Diet, alcohol and cancer in the UK - statistics.

This post includes information on diet and cancer risk including alcohol, fruit and vegetables, salt, meat, fibre and other carbohydrates, dairy products and fat.

What we eat and the amount of alcohol we drink affects the risk of several cancers.

Tables 4.1 and 4.2 summarise what we know about diet and alcohol and the risk of certain types of cancer.

Alcohol

Alcohol is well established as a cause of cancer. It has been estimated that alcohol consumption causes at least 13,000 cancer cases in the UK each year - around 9,000 cases in men and 4,000 in women. 

Alcohol consumption increases the risk of oral (oral cancer includes cancers of the oral cavity, pharynx excluding nasopharynx and lip), laryngeal, oesophageal, breast, bowel and liver cancer. Risk of cancers of the upper aerodigestive tract (oesophagus, oral cavity, pharynx and larynx) increases linearly with quantity of alcohol consumed above 25g/day . Someone drinking 100 g/day has a 4-6-fold increased risk of these cancers compared to light or non-drinkers.

Table 4.3 shows the alcohol content of some common drinks.

Smoking and drinking heavily in combination increases risk of cancers of the upper aerodigestive tract up to 80-fold, and in developed countries, smoking and alcohol consumption combined have been estimated to account for 75% of all upper aerodigestive cancers. 

It takes up to 16 years for the risk of these cancers in a former drinker to fall to the level of someone who has never consumed alcohol. 

Long-term heavy alcohol consumption increases the risk of liver cancer, with around a three-to-six-fold risk increase for the heaviest drinkers. Light drinking may also slightly increase liver cancer risk. 

Alcohol increases bowel cancer risk, with a pooled analysis of 14 cohort studies reporting a 19% increase in risk for an increase of 100g/week. There was an increase in colon cancer risk in men and women separately at this level of consumption, and an increase in rectal cancer for the same intake in men only. 

There are various possible mechanisms for the carcinogenic effect of alcohol consumption at these cancer sites. Acetaldehyde, the primary metabolite of alcohol, has been shown to alter DNA and cause cell proliferation. Alcohol may act as a solvent for other carcinogens (for example tobacco smoke), may produce reactive oxygen species and nitrogen species and may interfere with metabolism of folate or other micronutrients. 

Risk of breast cancer increases by approximately 7-12% for every additional 10 g/day of alcohol. This association is probably mediated by an increase in oestrogen levels.

There is some evidence that alcohol consumption protects against kidney cancer, with a 28% risk reduction for an intake of 15 g/day compared with non-drinkers reported in a pooled analysis. 

There is weaker evidence for a reduced risk of non-Hodgkin’s lymphoma in alcohol drinkers, with a pooled analysis showing a 27% risk reduction in current drinkers, but no trend of lower risk with increasing levels of alcohol intake. 

Setting safe limits for alcohol intake is complex. Among post-menopausal women and men aged 40- plus, drinking one to two units a day can reduce the risk of coronary heart disease by 30-50%. 

The Government’s current recommendation is that men should not regularly drink more than 3-4 units/day and women should not regularly drink more than 2-3 units/day. However, the  European Code Against Cancer recommends no more than two and one units/day respectively to minimise the risk of cancer.

In 2009, 26% of men in Britain drank on average more than 21 units/week, and 7% more than 50 units. Eighteen percent of women drank on average more than 14 units/week, and 4% more than 35 units. The proportion of men and women in Britain drinking, on average, more than 21 units/week and 14 units/week, respectively, has fallen since 2002, and the proportion of heavy drinkers fell between 2006 and 2009.

On average, men in Britain drink 16 units a week, and women 8 units a week. Between 2002 and 2006, average weekly consumption fell by 15% in Britain, and has appeared to continue to fall since 2006, although there was no significant difference between 2008 and 2009.

Figure 4.1 shows alcohol consumption in Britain by socioeconomic group.

 

Fruits and vegetables.

Vegetables and fruits contain antioxidant nutrients such as vitamin C and carotenoids, folate and a range of phytochemicals (glucosinolates, dithiolthiones, indoles, chlorophyll, flavonoids, allylsulphides and phyytoestrogens).

The complex mixture of chemicals means it is difficult to pinpoint which ones can prevent cancer, and it is likely that the effects of fruit and vegetable consumption are due to the interactive effect of many different chemicals. 

Studies indicate that each daily portion - 80-100 grams - of fruit or vegetables halves the risk of oral cancer, reduces risk of squamous cell carcinoma of the oesophagus by approximately 20%,  and of stomach cancer by about 30%. 

People with the highest intakes of fruit and vegetables have up to an 80% reduced risk of laryngeal cancer. An increase of one portion a day of fruit reduces lung cancer risk by up to 14%.

However, given that smoking and alcohol cause large increases in risk for these cancers, and that people who drink or smoke heavily usually have lower intake of fruit and vegetables, it is possible that the lower risk shown for fruit and vegetables is actually due to smoking and alcohol.

There is evidence that higher intake of carotenoids may protect against advanced prostate cancer and gastric cancer. There is some evidence that selenium protects against prostate and lung cancer and prevents bowel adenomas. 

High folate intake has been shown to reduce risk of breast cancer in moderate-heavy drinkers. Most of these studies are based on body levels or dietary intake rather than supplements.

There is good evidence that vitamin D protects against bowel cancer and weaker evidence for a protective effect against breast and prostate cancer. The main source of vitamin D for people is skin absorption from sunlight.

Current government advice, in line with WHO recommendations, is that adults and children over five should have at least five 80g portions of fruits and vegetables a day (excluding potatoes). Men and women in the UK consume on average 4.4 portions of fruit and vegetables a day and 33% of women and 37% of men consume the recommended five portions a day. Just 7% of girls and 22% of boys aged 11-18 years are eating the recommended amount.

Figure 4.2 shows the sources of dietary energy in UK adults.

Dietary fibre

There is evidence that dietary fibre intake is protective against bowel cancer.  Results from the European Prospective Investigation show that a high fibre intake (average of 27g/day) is associated with a 20% lower risk of large bowel cancer when compared with the lowest intake (average of 17g/day), after inclusion of covariates such as physical activity, alcohol, smoking, red and processed meat and folate. Fibre was found to be particularly protective in people who consumed high amounts of red and processed meat.

Fermentation of fibre (non-starch polysaccharides, NSP) in the bowel produces short-chain fatty acids, which have known anti-cancer properties. NSP also contributes to stool bulk and prevents constipation.

The average daily intake of fibre as NSP from dietary sources per person in the UK is 14g, while the Department of Health recommended average intake is 18g a day.

Red and processed meat

Red and processed meat increases the risk of bowel cancer. Risk estimates for an intake of 120 g of red meat (generally including processed red meat) per day are around 25-35%.

Risk estimates for processed meat vary more widely, from 9-36% for a daily intake of 30 g. While the mechanisms remain unclear, processed meat is relatively high in nitrosamines, which are linked to some cancers, and it is thought that consumption of red meat causes the body to increase its own production of nitrosamines.

In Britain adults get around 11% of their daily energy intake from red and processed meats. ( Figure 4.1)

Salt and nitrites

A high intake of salt and salt-preserved foods increases the risk of stomach cancer. People eating more than 16g/day of salt have two-three times the risk of people eating 10g/day or less. Most evidence comes from countries with higher salt consumption than the UK, and it is unclear to what extent salt causes stomach cancer here.

Salt may increase cancer risk by increasing sensitivity of the lining of the stomach to carcinogens such as nitrates, or by directly causing mucosal damage and inflammation. On average, British men consume twice the recommended maximum (6 g/day for an adult) intake of salt and British women consume about 50% more than is recommended. 

Dairy products

A recent pooled analysis of cohort studies found a 16% reduction in risk of bowel cancer in people with a higher consumption of milk, which remained after adjustment for total calcium and vitamin D intake. 

There is weaker evidence that a high intake of dairy foods causes a slight increase in prostate and ovarian cancer risk. In British adults, dairy products contribute around 10% to the average daily total energy intake ( Figure 4.1).

Fat

A recent cohort study of breast cancer in a group of mainly pre-menopausal women reported an increase in risk for a higher intake of animal fat, and a pooled analysis of nine breast cancer cohort studies reported a 9% increase in risk with each 5% increase in saturated fat. 

A study using a food diary found a two-fold increased risk of breast cancer in women who consumed an average of 34g per day of saturated fat, compared with women who consumed low amounts. Intake recorded in a food frequency questionnaire by the same women did not correlate with breast cancer risk.

http://info.cancerresearchuk.org/cancerstats/causes/lifestyle/diet/The authors of the paper interpreted the discrepancy between these results as evidence that the lack of association between fat and breast cancer in many cohort studies is due to inaccuracy in recording diet. British men eat an average of 84g fat per day and British women an average of 61g, meaning that on average British adults are getting around one-third of their daily energy intake from fat; around one quarter of this total is animal fat. However, there has been a fall in the proportions of energy derived from fat in British adults over the last 20 years