Vitamins Information
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Vitamin C: Tips For Increasing Your Intake
A new RDA?
According to a recent issue of the Journal of the American Medical Association (JAMA), the National Institutes of Health is taking another look at the Recommended Daily Allowance (RDA) for vitamin C. The current RDA for vitamin C is 60 milligrams per day—about the amount you get from one orange. Due to recent findings on the potential health benefits of this wonder vitamin, the NIH is now considering boosting the RDA to somewhere between 100 and 200 milligrams per day, two to three times the current recommendation.
Why all the hype?
Vitamin C has long been known for its value as an antioxidant. Antioxidants are natural compounds found in many of the foods we eat. The most well known antioxidants are vitamin C, selenium, beta carotene and vitamin E. Antioxidants work by inhibiting toxic substances in the body (also known as "free radicals") which may lead to the development of cancers, heart disease and the aging process. There has been a strong correlation between diets high in fruits and vegetables (which are rich in antioxidants) and reduced risk of chronic diseases. Vitamin C may account for much of this protection. However, we are also finding numerous other compounds within fruits and vegetables, collectively called "phytochemicals", that may also play a preventative role. Phytochemicals are defined simply as chemicals found in plants. They occur naturally in fruits, vegetables, grains, nuts and seeds. These substances, many of which also have an antioxidant effect, may protect our bodies from cellular damage that can lead to cancer and other chronic diseases.
Due to the strong correlation between diets abundant in fruits and vegetables and disease prevention, The National Cancer Institute launched the "5-A-Day" program. The basis of this campaign promotes the intake of a minimum of five fruits and vegetables daily as a good defense against cancer and other diseases. A specific recommendation of this program is to include vitamin C rich fruits and vegetables in the diet each day since vitamin C is a particularly well-researched antioxidant. The mainstay of the program, however, is that by eating five servings of produce daily we can easily take in not just a good dose of vitamin C, but the minimum amount of protective plant chemicals shown to be effective in reducing risk of chronic diseases. Remember, five is the minimum amount. In the case of fruits and veggies it's definitely a situation where more is better!
Soy Linked to Low Sperm Count
WEDNESDAY, July 23 (HealthDay News) -- Eating half a serving of soy food a day lowers sperm concentrations and may play a role in male infertility, particularly in obese men, Harvard University researchers report.
The reason for this relationship between soy and sperm count isn't clear. However, researchers speculate that soy increases estrogen activity, which may have a negative affect on sperm production and also interfere with other hormonal signals.
"There have been a lot of interest in estrogen and isoflavones in particular and a potential relationship to fertility and other reproductive disorders," said lead researcher Dr. Jorge Chavarro, a research fellow in the department of nutrition at the Harvard School of Public Health.
Research in animals has shown that isoflavones and estrogen can have a potentially negative affect on reproduction, including decreased fertility, Chavarro said. However, there is very little evidence of how these findings apply to humans, he said.
The new research, he added, lends support to how results of animal studies apply to humans. But Chavarro considers the findings preliminary and inconclusive. "It's way too early to say stop eating soy foods," he said. "It's not time to worry about whether you're eating too much soy. There's not enough information to conclusively say that. "
His report was published in the July 24 online edition of the journal Human Reproduction.
For the study, Chavarro and colleagues collected data on 99 men who attended a fertility clinic for evaluation. The men were asked about how much of 15 soy-based foods they ate in the past three months.
The foods men were asked about included tofu, tempeh, tofu or soy sausages, bacon, burgers, soy milk, cheese, yogurt, ice cream and other soy products like roasted nuts and energy bars.
Because different foods have different levels of isoflavones, half a serving of soy is equal to about one cup of soy milk or one serving of tofu or soy burgers every other day, Chavarro noted.
Chavarro's team found that men who ate the most soy had 41 million fewer sperm per milliliter of semen compared with men who did not eat soy foods. Normal sperm counts range between 80 million and 120 million per milliliter, according to a press release from the journal, a monthly publication of the European Society for Human Reproduction and Embryology.
In addition, the researchers found that the link between soy and sperm concentration was stronger among overweight and obese men. Overweight and obese men produce more estrogen than thinner men, and soy may increase those estrogen levels even further, they speculated.
Moreover, the link between soy and sperm concentration was strongest in men with higher sperm concentrations. Men who have normal or high sperm counts may be more susceptible to soy foods than men with low sperm counts, Chavarro said.
Infertility expert Dr. Hossein Sadeghi-Nejad, an associate professor of urology at UMDNJ New Jersey Medical School and Hackensack University Medical Center, agreed that soy may be one factor affecting fertility, especially in overweight and obese men.
"When patients are overweight, the fat tissue converts male hormones to more female hormones," Sadeghi-Nejad said. "So, it is possible that the combination of this estrogenic source [soy] and the extra internal estrogen that is caused by the conversion of androgen to estrogen through the fat has a more deleterious effect in that group of patients."
In addition, Sadeghi-Nejad noted that although sperm counts decreased most among men who have the highest counts, that should not affect fertility, since sperm counts were still in the normal range.
"But this is a good reminder that if you have an overweight patient, with abnormal semen parameters, and a very high soy intake, it may be wise for them to decrease this factor," Sadeghi-Nejad said.
More information
For more about obesity and infertility, visit the Obesity Action Coalition.
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