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Diet & Prostate Cancer
Natalie Ledesma, MS, RD

Fruit
Table 1- Dietary Sources & Their Effects of Nutrients and Food Components

Dietary Fiber
Refined Carbohydrates/Sugar

Fats
Meat
Dairy Products
Table 2 - Fatty Acids - Dietary Sources & their Effects

Table 3 - Research Highlights Regarding Calcium and Prostate Cancer
Vitamin D

Body Weight and Physical Activity
Summary - Healthy Diet for Prostate Cancer

Eating a healthy diet may reduce the incidence of prostate cancer and help reduce the risk of prostate cancer progression. It is estimated that over one-third of cancer deaths in the U.S. can be attributed to diet in adulthood. [1]

Research indicates that a plant based diet may help lower a man's risk of developing prostate cancer and may also beneficially affect the progression of the disease. In a study conducted by Dr. Dean Ornish and colleagues, men who modified their diet and lifestyle in a healthy way had a 4% decrease in their PSA (prostate specific antigen), a marker for prostate cancer growth.[2] The control group, who did not make the dietary and lifestyle changes experienced a 6% increase in PSA. A separate study found that a plant based diet, in combination with stress reduction, may decrease the risk of recurrence of prostate cancer.[3] PSA doubling time, the hallmark of recurrent prostate cancer, increased from 11.9 months (prestudy) to 112.3 months (intervention). Moreover, men who made such comprehensive lifestyle changes improved their quality of life.[4]


Fruits and Vegetables
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Fruits and vegetables are rich in vitamins, minerals, fiber, and various cancer-fighting phytonutrients. Color is one indicator of phytonutrient content - seek vibrantly colored fruits and vegetables. Various studies have reported that diets rich in fruits and vegetables are associated with a lower risk of many cancers;[2-6] evidence regarding prostate cancer is inconsistent, but is promising.[2-8] Men who ate 2-3 kg (50% lower risk) and more than 3 kg (60% lower risk) of fruits and vegetables per week compared with men who consumed less than 2 kg per week significantly reduced their risk of prostate cancer.[4]

You may ask if there are specific fruits and vegetables that you should be eating. Generally speaking, eat a variety of colorful fruits and vegetables, and ones that you enjoy. However, there is research that indicates certain fruits and vegetables may be particularly beneficial for prostate cancer. The chart below provides more details on these food components, their sources, and their potential benefits (see Table 1).

So, how many fruits and vegetables should you eat daily? Well, the answer is not exactly clear, but it may be that a minimum of 8-10 servings of fruit and vegetables are needed to provide the greatest protection against cancer.[9] Aim for five or more vegetable servings and three or more fruit servings daily. One serving is: ½ cup fruit or vegetable, 1 cup raw leafy greens, ¼ cup dried fruit or vegetable, and 6 fl oz fruit or vegetable juice.

Table 1
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Dietary Sources & Their Effects of Nutrients and Food Components
Nutrient or Compound Dietary Sources Potential Benefit for Prostate Cancer
Allium (organosulfur) compounds Garlic, leeks, onions, shallots Anti-cancer properties
Inactivate carcinogens
Beta-carotene Carrots, sweet potatoes, winter squash, cantaloupe, mango Antioxidant effects
Higher plasma levels→  ↓risk
Indole-3-carbinol, diindolylymethane (DIM), &/or isothiocyanates Cruciferous vegetables: arugula, broccoli, bok choy, Brussels sprouts, cabbage, cauliflower, collard greens, horseradish, kale, kohlrabi, mustard greens, radishes, rutabaga, turnips, watercress May ↓ risk of PC
May ↓ risk of aggressive PC ↓ prostate tumor growth
Induces PC cell death
May ↓ risk of PC recurrence
May upregulate phase II detoxifying enzymes
Isoflavones Soy foods: edamame (green soybeans), miso, soy milk, soy nuts, tempeh, tofu ↓ blood androgen levels
↓ IGF-I
Bind to hormone receptors
↓ 5-alpha reductase
May ↓ PSA
Lignans Flax seedsa May ↓ tumor growth
May ↓ angiogenesis
Improve immune response
↓ blood levels of testosterone
Lycopene Tomato productsb (tomato juice, vegetable juice cocktail, spaghetti sauce), guava, watermelon Higher plasma levels→  ↓ risk and ↓ risk of advanced PC
May ↓ IGF-I c
Polyphenols (catechins) Green tea Antioxidant effects
Anti-cancer effects
May ↓ tumor growth
May induce PC cell death
May inhibit IGF-I
May ↓ nitrosamines
May ↓ COX-2 activity Improve immune response
Pomegranate seed oil, fermented juice, fruit extract Pomegranate Anti-inflammatory effects
Antioxidant effects
Inhibit tumor growth
Induce PC cell death
May ↓ PSA
Inhibit angiogenesis
May ↓ risk of PC recurrence
Selenium Brazil nuts, seafood, enriched brewer's yeast, grains May ↓ risk of PC recurrence
↓ angiogenesis
Antioxidant effects
Induce PC cell death
↓ plasma levels→  ↓ PC risk
Vitamin E (alpha, gamma, beta, delta tocopherol and tocotrienols)   ↑ plasma levels→  ↓PC risk
↑ diet→  ↓ advanced PC risk
May ↑ PC growth

a Ground flaxseeds are preferred due to their greater bioavailability over whole seeds and their greater lignan content over flaxseed oil.
b Cooked tomato products or juices contain higher amounts of lycopene; the cellular wall is broken down with the heat resulting in increased lycopene absorption. Additionally, lycopene-rich foods are best absorbed in the presence of fat, such as a small amount of olive oil.
c Increased IGF-I levels in the blood have been implicated in the risk of various cancers, including prostate cancer.



Dietary Fiber
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When following a plant based diet, your diet is naturally high in fiber. A high fiber diet, one rich with fruits, vegetables, legumes, and whole grains, may reduce the risk of prostate cancer and/or its progression. Total dietary fiber intake and certain fiber-rich foods, such as cereals, nuts, and seeds have been associated with a lower risk of prostate cancer [10-41] and death from prostate cancer,[12] respectively. Fiber may act by binding to toxic compounds and carcinogens, which are then later eliminated from the body.[13] Foods rich in fiber not only have a beneficial effect on gut health, but also decrease hormone levels that may promote prostate cancer and/or its progression. [11,14]

Aim for 30-45 grams of fiber daily. Choose: a) breads with three or more grams of fiber per slice, b) foods where the first ingredient on the label is whole or sprouted grain flour, not white flour, unbleached white flour, or enriched wheat flour, and c) whole grains, such as oats, barley, brown rice, quinoa, amaranth, bulgur, millet, buckwheat, spelt, wild rice, and teff.


Refined Carbohydrates/Sugar
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Refined carbohydrates and high sugar foods offer little, if any, nutritional benefit. These foods, such as refined cereals (primarily breads and pasta)[15] and desserts [16] have been associated with prostate cancer. One reason why may be because sugars and refined carbohydrates tend to increase serum insulin and serum IGF-I levels, which lead to the development and promotion of cancer.[17-20] This idea was recently supported in a study where a diet high in refined carbohydrates led to higher insulin levels and increased tumor growth.[21] Avoid or limit the following foods: products made with refined flours (for example: white bread, white rice, white pasta) or refined grains, alcohol, and sweets, such as candy, cookies, cakes, and pastries.


Fats
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Dietary fat has been implicated as a risk factor for prostate cancer. A comprehensive review reported that 20 of 30 studies found positive, although not all statistically significant, associations between dietary fat and risk of prostate cancer.[22] Death from prostate cancer has also been associated with dietary fat.[23] Strong correlations have been noted for meat, added fats, and oils, ice cream, margarine, salad/cooking oil, and vegetable shortening. Most researchers agree to aim for close to 20% of total calories from fat.[24] However, the type of fat may be of greater significance than the total amount of fat.

For a quick bottom line on fats, it is suggested to limit the amount of saturated, trans fats, and omega-6 fatty acids in the diet. Instead, focus on increasing the omega-3 fatty acids in the diet and as a neutral fat, you can also include omega-9 fatty acids. Obtaining the right balance of omega-6 and omega-3 fatty acids likely plays a critical role in the prevention and treatment of prostate cancer.[25] It appears optimal to achieve a 1:1 to 4:1 ratio of omega-6:omega-3 fatty acids. Take a look at Table 2 for more detailed information on fats.

Table 2
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Fatty Acids - Dietary Sources & their Effects
Fatty Acid Dietary Source Effects
Saturated fatty acids Meats, butter, egg yolks, whole milk dairy products (i.e., cheese, ice cream), baked goods May ↑ risk of PC
May ↑ risk of metastatic PC
Trans fatty acids (hydrogenated oils) Margarine, fried foods, commercial peanut butter, salad dressings, and various processed foods May ↑ risk of PC
Omega-6 fatty acids (linoleic acid, arachidonic acid) Meats, butter, egg yolks, whole milk dairy products, corn oil, safflower oil, sunflower oil, cottonseed oil May ↑ tumor growth
May ↑ growth related genes
Omega-3 fatty acids (alpha linolenic acid, eicosapentaenoic acid, docasahexaenoic acid) Cold-water fish (salmon, sardines, trout, black cod, herring), flax seeds, walnuts, hemp seeds, pumpkin seeds, chia seeds May ↓risk of PC
May tumor growth
↑ immune response
Anti-inflammatory effects
Induce PC cell death
↓cancer cell initiation
Compete with arachidonic acid
Omega-9 fatty acids Extra-virgin olive oil, canola oil, macadamia nut oil, almonds, avocados No effect on PC


Meat
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Many studies have suggested that meat intake may increase the risk of prostate cancer. Why is not exactly known, but there are various possible mechanisms. For one, meat lacks the beneficial phytonutrients that plant foods provide. A second possible theory relates to the amount and type of fats in meats. And a third reason may be that animal protein increases IGF-I.[26] There is also the concern that conventionally raised livestock is generally treated with therapeutic drugs and production drugs, which may detrimentally affect our health. Lastly, research is growing stronger linking certain genotoxins, such as heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs), with the risk of prostate cancer.[27-30] These cancer causing compounds form when meat is cooked at high temperatures by dry-heat methods, including frying, grilling, broiling, and barbecuing. Eating well or very well done meat has been shown to increase the risk of prostate cancer by 26% and nearly doubled the risk of advanced prostate cancer when comparing those who ate more meat with those who ate the least.[30] It may be that HCAs significantly increase PSA levels, which would further explain their association with prostate cancer. [31]

Dairy Products
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Dairy foods have also been linked to prostate cancer. Men who ate 21 dairy servings weekly, compared with who consumed five or less weekly, more than doubled their risk of prostate cancer.[32] A recent study founds that a higher intake of dairy products (>2.75 vs. </=0.98 servings of total dairy/day), particularly low-fat dairy products, was weakly associated with an increased risk of prostate cancer.[33] Why dairy may increase the risk of prostate cancer may be related to the calcium content [22, 34-36] (see Table 3), the animal fats in dairy,[37-38] and/or that dairy foods increase IGF-I levels.[39]

Table 3
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Research Highlights Regarding Calcium and Prostate Cancer
Calcium Intake Effect on Prostate Cancer Reference
>2000mg/day vs. >1000 mg/day ↑ risk of nonaggressive PC [22]
1329-2250 mg/day vs. 228-802 mg/day 39% ↑ risk of PC [35]
>/= 2000 mg/day vs. 500-<750 mg/day ↑ risk of advanced PC [34]
>/= 1000 mg/day vs. 500-<750 mg/day ↑ risk of fatal PC
Not related to nonaggressive PC
[34]
Calcium from skim milk ↑ risk of PC [36]
>/= 1500 mg/day ↑ risk of advanced and fatal PC [36]
Nondairy calcium (>/= 600 mg/day vs. <250 mg/day) ↓ risk of nonaggressive PC [36]


Vitamin D
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While not all studies agree,[40] vitamin D appears to be an important factor in the risk of prostate cancer.[41-45] The risk of prostate cancer is greater in men with lower levels of vitamin D.[44-45] Increasing serum levels of vitamin D levels by 25nmol/l was associated with a 17% reduction in prostate cancer incidence and a 29% decrease in death from prostate cancer.[46] The issue of vitamin D becomes a bigger issue as we age because absorption of vitamin D decreases with age, and vitamin D deficiency is not uncommon among older adults.[47-50] Men with and at risk for prostate cancer, especially those on hormone therapy, may benefit from a serum 25 (OH)-vitamin D test. Optimal serum 25 (OH)-vitamin D levels have not been established though research suggests 90-400 nmol/L (36-40 ng/mL) may be ideal.[51]


Body Weight and Physical Activity
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It is well known that being overweight or obese increases one's risk of various chronic diseases. Advanced prostate cancer and death from prostate cancer appear to be no exception.[52] Of interest, some studies report that obesity may reduce the risk of nonaggressive prostate cancer.[53] However, this may not be a true effect and may instead be related to hemodilution due to the higher plasma volume in a larger individual, and hence a lower PSA level.[54] Thus, it's possible that obese men may be diagnosed later than a normal weight man. Maintaining a healthy body weight may also lower a man's risk of recurrence. [55]

There are various therapeutic benefits of physical activity, including increased muscular function,[56] reduced risk of prostate cancer,[57] lower risk of dying from prostate cancer,[58] decreased IGF-I [59-60], and an improved quality of life for cancer survivors.[56] Healthy weight control is encouraged through a healthful plant based diet and regular exercise to maintain or increase lean muscle mass.


Summary - Healthy Diet for Prostate Cancer
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Eat 8-10 colorful fruit and vegetable servings daily.
3 pieces of fruit
1 cup or more of vegetables with lunch and dinner
12 oz tomato-based juice

Eat 30-45 grams of fiber daily.
This goal can be achieved by meeting your fruit and vegetable goal plus one serving of legumes or at least two servings of whole grains.

Avoid refined carbohydrates and sugar.
Keep WHITE off your plate - bread, pasta, cereal, rice, cream sauces, cakes, and more.

Limit meats and dairy.

Include healthy fats daily.
Examples include cold-water fish, flaxseed, walnuts, avocados, soybeans, and extra-virgin olive oil.

Selenium (200 mcg)
2 Brazil nuts daily or supplement

Vitamin E (50-200 IU)
Natural vitamin E supplement that contains gamma-tocopherol

Vitamin D (400-2000 IU depending on age)
Maintain serum 25 (OH)-vitamin D over 35 ng/mL

Drink 1-4 cups green tea daily.

Drink plenty of fluids, water, or non-caffeinated beverages, daily to help meet fluid needs.

Engage in physical activity to help achieve and maintain a healthy body weight.



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