Download Lycopene: A Scientific Overview Although lycopene was first

Lycopene: A Scientific Overview
Although lycopene was first isolated in 1873, it is only in the last decade that it has
become widely recognized as potent antioxidant and a potential protector against the risk
of certain types of cancer and cardiovascular diseases. Even though the science is still
emerging and little intervention data is available, consumer interest in lycopene is
growing. Natural lycopene has been on the market as a concentrate for a number of
years and is present in a variety of supplements. Now, pure synthetic lycopene has been
introduced to the market by Roche.
Chart 1
Food Sources
Lycopene Con
of Common Fo
The major food sources of lycopene are tomato-based products. Other good sources are
watermelon, guava, papaya, apricots, pink grapefruit and blood oranges. However, 85%
of dietary intake of lycopene comes from tomatoes and tomato products.
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Functions of Lycopene
Lycopene is a potent antioxidant and has been shown to suppress cancer cell growth.
Also, lycopene has been demonstrated to be the most potent of all the carotenoids in
quenching singlet oxygen, a highly-reactive and short-lived molecule capable of causing
extensive cell damage. In vitro (outside the body) evidence suggests that lycopene has
the potential to prevent cancer cells from dividing, an important mechanism in cancer
prevention.
Absorption and Metabolism
Carotenoids are absorbed like fats and transported via the lymphatic system into the
liver. Absorption is dependent on the diet. Studies have demonstrated that higher fat
diets increase lycopene absorption, while Olestra and cholesterol-lowering drugs reduce
its absorption. Also, lycopene from processed tomato products is more readily absorbed
than that from raw tomatoes.
Human Research Studies
Chart 2
Cancer: Over 72 epidemiological studies have examined the relationship between either
lycopene intake or serum lycopene from a population consuming a diet high in tomato
Human Resea
Studies
and tomato-based products. Fifty-seven of these studies showed inverse associations, of
which thirty-five were statistically significant.
Associations were strongest for cancers of the prostate, stomach and lung. No studies
found an increase in cancer risk associated with high intakes or serum lycopene.
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The inverse association of lycopene with prostate cancer has recently received
considerable media attention. The data linking lycopene intake or lycopene plasma
levels from a diet rich in tomato products are considered by many to be the strongest
because they are based on two large population studies:
1. the 1989 Seventh Day Adventist Study (14,000 men), and
Chart 3
Lycopene and
Cancer Sites:
2. the 1995 US Health Professionals Follow-Up Study (48,000 men).
Major Associa
The reduction in risk ranged from 0% in the lowest quintile of intake (<1.5 serving/wk) to
35% in the highest quintile of intake (>10 serving/wk) for all cases and to 53% for
advanced cases of prostate cancer. The optimal protective intake level from these two
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studies is approximately 6.5 mg/day.
To date, only one intervention study with lycopene has been completed. In 1999, thirtythree prostate cancer patients at the Karmanos Cancer Institute in Detroit were randomly
assigned to receive 30 mg of natural lycopene extract or placebo for 30 days before their
Chart 4
operation. The cancer stopped spreading in 67% of the supplemented patients vs. 44%
U.S. Health
of the controls. Also, tumors were smaller in the supplemented group and PSA (prostate-
Professionals
specific antigen, an indicator of prostate cancer) declined.
Follow-Up Stu
Additional and larger intervention studies must be conducted before we can confidently
conclude whether or not lycopene prevents or slows the progression of prostrate or other
cancers.
Cardiovascular Disease: So far, studies of lycopene and cardiovascular disease have
been limited. In a multi-center European study, the risk for acute heart attack at the
highest level of lycopene in adipose tissue was reduced by 65% compared to adipose
lycopene at the lowest level.
In two other studies, an inverse relationship was found between lycopene in the serum
and the risk of cardiovascular mortality or the risk of stroke. However, a third study found
no association between lycopene serum levels and heart attacks.
Dietary Intake: Lycopene intake estimates vary considerably, depending on the
population group and sources of lycopene in the diet. According to a 1996 study,
lycopene intake in America averages 3.1-3.7 mg/day. However, a recent analysis of the
USDA CSFII 1994-96 food survey showed a corrected mean per capita intake of 5.2
mg/day, and half the population consumed <1.9 mg/day. Intake was higher in males than
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in females and decreased with age. Intake was highest for the 12-19 year age group.
As previously mentioned, the optimal protective lycopene intake level from two large
population studies is approximately 6.5 mg/day. However, there is often a big difference
between optimal diets and actual diets. In fact, according to the widely-accepted
Continuing Survey of Food Intakes by Individuals, 1994-1996, the median intake of
lycopene for Americans was only 1.9 mg/day, which indicates that a very substantial gap
exists.
Suggested Further Reading
1. Clinton SK. Lycopene: Chemistry, biology, and implications for human health
and disease. Nutr Rev 1998;56:35-51.
2. Gerster H. The potential role of lycopene for human health. J Coll Nutr
1997;16:109-126.
3. Giovannucci E. Tomatoes, tomato-based products, lycopene, and cancer:
Review of the epidemiologic literature. J. Natl. Cancer. Inst. 1999; 91:317-331.
4. Nguyen NL, Schwartz SJ. Lycopene: Chemical and biological properties. Food
Tech 1999;53:38-45.