The Truth About Vitamin C and Cancer

  • 13 Nov 2017
  • Reading time 25 mins
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Vitamin C, especially in large amounts, is one of the most effective natural and non-toxic ways to both prevent and treat several kinds of cancer. See the latest compelling evidence.

First shown to be a powerful anti-cancer agent in 1971, it wasn’t until the 90’s that vitamin C started to be accepted by the mainstream medical profession as having a role in cancer prevention. Eating a vitamin C-rich diet substantially reduces the risk of several cancers, and high intakes – above 5,000mg a day (the equivalent of 100 oranges) – substantially increases the life expectancy of cancer patients.

The overwhelming evidence is that a high intake of vitamin C correlates with a low risk for cancer. In 1991, Dr Gladys Block, formerly with the National Cancer Institute, published a review[1] of vitamin C research which concluded that there was very strong evidence of a protective effect of vitamin C for non-hormone cancers. Of the 46 such studies in which a dietary vitamin C index was calculated, 33 found statistically significant protection. After completing a further review in 1991, Dr Block published a review[2] later that year of studies linking vitamin C with cancer prevention, Dr Block concluded:

“Approximately 90 epidemiologic studies have examined the role of vitamin C or vitamin-C-rich foods in cancer prevention, and the vast majority have found statistically significant protective effects. Evidence is strong for ¬cancers of the oesophagus, oral cavity, stomach and pancreas. There is also substantial evidence of a protective effect in cancers of the cervix, rectum and breast. Even in lung cancer there is recent evidence of a role for vitamin C.”

Numerous studies have found a link between vitamin C intake and the incidence of several different cancers, especially non-hormonal cancers[6]. Also, having a high plasma level of vitamin C cuts your risk of dying from cancer[7]. While one analysis of 12 clinical studies found that, ‘Vitamin C intake had the most consistent and statistically significant inverse association with breast cancer risk&rsquo[8], the evidence of an associated decreased risk for breast cancer is not as strong. One study involving 34,000 post-menopausal women, reported no association between the intake of vitamins A, C and E and a reduced risk of developing breast cancer[9].

Since then studies have shown that a high intake of vitamin C and vitamin C rich foods is associated with lower risk of several types of cancer[6]. Also, having a high plasma level of vitamin C cuts your risk of dying from cancer[7]. In recent years vitamin C’s protective effect against lung cancer[25], gastric cancer[26], pancreatic[27] has strengthened. While one study did find a protective role in relation to prostate cancer[28], however other studies have not confirmed a significant role of vitamin C reducing risk of either prostate or breast cancer. While one analysis of 12 clinical studies found that, ‘Vitamin C intake had the most consistent and statistically significant inverse association with breast cancer risk[8], the evidence of an associated decreased risk for breast cancer is not as strong. One study involving 34,000 post-menopausal women, reported no association between the intake of vitamins A, C and E and a reduced risk of developing breast cancer[9]. Same as previous paragraph

The WCRF (World Cancer Research Fund) conclude that there is no evidence of a relationship between vitamin C intake and prostate cancer and insufficient evidence for breast cancer. The studies to date do suggest a big difference between the causes and treatment of hormone-related cancers and those of the lung or digestive tract. These lung and digestive tract cancers may be more related to oxidant carcinogens, and prevented by increasing one’s intake of anti-oxidant nutrients. Having an intake above 100mg a day cuts risk of lung cancer substantially[10].

However hormone-related cancers have hormonally driven risk factors such as raised insulin and IGF-1(elevated by dairy products) and excess oestrogens, also linked to weight gain and metabolic syndrome.

Overall, the research to date strongly supports the importance of eating a diet rich in vitamin C (see below). While ¬supplementing 1–5g vitamin C may help prevent some cancers, cancer patients are most likely to benefit from considerably higher doses.

In terms of your diet the table below shows which foods contain the most vitamin C per calorie of food. The figures in brackets are the amount of vitamin C in 100g, which is roughly equivalent to a cup or serving. 

Peppers (100mg) Papayas (62mg)
Watercress (60mg) Peas (25mg)
Cabbage (60mg) Melons (25mg)
Broccoli (110mg) Oranges (50mg)
Cauliflower (60mg) Grapefruits (40mg)
Strawberries (60mg) Limes (29mg)
Lemons (80mg) Tomatoes (60mg)
Kiwi Fruit (85mg) Tangerines (31mg)
Brussel Sprouts (62mg) Mangoes (28mg)

HIGH DOSE VITAMIN C IN CANCER TREATMENT

However, the real gold is the potential of high doses of vitamin C, either given orally or by intravenous infusion (IV vitamin C) to dramatically suppress cancer cell growth.

The first ever study in which vitamin C was given to cancer patients was carried out in the 1970s, by Dr Linus Pauling and Dr Ewan Cameron, a cancer specialist, working in Scotland. They gave 100 terminally ill cancer patients 10g (10,000mg) of vitamin C each day and compared their outcome with 1000 cancer patients given conventional therapy. The survival rate was five times higher in those taking vitamin C. By 1978, while all of the 1000 ‘......

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