How sweet is it? Along with its many nutritional attributes, the sweet potato may play a role in cancer prevention

American Fitness, Nov-Dec, 2002 by Velonda Thompson

According to the American Institute for Cancer Research, approximately 4 million cancer cases can be prevented each year by practicing healthy dietary patterns. Medical experts believe over 30 percent of all cancers can be avoided by following better balanced diets.

In The Cancer Recovery Eating Plan, Daniel W. Nixon, M.D., states that many macronutrients, micronutrients and trace elements found in food modify one or more of the steps in carcinogenesis. (1) Hence, good nutrition, along with other healthy lifestyle factors, reduces cancer risk and increases chances of cancer remission. Nixon provides two examples of how macronutrients (e.g., fiber) and micronutrients (e.g., vitamin A) may make a difference:

1) Colon cancer has been linked to carcinogenic substances acting on the colon lining when waste stays in the colon too long. A high-fiber diet speeds the passage of waste through the colon, so there is no prolonged contact with carcinogenic substances that may be present.

2) In some cancers, healthy cells become immature and out of control (i.e., invade glands, produce excessive levels of proteins, enzymes and various hormones) by a process called dedifferentiation. Evidence suggests vitamin A (i.e., beta-carotene in green and yellow vegetables) can interrupt and reverse the dedifferentiation process in its early phases.

Vitamins A, C and E are phytochemicals associated with altering the carcinogenic process. A 1996 study found that a combination of vitamins C and E supplementation boosts our immunity. (2) A 1993 study suggests a 21 percent decrease in stomach cancer deaths can be attributed to beta-carotene supplementation. (3) Results from the European Prospective Investigation of Cancer and Nutrition Study, the largest study of diet and cancer to date, showed fiber was particularly important in reducing colon and rectum cancer.

What does the sweet potato have to do with it?

Because the average sweet potato is low in cholesterol and sodium, virtually fat-free and loaded with fiber, many athletes consider it one of the top high-energy foods. Sweet potatoes are also an excellent source of provitamin A (i.e., carotene), which the body converts into vitamin A (i.e., retinal). (4) The Louisiana Sweet Potato Commission calls sweet potatoes "the virtuous vegetable," since a medium-sized sweet potato also provides over one-third of the recommended daily vitamin C requirements. According to the North Carolina Sweet Potato Commission, 23 cups of broccoli contain the same amount of beta-carotene as one medium sweet potato.

In addition to being a great source of complex carbohydrates, vitamin B6 and potassium, sweet potatoes also contain significant amounts of folate. Research on the role of folate in preventing neural tube defects suggests that supplements, taken a month prior to conception and continued through the first trimester of pregnancy, can prevent neural tube defects. Folate deficiency can impair cell division and protein synthesis, which are critical to growing tissues. Half a cup of cooked sweet potatoes provides approximately 25 micrograms of folate--about 14 percent of the recommended daily allowance.

According to Albert Purcell, an eight-ounce sweet potato provides nearly a fifth of the minimum daily protein requirement and a two and a half day supply of iron for a woman. (5) Recently, the Center for Science in the Public Interest (CSPI) stated that the single most important dietary change for most people would be to replace fatty foods with rich complex carbohydrates, such as those found in sweet potatoes.

Looking Ahead

In the 1930s, Americans consumed about 23 pounds of sweet potatoes, per person, each year. (6) By 1993, per capita consumption dropped to an all-time low of 3.9 pounds per person. Agricultural research scientists in the USDA-ARS Food Science Research unit at North Carolina State University hope to change the trend by fueling interest in this nutritious vegetable with the creation of frozen sweet potato products.

Buoyed by current reports and ongoing research concerning beta-carotene, fiber and vitamins A, C and E, the sweet potato may become the anti-cancer food of the future. Figures one through four show comparisons of recommended daily allowances and nutrient levels in a medium-sized sweet potato for vitamins A, C, E and fiber. (7-8)

The investigation of the sweet potato in relation to the occurrence of cancer is likely to further our basic understanding of this disease and provide dietary guidance. However, we must remember that no single food can provide complete disease prevention. A balanced diet is preferred to the elusive perfect food and the sweet potato could contribute greatly to balancing a diet.

Figure One

Recommended Daily Allowance (RDA) for vitamin A
compared to one medium baked sweet potato.

Vitamin A

RDA-Women       800
RDA-Men        1000
Sweet Potato   2487

Note: Table made from bar graph

Figure Two

Recommended Daily Allowance (RDA) for vitamin C
compared to one medium baked sweet potato.

Vitamin C

RDA-Adults      60
RDA-Smokers    100
Sweet Potato    28

Note: Table made from bar graph

Figure Three

Recommended Daily Allowance (RDA) for vitamin E
compared to one medium baked sweet potato.

RDA-Women       8
RDA-Men        10
Sweet Potato    5

Note: Table made from bar graph

Figure Four

Recommended Daily Allowance (RDA) for fiber
compared to one medium baked sweet potato.

RDA-Minimum    20
RDA-Maximum    35
Sweet Potato    3.4

Note: Table made from bar graph