How Carotenoids Help Protect Against Cancer

The Physicians Committee

How Carotenoids Help Protect Against Cancer

Carotenoids are the pigments that give fruits and vegetables such as carrots, cantaloupe, sweet potato, and kale their vibrant orange, yellow, and green colors. Beta-carotene, lycopene, and lutein are all different varieties of carotenoids. They all act as antioxidants with strong cancer-fighting properties. Antioxidants protect cells from free radicals, substances that work to destroy cell membranes and DNA. Smokers tend to have higher concentrations of free radicals in the blood due to the chemicals they inhale. So, it's no surprise that studies have confirmed that antioxidants lower the risk of lung cancer for smokers.1 (This is no reason to smoke, of course, as it is impossible to predict who will develop cancer in every instance.) Studies have also suggested that carotenoids may help prevent skin, breast, and prostate cancer.2-4Some carotenoids are also converted to vitamin A, which is necessary for healthy vision and cell growth.

Food Sources

Carotenoids are found in nearly all brightly colored fruits and vegetables. Not all of these carotenoids can be converted into vitamin A, however. For example, lutein is an important antioxidant, but it has no vitamin A activity. Beta-carotene, on the other hand, has a very high amount of vitamin A activity.

It is best to consume naturally occurring carotenoids from foods rather than supplements because they come teamed up with an abundance of other cancer-fighting compounds that are lacking in pill form. In addition, the body is able to convert natural carotenoids to vitamin A in the amount it requires. On the other hand, vitamin A supplements given in doses of just four to five times the Recommended Dietary Allowance can be toxic. The body is unable to rid itself of excess vitamin A and stores it in the liver indefinitely. Toxicity from vitamin A can cause dry, peeling skin, and, in severe cases, thinning of the bones and even liver failure.

Beta-carotene supplements are not the same as beta-carotene-rich roods. In large studies, high doses of beta-carotene given in supplemental form to cancer patients actually worsened their risk of lung cancer rather than improving it, perhaps because the doses were so large or because the huge intake of beta-carotene interfered with absorption of other nutrients. Instead, it is better to get your antioxidant vitamins safely from the packages nature intended—fruits, vegetables, grains, and legumes.

The following foods have large quantities of beta-carotene.

Food Beta-Carotene

Apricots, 1 cup raw

Broccoli, 1 cup raw 807
Brussels sprouts, 1 cup cooked 669
Cantaloupe, 1/8 melon 1,325
Carrot, 1 large 15,503
Guava, 1 cup raw 750
Kale, 1 cup raw 3,577
Mango, 1 cup raw 3,851
Pumpkin, 1 cup raw 31,908
Red bell pepper, 1 cup raw 2,840
Spinach, 1 cup raw 1,196
Sweet potato, 1 cup raw 26,184
Tomato, 1 cup raw 446
Watermelon, 1/16 melon 634

Tips for Increasing Carotenoids in Your Diet

  • Be creative! The more colorful your meal is, the more likely it is to have an abundance of carotenoids, as well as other healthy nutrients.
  • Keep a bag of baby carrots nearby—most likely the perfect snack. Try them plain or dipped in hummus, almond butter, or light vinaigrette.
  • Limit storage of fruits and vegetables. Once plants containing carotenoids are pulled from the vine, their active antioxidants gradually lose their potency. For fresh, seasonal produce, check out your local farmer's market.
  • Don't overcook vegetables. While you still get a substantial amount carotenoids in cooked vegetables, you will definitely get much more if you enjoy them raw. There are a few exceptions. Carrots, for example, actually release more of their carotenoids if you cook them; pur³eing them has a similar effect.

1. Ruano-Ravina A, Figueiras A, Barros-Dios JM. Diet and lung cancer: a new approach. Eur J Cancer Prev. 2000;9:395-400.
2. DiGiovanna JJ. Retinoid chemoprevention in patients at high risk for skin cancer. Med Pediatr Oncol. 2001;36:564-567.
3. Zhang S, Hunger DJ, Forman MR, et al. Dietary carotenoids and vitamins A, C, and E and risk of breast cancer. J Natl Cancer Inst. 1999;91:547-556.
4. Cook N, Stampfer MJ, Ma J, et al. Beta-carotene supplementation for patients with low baseline levels and decreased risks of total and prostate carcinoma. Cancer. 1999;86:1783-1792.