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