In 1989, a poll found that 3% of the UK’s population was vegetarian. This figure has recently been estimated to be 5.7%. There are, of course, many ethical and environmental reasons to choose a plant-based diet, however, there is debate surrounding the health implications. Is eating meat good for us or are we better off without it? This article considers recent research concerning vegetarian’s health, leaving aside any ethical debate. Is the vegetarian diet the best option for our health and how can common deficiencies be avoided?
There are many statistics that are commonly quoted in favour of vegetarianism. For example, vegetarians have:
Lower cholesterol (LDL) and blood pressure
Lower risk of cancer
Lower risk of type-2 diabetes
Average life expectancy of 9.5 years longer for men and 6.1 years for women
Lower average BMI
Lower obesity rates (16.7% compared to 33.3% for meat eaters)
Lower rate of food allergy development
The BBC’s recent programme ‘How To Stay Young’, follows this line of research. The study of Loma Linda is discussed, highlighting that people here ‘live up to 10 years longer than the average Californian’. Within this town, the main religion encourages vegetarianism and a high proportion of the population is vegan. A questionnaire carried out here also found the vegan diet to be associated with the best overall health, and mortality being reduced by one quarter.
However, vegetarians also generally have a higher level of education, exercise more regularly and are less likely to smoke or drink alcohol excessively. This data has repeatedly been found by studies, for example the American Journal of Clinical Nutrition 2009, and the Journal of American Diet Association. This means that it is difficult to establish a causal relationship between the correlations found between improved health and vegetarianism.
The difficulty of drawing conclusions from this data is demonstrated by the 1996 BMJ study of 11000 health conscious individuals. These people were recruited from health food shops, vegetarian societies and magazines. The group had a mortality rate around half of that of the general population. Within the group, 43% of the subjects were vegetarian, and they were not found to have any significant differences in mortality. It appears that intervention studies would provide clearer health advice than observational studies when assessing the impacts of a vegetarian diet. However, this sort of data is not easy to come by.
Following a vegan or vegetarian diet also increases the risk of several deficiencies. There are ways to avoid these, but this often requires a fair amount of planning that would not need to cross the minds of meat eaters.
Deficiency of vitamin B12 is fairly rare amongst meat eaters (only 5%), compared to 68% of vegetarians and 83% of vegans. This is because vitamin B12 is found only in animal-based products, such as meat, fish, eggs and dairy. This means that in a vegan diet this vitamin must be obtained through dietary supplements.
Deficiency is not to be taken lightly, as it can cause anaemia and nervous system damage. Common symptoms include low energy levels, tingling, numbness, blurred vision, confusion and poor memory.
This is an amino acid that is found exclusively in meat and fish. It is not an essential amino acid as it can be manufactured by the liver, however, around half of the body’s creatine is obtained from the diet. The synthesis of creatine also requires several dietary substances, including vitamin B6 and B12., which are generally lacking in a vegetarian diet. Creatine is necessary for muscle energy and nervous system function. A deficiency of creatine is not common, however, lower levels are generally found in vegetarians with could still be detrimental. Increasing levels of creatine have, for example, been found to be associated with memory improvement (2010 British Journal of Nutrition). Creatine can also be taken as a supplement, which may therefore be advisable for many vegetarians.
This is a dipeptide formed from beta-alanine and histidine. When carnonise is eaten it is digested by enzymes into these two amino acids. Therefore, the body must produce its own carnosine using the building blocks. Beta-alanine is found in meat and fish, so is usually lacking in vegetarians. Carnosine is a popular supplement against ageing as it protects against several of these processes. Carnosine is mainly found in our muscles and is known to improve their performance. Dietary supplements of Beta-alanine have been shown to be the most effective way of increasing carbonise in the body.
Vitamin D deficiency is extremely common amongst both omnivores and vegetarians. The most common dietary sources are meat, fish and eggs, however even eating large amounts of these foods may not be satisfactory. The National Health and Nutrition Examination Survey found 45% of the US population to be deficient between 1988 and 1994, whereas 77% were found to be deficient 10 years later. Statistics on vitamin D deficiency are usually based on a level of 10ng/ml in the blood, whereas several studies have found 30ng/ml to be an optimum level for health. By these standards, 90% of the UK population would be deficient throughout the winter. There are two main types of vitamin D in the diet. These are vitamin D2 (which is found in plant-based foods) ad vitamin D3 (which is found in animal products). These two types of the vitamin are metabolised very differently in the body and a study published in the American Journal of Nutrition very clearly stresses the advantages of D3 over D2. There are, however, vegetarian vitamin D3 supplements available and the body naturally synthesises vitamin D3 when exposed to sunlight. Since over 90% of our vitamin D should be produced due to sunlight anyway, the dietary factors are less significant. The risk for everyone in the population is high, not only vegetarians.
This is an omega-3 fatty acid which is found in animal products, especially in fish. It is used throughout the body as a structural fat, such as in the brain, eyes and heart. 30% of the structural fat in the grey matter of the brain consists of DHA, and it is thought to be important in the development and maintenance of the brain.
It is possible for the body to manufacture DHA from a different omega-3 (ALA). ALA can be easily consumed as part of a vegetarian diet, as it is found in flaxseeds, chia seeds and walnuts. The trouble here is that the body is not very efficient at this conversion and so lower levels are usually found in the blood plasma of vegetarians and vegans. Lower levels are also found in the breast milk of vegan mothers, however, the impact of this on infants is unclear. Vegan sources of DHA are available in the form of supplements made from algae. It is therefore easily possible to avoid deficiency whilst following a plant based diet.
Iron deficiency is the most common deficiency across the world. It is estimated that 30% of the total population are anaemic and this figure varies hugely between different groups. For example, menstruating and pregnant women have larger daily requirements of iron, causing higher incidence of deficiency. 8.7mg or iron are required daily for men, compared to 14.8 for women. The average daily intake of iron from food sources is 16.3–18.2 mg/day in men and only 12.6–13.5 mg/in women.
Vegetarians generally do not have higher rates of anaemia than average, but this is likely to be due to other lifestyle differences. Following a vegetarian diet significantly reduces the number of iron sources available, so paying more attention to iron consumption is important.
There are 2 main types of iron: heme-iron and non-heme iron. Heme-iron is found in meat, and is readily absorbed into the body. Non-heme iron (unfortunately for vegetarians) is less easily absorbed, and is more easily absorbed in the presence of heme-iron. Despite this, it is possible for a vegetarian to consume an adequate amount of iron, without supplementation.
Good sources of non-heme iron include:
Sulphur is mainly found in animal based foods, and is a necessary component of 4 amino acids. Meat and fish are described as ‘complete’ protein sources because they contain all 9 essential amino acids (including methionine which contains sulphur). With these 9 amino acids, the body is capable of synthesising any other amino acid we need.
The sulphur that we need to manufacture amino acids in our bodies is mainly obtained from protein in our diets, and vegetarians are at higher risk of sulphur deficiency. Sufficient sulphur can easily be found in a vegan diet in the form of legumes, soy products, nuts, seeds and grains. Processing of foods can, however, reduce sulphur content, as can growing crops in sulphur deficient soils.
PubMed (Vegetarian diets: what do we know of their effects on common chronic diseases)
BMJ (Dietary habits and mortality in 11,000 vegetarians and health conscious people: results of a 17 year follow up)
The Vegan Society
mercola.com(How to avoid common nutrient deficiencies if your a vegan)
The Health Delusion
The Western A.Price Foundation (Vegetarianism and Nutrient Deficiencies)
British Journal of Nutrition (the influence of creatine supplementation on the cognitive functioning of vegans and omnivores)
Vegetarian Journal (about vitamin)
JAMA International Medicine (Demographic differences and trends of vitamin D insufficiency in the US population 1988-2004)
Journal of the Academy of Nutrition and Dietetics
The American Journal of Nutrition
PubMed-Health benefits of docosahexaenoic acid
British Nutrition Foundation (Briefing Paper)
Dr. Fuhrman – Smart Nutrition website
World Health Organisation – Micronutrient deficiencies
The American Journal of Clinical Nutrition – Iron status of vegetarians
healthise – sources of iron
USDA – National Nutrient Database for Standard Reference Release
The Journal of Nutrition – the sulphur-containing amino acids: an overview