and colleagues, 2007). Hyperinsulinemia found with excess weight and kcalorie intake with low physical activity also has been associated with colorectal cancer. Other factors include excess alcohol intake, smoking, and low consumption of folate and the amino acid methionine—see Chapter 2 (Campos and colleagues, 2005).

Women with low levels of insulin-like growth hormone and C-peptide (see Chapter 5) were found to have low risk of colon cancer, whereas elevation of either was associated with increased risk (Wei and colleagues, 2005). In persons with type 2 diabetes mellitus, epidemiologic studies show an increased risk for colorectal cancer and an even higher risk if patients are treated with sulfonylureas (see Chapter 8) or insulin. Individuals with type 2 diabetes who are on chronic insulin therapy were found to have three times the risk of colon cancer compared with those without insulin therapy (Chung and colleagues, 2008). It is advised that all patients with type 2 diabetes mellitus undergo colonoscopy before starting insulin therapy and have regular screening at least every 5 years (Berster and Göke, 2008).

Diet and alcohol have an impact. Alcohol is associated with colon cancer. Men who consume greater than or equal to 5 oz of alcohol weekly have twice the risk of colorectal cancer of those who drink less alcohol. Low intake of vitamin B₆ (see Chapter 3) is related to colon cancer, especially when combined with higher alcohol intake (Ishihara and colleagues, 2007).

A number of dietary factors are linked with lower risk of colon cancer. Salt and other substances as found in smoked or salted fish increase risk (Marques-Vidal, Ravasco, and Ermelinda Camilo, 2006). Sweets, refined white flour products, and red meat products are linked with increased risk, whereas a variety of high-fiber foods, low-fat dairy products, white meat, and fish are recommended to lower risk (Ströhle, Maike, and Hahn, 2007). This type of dietary pattern helps increase intake of folate and vitamin B₆ (see Chapter 3), which are associated with reduced colorectal cancer risk. The use of multivitamin supplements is not related to colorectal cancer risk (Zhang and colleagues, 2006). Vitamin B₆ may further play a role in the prevention of colorectal cancer among those who drink alcohol, especially women (Larsson and colleagues, 2005). A dose of 1000 International Units of vitamin D per day is associated with a 50% reduction in colorectal cancer incidence (Grant, Garland, and Gorham, 2007).

The association of the metabolic syndrome with colon cancer suggests dietary advice should be aimed at reducing carbohydrate intake, rather than focusing on total fat intake. It was found a low-fat dietary pattern did not reduce the risk of colorectal cancer in postmenopausal women during an 8-year period (Beresford and colleagues, 2006). Increasing omega-3 fatty acids is related to reduced risk (Theodoratou and colleagues, 2007).

High–glycemic load meals, fructose, and sucrose have been linked with increased colorectal cancer risk among men (Michaud and colleagues, 2005). Research on fiber intake is less conclusive, but it may be related to other aspects of diet and lifestyle (Michels and colleagues, 2005). A Mediterranean diet, which has a low glycemic index and with traditional small quantities of food, a low glycemic load as well, is associated with reduced risk. This type of diet is similar to public health initiatives such as the 2005 U.S. Dietary Guidelines, MyPyramid Food Guidance System, and the Dietary Approaches to Stop Hypertension (DASH) diet—see Chapters 1 and 7 (Dixon and colleagues, 2007).

There is conflicting evidence regarding intake of calcium and vitamin D from dairy intake or supplements. Some research links intake with lower rates of colon cancer (Larsson and colleagues, 2006a; Park and colleagues, 2007). Other research, such as the large, prospective, female cohort from the U.S. Women’s Health Study found no association with reduced risk (Lin and colleagues, 2005).

ENDOMETRIAL AND OVARIAN CANCER

The endometrial lining of the uterus is a common site of cancer in women. Conditions found with the metabolic syndrome are linked with both endometrial and ovarian cancers. This includes the link between inflammation and gynecologic cancers (Goswami and colleagues, 2008). Obesity and hyperinsulinemia are linked. High estrogen levels, as found with obesity, appear to be a major risk factor for endometrial cancer (Gunter and colleagues, 2008). Women with polycystic ovary syndrome, found with the metabolic syndrome and obesity, have increased risk of endometrial cancer (Costello, 2005). Altered lipid levels also are linked. Ovarian cancer is associated with significantly lowered HDL and total cholesterol levels (see Table 10-1).

Table 10-1

Relationship of Plasma Lipid Levels With Gynecologic Cancer

CANCER TYPE	TOTAL CHOLESTEROL	TRIGLYCERIDES	LOW-DENSITY LIPOPROTEIN	HIGH-DENSITY LIPOPROTEIN
Breast	Up 21%	Up 18%	Up 43%	Down 30%
Ovarian	Down 28%	Down 31%	Down 11%	Down 39%
Other gynecologic cancers	Down 21%	Down 25%	Down 6.2%	Down 27%

Data from Qadir MI, Malik SA: Plasma lipid profile in gynecologic cancers, Eur J Gynaecol Oncol 29(2):158-161, 2008.

Folate plays an important role in cancer prevention. Dietary folate intake was linked with reduced endometrial cancer risk among Chinese women (Xu and colleagues, 2007). Leafy greens, rich in folate, also are high in retinoids and carotenoids that are related to low risk of ovarian cancer. It further appears that carotenoids have a role in treatment of ovarian cancer (Czeczuga-Semeniuk and Wolczynski, 2005).

Research on the role of carbohydrates with diet and cancer is limited. There is some evidence that plasma insulin levels from a high–glycemic load diet may influence ovarian cancer risk (Silvera and colleagues, 2007a). Limited evidence has indicated high intakes of lactose might increase the risk for ovarian cancer (Key and Spencer, 2007). However, a meta-analysis did not find any association between milk and dairy products and ovarian cancer except for a nonsignificant increased risk from whole milk and butter (Qin and colleagues, 2005).

A 20% low-fat, high-fiber approach has not been shown to be effective at reducing endometrial or ovarian cancer in the short-term, but over an 8-year-period there was a lower rate for ovarian cancer (Prentice and colleagues, 2007).

Ovarian cancer risk was minimally linked among women who drank more than four cups coffee daily compared with women who did not drink coffee. No association was found among tea drinkers (Silvera and colleagues, 2007b).

A relatively new compound, called acrylamide, was found in starchy foods prepared at high temperatures, such as with fried foods. This substance has been associated with increased risk of postmenopausal endometrial and ovarian cancer (Hogervorst and colleagues, 2007).

Cultural Considerations

Women with gynecologic cancer and survivors often use complementary and alternative medicine (CAM). One study found about one third of women reported using three or more forms of CAM. The most commonly used were mind-body therapies and supplements. Older, more educated women were most likely to use CAM, especially if worried about ovarian cancer risk or if they had a previous cancer diagnosis. It is advised that providers inquire about and discuss the pros and cons of CAM with their patients—see Chapter 3 on herbal preparations (Mueller and colleagues, 2008).

ESOPHAGEAL CANCER

The incidence of esophageal adenocarcinoma is on the rise in the United States. Its precursor condition, Barrett’s esophagus (a premalignant lesion related to ulceration of the lower esophageal section that can lead to strictures inhibiting the movement of food into the stomach), also is on the rise. Zinc deficiency may contribute to Barrett’s esophagus (Guy and colleagues, 2007).

Studies suggest a reduced risk of esophageal cancer in populations with a high intake of fish. One study found supplementation with the omega-3 fatty acid EPA significantly reduced inflammation related to Barrett’s esophagus (Mehta and colleagues, 2008).

There is a strong correlation with an increased intake of carbohydrate, especially related to intake of corn syrup as found in sweetened beverages. This may be due to the rise in obesity rates as linked with higher intake of kcalories from sugar-based beverages (Thompson and colleagues, 2008).

Esophageal cancer is related to smoking and use of alcohol. There is an increased risk with the combination of excess alcohol intake and smoking (La Vecchia, Zhang, and Altieri, 2008).

Eating food rapidly and frequent intake of pickled vegetables also have been implicated in increased risk of esophageal cancer (Yang and colleagues, 2005). How increased pace of eating is associated with esophageal cancer is unknown. The reduced saliva release with reduced chewing may play a role. Saliva helps to neutralize acidity of the oral cavity, which may play a role in esophageal cancer.

Increased consumption of fruits (including oranges/tangerines), seafood, and milk were found to be protective against the development of esophageal cancer (Fan and colleagues, 2008). This may be due to the intake of vitamin C, with research of supplements showing a beneficial impact. It was found that those who took a multivitamin, 250 mg of vitamin C, or 180 mg of vitamin E had lower risk of esophageal cancer (Dong and colleagues, 2008).