Re: Re: here's an article on Vit A and bone health

[Guest guest]

{I'm not sure what exactly was trying to be overcome wuith the " enrichment " of

foods. Maybe just to replace that which was removed.

The medline articles don't seem to separate retinol from carotenoids. There are

other problems with excess Vit A.}

J Bone Miner Res 2001 Oct;16(10):1899-905

Vitamin A antagonizes calcium response to vitamin D in man.

Johansson S, Melhus H.

Department of Medical Sciences, University Hospital, Uppsala, Sweden.

For unknown reasons, the highest incidence of osteoporosis is found in northern

Europe. In these populations, the sunlight exposure is limited and the vitamin A

intake is high. The interaction between vitamin A and D has been the subject of

several in vitro and animal studies. We have studied the acute effects of

vitamin A and D on calcium homeostasis in 9 healthy human subjects. We compared

the effect of (i) 15 mg of retinyl palmitate, (ii) 2 microg of

1,25-dihydroxyvitamin D3 [1,25(OH)2D3], (iii) 15 mg of retinyl palmitate plus 2

microg of 1,25(OH)2D3, and (iv) placebo in a double-blind crossover study. The

subjects took vitamin preparations at 10:00 p.m. and the following day blood

samples were collected five times from 8:00 a.m. to 4:00 p.m. Serum levels of

1,25(OH)2D3 and retinyl esters increased (1.7-fold and 8.3-fold, respectively; p

< 0.01). As expected, serum calcium (S-calcium) increased (2.3%; p < 0.01) and

S-parathyroid hormone (PTH) decreased (-32%; p < 0.05) after 1,25(OH)2D3 intake.

In contrast, retinyl palmitate intake resulted in a significant decrease in

S-calcium when taken alone (-1.0%; p < 0.05) and diminished the calcium response

to 1,25(OH)2D3 after the combined intake (1.4%; p < 0.01). S-PTH was unaffected

by retinyl palmitate. No significant changes in serum levels of the degradation

product of C-telopeptide of type I collagen (CrossLaps), or U-calcium/creatinine

levels were found. In conclusion, an intake of vitamin A corresponding to about

one serving of liver antagonizes the rapid intestinal calcium response to

physiological levels of vitamin D in man.

J Theor Biol 2000 Sep 7;206(1):47-54

Possible role of endogenous retinoid (Vitamin A) toxicity in the pathophysiology

of primary biliary cirrhosis.

kson JM, Mawson AR.

Possible role of endogenous retinoid (Vitamin A) toxicity in the pathophysiology

of primary biliary cirrhosis.

J Theor Biol. 2000 Sep 7;206(1):47-54.

PMID: 10968936

(And in this article vit a is good for bladder cancer with the note about

prostate cancer.}

Chemoprevention of bladder cancer.

Kamat AM - Urol Clin North Am - 01-Feb-2002; 29(1): 157-68

NLM Citation ID:12109342 (PubMed) 22104700 (MEDLINE)

Full Source Title:Urologic Clinics of North America

Publication Type:Journal Article;

Author Affiliation:Department of Urology, UT MD Cancer Center, Houston,

TX 77030, USA. akamat@...

Authors:Kamat AM; Lamm DL

Summary

The data presented herein, although highly supportive for a protective role of

various nutrients against bladder cancer, are far from definitive. Many

authorities question the validity of current recommendations for nutritional

chemoprevention against bladder cancer. The reason for the wide variations

reported in epidemiologic studies lies in the nature of observational studies.

Dietary studies are limited in their conclusions because the protection afforded

by the consumption of a particular nutrient may be multifactorial, with

different components of the food exerting potential chemopreventive effects.

Furthermore, measuring levels of nutrients in the food intake of populations is

confounded by factors that might affect these levels and also the incidence of

cancer. For example, vitamin A can come from animal or vegetarian sources.

Because animal fat has been identified as a potential carcinogen in man,

depending on the source of the vitamin, varying levels of protection might be

deduced. In addition, chemoprevention studies using dietary supplements are

expected to have mild effects, and large studies would be required to confirm

statistical significance. Even with agents such as intravesical chemotherapy,

only half the studies achieve statistical significance [29] . Prospective

randomized trials with a large sample size, longer follow-up, and an extended

duration of treatment are needed to clarify the association between

micronutrients and cancer protection.

With these caveats in mind, several recommendations can be made. Simple

measures, such as drinking more fluids (especially water), can have a profound

impact on the incidence of bladder cancer. Vitamins are being extensively

studied in chemopreventive trials for different cancers. There is strong

evidence for a chemoprotective effect of vitamin A in bladder cancer. The

authors recommend 32,000 IU/day of vitamin A initially, with lower doses (24,000

IU) for persons less than 50 kg. Because liver toxicity is a possibility with

long-term administration, the dose should be decreased to 16,000 IU after 3

years. High doses of beta-carotene should be avoided based on a large clinical

trial reporting a 25% increase in the number of cases of prostate cancer and a

statistically significant increase in the incidence of lung cancer. Vitamin B6

has been studied in several clinical trials in bladder cancer. The US-based

Veterans Administration cooperative study found benefit for vitamin B6 when

given as a single agent. Data for vitamins C and E are insufficient to recommend

either agent as stand-alone treatment. Nonetheless, each of these vitamins is

known to have beneficial effects, including improved function of the immune

system. It is possible that only a small percentage of patients with bladder

cancer respond to vitamins B6, C, or E, yet each is safe, nontoxic, and

inexpensive. In an effort to pool the efficacy of individual agents and to

increase the power of study, the authors evaluated the combination of vitamins

A, B6, C, and E in a double-blind trial. The observed 50% 5-year reduction in

tumor recurrence was highly significant and greater than would be expected for

any of the individual ingredients and suggests that combinations of nutritional

agents may be most appropriate. A large-volume study along similar lines is

being conducted.

Among the numerous other compounds and dietary substances purported to have

chemopreventive effect, soybeans, garlic, and green tea stand out as having the

greatest promise and can freely be recommended to patients. For synthetically

synthesized agents such as celecoxib, piroxicam, or DFMO, recommendations must

be deferred until the results of clinical trials are conclusively in favor of

their use.

Many of the dietary factors found to be protective against bladder cancer are

being investigated in other cancers and are beneficial to general health.

Although naturally occurring nutrients are ideal, especially because the

delicate balance of various micronutrients might be impossible to synthesize in

the laboratory, the general population finds it easier to take vitamin

supplements. Unfortunately, dietary changes such as decreasing fat and

increasing fruit and vegetable intake are more difficult to initiate. There is a

mistaken notion that simply because an agent is naturally occurring, it cannot

be as beneficial as taking a substance synthesized in the laboratory. Even in a

high-risk group such as nuclear-bomb survivors in Japan, high consumption of

vegetables and fruit is protective against bladder cancer [44] . Encouraging

patients to follow an essentially healthy food habit lifestyle will be a

significant contribution in the fight against cancer.

{I notice the CR guys seem to think turning yellow from carotenoids is ok. I'm

not buying that.}

Regards.

----- Original Message -----

From: somejoanne2002 <bhsnz@...>

Sent: Tuesday, February 04, 2003 8:24 PM

Subject: [ ] Re: here's an article on Vit A and bone health

> If the articles is true, it would almost mandate that vit a

>enrichments to food be stopped.

Yes - although perhaps more people benefit from vitamin A

supplementation than those whom are harmed by it - and so we all have

to have our food enriched no matter the damage to us personally - doh.

Anyway, the article states that: " Sweden is the only European

country that fortifies low-fat milk products with retinol " . Very

well, it may be the only *European* country but many low-fat milk

products in the U.S. are fortified with vitamin A palmitate. In

fact, I'm not even sure it's possible to buy milk in the U.S.

*without* vitamin A retinol supplementation.

> In addition, beta carotene has a limit if you believe the

>association with Prostate Cancer. I'm using 32000 IU in my

>spreadsheet now although that is what I inferred from the article

>abstract. I don't have access to the whole article.

Question: carotenoids are not implicated in osteo are they?

> I've been wondering where the redlines were for several years and

>now it seems someone is beginning to look at them.