Vegetarian Diets

limiting amino acids

essential aa in protein only occurring in small amount - cereals = lysine and isoleucine - legumes = methionin and tryptophan

fruitarianism

extreme form of vegetarianism where dietary intake is restricted to raw fruits, nuts, berries, seeds & vegetable oils

health benefits : cancer

lower incidence of colo-rectal cancer - red and processed meats implicated - also vego = lower proportion of secondary bile acids in faeces and faster transit time lower incidence of breast cancer - most strongly related to obesity and alcohol - also soybeans high in phytoestrogens lower incidence of prostate cancer

n-3 fatty acids

plants provide alpha-linolenic acid not but not the LC n-3 FAs EPA and DHA vego diets are usually high in n-6 FAs which inhibits conversion of alpha-linolenic acid to EPA & DHA

legumes contain ?

protease inhibitors - decrease digestibility of proteins - inactivated by heat treatment

Iodine

small UK study suggests vegans at increased risk of both I deficiency or toxicity (depending on intake of iodised salt and seaweed) - milk is also a significant contributor to I intake - goitrogens (e.g. soy, cruciferous veg, and sweet potatoes) prevent I from being absorbed

Selenium

small UK study suggests vegetarians and vegans at risk of SE deficiency

dietary adequacy

- DIVERSITY = important - growth retardation in veg infants usually to do with other factors e.g. poverty and intestinal infestation - high fibre diets may restrict energy intake of young children - well-planned veg diet = adequate for all life stages

Iron

- Fe content of vegetarian diets similar to non-vegetarian diets - bioavailability of Fe is less (no haem iron and MFP factor, more inhibitors of Fe absorption i.e. phytates, oxalates, soya) - vegans = higher absorption of Fe than vegetarians (Ca++ competes with Fe) - low Fe stores common in premenopausal women - risk of anaemia is highest amongst those who rely on rice rather than wheat

health benefits: bone health

- absence of meat reduces "acid load" - acid loading and acidosis are associated with hypercalciuria and negative Ca balance - K from fruit and veg has alkalising effect - vit K = positive effect on bone health - phytoestrogens may have a positive effect on bone health

vegan

- avoids all animal derived food & won't use products derived from animals

vego diets relatively rich in

- carbohydrates - n-6 fatty acids - dietary fibre - carotenoids - folic acid - vitamins c & e - magnesium - non-haem iron (not bioavailable)

macrobiotic

- excludes most animal-derived foods and emphasises unprocessed organic foods; large amounts of brown rice, accompanied by small amounts of fruit, veg & pulses - meat and fish permitted if wild or hunted

semivegetarian (vegivore)

- excludes some but not all, animal derived foods; most often red meats avoided / consumed in limited amounts

lactovegetarian

- includes dairy products - excludes eggs and other animal-derived products

ovovegetarian

- includes eggs - excludes milk, dairy products, meat, poultry, fish, seafood

lacto-ovo vegetarian

- includes milk, dairy products, eggs - excludes meat, poultry, fish, seafood

Zinc

- lower bioavailability from vegan diets - high phytate (inhibitor) intake from unrefined grains and legumes - requirements may be higher than RDI - availability improved by - leavening bread - soaking & sprouting beans, grains and seeds

health benefits : heart disease

- lower mortality from ischaemic heart disease (IHD) (lower blood cholesterol levels and BMI) - death rate from stroke is slightly lower - plant foods contain (only sc FA, phytosterols which inhibit reabsorption of cholesterol from GIT) - intake of PUFAs can be higher (omega 6 - lowers LDL cholesterol)

confounding factors regarding health benefits of vegetarian diets

- may just be healthier people to start with - health conscious ?? no smoking, low alc etc - majority = middle aged white women

Vitamin B12 deficiency causes

- megaloblastic anaemia and/or neuropathy - hyperhomocysteinaemia - severe neurological damage in infant or unsymptomatic yet deficient mother

benefits of veg diet

- more likely to hit fruit and veg targets - more likely to have low saturated fat intake - 50-100% higher NSP (fibre) intake - ie. faster transit time and larger faecal bulk - more complex carb but sugar consumption usually similar

incomplete proteins

- most plant proteins are incomplete in amino acids, containing some but not all aa's - have to mix types of proteins with different limiting amino acids - soya may be a complete protein

Vitamin B12

- plant foods do not contain - reliable sources = dairy products, eggs, fortified foods, dietary supplements, seaweed - intake and plasma concentrations of B12 are lower in vego's than meat eaters - deficiency = biggest problem for vegans - deficiency can also be due to low animal product due to poverty

adverse effects of vego diets

- poorer mental health (depression, anxiety, self harm) - menstrual problems (low Fe, PMT, irregular or heavy periods) - underweight (eating disorders? constipation)

vego diets relatively low in

- protein - saturated fat - LC n-3 fatty acids - retinol - vitamin b12 - available iron - zinc - calcium - iodine (especially vegans) and selenium

possible reasons for vegetarianism

- religious reasons - health - animal welfare - environmental reasons - economic reasons - ecological - ethical - world hunger issues - normally do not start consuming a vegetarian diet until early adult life

Calcium

- vegetarians consuming dairy products usually have relatively high Ca intakes - vegans tend to have low Ca intakes - Ca absorption inhibited by - phytate (legumes & unrefined cereals) - oxalates ( from spinach and swish chard) - low oxalate greens = good source of Ca e.g. bok choy, broccoli, kale - low calcium & protein intake linked with osteoporosis (vegans 30% higher risk)

meat production effects

- worldwide: fertilisers, pesticides, feed formulations - unsustainable use of finite resources - intensive production (1kg beef requires 9kg cereal grain, pork = 4:1, chickens = 2:1) - high waste and demand for fresh water - high demand - international food chains - meat demanded predicted to double over coming decades - transition from small farms to agribusiness - impact on infectious disease ecology - global climate change