Cancer Prevention with Diet and Nutrition

Vegetables — Photo: Arnaud 25/Wikimedia Commons

By Casey Carlgren, MS, RD, LD

According to the National Institute of Occupational Safety and Health (NIOSH), U.S. firefighters have a 9% higher chance of a cancer diagnosis and a 14% higher chance of a cancer-related death when compared to the general population. This is due to exposure to a variety of substances and situations that most people outside of the fire service will never experience. In 2022, the International Agency for Research on Cancer labeled firefighting as “carcinogenic” based on the growing body of literature investigating firefighting and cancer.

Cancer is a group of diseases characterized by the uncontrolled growth and spread of abnormal cells. There were approximately two million new cancer cases in the U.S. in 2023, with roughly 609,000 cancer related deaths. Much is still unknown about cancer development, however there are a number of factors known to increase the risk of developing cancer.

Major risk factors for developing cancer:

Obesity
Inflammation
Diet
Lifestyle
- Smoking
- Inactivity

“Up to ⅓ of all cancer deaths in the U.S. could be avoided through dietary changes.”

Obesity and Inflammation

The link between obesity and chronic diseases like heart disease, diabetes, and cancer is well established. Approximately 20% of all cancer incidences are related to obesity. Obesity is defined as abnormal or excessive fat accumulation that presents a risk to health. In both men and women, it is attributed to having a BMI (kg/m²) of 30 or greater, although other criteria can be used.

*A BMI between 18.5-24.9 is considered to be in the ‘normal’ category, while a BMI between 25-29.9 is considered to be in the ‘overweight’ category. However, many people with more muscle mass will often fall within the overweight category and would not be considered at risk based on that criteria alone.*

The reasoning behind why obesity increases the risk of developing cancer is related to being in a positive energy balance (i.e. intake of more calories than are needed) over a period of time. This leads to increased/abnormal levels of insulin (regulates blood sugar levels), IGF-1 (promotes normal bone/tissue growth and development), sex steroids/hormones (estrogen, testosterone, etc.), and inflammatory markers. All of these are associated with an increased risk of cancer growth.

Obesity results in chronic or low-grade inflammation lasting months to years. Left untreated, this can cause damage to healthy cells, tissues/organs, and DNA. Many of the proinflammatory molecules produced are released from fat tissue. The more body fat you have, the more proinflammatory molecules are produced, the greater the degree of inflammation in the body.

Being obese is also associated with low 25-hydroxy (vitamin D) levels in the body, and may be directly related to nearly 20% of cancer risk derived from having a higher body fat percentage. Without adequate levels of vitamin D, our body has a decreased ability to defend against cancer cell growth. The minimum level of 25-hydroxy (vitamin D) thought to be sufficient for health is 30 ng/ml. This can be achieved via a combination of diet (fortified dairy, fish, eggs, beef liver, etc.), sun exposure (15-20 min/day sunlight on the skin during the middle of the day), and supplementation (1000 IU’s or 25 mcg per day; more may be necessary if already deficient, but discuss with clinician/RD).

*Sun exposure requirements are longer for those with darker skin: ~25-45 min/d. Required time in the sun increases in winter for everyone, due to the angle of the sun at your respective latitude and less skin exposure as people are generally wearing more clothing.*

As you can see, the link between obesity, inflammation, and cancer is complex and often overlapping. This highlights the importance of a nutritious diet and physical activity in maintaining a healthy weight as one of the foundations of cancer prevention. There are also specific nutrients (phytonutrients) found in certain foods, most often fruits and vegetables, that also play a role in cancer prevention beyond those associated with maintaining a healthy bodyweight.

Diet: Phytochemical-rich foods and cancer prevention

Phytonutrients (phyto = plant) are found in fruits and vegetables, such as isoflavones, carotenoids, anthocyanins, flavonoids, polyphenols, resveratrol, lycopene, etc. They are health-promoting nutrients that provide no calories themselves. The source of the bright colors in fruits and vegetables comes from their phytonutrient profile, which is one reason why many health professionals advocate eating a “colorful” plate. Many of these compounds have anticancer properties and when consumed regularly. In conjunction with an overall healthy diet and lifestyle, they provide an easy and attainable strategy for cancer prevention. Below is a list of some of the foods and specific compounds found in foods that can play a role in reducing the risk of cancer.

Green tea catechins and EGCG
- Green tea contains flavanols (a group of phytonutrients) called catechins found to suppress cancer development and growth. EGCG is a specific catechin.
Berries
- They are rich in flavonoids that slow the growth and spread of cancer cells and decrease oxidative damage that contributes to inflammation.
Turmeric
- Curcumin is a polyphenol found in turmeric with anti-inflammatory and anticancer properties. Turmeric is a common cooking spice, often found in curry powder.
Carotenoids
- These are the most abundant phytonutrients in fruits/vegetables. They reduce cancer risk via their anti-oxidant properties.
  - It’s important to get these from food sources and not supplements, as some carotenoid supplements have actually been shown to increase risk for certain types of cancer.
Cruciferous vegetables
- Examples include broccoli, cauliflower, kale, and cabbage. They contain many phytonutrients with strong anticancer and antioxidant properties.
Cocoa
- It is high in flavonoids and proanthocyanidins, with antioxidant and anti-inflammatory properties.
Soy Isoflavones
- There is strong evidence for soy consumption reducing the risk for many cancers, decreasing inflammation, and reducing heart disease.
- Other benefits are that soy is high in fiber and is a complete protein source.

Supplements and Cancer Prevention

This is a highly debated topic when it comes to cancer. The best answer at the moment is to try and get your vitamins, minerals, and phytonutrients from food sources via your diet and not from supplements. Discuss with your physician/RD before starting a supplement regimen.

General Diet and Nutrition Recommendations for Cancer Prevention

Eat a diet rich in whole grains, fruits, vegetables, and beans—that is, a colorful plate.
- Minimum amount of fiber intake is ~30g/day
  - Or, ~14g/1000 kcal consumedFor every 10g/day over the initial 30g provides an added benefit
  The greatest reduction in cancer risk is seen between a low intake of one to two servings and five or more servings/day.
- Fresh, frozen, or canned are all good options.
Limit consumption of “fast foods” and other processed foods high in fat, starches, and refined sugars.
- This is related to their overconsumption leading to overweight/obesity
Limit your consumption of red and processed meat.
- Max of 100 g/d or 18 oz/week, mainly beef, pork, and lamb.
- Consume lean cuts for heart health, not lower cancer risk
  - Processed meats: smoked, cured, salted, preservatives
    - Very little: bacon, sausage, deli meats
Limit consumption of sugar sweetened beverages and 100% fruit juices
- These represent the largest source of added sugar in the diet.
Limit alcohol consumption.
- Intake beyond moderation increases blood pressure, triglycerides (blood lipids), and cancer risk.
  - Men: Two or fewer drinks per day.
  - Women: One or fewer per day.

Lifestyle: General Activity and Bodyweight Recommendations for Cancer Prevention

Be at a healthy body weight for your height and frame
- Avoid excess body fat gain during adulthood
Be physically active
- This is important even without weightloss, as it
  - Benefits hormones, immune system, GI function
  - Psychological health, stress management.

Final Thoughts

Doing your best to follow these diet and lifestyle recommendations will go a long way in the fight for health and resilience throughout your lifetime. Small lifestyle changes over time, in accordance with these general guidelines, can drastically impact your health. Given the fact that some risk factors for developing cancer remain outside of our control (family health history/genetics, aging, substance exposure, etc.), it is important to focus on the things that we can control (diet, lifestyle, bodyweight, etc.).

REFERENCES

Jahnke, S. A., Jitnarin, N., Haddock, C. K., Kaipust, C., Poston, W. S. C., Hollerbach, B. S., Crisp, C., & Naylor Metoyer, B. (2024, March 1). Meta-analysis of incidence and mortality of firefighter cancer: An update on emerging science. Asian Pacific Journal of Cancer Prevention. https://journal.waocp.org/article_91044.html
FAQ – You Have Questions, We Have Answers. Firefighter Cancer Support Network. (n.d.). https://www.firefightercancersupport.org/resources/faq
Langevin, L. (2018, February). CPE monthly: Cancer prevention – The Role of Inflammation, Phytochemicals, and the Microbiome. Today’s Dietitian. https://www.todaysdietitian.com/newarchives/0218p42.shtml
Brockton, N., & Collins, K. (2023, October 18). Diet & Lifestyle for Cancer Prevention and Survivorship – Evidence over Opinion. YouTube. https://www.youtube.com/watch?v=qrRVBaKaUXk
Collins, K. (2024, October 17). Top Questions from Dietitians about Diet and Cancer . American Institute for Cancer Research. https://www.aicr.org/resources/blog/top-questions-from-dietitians-about-diet-and-cancer/

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