Nutrition Notes: Carotenoids, Retinoids, Vitamin A

[liveonearth]

NUTRITION NOTES 5/5/09
ANTIOXIDANTS

CAROTENOIDS
six major types: alpha and beta carotenoids, lycopene, lutein, zeaxanthin, beta-cryptoxanthin
some carotenoids are precursors of vit a
Provitamin A carotenoids are alpha, beta carotenoids, and beta cryptoxanthin
Prevent CA by: Control prolif, Control differentiation
Prevent heart dz, diabetes?
Immune system performs better with more
Also more vit A increases immune fx
Alpha and beta are found in many of same foods, orange, yellow, red or dark green colors
Pumpkin, carrot, sweet potatoe, spinach, squash, plantain, collar, kale, tomato, tangerine, dandelion, peas, cantaloupe
Top 5% of western diets contain 10,000-12,000 micrograms of carotenoids

INSUFFICIENCY
Carotenoid deficiency or more like insufficiency (lower than optimum)
Pts don’t look deficient unless vitamin A also def
Inadequate intake defined by short and long term consequences, depends on degree of inadequacy
No deficiency occurs if other sources of vit A present
Nutritional “deficiency” means characteristic sx appear a short time after a period of low intake
Healthy diets have over 2x the carotenoids of SAD

BETA CAROTENE
100 years ago study began
Vit A was 1st discovered
Of all the carotenoids, the one that turns into A most efficiently is BETA CAROTENE
-->50 years science was interested in beta carotene, neglected alpha
More beta in diet--> more health incl less ca (early studies)
Recent studies using synthetic beta carotene find no protection from lung cancer
Studies gave pts more beta than they could possibly get in diet, smokers and asbestos exposure
Group w/ beta carotene OD'd pts got MORE CANCER (two studies)
Perhaps in early studies, beta carotene indicator of high fruit/veg diet (overall protective)
Page 9 in notes on the enigma of beta carotene
New research on this theory:
Carotenoids circ in lipoprots and may protect LDL vs odication
High diet or blood carotenoids assoc w/ lower atherosclerosis and CV dz risk
Other nutritents mb more imp
Synthetic beta carotene provided NO protection
beta can be converted to vit a but won't be if it is not needed
beta doesn't prevent lung cancer and may increase it in smokers if high doses

LYCOPENE
birth defects over 10,000 IU/day
bone loss >5,000 IU/day
More abundant in diet than beta carotene in human diet
Concentrated in tomatoes
Reduced prostate cancer risk, lycopene is concentrated there 6x more than in blood
Tomatoes contain vit c, alpha and beta carotene
questions about supplements
tomato, watermelon, grapefruit, baked beans, sweet red peppers

LUTEIN
is yellow pigment
lutein and zeaxanthin most in retina of eyes
proven protective vs macular degeneration, cataracts,
10-30 mg/day improve vision (medline)
dark green leafy vegetables, egg yolk, marigolds used for extracts
spinach, kale, turnip greens, collards are best sources by far
also present in mustard greens, dandelion, summer squash, peas, winter ssquash, broccoli, pumpkin, brussel sprouts, sweet yellow corn

OTHER CAROTENOID SUPPLEMENTS
natural beta carotene from live healthy 25,000 IU or from nature's life
not known yet what effect these will have
mixed carotenoids also available but are mostly beta carotene
beta carotene is cheaply synthesized

SAFETY
vitamin A toxicity? Gerber says there is none but later he goes on to mention:
there have been deaths from vit A toxicity
eating livers of wild animals
acute or chronic toxicity sx at >25,000 IUday, 10x RDA or more
Sx: headache, bone/joint pain, systemic sx, liver damage
lower threshhold with liver compromise
birth defects over 10,000 IU/day
bone loss >5,000 IU/day (could this be dt competition with vit D)
he says vit A increases osteoclast fx

no evidence that more vit A is better for you
high dosing does cause harmless pigmentation of skin, subcu fat, so see in palms/soles
pigmentation protects vs UV damage in skin, maybe vs skin cancer
high dose beta carotene contraindicated in smokers and those with lung ca risk
better absorption mixed with digestible fat, impaired absorption w/ fat digest/absorb prob
olestra depresses absorption of carotenoids
long term consequences of long term consumption unknown

UL based on most likely sx that could occur at lowest intakes
based on proven amounts not causing adverse
not applying to therapeutic uses
UL vit A 10,000 IU
based on preventing birth defects, liver damage, bone loss risk not considered yet

RETINOIDS
shorter chain than carotenoids, not quite so antioxidant
preformed vit A
retinol, retinal, retinoic acid produced from retinal
some carotenoids are precursors of vit a
Provitamin A carotenoids are alpha, beta carotenoids, and beta cryptoxanthin
early Sx of low vitamin A: night blindness
can't see in low light, levels must be very low, tissue destruction may be irreversible
deficiency Sx: follicular hyperkeratosis, tissue degeneration, impaired growth and development
all cells challenged
eye looses gloss, cornea looses moisture: zeropthalmia, Bitot's spots
Bitot's spots are on sclera, a dry and granular looking spot
leading cause of preventable blindness in developing countries
starving country: they're after calories and protein first
Mexico, south america, africa, S Asia, milder in N Africa, China
infectious diseases much more severe when vit A deficient
he mentions measles specifically as being tx'd with A even in Western world

MEASURING VIT A
units: IU's are familiar, micrograms more precise
vit A ingredient on label may be retinyl acetate, beta carotene, other or mix
beta carotene does not convert directly to vit A
IU's claim equivalency
IU's measure activity, not weight, quantified by what they do
in the past activity was sometimes easier to measure than very small mass
also helpful when different forms ahve different activities
most research talks about micrograms
variable absorption, variations in conversion
1 mcg retinol = 2 mcg supplement beta carotene = 12 mcg dietary beta carotene
12 mcg dietary beta carotene = 24 mcg alpha carotene or beta cryptoxanthin

DRI = DIETARY REFERENCE INTAKES
RDA = RECOMENDED DIETARY ALLOWANCE based on consensus
AI = ADEQUATE INTAKE instead of RDA when no consensus on evidence
won't have both RDA or AI
UL = tolerable upper level of intake
DV = Daily Value (on food and supplement labels), legislated, depends on 40 year old RDA's

tomorrow: vitamins E, C, and selenium