Could vitamins reduce the risk of cancer?
Bupa investigative news - 8 August 2003
written by Rachel Newcombe, reporter for Bupa's Health Information Team
A poor diet and nutrient intake are already known to have links with illness and disease, but according to a new French study, taking a vitamin and mineral supplement could help reduce the risk of cancer. But what did the study actually involve? And is it really possible that a daily pill could provide all the health protection we need?
KEY POINTS
The cells in our bodies can be damaged by molecules called free radicals. This cell damage can sometimes lead to cancer.
Nutrients in fruit and vegetables (known as antioxidants) protect our cells by neutralising these free radicals. Antioxidants include vitamins A, C and E.
French researchers carried out a large study involving 13,000 men and women to investigate the effects of a pill containing a number of vitamins and minerals.
Half the study volunteers were given a placebo pill and the other half were give a supplement pill, containing beta-carotene, vitamin C, vitamin E, selenium and zinc. They were followed up for an average of 7.5 years.
The researchers discovered that the supplements appeared to have an effect on men, but not on women. The supplements reduced men's risk of developing cancer by 31 per cent and lowered the overall male death rate by 37 per cent.
Experts agree that vitamins and minerals are beneficial for health and offer some protective effects against cancer and heart disease, but say the primary source should be from fruit and vegetables in the diet.
It's unclear exactly why only men seemed to benefit from the supplements, although it's suggested that perhaps they had a poorer diet to start with.
What were the headlines?
The news of the cancer-busting properties of this vitamins and minerals combination was picked up by a few publications in the UK. Reports carried headlines such as, "Vitamin cocktail cuts cancer deaths", "Vitamins 'cut cancer death rates by 37 per cent'", "Healthy diet sees cancer rate fall 37 per cent" and "Pill cancer KO".
The length and depth of coverage varied considerably, from a brief mention to a more detailed report of the key findings.
What is the bigger picture?
The research was carried out in France, led by Dr. Serge Hercberg from the Scientific and Technical Institute for Nutrition and Diet in Paris, and was called the SuViMax study. A total of 13,017 men and women aged between 35 and 60 years old were recruited to take part. Half were given a daily supplement containing a combination of antioxidant vitamins, while the others received a placebo pill.
The results were recently presented at a meeting and are due to be published in Inserm's Formation Sante publication.
The vitamins and minerals supplement pill contained:
- 6mg beta-carotene
- 120mg of vitamin C
- 30mg of vitamin E
- 100 micrograms of selenium
- 20 milligrams of zinc
The participants were followed up over a 7.5- year period. Over the course of the follow up, 103 men and 71 women died. Cancer affected 562 people and was the major cause of death (56 men and 47 women died from cancer) and 271 people were affected by heart disease (28 men and 5 women died from heart disease).
The overall results showed that the supplement didn't appear to have an effect on heart disease, and nor did it affect cancer rates in women. However, it did seem to correlate with a 31 per cent reduction in the risk of all cancers in men, plus the overall death rate in men was 37 per cent lower in those taking the supplement.
According to the researchers, the pill's lack of effect on women's health risks might be due to the women volunteers having a better balanced diet than men. In this way, the women would be getting all the vitamins and minerals they needed from the fruit and vegetables in their regular diet.
Although the supplements seemed to be beneficial, the researchers are not suggesting that people should take vitamins instead of eating healthily. One reason for this is that a diet that high in fruit and vegetables can help with other health issues. Instead, the researchers recommend including more fruits and vegetables into one's diet to act as a natural source of antioxidants.
"This study highlights the health benefits of essential vitamins and minerals. The best source of these nutrients is a healthy balanced diet that includes plenty of fresh fruit and vegetables."
Dr Rebecca Small,
associate medical director
Bupa Group
What does this mean?
Pamela Mason, a spokesperson for the Health Supplements Information Service (HSIS), was interested in the study. "On the face of it, it looks like quite a good study," she explained to Bupa. "It was well-planned, they used a lot of subjects and it took place over several years."
Pamela Mason says that supplements can be beneficial in certain situations, but she believes that "in the first instance, people should always try to get the nutrients through their diet". She also expressed caution at the fact that the French researchers included beta-carotene in the supplements. Some previous studies of this vitamin, including a Finnish study in 1994, have indicated that smokers who take beta-carotene are at a higher risk of lung cancer. "We've got a lot yet to learn about beta-carotene," she said, "but I certainly wouldn't want to recommend it in smokers."
Dr. Sarah Schenker, a dietician from the British Nutrition Foundation, agrees that fruit and vegetables should be the main source of vitamins and minerals. She told Bupa, "There's far more evidence to show that eating fruit and vegetables containing vitamins and minerals is more beneficial than taking vitamin supplements. We do know that some of the supplements work, and that some do have antioxidant effects, but the research is overwhelmingly for fruit and vegetables, rather than for particular supplements and vitamins."
The Food Standards Agency FSA were also keen to emphasise that the primary source of vitamins and minerals should be from foodstuffs and not supplements. The agency warned that some research has shown that "taking large amounts of beta-carotene supplements could increase the risk of cancer in some people". As such, they say that it is best not to take more than 7mg beta-carotene per day in supplements - food sources, however, are believed to be safe.
Dr. Julie Sharp, science information officer at Cancer Research UK, told Bupa, "Eating a healthy diet could prevent up to one third of all cancers. There is good evidence that a diet rich in fruit, vegetables and fibre, and low in fat and red meat, can reduce the risk of the disease. Antioxidants [including some vitamins] are thought to protect our cells from the damage that causes cancer by 'mopping up' free radicals."
She added that, "It is only just being established which components of our diet protect against cancer or indeed place us at increased risk of some forms of the disease. Large studies are in progress to establish which components of our diet have the greatest effect on cancer risk."
ACTION POINTS
Aim to consume a healthy, balanced diet with a wide variety of fresh foods, including fruit and vegetables.
The daily recommendation is to eat five portions of fruit and vegetables. For more on this, please see our Bupa What is a portion of fruit or vegetables? article.
If you want to take supplements and need advice, Pamela Mason advises consulting a GP, practice nurse, dietician or pharmacist.
Food sources rich in the particular vitamins and minerals included in this study's supplement pill include:
- Beta-carotene: carrots, red pepper, spinach, dark leafy vegetables, mango, peaches, apricots
- Vitamin C: oranges, kiwi, brussel sprouts, sweet potatoes, peppers, broccoli
- Vitamin E: vegetable oils, eggs, green vegetables, nuts, whole grains
- Selenium: Nuts (particularly brazil nuts), fish, meat, seeds, bread
- Zinc: Meat, liver, seafood, milk, bread, cereals
What does this mean to me?
All vitamins and minerals have a range of key functions, but according to the FSA:
- Vitamin C helps to protect cells and keep them healthy, and helps the body absorb iron from food.
- Vitamin E helps to protect cell membranes.
- Selenium helps to protect cells.
- Zinc helps to make new cells and enzymes, helps the body process fat, protein and carbohydrate from food and aids in the healing of wounds.
- Beta-carotene is turned into vitamin A, and helps strengthen immunity, aids vision and helps to maintain the health of skin and mucus.
The key to healthy eating, however, is not to concentrate solely on eating foods that contain the vitamins listed above. Instead, Dr. Schenker told Bupa, it's important to eat all types of fruits and vegetables. "They all have a different array of antioxidant vitamins and minerals in them," she explained. "So, whereas you get some of the plant chemicals in the broccoli or cabbage group of vegetables, you wouldn't find those in the ones containing beta-carotene, for example, but that's just as important." In other words, variety is the key.
Cancer Research UK's Dr. Julie Sharp had similar advice. "People should try to eat five different portions of fruit and vegetables per day which provide both vitamins and fibre. Supplements should not be used as a substitute for a healthy balanced diet. Fruit and vegetables contain many different compounds, including vitamins, flavonoids and carotenoids, which are classed as antioxidants."
And, the good news is, that our diets is one area that we can control to lower our risk of developing cancer. Pamela Mason summed up, "Diet is considered to be linked to about one third of cancers. Although there are a lot of other risk factors, such as genetics, gender and family history, at least with lifestyle factors, such as diet, exercise and smoking, you've got the potential to change them."
Summary
The results of this French research add to our existing knowledge of the benefits of antioxidant vitamins and minerals for health. Although supplements can be helpful in some situations, the overwhelming view is that eating a balanced diet that includes five portions of fruit and vegetables a day is best way to obtain the nutrients we need.
Links for more information
- Bupa's vitamin article
- Bupa Vitamins and exercise article
- Bupa What is a portion of fruit or vegetables? article
- Previous Bupa news about selenium and cancer
- Cancer Research UK
- British Nutrition Foundation
- Food Standards Agency website
