Iron deficiency Meat is an important iron source, so vegetarians must be careful to include good iron sources such as eggs, leafy green vegetables, dried fruit, fortified cereals, peas, beans, nuts and pulses. Iron from vegetable sources is less easily absorbed than from meat sources, but the absorption is improved by vitamin C, so a good vitamin C source such as fruit or fruit juice should be included with every meal. Iron absorption is reduced by tannins in tea and coffee, so these, ideally, shouldn't be drunk with a meal.
Vitamin B12 deficiency and calcium deficiency These are only usually a problem if dairy products are not included in the diet. Although meat is a good source of B12, sufficient quantities can be found in eggs, cheese, milk and yoghurts. Yeast products such as Marmite are also a good source. Non-dairy sources of calcium include sesame and sunflower seeds, and pulses such as peas, beans and lentils.
Vitamin D deficiency Fish and fish oils are the best dietary source of Vitamin D, but eggs and milk products provide some. In the UK, margarines are re-inforced with vitamin D, as are some cereals. The main source of vitamin D is through the action of sunlight on the skin, so dietary sources are less important for many vegetarians, but can still be important for those who get little sun exposure, or for children, whose bones are growing.
Amino-acid balance and protein content Body proteins are made from amino acids, many of which are derived from dietary proteins. Animal proteins are the most easily accessible form of protein, and contain a wide range of amino acids. Although dairy products provide a good protein source for most vegetarians, it is important to have protein from other sources also. Vegans are at highest risk of protein deficiency, as vegetable proteins are often low in certain essential amino acids such as lysine and methionine. Regular inclusion of rice, nuts, seeds and grains is important to ensure a good amino-acid balance.
Minerals Vegetarians have often been found to have lower blood levels of some minerals such as copper, zinc and selenium. Crops grown with artificial fertiliser are particularly low in minerals. It may be sensible for vegetarians to take a multimineral supplement.
Meat-eating
Good points
Meat is a good source of protein, iron, B-group vitamins, and calories. The wide variety of meat products available makes it easy to have a varied and enjoyable diet without much inconvenience. As a meat and fish eater myself, I would add that they simply taste great, and for many people, turn eating into a source of great pleasure. Nutrition experts generally agree that there is little convincing evidence that meat itself is bad. The amount of meat eaten, and especially the amount of red meat (beef, lamb and pork) is more important when looking at health risk. Inclusion of some low-fat meat and fish doesn't seem to be in any way harmful, and can be beneficial in lowering the risk of nutrient deficiencies.
Bad points
There are health concerns relating to diets with a high meat content. Many nutritionists advise limiting red meat intake to less than 80g (about 3oz) a day, and eating more fish and poultry.
The two main concerns relating to high red meat intakes are:
High saturated-fat intake, leading to increased levels of blood cholesterol, and an increased risk of coronary heart disease and strokes
A possible increased cancer risk, especially colon cancer.
These risks may be a direct effect of the meat itself, but may possibly be due to the filling effect of the meat, and so the relatively poor intake of fruit, vegetables, pulses and grains in big meat eaters. There is only so much room on your plate and in your stomach, and a meat-rich meal doesn't leave much scope for plant-based foods. It has been suggested that meat should be 'used as a condiment', to add flavour and interest to a plant-food diet.
Other detrimental effects of a diet with a high meat content include:
Low fibre intake
Higher salt intake, particularly with products such as bacon, sausages, burgers and processed meats. Cold meats such as ham and salamis have a high salt content.
So which is healthier?
A well-balanced diet of either kind is good for you. With any diet, it is important to incorporate a wide range of foods to ensure a good nutrient intake. An omnivorous diet that has a limited red meat content and includes plenty of fruit and vegetables doesn't appear to be any less healthy than a vegetarian diet. A recent study showed that people who ate raw/salad vegetables three to four times a week suffered up to 50% less heart disease and cancer than non-salad eaters, regardless of how much meat they ate.