Foods That Fight Cancer™
Black walnuts are American natives, but English walnuts have become one of the most popular nuts in the United States. Although all nuts fit into a cancer-preventive diet, walnuts are most studied for cancer. They contain the omega-3 fat – alpha-linolenic acid – which can make walnuts more susceptible to becoming rancid. That's why you won’t find them in most commercial nut mixes.
What's in Walnuts?
Walnuts contain high amounts of polyphenols, phytochemicals that have antioxidant properties. They also contain a broad range of other potentially protective compounds:
- Elligitannins, which are broken down to ellagic acid
- Gamma-tocopherol, one of several types of vitamin E compounds
- Alpha-linolenic acid, an omega-3 fatty acid
- Polyphenols including flavonoids and phenolic acids
- Phytosterols, plant compounds known to help lower blood cholesterol that are under study for their potential antioxidant and anti-inflammatory effects in the body.
- Melatonin, a hormone and antioxidant
Walnuts are an excellent source of copper and manganese, and a good source of magnesium.
The Cancer Research
For cancer risk, walnuts are the most studied among the nuts.
There are a few dozen studies investigating cancer and whole walnuts, with many more on the compounds they contain. Walnut’s alpha-linolenic acid, ellagic acid and flavonoids are well studied in the laboratory.
Current Evidence: AICR/WCRF expert report and its updates (CUP)
AICR’s report and its continuous updates find evidence currently too limited to draw any conclusions about walnuts – or any nuts – and cancer risk.
"Several animal studies show that including walnuts in the diet slows or prevents the growth of breast and prostate cancers. The addition of walnuts to your plate is a good cancer preventive measure.”
- Lauri Byerley, PhD, LSU Health New Orleans
Open Areas of Investigation: Laboratory Research
In mice, several studies found that consuming walnuts resulted in decreased breast and colon tumor growth compared to the animals eating a standard diet. Limited studies in mice also show reduced growth of prostate cancer. One study indicated that consuming a walnut diet altered the expression of genes that regulate cell growth. Walnuts’ omega-3 fat, alpha-linolenic acid, seemed to account for some, but not all, of the protection seen.
Walnuts also contain ellagic acid, a phytochemical also found in raspberries, strawberries and pecans. Bacteria in our digestive tract convert ellagic acid into compounds called urolithins. In cell and animal studies, urolithins show antioxidant, anti-inflammatory and direct cancer-inhibiting effects.
Cell and animal studies studies have also investigated gamma-tocopherol, one of the eight forms of vitamin E. Most studies on the fat-soluble types of vitamin E have focused on alpha-tocopherol, the form listed on nutrition labels and recognized as most important for our health. Yet several studies suggest that walnuts’ gamma-tocopherol has stronger anti-inflammatory and cancer-protective effects than alpha-tocopherol.
Open Areas of Investigation: Human Studies
A couple of short-term studies suggest that eating walnuts can raise antioxidant levels in the body. One study also suggested it decreased signs of DNA damage. Yet one of the longer human studies involving 21 people found that their blood level of antioxidants were the same both before and after eating walnuts every day for six weeks.
Intervention trials including walnuts as part of a Mediterranean diet show potential benefits, such as helping people lose abdominal fat, lower blood pressure and lower their triglycerides. Yet overall, more human studies are needed to clarify walnuts’ effects on inflammation, antioxidants, and cancer risk.
In the Kitchen
- Choose shelled walnuts that are not shriveled or discolored.
- Walnuts should smell fresh and not rancid.
- For the same size shelled walnuts, the heavier the better.
- Select walnuts with shells unstained, intact and with no signs of mold.
- For freshest flavor, store shelled walnuts in the refrigerator for up to one month.
- Store in an airtight container. If you buy shelled walnuts in sealed packaging, transfer to an airtight container once open.
- Shelled walnuts will keep up to a year in a sealed container in the freezer.
- It’s best to keep unshelled walnuts in the refrigerator, but they will stay fresh up to six months if you store them in a cool, dry and dark place.
- Unshelled walnuts remain freshest if you crack them just before eating.
Walnuts make a great energy-sustaining snack on their own. What else can you do with them?
- Add walnuts to hot or cold cereal.
- Enjoy them in salads as a healthy way to add crunch.
- Toss with stir-fried vegetables, pasta or cooked grains like brown rice or quinoa.
- Coat fish or poultry with chopped walnuts and herbs.
- Combine walnuts with dried fruit for a portable trail mix snack.
- Make a walnut-apple-dried fruit chutney to serve with poultry or seafood.
- Toast walnuts to releases their rich, sweet flavor. For small batches, toast walnut halves in a dry, heavy skillet over medium heat for 2-3 minutes or until golden brown. To toast larger amounts, place walnut halves in a single layer in a shallow pan and bake in a 350 degree F oven for 5-10 minutes. Stir the walnuts a couple of times during toasting for even browning.
Walnut Chai Tea Loaf
- Canola oil cooking spray
- 3 chai teabags
- 1/2 cup boiling water
- 3/4 cup whole-wheat pastry flour
- 1 1/4 cups unbleached all-purpose flour
- 1 tsp. baking powder
- 1/2 tsp. baking soda
- 1/4 tsp salt
- 1/3 cup unsweetened applesauce
- 1/4 cup canola oil
- 3 large egg whites (can substitute 2 large eggs)
- 1/4 cup sugar
- 1/3 cup firmly packed brown sugar
- 1 tsp. grated orange zest
- 2/3 cup chopped walnuts
Preheat oven to 350 degrees F. Coat 8-inch x 4-inch loaf pan with cooking spray and set aside.
In heatproof measuring cup, steep teabags in boiling water for 10 minutes. Remove bags, squeezing well. Cool tea to room temperature.
In small bowl, whisk together flours, baking powder, baking soda and salt. In another bowl, combine applesauce, oil and tea. Set both bowls aside.
In mixing bowl, beat egg whites (or eggs) with electric mixer or whisk, 1 minute. Add sugars, beat together, then add wet ingredients. Add dry ingredients and zest and mix just until combined; there will be small lumps. Use rubber spatula to blend in small lumps, taking care not to over mix. Stir in walnuts. Scoop batter into prepared baking pan.
Bake for 45-55 minutes, or until straw inserted into center comes out clean. Cool loaf in pan on wire rack for 15 minutes. Turn loaf out of pan and cool completely.
Wrap loaf in foil and let sit for 8-24 hours, to allows flavors to ripen and loaf to become more moist.
Makes 12 servings.
Per serving: 210 calories, 10 g fat (1 g sat fat), 27 g carbohydrates,
4 g protein, 2 g fiber, 156 mg sodium.
Below are answers to some of the most frequently asked questions we get asked.
Does it matter whether I get my omega 3 fats from fish or walnuts?
It would be challenging to get the amount of omega 3 fats that studies show has health benefits through walnuts alone. Walnuts, as well as flaxseed, contain the plant-based form of omega 3 fat, alpha-linolenic acid (ALA). The omega-3 fats found in fish are EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), the fats linked with health benefits. When you eat walnuts, the body converts only a small amount of ALA into EPA and DHA.
If you were to eat fish a couple times a week, this amount of omega-3 fats is linked to lower risk of heart disease and lower rates of heart disease death. EPA and DHA consumption at this level are linked to reduced arrythmias, reduced risk of sudden cardiac death and have protective effects on blood triglyceride levels. It's not clear that very high levels provide any further protection from heart disease or heart mortality.
How does walnut oil compare to other oils?
Health-wise, walnut oil contains mostly unsaturated fats, which are more heart healthy than saturated fats. It has about three times as much polyunsaturated fat as monounsaturated. But the oil does not contain the same amount of phytochemicals, protein and fiber found in walnuts.
Money-wise, walnut oil is pricier than other common oils. High heat changes walnut oil’s flavor so it is often used as salad dressings or as a finishing oil, lightly drizzled on after cooking steamed vegetables or fish, or tossed with pasta.
Which fruits and vegetables should I be eating?
Eat as many different vegetables and fruits as you can. Variety is the key to obtaining the many protective phytochemicals. Each vegetable and fruit has its own profile of health-promoting substances.
The phytochemicals found in cantaloupe are different from those in broccoli or leeks or cherries. Try to include a lot of colors on your plate. Aim to eat some bright red, green, orange, blue, purple and yellow vegetables and fruits each day.
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