This section is compiled by Frank M. Painter, D.C.
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Could Synthetic Beta-Carotene Be the Real Problem?
Smokers who took beta-carotene supplements in recent experiments may have faced a greater risk of lung cancer because they took the synthetic form of the nutrient, a new study suggests. The subtle differences between synthetic and natural beta-carotene do appear to influence how the body uses the nutrient.

A Randomized Trial of Beta Carotene Supplementation and
Cognitive Function in Men: The Physicians' Health Study II

Arch Intern Med 2007 (Nov 12);   167 (20):   2184–2190 ~ FULL TEXT

We added cognitive testing to the Physicians' Health Study II (PHSII), a randomized trial of beta carotene and other vitamin supplements for chronic disease prevention. The PHSII is a continuation of the Physicians' Health Study (PHS), which had randomized male participants to low-dose aspirin and beta carotene. Participants include those continuing their original beta carotene assignment from the PHS, begun in 1982. Among 4052 continuing participants from the PHS (mean treatment duration, 18 years), the mean global score was significantly higher in the beta carotene group than in the placebo group (mean difference in z scores, 0.047 standard units; P = .03). On verbal memory, men receiving long-term beta carotene supplementation also performed significantly better than the placebo group (mean difference in z scores, 0.063; P = .007).

Effects of Beta-carotene Supplementation for Six Months on Clinical
and Laboratory Parameters in Patients with Cystic Fibrosis

Thorax 2001 (Jan);   56 (1):   48–52

Oral beta-carotene supplementation in a dose of 1 mg/kg/day only was effective in normalising the plasma concentration of beta-carotene and resulted in a decrease in pulmonary exacerbations. These data suggest that patients with CF may benefit clinically from supplementation with beta-carotene and further studies are warranted.

Beta-Carotene: The Controversy Continues
Alternative Medicine Review 2000 (Dec);   5 (6):   530-545 ~ FULL TEXT

The safety of synthetic b-carotene supplements and the role of isomeric forms of b-carotene (synthetic all-trans versus "natural" cis-trans isomeric mixtures), in addition to the importance of the protective role of other carotenoids like lycopene and lutein, have become topics of debate in the scientific and medical communities. This review addresses the biochemistry and physiology of the cis versus trans isomers of b-carotene as well as relevant studies comparing the absorption and storage of the synthetic versus natural forms of b-carotene.

Nutrients and HIV Part I: Beta Carotene and Selenium
Alternative Medicine Review 1999 (Dec); 4 (6): 403–413 ~ FULL TEXT

Micronutrient deficiencies are common in HIV/AIDS, resulting from both malabsorption and virally-caused depletion. Beta carotene and selenium deficiencies, two of the most common nutrient deficiencies, are important due to their dual function as nutrients necessary for immune modulation and as antioxidants. Beta carotene deficiencies are common in all stages of HIV/AIDS and may signal malabsorption. Supplementation has been shown to affect specific T lymphocyte populations and decrease markers of lipoperoxides. Selenium levels are highly significant in predicting AIDS-related mortality; and the HIV virus manufactures selenoproteins that are involved in the regulation of viral replication, possibly depleting host levels of selenium. Supplementation trials with individual antioxidants have shown improvement in immunological parameters and decreased evidence of lipid peroxidation.

Plasma Antioxidant Vitamins and Carotenoids in Five Japanese Populations
with Varied Mortality from Gastric Cancer

Nutr Cancer 1999;   34 (1):   56–61

The results suggest that plasma levels of beta-carotene and alpha-tocopherol, and possibly alpha-carotene, lycopene, and ascorbic acid, may partly account for the regional difference in gastric cancer mortality in Japan.

Beta-Carotene Cuts New Mothers' Mortality
Nutrition Science News (Jun 1999)

Just how critical is basic nutrition? One study shows certain vitamins mean life or death for malnourished pregnant women in southern Nepal, where beta-carotene and vitamin A supplementation nearly halved maternal deaths.

Alpha-Tocopherol and Beta-carotene Supplements and Lung Cancer Incidence
in the Alpha-tocopherol, Beta-carotene Cancer Prevention Study:
Effects of Base-line Characteristics and Study Compliance

J Natl Cancer Inst 1996 (Nov 6);   88 (21):   1560–1570

Beta-Carotene supplementation at pharmacologic levels may modestly increase lung cancer incidence in cigarette smokers, and this effect may be associated with heavier smoking and higher alcohol intake. While the most direct way to reduce lung cancer risk is not to smoke tobacco, smokers should avoid high-dose beta-carotene supplementation.

Natural Killer Cell Activity in Elderly Men is Enhanced by
Beta-carotene Supplementation

Am J Clin Nutr 1996 (Nov);   64 (5):   772–777

Our results show that long-term beta-carotene supplementation enhances NK cell activity in elderly men, which may be beneficial for viral and tumoral surveillance.

The Role of Free Radicals in Disease
Australian and New Zealand Journal of Ophthalmology 1995 (Feb);   23 (1):   3–7

The human species is not genetically adapted to survive past middle age, and it appears that antioxidant supplementation of our diet is needed to ensure a more healthy elderly population.

Carotenoids and the Immune Response
J Nutr 1989 (Jan);   119 (1):   112–115

There is growing evidence from in vitro and in vivo laboratory animal studies that beta–carotene can protect phagocytic cells from auto–oxidative damage, enhance T and B lymphocyte proliferative responses, stimulate effector T cell functions, and enhance macrophage, cytotoxic T cell and natural killer cell tumoricidal capacities, as well as increase the production of certain interleukins.

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