This article, written by an expert vegetarian Nutritionist explains how a vegetarian diet differs from that of a meat diet in terms of vitaminEssential substances that cannot be produced by the body and so must be acquired from the diet. sources and advises on how vegetarians can ensure they have a healthy diet.
Vegetarian diets that are appropriately planned are both nutritionally adequate and healthy (1). However, as with any diet, if not appropriately planned a vegetarian diet can be low in some essential nutrients, in particular proteinCompounds that form the structure of muscles and other tissues in the body, as well as comprising enzymes and hormones., vitamins A, B12, riboflavin, D, ironAn element present in haemoglobin in the red cells., zinc, calciumAn element that forms the structure of bones and teeth and is essential to many of the body's functions. and omega 3. Plant foods often have lower nutritional density and are absorbed less efficiently.
The scope of this article is to discuss the vitamins which are most likely to be below recommended levels in a vegetarian diet and whether supplementation is necessary.
Vitamin A is essential for a healthy immune systemThe organs specialised to fight infection., night vision and healthy skin. The active form of vitamin A is found only in animal products, lacto-ovo-vegetarian forms of which include dairy products and eggs. Vegan diets rely on the conversion of carotenoids to vitamin A. Carotenoids are found in red and orange foods such as carrots, sweet potatoes, peppers and dried apricots, as well as green leafy vegetables. One large carrot alone provides adequate levels of carotenoids so if included in the diet on a daily basis this will ensure adequate levels of vitamin A. (Recommended daily levels of vitamin A retinol for men are 2310iu or 700µg, recommended levels for women are 1980iu or 600µg.)
Vitamin B complex is important for the nervous systemThe network of nerves, which are bundles of nerve fibres carrying information in the form of electrical impulses., including digestion and stressRelating to injury or concern. response as well as energy creation. Vegetarian foods rich in B vitamins include whole grains, beans and pulses. These are foods that should be at the core of any vegetarian diet – they are good, low calorie sources of many of the vitamins and minerals that would alternatively be obtained from meat. However vegetarian diets, in particular vegan diets, are commonly low in riboflavin (B2) and B12. Riboflavin is essential for healthy red bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. cells and is found in the most concentrated forms in animal products, lacto-ovo-vegetarian sources of which include eggs and dairy. Plant-based sources include whole grains, nuts, mushrooms and soya beans. For vegans, a large bowl of oats, almonds and soya milk/yoghurt for breakfast would provide roughly half the daily recommended level of riboflavin. Adding mushrooms, whole grain rice and more soya products later in the day will enable a vegan to meet the recommended intake – just. In order to maintain the most vitamins while cooking, it is advisable to cook the water soluble vitamin B complexes without water. Read " Does cooking destroy micronutrients in food? "
Vitamin B12, also essential for healthy red blood cells, is only active in animal products such as dairy and eggs. A lacto-ovo-vegetarian needs to consume one egg, 100g of yoghurt and quarter of a pint of milk (or similar) a day to meet their recommended intake. Vegans should eat fortified foods such as marmite, fortified breakfast cereal, fortified soya milk or take a supplement. (Recommended daily levels of riboflavin for men are 520iu or 1.3mg, recommended levels for women are 440iu or 1.1mg. Recommended daily level of B12 for men and women is 1.5µg.)
Research is increasingly providing new information on the importance of vitamin D. It has been known for some time that vitamin D is essential for bone health but now we are seeing that the body needs it for a whole range of metabolic uses. Vitamin D has also been found to be essential to the immune system and low vitamin D levels are linked to depressionFeelings of sadness, hopelessness and a loss of interest in life, combined with a sense of reduced emotional well-being. The main source of vitamin D is the sun. Fifteen minutes a day in the sunshine is thought to be sufficient for fair skinned people, dark skinned people require longer. Dietary sources of vitamin D are found only in animal foods, the only lacto-ovo-vegetarian source of which is egg yolk. Vegan diets rely on fortified products such as cereal and soya milk. Current Department of Health recommendations are that a 10µg (400iu) vitamin D supplement should be taken by:
all pregnant and breastfeeding women, especially teenagers and young women
infants and young children under 5 years of age (7–8.5 µg)
older people aged 65 years and over
people who have low or no exposure to the sun, for example those who cover their skin for cultural reasons, are housebound, or confined indoors for long periods
people who have darker skin, for example people of African, African-Caribbean and South Asian origin
However, there is much debate at present on whether the ‘at risk’ category should be widened. Vegetarians receive low amounts of vitamin D in their diet and should consider taking a supplement, especially in the winter months. Vitamin D supplements come in two forms, D3 and D2. D3 is obtained from fish oil and lanolin so is not suitable for vegetarians, D2 is made from yeast but is only 60% as effective so needs to be taken in larger quantities.
Vegetarians can consume adequate levels of essential vitamins through their diet, with the exception of B12 for vegans and vitamin D. However it is particularly important for vegetarians to make every meal and snack nutrient dense. To eat the wide range of food required in the necessary quantity to meet recommended levels there is little room left to consume empty calories and stay within a healthy weight range. I would strongly recommended that vegetarians aim to receive all the nutrients they need through their diet but if meals and snacks do not provide a wide range of nutrients then a supplement should be taken.
1. American Dietetic Association (ADA) Position of the American Dietetic Association of Canada: Vegetarian diets. Journal of the American Dietetic Association 2003:103 748 - 765