Vegetarian

Vegetarian diets have increased greatly in popularity in the last 20 years, with a growing number of studies linking eating meat to a greater risk of heart disease and other degenerative disorders. A balanced vegetarian diet supplies all the vitamins and minerals the body requires and is usually higher in fiber and lower in fat, cholesterol, protein and sugar than the typical Western diet.

Vegetarian Diet and Disease

Many medical studies have shown that a low fat vegetarian diet can lessen the risks of developing cardiovascular disease, diabetes, osteoporosis, kidney stones and other common diseases. Vegetarians usually have lower cholesterol and blood pressure than people who eat meat. Low fat, high fiber diets that include a variety of fruits, vegetables, whole grains and beans also help to prevent cancer.

The results of a 17-year study involving 11,000 vegetarians were published in the British Medical Journal in 1996. Researchers investigated the links between dietary habits and disease in vegetarians and health conscious people. The results showed that overall, the mortality rate in this group was around half that of the general population, and that daily consumption of fresh fruit was associated with a lower risk of death from any disease.1

 

The Vegetarian Diet

Vegetarians choose their diets for reasons of culture, belief or health. There is no single vegetarian eating pattern, and diets differ in the extent to which they avoid animal products. Vegans completely exclude meat, fish, poultry, eggs and dairy products. Lacto-vegetarians avoid meat, fish, poultry and eggs. Lacto-ovo vegetarians avoid meat, fish and poultry.

The more restricted the diet, the more care must be taken to ensure that all nutrient needs are met. A vegetarian diet does exclude rich sources of several nutrients such as iron, zinc and vitamin B12, and it is important to include plenty of alternative plant sources of the vitamins and minerals commonly found in meat, fish and eggs. Milk is a good source of calcium and riboflavin, and may supply as much as half the daily needs. Other sources, such as dark green leafy vegetables, must be eaten in quite large quantities in order to meet these needs.

A balanced diet for a lacto-ovo vegetarian might include all of the following foods in a day:

l two to three servings of low fat milk or milk products.

l three to four servings of protein-rich cooked dried beans and peas, seeds or nuts.

l at least five servings of fruits and vegetables.

l at least six servings of whole grain breads and cereals.

Protein

Proteins are made up of 20 main naturally-occurring amino acids and some other minor ones. Some of these amino acids are essential constituents of the diet as they cannot be made in the body, whereas others are nonessential. Meat, fish, eggs, milk and soybeans contain all the essential amino acids and are known as complete proteins. Grains, beans, peas, nuts and seeds contain some amino acids and not others, and are called incomplete proteins. Two incomplete protein foods, eaten together, can provide a complete protein, for example, baked beans on toast or lentils and rice.

A varied vegetarian diet provides adequate amounts of amino acids and usually meets or exceeds requirements for dietary protein. A typical Western diet is probably too high in protein, and vegetarians often eat less protein than meat eaters. This may partly explain their reduced risk of many degenerative diseases as high protein intakes promote excretion of essential minerals.

Fats

Vegetarians often have a higher intake of omega-6 polyunsaturated fats from nuts, seeds and vegetable oils. A high intake of these fats has been linked to an increased risk of cancer, particularly when the omega-6 to omega-3 fatty acid ratio becomes too high. Those who avoid fish may not get adequate amounts of omega-3 oils in their diets and should make sure to include plant sources of omega- 3 oils such as flaxseed oil in the diet. Population studies have shown that, compared to vegetarians, those who eat fish tend to have lower blood pressures and lower blood fat levels.2

 

Vegetarians and Vitamins

Riboflavin

Riboflavin may be low in vegan diets as the main sources are milk and milk products. Other sources include fortified breakfast cereals, yeast extract and mushrooms. Someone who eats no milk or meat can meet the RDA for riboflavin by including all of the following in a daily diet: three slices of whole meal bread, a cup of almonds, half an avocado and average servings of spinach, broccoli and mushrooms.

Vitamin B12

Animal foods are the only reliable sources of vitamin B12. Vegetarians who eat dairy products generally obtain adequate vitamin B12 from these sources. Vegans tend to have lower vitamin B12 intakes which may not reach recommended levels, and should make sure they include vitamin B12-fortified foods or supplements in their diets. This is particularly important for women who are, or who plan to become, pregnant.

Sea vegetables and fermented soybean products such as miso also contain forms of vitamin B12, although some research suggests that the human body may not be able to absorb these forms and they may even block true vitamin B12 absorption.3 Many vegetarian and vegan products are fortified with vitamin B12, including yeast extract, vegetable stock and soya milk. In developing countries, food may contain bacteria and other micro-organisms which are a source of vitamin B12. In Western countries better hygiene and food processing removes these sources of vitamin B12.

Vitamin D

Vitamin D is present in vegetarian diets in dairy products. Vegans tend to have low vitamin D intakes, fortified margarine being the major dietary source. In most countries, sufficient vitamin D can be obtained through manufacture in the skin in response to sunlight. Vegans who do not get enough exposure to sunlight may be advised to take a vitamin D supplement; although pregnant women should not take large amounts as there is an increased risk of fetal deformities.

Vitamin E

Vitamin E needs increase in those whose diets are higher in polyunsaturated fats from nuts, seeds and vegetable oils. As vegetarians often have a higher intake of such fats, they need to make sure their vitamin E intake is adequate to protect against harmful free radical damage to these fats.

Vegetarians and Minerals

Refining removes most of the vitamin and mineral content from grains. For example, flour refining causes a 77 per cent loss in zinc; rice refining causes a loss of 83 per cent; and processing cereals from whole grains causes an 80 per cent loss. It is particularly important for vegetarians who avoid animal sources of minerals like zinc and iron to ensure their intake of whole grains is adequate.

Iron

Both vegetarians and nonvegetarians often have difficulty in meeting RDA for iron, but this is particularly the case in premenopausal vegetarian women. Iron is present in animal foods in organic 'heme' form and in plant foods in inorganic 'nonheme' form. The heme and nonheme forms of iron are absorbed by different mechanisms.4 About 20 to 30 per cent of heme iron is absorbed, compared with only around 2 to 5 per cent of nonheme iron. Vitamin C consumed in the same meal as nonheme iron improves absorption by up to 50 per cent as it helps to convert dietary iron to a soluble form and also helps counteract the reduction in absorption that occurs in the presence of phytates. Vitamin A and beta carotene can also improve nonheme iron absorption.5 Tea reduces the absorbability of iron and should be drunk between meals rather than with them.

A premenopausal woman can meet the RDA for iron by including all the following in a daily diet: ten dried apricots; three slices of whole wheat bread; one cup of lentils; and one cup each of cooked spinach, broccoli and green beans.

Iron levels in the body are controlled by absorption. When intakes in the diet are lowered, absorption ability can improve. Some research suggests that this gradually happens in vegetarians. In cases of iron deficiency absorption efficiency increases from around 5 to 10 per cent to about 10 to 20 per cent.

Zinc

Some vegetarians have lower than recommended zinc intakes as they avoid meat and seafood, which are good sources. Phytates also reduce zinc absorption. Vegetarians need to make sure that they include enough zinc-rich pulses, seeds and whole grains in their diets.

The RDA for zinc can be obtained by including all of the following in a daily diet: three slices of wholemeal bread, one cup of cooked chickpeas, a handful of pumpkin seeds, a serving of muesli, two tablespoons of wheatgerm, half a cup of almonds, a serving of peas and one ounce of peanut butter.

Calcium

Although vegans do not eat dairy products - which are the main sources of calcium - with careful planning, it is possible to get enough calcium from plant foods. Vegans may need slightly less calcium than meat eaters as they appear to have better absorption and lower excretion. However, studies of women who have followed vegan diets for long periods indicate that they may be at higher risk of osteoporosis and may benefit from calcium supplements.6

Leafy green vegetables, seaweed and tofu made with calcium sulfate are good vegetarian sources of calcium. The amount of calcium in tofu varies from brand to brand, and it is worth comparing quantities between different brands.

The RDA for calcium can be obtained by including all of the following in the daily diet: four ounces of firm tofu processed with calcium sulfate, a cup of cooked spinach, two oranges, a cup of broccoli, four slices of whole wheat bread and a cup of almonds. It can be difficult for vegan children to get enough calcium in their diets as they have to eat relatively large quantities of bulky food.

Iodine

Milk and milk products are important sources of iodine so vegans must be careful to include other iodine-rich foods in their diets. These include seaweed, cereals and vegetables grown in iodine-rich soil.

Vegetarians and Supplements

Vegetarians who are not always able to follow a varied, balanced diet may benefit from supplements. Women who are, or who hope to become, pregnant or who are breastfeeding may be advised to take vitamin B, calcium, iron and zinc supplements.

Iron supplements can be useful for premenopausal vegetarian women who often find it difficult to get enough iron. Zinc supplements are also useful and if taken for long periods, it is also advisable to take a copper supplement of around 2 mg per day.

Vegetarian Teenagers

Vegetarian diets can be safe for teenagers; although this presents special challenges as teenagers need sufficient calories, protein, vitamins and minerals for rapid growth. Again the key is to eat a variety of foods; including fresh fruit and vegetables, whole grain products, nuts, seeds, beans and peas, and preferably dairy products and eggs.

Vegetarian Children

A vegetarian diet can provide the nutrients needed for a child's growth and development. Research into vegetarian children has shown that they are similar to meat eaters in height, weight and skinfold measurement.7 They are also less likely to be obese. Vegan children tend to be lighter and leaner and may be shorter. Nutritional deficiencies are generally no more common in vegetarian children than among those who do eat meat, although in some cases iron levels may be lower.8

Children who eat vegetarian diets often eat fewer convenience foods and dairy products, and more starchy foods such as pulses, fruit and vegetables. Vegetarian girls may start menstruation at a slightly later age which may be protective against breast and other hormone-dependent cancers later in life. Vegetarian diets in children may be beneficial in protecting against disorders such as bowel problems, obesity, cardiovascular disease and cancer by establishing healthy dietary patterns which may be carried on into adult life.

Vegan diets are not usually recommended for children under 18 years of age due to sporadic eating habits and the relatively large volumes of food needed to meet the recommended intakes for nutrients such as calcium, iron and zinc.

Children Under Five

A diet that is healthy for an adult may not be appropriate for a very young child and high fiber, low fat diets may not be sufficiently high in certain nutrients. Young children need energy and nutrient-dense foods such as cereals, vegetable oils, bananas and avocados. Large intakes of high fiber or watery foods typically found in vegetarian and vegan diets may not be advisable in very young children.

 

1 Key TJ; Thorogood M; Appleby PN; Burr ML Dietary habits and mortality in 11,000 vegetarians and health conscious people: results of a 17 year follow up. BMJ, 1996 Sep, 313:7060, 775-9

2 Pauletto P et al. Blood pressure and atherogenic lipoprotein profiles of fish-diet and vegetarian villagers in Tanzania: the Lugalawa study. Lancet, 1996 Sep, 348:9030, 784-8

3 Dagnelie PC; van Staveren WA; van den Berg H. Vitamin B-12 from algae appears not to be bioavailable. Am J Clin Nutr, 1991 Mar, 53:3, 695-7

4 Uzel C; Conrad ME Absorption of heme iron. Semin Hematol, 1998 Jan, 35:1, 27-34

5 García Casal MN et al. Vitamin A and beta-carotene can improve nonheme iron absorption from rice, wheat and corn by humans. J Nutr, 1998 Mar, 128:3, 646-50

6 Chiu JF; Lan SJ; Yang CY; Wang PW; Yao WJ; Su LH; Hsieh CC Long-term vegetarian diet and bone mineral density in postmenopausal Taiwanese women. Calcif Tissue Int, 1997 Mar, 60:3, 245-9

7 Nathan I; Hackett AF; Kirby S A longitudinal study of the growth of matched pairs of vegetarian and omnivorous children, aged 7-11 years, in the north-west of England. Eur J Clin Nutr, 1997 Jan, 51:1, 20-5

8 Nathan I; Hackett AF; Kirby S. The dietary intake of a group of vegetarian children aged 7-11 years compared with matched omnivores. Br J Nutr, 1996 Apr, 75:4, 533-44