Vegetarian diet and health problems
In this fact sheet: Coronary heart disease, Cholesterol, Hypertension, Cancer, Diabetes, Osteoperosis
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What effect can a vegetarian or vegan diet have in avoiding or reducing the impact of health problems and serious medical conditions?
Diet influences our health and contributes to major degenerative diseases such as heart disease, stroke and diabetes. Meat consumption, low fruit and vegetable intake, obesity and high cholesterol are all contributory factors of these diseases. A balanced vegetarian diet is one of the easiest ways to follow official healthy eating guidelines, with 5 portions of fruit and vegetables a day, plenty of complex carbohydrates and antioxidants, as well as lower saturated fat and cholesterol. A balanced vegetarian diet tends to be lower in calories and higher in fibre so can also help maintain a healthy weight. Important studies focusing on the health of vegetarians include these large cohort studies:
- Oxford Vegetarian Study
- Oxford EPIC study of cancer and nutrition
- American Adventist Health Study
Vegan and vegetarian diets are nutritionally adequate if they are carefully planned. The British Dietetic Association and the American Dietetic Association provide guidelines for a healthy vegetarian diet. For both vegetarians and meat eaters, the key to a nutritionally adequate diet is balance and ensuring that, where foods are specifically omitted, suitable alternatives are included so that dietary quality is not compromised (BNF 2005).
Coronary heart disease (CHD) and Mortality
The largest study ever conducted in the UK (EPIC-Oxford study) comparing rates of heart disease between vegetarians and non-vegetarians found that vegetarianism can reduce the risk of heart disease by 32%. This study also showed that meat eaters had a 47% increased risk of heart disease if an inverse hazard ratio was applied to the statistics (Crowe et al. 2013).
The Adventist Health Study assessed the link between vegetarian diets and reduced mortality and found that vegetarians, vegans and 'pesco-vegetarians' were 12% less likely to die in a 6 year follow up than non-vegetarians. Vegetarian men had more to gain than women, with significant reductions in cardiovascular disease and ischemic heart disease (Orlich et al. 2013).
Phillips et al (2004) found that changing to a vegetarian diet may lead to a change in body composition with results showing vegetarians typically had a BMI approximately 1-2kg/m2 less than non-vegetarians.
Soluble fibre can help keep cholesterol under control and a balanced vegetarian diet has up to twice as much fibre as the national average. Soya foods and nuts have been shown to be especially helpful in keeping cholesterol down.
Hypertension (high blood pressure)
Raised blood pressure is a major contributory factor for heart disease and stroke. A 5 mmHg increase in diastolic blood pressure increases stroke risk by 34% and heart disease by 21%. (MacMahon et al 1990). The EPIC-Oxford study reported lower systolic (men - 4.2 mmHg and women - 2.6 mmHg lower) and diastolic blood pressures (men - 2.8 mmHg and women - 1.7 mmHg lower) and a lower prevalence of hypertension among vegans compared to meat-eaters. This was largely attributable to differences in BMI between the groups (Appleby et al. 2002).
Cancer is the number one cause of death in the world and diet is estimated to cause approximately 30% of all cancers in developed countries. An Adventist Health Study in 2012 assessed the link between different types of vegetarian diets and overall cancer incidence. Statistical analysis showed a clear association between vegetarianism and a lower risk of cancers. This association was clearest with a vegan diet, where there was a lower incidence of all cancers. Lacto-ovo-vegetarians showed a decreased risk of cancers of the stomach and bowel, and vegan women had fewer female-specific cancers (Tantamango-Bartley et al 2012). In the EPIC-Oxford study, Key et al (2009) found that the total cancer incidence was significantly lower in vegetarians than meat eaters, but this could not be ascribed to one of the major cancer sites.
The World Cancer Research Fund describe meat eating as a 'convincing' risk for colon cancer and highlights strong evidence linking red meat to a higher risk of cancer and processed meat to a higher risk of bowel cancer.
High temperature cooking of meat (e.g. barbecuing, grilling and frying) has been associated with raised cancer risk (Knize et al. 1999) because these cooking methods are thought to produce potentially carcinogenic substances (such as heterocyclic amines).
Diabetes is often associated with raised blood cholesterol levels but a vegetarian diet can help lower cholesterol levels. Soya foods and nuts, rich in plant proteins and slowly absorbed carbohydrates with a low glycaemic index, can be beneficial in avoiding and managing type 2 diabetes.
Osteoporosis is a complex disease characterised by low bone mass and deterioration of bone tissue, leading to increased bone fragility and greater risk of fracture. Studies examining the association between vegetarianism and bone density have found conflicting results. However, as a meat-free diet results in reduced consumption of sulphur-containing amino acids, it is suggested that the lower acidity may reduce bone loss in postmenopausal women and help protect against osteoporosis (Itoh et al. 1998).
Any questions regarding this information sheet please contact firstname.lastname@example.org | Last updated October 2013