Foods That Fight Cancer™
True American natives, winter squash have hard skins unlike the soft-skinned summer squash. They also come in a wonderful variety of colors, textures and flavors. Names like buttercup, banana, turban and delicata may sound delightful and pique your interest, but if you’re like many Americans, their irregular shapes and textures have kept you from venturing beyond the convenient canned pumpkin. The most common varieties you’ll see in supermarkets are acorn, butternut, spaghetti and hubbard.
What's in Winter Squash?
Winter squash are excellent sources of vitamin A, good sources of vitamin C and dietary fiber. They are also a good way to get potassium.
Winter squash, including pumpkins, are rich in carotenoids, including:
- beta-carotene and alpha-carotene: these carotenoids can act as antioxidants. Also, our bodies convert these to vitamin A, a nutrient important for immune function and maintaining healthy cells among other roles.
- lutein and zeaxanthin: these yellow pigmented carotenoids help protect eye health by filtering high-energy ultraviolet rays that can damage our eyes’ lens and retina. They act as antioxidants here and possibly elsewhere in our bodies.
The Cancer Research
Many of the phytochemicals and nutrients in winter squash are well studied in the laboratory. Winter squash also contain dietary fiber, which can act in several ways to lower cancer risk, including helping with weight control. Excess body fat increases the risk of 12 different cancers, and dietary fiber can increase the feeling of fullness.
Current Evidence: AICR/WCRF Expert Report and its Updates (CUP)
Squash is a starchy vegetable that contain fiber. After a systematic review of the global scientific literature, AICR/WCRF analyzed how these vegetables and dietary fiber affect the risk of developing cancer. This comprehensive review of decades of research concluded that there is strong – probable– evidence that:
- foods containing dietary fiber DECREASE the risk of colorectal cancer
Evidence categorized as "probable" means there is strong research showing a causal relationship to cancer – either decreasing or increasing the risk. The research must include quality human studies that meet specific criteria and biological explanations for the findings. A probable judgement is strong enough to justify recommendations.
Source: AICR/WCRF. Diet, Nutrition, Physical Activity and Cancer: A Global Perspective, 2018.
”… Supplements of beta-carotene in high-doses, especially in smokers, do not offer any cancer protection and seem to increase lung cancer risk.”
Open Areas of Investigation: Laboratory Research
Laboratory research is extensive on squash compounds such as beta-carotene and vitamin C .
- Lab research shows that vitamin C protects cells’ DNA by trapping free radicals and inhibiting formation of carcinogens.
- Alpha-carotene and beta-carotene are related carotenoids. Lab research shows that both act as antioxidants that also promote cell-to-cell communication, helping control cell growth.
- Lutein and zeaxanthin are concentrated not only in our eyes, but also in skin. A recent animal study suggests that dietary intake may decrease development of skin cancer related to sun exposure.
- Lab research shows that dietary fiber reduces cells’ exposure to cancer-causing substances and gut bacteria use it to produce short-chain fatty acids that protect colon cells.
Open Areas of Investigation: Human Studies
Human studies related to winter squash and cancer risk compare groups of people who consume relatively high and low amounts of total vegetables, squash, and/or levels of carotenoids.
Further research is underway in all the noted areas.
- Population studies that compare people with high and low amounts of beta-carotene in their diet or their blood link beta-carotene with lower risk of esophageal cancer.
- Both beta-carotene and lutein consumption are related to lower risk of renal cell cancer – a type of kidney cancer – in several large population studies.
- One study, which included almost 15,000 adults, found those with higher blood levels of alpha-carotene suffered fewer deaths from cancers of the aerodigestive tract after almost 14 years. Aerodigestive cancers include cancers of the esophagus, stomach, colon, liver, and pancreas, and larynx.
In the Kitchen
- When selecting squash such as acorn, compare equal sizes and purchase the heavier one to get more edible flesh.
- Inspect squash to find those with a hard rind and no soft spots.
- For canned pumpkin, make sure you buy pure pumpkin and not high-sugar pumpkin pie mix.
- Winter squash lasts two to three months at room temperature or slightly cooler. Refrigerating whole squash makes it spoil more rapidly.
- Cut pieces of squash keep about two days tightly wrapped in the refrigerator.
- You can freeze squash in uncooked chunks or as cooked purée.
- For most winter squash, it’s easy to cut them in half, remove seeds and bake.
- Butternut, delicata and spaghetti squash can be peeled and cut in cubes for stir-fries, casseroles, stews, pasta, soup, and even enchiladas.
- Roast in the oven alone or with other vegetables, drizzled with a bit of olive oil.
- Baked squash halves are perfect for stuffing. Try apples, raisins and cinnamon, or spinach or kale with soy and ginger.
- Steam, microwave or bake winter squash and then purée. Enjoy it as a side dish or to thicken and flavor soups and stews. Or use canned or frozen squash or pumpkin that is already puréed.
- Top "strings" of spaghetti squash with pasta sauce.
- Seeds from winter squash and pumpkin make a great snack or salad topping. Rinse, air dry, add a touch of oil, and bake at 350°F for 15-20 minutes.
Caramelized Carrots and Orange Squash
- 1/2 cup raisins
- 2/3 cup apple juice
- 2 lbs. carrots, peeled and sliced diagonally, 1/4-inch pieces
- 1 small butternut squash, peeled, and cubed, 1/2-inch cubes
- 1 small acorn squash (about 1 lb), seeds removed, peeled, cubed, 1/2-inch cubes
- 3 Tbsp. light olive oil
- 2 1/2 Tbsp. date syrup/honey (or dark honey)
- 1/2 tsp. ground cinnamon
- Sea salt and coarsely ground black pepper, to taste
- 1/2 cup apricot halves cut into small pieces
Preheat oven to 400 degrees F.
Soak raisins in apple juice.
Line large baking sheet with two sheets of parchment paper.
In large bowl, mix vegetables, oil, syrup, cinnamon and add salt and pepper to taste. Spread mixture on baking pan.
Bake until carrots (the longest to bake) are just soft then add raisins and apricots. Bake about 10 minutes longer, until carrots are soft enough for fork to prick through. Serve immediately or, if refrigerating for several hours or more, pour 1/3 cup apple juice over vegetables to keep moist before reheating.
Makes 10 servings.
Per serving: 188 calories, 4 g total fat (<1 g saturated fat), 39 g carbohydrate, 3 g protein, 6 g dietary fiber, 70 mg sodium.
Below are answers to some of the most frequently asked questions we get asked.
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.
Should I buy organic foods whenever possible?
There are many reasons to eat organic foods, but currently, there is no convincing evidence that shows a difference between organic and conventionally grown foods related to cancer risk. Studies show pesticide residues on conventionally grown foods are almost always within safety tolerance limits.
If you are concerned about pesticide residues and can afford to spend more, organic produce may be a choice for you. Eating generous servings of a large variety of veggies and fruits - whether organic or not will benefit your health. The advantages of including more vegetables and fruits in your diet outweigh the potential risks from pesticides.
Can grilled meats really cause cancer?
Lab studies show that exposing meats to direct flame, smoke and intense heat (like when you grill or broil) can cause the formation of carcinogens (cancer-causing substances). Cooking methods that involve less heat, such as microwaving, baking, steaming and poaching, do not promote the formation of these substances.
Several strategies you can use to cut carcinogen formation on meat include marinating, flipping frequently, removing excess fat from meat before cooking, and microwaving for part of the cooking time. So for delicious and healthful options, try grilling vegetables, veggie burgers and fruit slices and cut down on meat, fish and poultry.
- World Cancer Research Fund / American Institute for Cancer Research, Food, Nutrition, Physical Activity and the Prevention of Cancer: a Global Perspective, 2007: Washington, DC. p. 82-113.
- Astner, S., et al., Dietary lutein/zeaxanthin partially reduces photoaging and photocarcinogenesis in chronically UVB-irradiated Skh-1 hairless mice. Skin pharmacology and physiology, 2007. 20(6): p. 283-91.
- Kubo, A., et al., Dietary factors and the risks of oesophageal adenocarcinoma and Barrett's oesophagus. Nutrition research reviews, 2010. 23(2): p. 230-46.
- Musa-Veloso, K., et al., Influence of observational study design on the interpretation of cancer risk reduction by carotenoids. Nutrition reviews, 2009. 67(9): p. 527-45.
- Gallicchio, L., et al., Carotenoids and the risk of developing lung cancer: a systematic review. The American journal of clinical nutrition, 2008. 88(2): p. 372-83.
- Druesne-Pecollo, N., et al., Beta-carotene supplementation and cancer risk: a systematic review and metaanalysis of randomized controlled trials. International journal of cancer. Journal international du cancer, 2010. 127(1): p. 172-84.
- Lee, J.E., et al., Intakes of fruit, vegetables, and carotenoids and renal cell cancer risk: a pooled analysis of 13 prospective studies. Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology, 2009. 18(6): p. 1730-9.
- Li, C., et al., Serum alpha-carotene concentrations and risk of death among US Adults: the Third National Health and Nutrition Examination Survey Follow-up Study. Archives of internal medicine, 2011. 171(6): p. 507-15.