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Welcome to the Quality Counts. For those health conscious consumers and medical professionals that are looking to purchase nutritional supplements, vitamins, herbs, learning about medications, losing weight, health food, low carbs, high protein nutrition, and exercise, you have come to the right place. Quality Counts serves both the medical practitioner and consumer interested in nutritional therapy and alternative medicine.
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Anti-aging Research > Vitamin A
Vitamin A
Specific Recommendations:
- carotenoids
- (beta carotene, a carotenoid, is converted to vitamin A as needed.
However, taking just one of over 600 carotenoids can cause a deficiency of
the others)
-
Vitamin A products at iHerb
General Information:
-
Vitamin A and Carotenoids - NIH
- Vitamin A - The Natural
Pharmacist
-
Vitamin A and
Pregnancy - thenutritionreporter.com
News & Research:
-
Listen up! Antioxidants may slash risk of hearing loss, says study -
Nutra USA, 7/19/11 - "People with the highest
average intakes of vitamin A had a 47 percent reduced risk of moderate or
greater hearing loss, compared to people with the lowest average intakes ...
In addition, increasing dietary vitamin E intakes were linked with a 14
percent reduction in hearing loss"
-
Vitamin A plays key role in the human body, study suggests - Science
Daily, 3/17/11 - "Our study found that Vitamin A
itself is active for activating nuclear receptor TR4 ... Because TR4 plays
roles in sperm cell production, lipid and lipoprotein regulation, the
development of the central nervous system, and the regulation of hemoglobin
production in the embryo, we can imagine that Vitamin A may play more
important roles in human physiology than was previously believed"
-
Researchers discover additional benefit of vitamin A - Science Daily,
5/12/10 - "Children of mothers who received vitamin
A supplementation before, during and after pregnancy had significantly
improved lung function when compared to those whose mothers received
beta-carotene supplementation or placebo"
-
Vitamin A: Key mechanism that guides cells to form heart tissue -
Science Daily, 3/19/10 - "Second Heart Field (SHF)
... retinoic acid (RA), a derivative of vitamin A, regulates the SHF tissue
formation and the septation, or division, of the outflow tract into the
ascending aorta and the pulmonary artery ... We now know that vitamin A is a
critical regulator of this process, and too much or too little RA can lead
to common congenital defects"
-
Antioxidant compound reduced incidence of colorectal metachronous adenomas
- Science Daily, 12/7/09 - "The researchers
randomized 411 participants to the placebo group or to receive an
antioxidant compound -- specifically selenomethionnine 200 μg, zinc 30 mg,
vitamin A 6,000 IU, vitamin C 180 mg and vitamin E 30 mg ... individuals who
consumed antioxidants had a 40 percent reduction in the incidence of
metachronous adenomas of the large bowel ... It is noteworthy that the
benefit observed after the conclusion of the trial persisted through 13
years of follow up"
-
Too
Much Of A Good Thing? Scientists Explain Cellular Effects Of Vitamin A
Overdose And Deficiency - Science Daily, 10/8/09 -
"retinol, the key component of vitamin A, is
essential for the metabolic fitness of mitochondria and acts as a
nutritional sensor for the creation of energy in cells. When there is too
much or too little vitamin A, mitochondria do not function properly,
wreaking havoc on our organs ... It goes to the nucleus of our cells and can
affect our health for better or worse"
-
Oxidized Form Of A Common Vitamin May Bring Relief For Ulcerative Colitis
- Science Daily, 10/1/09 - "Here's another reason
why you should take your vitamins. A new research report appearing in the
October 2009 print issue of the Journal of Leukocyte Biology suggests that
retinoic acid, the oxidized form of vitamin A, could be a beneficial
treatment for people suffering from ulcerative colitis and other irritable
bowel diseases"
-
Don't Forget The Vitamin A When Working With Its Carrier Protein -
Science Daily, 9/26/08
-
How
Embryos Regulate Vitamin A Derivatives: Too Much Or Too Little Linked To
Birth Defects - Science Daily, 11/19/07
-
Drug
Slows Prostate Tumor Growth By Keeping Vitamin A Active - Science Daily,
11/7/07 - "A novel compound that blocks the
breakdown of retinoic acid, derived from vitamin A, is a surprisingly
effective and "promiscuous" agent in treating animal models of human
prostate cancer ... Daily injections of the agent VN/14-1 resulted in up to
a 50 percent decrease in tumor volume in mice implanted with human prostate
cancer cells ... Vitamin A, when converted by the body into retinoic acid,
is known to be involved in maintaining the normal growth of cells, and other
research has shown that prostate cancer cells contain five to eight times
less retinoic acid than normal prostate cells"
-
Vitamin A Reduces Infant Deaths from Measles, Studies Confirm - Doctor's
Guide, 10/29/05
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New findings on vitamin A's role in cancer prevention
- Nutra USA, 1/6/05
- Vitamin A Levels Affect Hip Fracture Risk -
Physician's Weekly, 10/4/04 - "women with the lowest concentrations of vitamin A had a 90% higher risk of
hip fracture. Those with the highest concentrations were twice as likely
as those with normal levels to sustain a hip fracture"
- Too Much or Too Little Vitamin A Raises Hip-Fracture Risk in Post-Menopausal
Women - Doctor's Guide, 6/24/03 - "the highest and lowest quintiles were at twice the risk of
hip fracture compared to the middle quintile ... without knowing the
vitamin A status of an individual, eliminating vitamin A supplements could
actually increase the number of vitamin A-deficient individuals, which would
put them at risk not only of hip fractures, but also for other health risks
associated with low vitamin A"
- Vitamin A
Safety - Dr. Janson's Newsletter, 2/03 - "what they did not mention was that those in the next to highest and middle
ranges had a significantly lower risk than those with lower blood levels.
The amounts in normal vitamin supplements appear to be quite safe ...
One problem with the latest study is that they measured blood levels just
once at the beginning of the study 30 years ago. They assessed dietary
intake with a questionnaire in only half of the subjects, when they were 20
years into the study. While this study gives cause for some concern, other
studies are contradictory, so we have to be careful before drawing firm
conclusions"
- Vitamin A Supplements Raise Risk Of Broken Bones -
Intelihealth, 1/22/03
- Vitamin A: Bone Poison? - WebMD, 1/22/03
- Watermelon
for Prostate Cancer? - Dr. Weil, 12/10/02 - "The body converts about 500 different carotenoids into vitamin A"
- Vitamin
A Supplementation Does Not Cause Osteoporosis -
New Hope Natural Media, 9/26/02
- Too Much or Too Little Vitamin Associated With Low BMD in Elderly
- Doctor's Guide, 8/16/02
- How Much
Vitamin A Is Safe? - Dr. Weil, 2/21/02
- Study: Vitamin A Helpful Vs. Disease -
Intelihealth, 1/7/02
- Study: Vitamin [A] Linked To Fractures -
Intelihealth, 1/2/01
-
Vitamin A, Steroids Could Help Keep Body Clocks in Sync - WebMD, 6/28/01
- "I think it will turn out that
vitamin A will be a novel signaling mechanism, and that it will play a role
maybe in [controlling] peripheral clocks [throughout the body]," says lead
author Peter McNamara, PhD."
-
Canceling Cancer: New Cancer Prevention Strategies on the Horizon -
WebMD, 3/26/01 - "an enzyme called
telomerase is important for the growth of most cancer cells but not so
crucial for the growth of normal cells ... By giving a compound similar to
vitamin A to a group of heavy smokers, they were able to reduce the amount
of telomerase activity. Their findings indicate that this compound might be
useful in the future to prevent lung cancer in former smokers"
- Vitamin
A : Safe at Intake of 10,000 IU - Council for Responsible Nutrition,
1/12/01
-
Some Fruits and Veggies Have Half the Vitamin A Once Thought - WebMD,
1/10/01
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Report: Too Much Vitamin A Dangerous - Intelihealth, 1/10/01
-
Nontoxic Drug Shown To Help Reduce Return Of Breast Cancer -
Intelihealth, 11/3/99
- A Shield of Immunity - Nutrition Science News,
9/99
-
Study Finds High-Dose Vitamin A Safe For Eye Disease - Intelihealth,
4/16/99
- Too Much Vitamin A Poses Hip Fracture Risk -
Nutrition Science News, 3/99
- Moderate
Doses Of Vitamin A Do Not Pose Risk Of Birth Defects - Doctor's Guide,
7/22/97
Abstracts:
-
Plasma
retinol: A novel marker for cardiovascular disease mortality in Australian
adults - Nutr Metab Cardiovasc Dis. 2011 Nov 25 -
"Vitamin A affects inflammation and immune function and is thus a factor of
interest in relation to cardiovascular disease (CVD). As vitamin A
circulates in the plasma in the form of retinol, this study aims to describe
the relationship between plasma retinol and the 5-year incidence of CVD
mortality ... Community-dwelling adults (n = 441, 45% with type 2 diabetes)
were recruited in Melbourne, assessed at baseline and followed for 5 years.
At baseline, CVD risk factors were assessed by clinical evaluation, by
personal lifestyle questionnaire and from biochemistry (plasma fasting
glucose, lipids, total homocysteine, C-reactive protein, retinol and
carotenoids plus the urinary albumin excretion rate over 24 h.). Dietary
intake was assessed by a validated food frequency questionnaire. CVD
mortality over 5-years was determined by consulting state or national
registries. The majority of participants had adequate plasma retinol
concentrations (≥30 μg/dL). The final Cox regression model indicated that
those in the highest tertile of plasma retinol (mean ± SD) 76 ± 14 μg/dL)
had a significantly lower risk of 5-year CVD mortality (hazard ratio 0.27
[95% confidence interval 0.11, 0.68], P = 0.005), an effect that was not
readily explained in terms of traditional CVD risk factors or dietary
intake"
-
Associations of serum vitamin A and carotenoid levels with markers of
prostate cancer detection among US men - Cancer Causes Control. 2011 Jul
29 - "Associations of serum vitamin A and carotenoid
levels with markers of prostate cancer detection were evaluated among 3,927
US men, 40-85 years of age, who participated in the 2001-2006 National
Health and Nutrition Examination Surveys. Five recommended definitions of
prostate cancer detection were adopted using total and free
prostate-specific antigen (tPSA and fPSA) laboratory measurements. Men were
identified as high risk based on alternative cutoffs, namely tPSA > 10 ng/ml,
tPSA > 4 ng/ml, tPSA > 2.5 ng/ml, %fPSA < 25%, and %fPSA < 15%. %fPSA was
defined as (fPSA÷tPSA)× 100%. Serum levels of vitamin A (retinol and retinyl
esters) and carotenoids (α-carotene, β-carotene, β-cryptoxanthin, lutein +
zeaxanthin, lycopene) were defined as quartiles and examined as
risk/protective factors for PSA biomarkers. Odds ratios (OR) and 95%
confidence intervals (CI) were estimated using binary logistic models. After
adjustment for known demographic, socioeconomic, and lifestyle confounders,
high serum levels of retinyl esters (tPSA > 10 ng/ml: Q4 vs. Q1 → OR = 0.38,
95% CI: 0.14-1.00) and α-carotene (%fPSA < 15%: Q4 vs. Q1 → OR = 0.49, 95%
CI: 0.32-0.76) were associated with a lower odds, whereas high serum level
of lycopene (tPSA > 2.5 ng/ml: Q4 vs. Q1 → OR = 1.49, 95% CI: 1.01-2.14) was
associated with a greater odds of prostate cancer detection. Apart from the
three significant associations observed, no other exposure-outcome
association was significant. Monitoring specific antioxidant levels may be
helpful in the early detection of prostate cancer"
-
Retinol,
vitamins A, C, and E and breast cancer risk: a meta-analysis and
meta-regression - Cancer Causes Control. 2011 Jul 15 -
"Overall, 51 studies met the inclusion criteria.
Comparing the highest with the lowest intake, total vitamin A intake reduced
the breast cancer risk by 17% (pooled OR = 0.83, 95% CI: 0.78-0.88). Further
subgroup analysis based on study design did not change the significant
reduction. Although the dietary vitamin A, dietary vitamin E, and total
vitamin E intake all reduced breast cancer risk significantly when data from
all studies were pooled, the results became nonsignificant when data from
cohort studies were pooled. The significant association between total
retinol intake and breast cancer in all studies became nonsignificant in
case-control studies but remain significant in cohort studies. No
significant dose-response relationship was observed in the higher intake of
these vitamins with reduced breast cancer risk"
-
Vitamin
A Decreases Pre-receptor Amplification of Glucocorticoids in Obesity: Study
on the Effect of Vitamin A on 11beta-Hydroxysteroid Dehydrogenase Type 1
Activity in Liver and Visceral Fat of WNIN/Ob Obese Rats - Nutr J. 2011
Jun 23;10(1):70 - "11beta-hydroxysteroid
dehydrogenase type 1 (11beta-HSD1) catalyzes the conversion of inactive
glucocorticoids to active glucocorticoids and its inhibition ameliorates
obesity and metabolic syndrome. So far, no studies have reported the effect
of dietary vitamin A on 11beta-HSD1 activity in visceral fat and liver under
normal and obese conditions. Here, we studied the effect of chronic feeding
of vitamin A-enriched diet (129mg/kg diet) on 11beta-HSD1 activity in liver
and visceral fat of WNIN/Ob lean and obese rats ... Control groups received
stock diet containing 2.6mg vitamin A/kg diet, where as experimental groups
received diet containing 129mg vitamin A/Kg diet for 20 weeks ... Vitamin A
supplementation significantly decreased body weight, visceral fat mass and
11beta-HSD1 activity in visceral fat of WNIN/Ob obese rats. Hepatic
11beta-HSD1 activity and gene expression were significantly reduced by
vitamin A supplementation in both the phenotypes. CCAAT/enhancer binding
protein alpha(C/EBPalpha), the main transcription factor essential for the
expression of 11beta-HSD1, decreased in liver by vitamin A fed-obese rats,
but not in lean rats. Liver X receptor alpha (LXR alpha), a nuclear
transcription factor which is known to downregulate 11beta-HSD1 gene
expression was significantly increased by vitamin A supplementation in both
the phenotypes" - Note: See my
11beta-HSD1 page. 11beta-HSD1 goes hand in hand with cortisol.
-
Serum
Retinol and Prostate Cancer Risk: a Nested Case-Control Study in the
Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial - Cancer
Epidemiol Biomarkers Prev. 2009 Mar 31 - "Vitamin A
(retinol) plays a key role in the regulation of cell growth and
differentiation, and has been studied as a potential chemopreventive agent
for prostate cancer ... the highest versus lowest concentrations of serum
retinol were associated with a 42% reduction in aggressive prostate cancer
risk (Ptrend = 0.02), with the strongest inverse association for high-grade
disease (Gleason sum >7; odds ratio, 0.52; 95% confidence interval,
0.32-0.84; Ptrend = 0.01)"
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