Can the food we eat promote or protect us from cancer?

Many studies have investigated the impact of certain nutrients on the development of cancer.

The possibility that specific nutrients may be associated with increases or decreases in cancer risk has been a subject of study for a long time. Add in urban legend and sensational headlines, and it can be a difficult path to navigate. Here we recap the scientific evidence on a number of conversation points.

Orange juice

A recent study in the Journal of Clinical Oncology reported that regularly drinking grapefruit and orange juice or consuming higher than normal servings of these citrus fruits makes people a third more likely to develop melanoma.

Although researchers have not clarified the mechanism by which these citrus fruits and juices raise the risk of melanoma, they speculate that it may be because the fruits are rich in compounds called psoralens and furocoumarins, which are believed to make the skin more sensitive to the sun, potentially interacting with UV radiation to stimulate melanoma cells.

The authors of the study warn people not to overreact to the results, saying it’s too early to make any dietary changes based on their findings. As always, moderation is the key to a balanced eating plan.

Artificial sweeteners

Researchers have conducted studies on the safety of the artificial sweeteners, such as saccharin; cyclamate; aspartame; acesulfame potassium; sucralose; and neotame and found no evidence that they cause cancer in humans. All of these artificial sweeteners except for cyclamate have been approved by the US Food and Drug Administration.

Antioxidants

Although antioxidants have been shown to help prevent the free radical damage associated with the development of cancer in laboratory and animal research, research in humans has not demonstrated convincingly that taking antioxidant supplements can help reduce the risk of developing cancer.

Cruciferous vegetables

In addition to several carotenoids, vitamins C, E, and K, folate, fibre and minerals, these veggies contain chemicals known as glucosinolates, which break down into several compounds that are being studied for possible anti-cancer effects.

In cruciferous vegetables (including broccoli, cabbage, cauliflower, watercress and radishes) these compounds have shown anticancer effects in cells and animals, reports the US National Cancer Institute.
Researchers have suggested several ways these compounds may help prevent cancer, ie:

• Protecting cells from DNA damage,
• Helping to inactivate carcinogens,
• Through antiviral and antibacterial effects,
• Anti-inflammatory effects,
• Prompting abnormal cell death,
• Inhibiting tumour blood vessels forming and tumour cells migrating (as in metastasis).

Carrots

Some people have claimed their cancer was cured by drinking large amounts of raw carrot juice daily. While some tests have shown that natural compounds known as polyacetylenes in carrots can have beneficial effects, and some studies have found the anti-cancer compound falcarinol reduced tumours in rats by a third, there are no studies that show the same effects in humans. Further studies on the compounds in carrots are currently underway at Newcastle University in the UK.

Red and processed meat

In 2015 the WHO warned against the high consumption of red meat, as well as processed meats, declaring that red meat is ‘probably’ carcinogenic and processed meat (such as sausages, bacon, ham, corned beef, boerewors and biltong) is carcinogenic to humans.

An analysis of data by the International Agency for Research on Cancer (IARC) showed that

• every 50g of processed meat eaten daily increases the risk of colorectal cancer by about 18%.
• For an individual, the risk of developing colorectal cancer because of their consumption of processed meat remains small, but this risk increases with the amount of meat consumed,” says Dr Kurt Straif of IARC.
• The risks of overconsumption relate to the saturated fat content of red meat. These fats have been proven to be bad for certain types of cancer, as well as cholesterol and heart health. Too much red meat would invariably increase fat intake,” says René Smalberger, dietitian and former president of the Association for Dietetics in SA.
• Anti-inflammatory effects,
• Prompting abnormal cell death,
• Further, when muscle meat is cooked with high-temperature methods, including flame-grilling and braaing, chemicals called HCAs and PAHs are formed. Exposure to high levels of HCAs and PAHs can cause cancer in animals; however, it’s not yet clear whether this exposure causes cancer in humans.

Garlic

Some studies have suggested that garlic consumption may reduce the risk of developing several types of cancer, especially cancers of the gastrointestinal tract. An analysis in the Journal of Nutrition showed that the more raw and cooked garlic eaten, the lower the risk of stomach and colorectal cancer.

Garlic’s potential effects may be due to its antibacterial properties or from its ability to block the formation of cancer-causing substances and enhance DNA repair. The National Cancer Institute, does not recommend any dietary supplement for the prevention of cancer, but recognises garlic as one of several vegetables with potential anticancer properties.

Tea

Polyphenols in green tea and black tea have antioxidant activity, which may protect cells from DNA damage by destroying potentially damaging free radicals. Tea polyphenols have also been shown to inhibit tumour cell proliferation and invasion. They might also have protective effects against UV radiation. Although many of the potential beneficial effects of tea have been attributed to the powerful antioxidant polyphenols, the exact mechanism that tea might help prevent cancer is not clear.

Vitamin D

The ‘sunshine vitamin’ D helps the body use calcium and phosphorus to make strong bones and teeth. We get it mostly via sunlight on the skin, but it can also be sourced from some foods and dietary supplements. Studies suggest that higher levels of vitamin D in the blood may be associated with a reduced risk of colorectal cancer. Most South Africans get plenty of vitamin D through a few minutes’ daily exposure to the sun.

General diet

Some studies of cancer cells in the lab and in animal models have provided evidence that isolated compounds may be carcinogenic or have anticancer activity. But with few exceptions, studies of human populations have not yet shown definitively that any dietary component causes or protects against cancer.

Rather, eat well and exercise regularly to boost overall health, physical functioning and immunity. Reducing the risk of being overweight/ obese in turn reduces your risk of several chronic illnesses, including some cancers.

Discovery Vitality rewards healthy eating by giving you cash back on healthy food purchases through the Healthy Food Benefit.
Fruit and vegetables on the benefit are treated as follows:

• Healthy: all fresh and frozen vegetables and fruit and fresh herbs, dried fruit with no added sugar and dried vegetables with no added ingredients to be considered
• Neutral: canned fruit and vegetables, dried fruit with added sugar, dried vegetables with added ingredients
• Unhealthy: None