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CAROTENOIDS MAY PROTECT AGAINST PROSTATE CANCER
Cancer Decisions ^
| Ralph Moss, PhD
Posted on 05/14/2005 7:21:18 PM PDT by Coleus
CAROTENOIDS MAY PROTECT AGAINST PROSTATE CANCER
Asians are well known to have a low incidence of prostate cancer. Australian and Chinese researchers conducted what is called a "case-control study" in southeast China, the first of its kind in an Asian population. They discovered that dietary lycopene and other carotenoids may protect against prostate cancer.
The researchers compared 130 patients with adenocarcinoma of the prostate to 274 controls - men who were in the hospital for conditions other than prostate cancer. They found that the more carotenoid-rich foods the men ate, the less their risk of developing prostate cancer.
Carotenoids are a class of compounds that are found abundantly in many fruits and vegetables. The main dietary carotenoids are lycopene, alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein and zeaxanthin. The researchers found that certain foods, including tomatoes, pumpkins, spinach and citrus fruits, were particularly strongly associated with a protective effect against prostate cancer.
Compared to those patients who had the lowest intake of lycopene, those with the highest had an odds ratio for prostate cancer of 0.18. This means that they had an 82 percent reduction in risk.
- With alpha-carotene the odds ratio was 0.43, i.e., a 57 percent risk reduction.
- With beta-carotene, the odds ratio was 0.34, i.e., a 66 percent reduction.
- With beta-cryptoxanthin the odds ratio was 0.15, i.e., an 85 percent odds reduction.
- The odds ratios for lutein and zeaxanthin were even more impressive, although in a personal communication the authors cautioned that the study would have to be repeated with a larger number of patients in order to yield a scientifically meaningful result.
There was a dose-response curve for each of these variables. In other words, the more of these dietary carotenoids a man received, the lower his risk of developing prostate cancer. Such dose-response curves are very important to scientists, since they indicate that the agent in question is having the suspected effect and that the effect is not due to chance.
The authors, who included scientists at the School of Public Health, Curtin University of Technology, Perth, Australia, and the School of Medicine, Zhejiang University, Hangzhou, People's Republic of China, concluded that "[dietary intake of] carotenoids in vegetables and fruits may be inversely related to prostate carcinogenesis among Chinese men."
Focus on Carotenoids
This study has focused increased attention on carotenoids, and lutein and zeaxanthin in particular. These compounds belong to the vitamin A family, also known as xanthophylls. The root 'xanthos' in Greek means reddish-yellow; 'zeaxanthin' means corn yellow.
Not surprisingly, fruits and vegetables with a yellow or red-yellow hue such as corn, peaches, mangoes and persimmons, are all high in zeaxanthin. The closely-related carotenoid, lutein, can be found in dark leafy greens, such as spinach, kale, broccoli, and collard greens. Lutein and zeaxanthin are also found in eggs, particularly from chickens that have been fed marigold leaves to make their egg yolks more attractive.
UCLA Avocado Study
A 2005 study from the University of California, Los Angeles (UCLA), showed that the most abundant source of lutein among 20 frequently consumed fruits and vegetables was avocado. In this study, lutein accounted for 70 percent of the measured carotenoids in the avocado. Avocados also contain significant quantities of vitamin E (Lu 2005).
The same group of researchers has also shown that lutein reduces prostate cancer cell growth by 25 percent, while lycopene reduces such cell growth by 20 percent. But when lutein and lycopene are combined, the prostate cancer cell growth rate can be reduced by 32 percent. This indicates that both nutrients together help protect against prostate cancer better than either one alone (California 2005).
"Lutein and lycopene in combination appear to have additive or synergistic effects against prostate cancer," said Dr. David Heber, director of the UCLA Center for Human Nutrition. "Our results suggest that further studies should be done to investigate the nutrient-nutrient interactions of lutein and lycopene at a subcellular and molecular level."
Lutein can be converted to zeaxanthin in the body. But the macula of the eye, which needs this vitamin, relies solely upon dietary sources for 50 percent of its zeaxanthin.
In addition to protecting against prostate cancer, lutein and zeaxanthin have other potential health benefits. For instance, people with high levels of lutein and zeaxanthin in their blood are less likely to develop age-associated eye problems such as cataracts and macular degeneration.
Some commercial brands of vitamins state that they are "now with lutein." But the dose used in clinical studies varies between 5 to 11.7 mg of lutein and 200 mcg of zeaxanthin. You would need to take 25 pills a day of some of these "now with lutein" multivitamins to achieve the study dose! You can, of course, get supplements with higher amounts. But in my opinion, the most reliable way to get such desirable nutrients is through foods, rather than relying on supplements. Supplements provide nutrients in isolation, whereas foods supply complex mixtures of nutrients that often modulate each others' biological effects in a beneficial way. A bountiful intake of corn, avocados, organic eggs, etc. is a reliable source of these healthful nutrients.
In addition to investigating the role of carotenoids in the prevention of prostate cancer, scientists have studied the effect of carotenoids on the walls of the major arteries supplying the brain. When the walls of these arteries become thickened due to atherosclerosis, the internal diameter of the arteries narrows until eventually a blockage can occur, causing a stroke. Lutein supplementation has been shown to slow the progression of carotid artery thickening in humans. Some scientists therefore believe that lutein is protective against the early development of atherosclerosis.
These studies all point to the vital importance of a diet that includes lots of carotenoid-rich fruits and vegetables. Here is yet more evidence that people seeking to prevent cancer and certain other chronic degenerative diseases should consider going on a diet that emphasizes raw or lightly cooked organic produce, rich in carotenoids.
How much to take?
There is presently no government recommendation for the daily intake of either lutein or zeaxanthin. However, one can extrapolate from studies that a total combination of about 6 milligrams (mg) per day of these two compounds is associated with a reduced risk of both age-related macular degeneration and cataract formation.
The average US adult consumes a total of only 2 to 4 mg per day of lutein and zeaxanthin from foods. One therefore may logically need to change one's diet to get the higher amount, or else take a lutein/zeaxanthin supplement. Most lutein products on the market contain either 6 or 20 mg. It is not clear that products that contain either much less or more much than 6 mg are helpful.
Lutein supplements come in either the "ester" or the free form. There is a commercial battle underway between these two, especially between such XANGOLD and FloraGLO lutein. The lutein and zeaxanthin that are found in green vegetables, fruits and certain egg yolks all exist in the free (i.e., non-esterfied) form. According to www.consumerlab.com, both forms are equally well absorbed by the body, but are best absorbed when taken with fats or oils. It is therefore generally recommended that one take lutein or zeaxanthin supplements with meals, preferably high-fat rather than low-fat meals.
Here are some reasons to get one's lutein/zeaxanthin in foods rather than in supplements:
1) It is less expensive.
2) If you are NOT getting enough lutein/zeaxanthin it definitely means that you are not eating enough fruit and green leafy vegetables.
3) Lutein and zeaxanthin work better in the presence of other nutrients, such as vitamin C, vitamin E, beta-carotene and zinc. These can also be gotten from nutrient-dense foods.
4) Avocados, an abundant source of lutein, already contain the fat that you need to properly absorb this carotenoid.
5) There is a lingering concern over the results of a clinical trial in which smokers who received high doses of synthetic beta-carotene had an increased risk of lung cancer (Goodman 2004)
In general, try to eat your produce fresh, organic and minimally cooked or processed. For spinach, the US Department of Agriculture has shown that the raw form contains roughly twice as much zeaxanthin as the cooked. Some foods that are traditionally eaten cooked (e.g., corn or collard greens) can also be eaten raw, especially if marinated first in an oil and vinegar based dressing. Although they are calorie-dense, avocados are a surprisingly good source of carotenoids as well.
Freshness is a very important determinant since fresh produce generally contains more of these carotenoids than factory-prepared items. As an example, there are over 2,445 micrograms of lutein + zeaxanthin in raw broccoli, 2,226 in cooked fresh broccoli, but only 830 in broccoli that has been frozen, chopped, cooked, boiled, and then drained.
Here are the lutein/zeaxanthin microgram values for various foods:
Corn, sweet, yellow, canned, whole kernel, drained solids 528
Persimmons, Japanese, raw 488
Cornmeal, de-germed, enriched yellow 457
Spinach, raw 331
Turnip greens, cooked, boiled, drained, without salt 267
Collards, cooked, boiled, drained, without salt 266
Lettuce, cos or romaine, raw 187
Kale, cooked, boiled, drained, without salt 173
Spinach, cooked, boiled, drained, without salt 179
(All values are per 100 grams of the edible portion)
Source: USDA, retrieved from
--Ralph W. Moss, PhD
References and Resources:
Beatty S et al. Macular pigment and risk for age-related macular degeneration in subjects from a Northern European population. Invest Ophthalmol Vis Sci 2001 Feb;42(2):439-46.
Berendschot TT et al. Influence of lutein supplementation on macular pigment, assessed with two objective techniques. Invest Ophthalmol Vis Sci 2000 Oct;41(11):3322-6.
California Avocado Commission. Lutein In avocados and green vegetables can help prevent prostate cancer. Press release. 2004. Retrieved February 25, 2005 from:
Curran-Celentano J et al. Relation between dietary intake, serum concentrations, and retinal concentrations of lutein and zeaxanthine in adults in a midwest population. Am J Clin Nutr 2001 Dec:74(6):796-802.
Dwyer JH et al. Oxygenated carotenoid lutein and progression of early atherosclerosis: the Los Angeles atherosclerosis study. Circulation 2001 Jun 19;103(24):2922-7.
Goodman GE, Thornquist MD, Balmes J, et al. The Beta-Carotene and Retinol Efficacy Trial: incidence of lung cancer and cardiovascular disease mortality during 6-year follow-up after stopping beta-carotene and retinol supplements. J Natl Cancer Inst. 2004;96:1743-50.
Jian L, Du CJ, Lee AH, et al. Do dietary lycopene and other carotenoids protect against prostate cancer? Int J Cancer. 2005;113:1010-4
Lu QY, Arteaga JR, Zhang Q, et al. Inhibition of prostate cancer cell growth by an avocado extract: role of lipid-soluble bioactive substances. J Nutr Biochem. 2005;16:23-30
Marees-Perlman JA et al. Lutein and zeaxanthine in the diet and serum and their relation to age-related maculopathy in the third national health and nutrition examination survey. Am J Epidemiology 2001 Mar 1;153(5):424-32.
Moeller SM et al. The potential role of dietary xanthophylls in cataract and age-related macular degeneration. J Am Coll Nutr 2000 Oct;19(5Suppl):522d-527S.
Ramalanjaona G. Lutein and Ocular Disease. Alternative Medicine Alert 2002 May; 5(5):54-56.
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TOPICS: Health/Medicine; Science
KEYWORDS: adenocarcinoma; asia; avocado; cancer; cancerlist; carotenoids; china; fruits; health; lutein; lycopene; nutrition; prostate; prostatecancer; ralphmoss; science; supplements; vegetables; vitamins; zeaxanthin
posted on 05/14/2005 7:21:18 PM PDT
We all have to die from something...Live your life...
posted on 05/14/2005 7:23:46 PM PDT
(Aging Warrior -- Aim High -- Who Dares Wins)
such a defeatist attitude, we all will die, some sooner than others and the latest research indicates that some very basic dietary habits may prohibit certain neoplasm from forming.
posted on 05/14/2005 7:33:18 PM PDT
(Abortion and Euthanasia, Don't Democrats just kill ya! Kill babies, Save the Bears!! and ducks)
What you call defeatism I call realism. I applaud your efforts to inform FReepers of what they may do to prolong their well being. It is a noble gesture. Perhaps had I known these things years ago things would be different. However, as a soldier I have more immediate concerns...like how do we extend the lives of those we send into battle to protect our freedoms? While I fully recognize that the 3000 or so troops we have lost so far in Iraq and Afghanistan pale in terms of the numbers lost each year to cancer, they did not enjoy the life that so many of us enjoy. They gave theirs for ours. I don't mean to rant on you but a few extra years for someone like me is nothing like what I wish I could give to the kids who will never see what I have seen or experienced.
posted on 05/14/2005 7:50:37 PM PDT
(Aging Warrior -- Aim High -- Who Dares Wins)
The topic of prostrate cancer is an interesting one and I'm convinced that some day there will be a class action lawsuit involving the number of healthy prostrates that have been removed. For many, there has been absolutely no reason for doing so except some doctor got carried away with no more information other than some PSA numbers he/she reckoned had gotten a little high. John Kerry is a pretty typical example - PSA numbers go up a little and doc recommends getting prostrate removed. Patent ends up suffering consequences for rest of his life. I wonder how many people are aware that Dr Stamey, the doctor who published the original paper in 1987 that said that PSA was a good indicator for the presence of cancer has since refuted his own study and basically has said that PSA is worthless as a screening tool. It's the problem of turning everything into a cookie cutter approach instead of using common sense.
I speak from some personal experience on this one. Two years ago, my doc wanted me to have a biopsy because my PSA levels had gone from 2 to a little under 10 as determined during the annual checkup. I decided to not do the biopsy for a number of reasons. What I did do is go the route of this article - changed diet, added lots of vitamins and other things I found in the local health food store. I did however get my blood checked monthly and over the course of the next 4 months, I watched the PSA dropped steadily and linearly until it was under one where it has stayed since.
Some men with PC can actually live for 20 years before PC can do them in, since in many cases, it's a very slow moving cancer.
I wish you well
posted on 05/14/2005 9:54:56 PM PDT
(Abortion and Euthanasia, Don't Democrats just kill ya! Kill babies, Save the Bears!! and ducks)
posted on 05/14/2005 10:08:58 PM PDT
I can't even begin to tell you the thought process that I went through to make the decision that I did - it would be a small book. Your link points out one of the downsides - that the biopsy itself is not without some potentially serious medical side-effects such as the spread of the cancer throughout the prostate and the danger of infection. Then there is the fact that the needle might miss it completely - certainly defeats the purpose. Then there is the fact that it might find something but it might be a 'so what' finding. In the end, I made myself up a flowchart complete with options, yes-no decision points etc. What really convinced me not to do the biopsy was that a) a negative result doesn't mean there is no cancer, b) a positive result doesn't mean that the cancer is worth worrying about and c) if it does show cancer and a decision is made to have the prostate removed, there is no guarantee that the quality of life afterwards will be there.
One of the things that was really funny in my case is that after I made the decision to cancel my biopsy (after having given the thing due consideration), it was found that the procedure that hospitals were using to sterilize the needles was seriously flawed (this pronouncement came out the week before my scheduled date). Like I needed more convincing NOT to do it?
I read an interesting study on the net a little while ago where the researchers indicated that they had been doing dissections on the prostrate of teenagers (who had died for whatever reason) and found that approximately 20% of the boys had prostate cancer by the time they were 18 years old (don't quote me on the exact number as I've given the article away to a friend who was going through a similar experience to me). So not only is it slow-growing, it is often there from a very young age. I also recently saw the results of a survey which showed a phenomenal number of doctors themselves who believed that PSA tests and biopsies were so useless that they refuse to do it. Then there is another study that shows that only 2% of the prostate cancer cases become so serious that it kills the patient. I think my Dad was a typical case. He died a few years ago at age 90. He had prostate cancer but it never bothered him and what he died of was congestive heart failure. And as he often said, 'it's better to place your faith in things above....'
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