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Vitamins & Supplements
Vitamins & Supplements Articles
Vitamin B12 is needed to produce an adequate amount of healthy red blood cells in the bone marrow. Vitamin B12 is available only in animal foods (meat and dairy products) or yeast extracts (such as brewer's yeast). Vitamin B12 deficiency is defined by low levels of stored B12 in the body that can result in anemia, a lower-than-normal number of red blood cells.
Vitamin B12 deficiency can develop for the following reasons:
Absence of intrinsic factor, also called pernicious anemia — Intrinsic factor is a protein secreted by cells of the stomach lining. Intrinsic factor attaches to vitamin B12 and takes it to the intestines to be absorbed. An absence of intrinsic factor is the most common cause of pernicious anemia. Absent intrinsic factor is often associated with a condition called atrophic gastritis, a thinning of the lining of the stomach. Atrophic gastritis is more common in elderly people of African-American or Northern-European descent. In these people, pernicious anemia develops at about age 60.
In children, decreased levels of intrinsic factor can be an inherited (genetic) condition. When this happens, low levels of intrinsic factor produce symptoms of juvenile pernicious anemia in patients younger than age 10.
Pernicious anemia occurs more commonly in people who already have diseases that are linked to immune-system abnormalities, such as Graves' disease, hypothyroidism (under-functioning thyroid gland), thyroiditis (inflammation of the thyroid), vitiligo and Addison's disease (adrenocortical insufficiency).
Tropical sprue is a digestive problem that occurs in the tropics and subtropics. People with tropical sprue do not absorb nutrients properly, especially vitamin B12 and folic acid.
Normal small intestines have fingerlike projections called villi that provide more surface area for nutrients to be absorbed. In people with tropical sprue, these villi are flattened, making absorption difficult.
Tropical sprue is rare except in a specific geographical zone. It occurs from about 30 degrees north of the equator to 30 degrees south of it. It is more common in certain countries within this tropical area, including India, Southeast Asian countries, Haiti, Cuba, Puerto Rico and the Dominican Republic. The condition afflicts residents of the affected countries as well as travelers, though usually it affects only travelers who stay for a month or longer.
The cause of tropical sprue has not been identified, but many experts suspect that an intestinal infection is to blame. When tropical sprue occurs, the lining of the small intestine is damaged so that it is unable to absorb nutrients efficiently.
After the death of Baltimore Orioles pitcher Steve Bechler more than 10 years ago, many questions arose about the safety of ephedra and the government's role in regulating the herb. Bechler died of heat stroke while taking ephedra, which occurs naturally in the Chinese herb ma huang. The speed-like drug contains the chemical ephedrine, an amphetamine-like compound closely related to adrenaline. Athletes and average people alike started taking ephedra when word started spreading about its ability to aid weight loss and increase energy and alertness.
But just because a supplement comes from natural sources doesn't make it safe. Ephedra can cause a quickened heartbeat and elevated blood pressure. Side effects include heart palpitations, nausea, and vomiting. More than 800 dangerous reactions have been reported with use of the herb. These include heart attacks, strokes, seizures, and sudden deaths. According to a study in the Annals of Internal Medicine, ephedra products make up only 1% of herbal supplement sales in the U.S., but they are responsible for 62% of herb-related reports to poison-control centers.
The authors of one analysis concluded that supplements containing ephedra and ephedrine trigger modest short-term weight loss (about 2 pounds per month more than placebo). But none of the 52 trials they looked at lasted more than six months, so there is no evidence to support ephedra use for long-term weight loss. And no studies were found that evaluated ephedra use for enhancing athletic performance. Data from 50 trials did show, however, that ephedra and ephedrine are associated with 2- to 3-fold increases in psychiatric symptoms (such as irritability and anxiety), autonomic symptoms (jitteriness, trouble sleeping), upset stomach, and heart palpitations.
In the mid-1990s, doctors at a clinic in Belgium treated 43 patients with end-stage kidney failure, requiring dialysis or transplant. Not surprisingly, these individuals had something in common in their medical histories. Between 1990 and 1992, each had used a Chinese herbal remedy in combination with two other drugs for weight loss. The herbal preparation supposedly contained Stephania tetrandra and Magnolia officinalis. But the sudden appearance of kidney failure in these patients, caused their doctors to suspect that the herb Aristolochia fangchi, which is poisonous to the kidneys, had unintentionally been substituted for S. tetrandra. The Chinese names for A. fangchi and S. tetrandra sound similar and the two are often confused. Analysis showed that the herbal remedy did, in fact, contain aristolochic acids, which are derived from A. fangchi. Aristolochic acids cause cancer in rats and mutations in bacteria and mammals.Reports of patients who had developed urothelial carcinoma (cancer of the tissues lining the bladder, ureter, and part of the kidney), as well as kidney failure related to the Chinese herbs, drew concern among the Belgian doctors. When one of their patients also developed this cancer, the doctors decided that all patients with end-stage kidney failure related to the use of Chinese herbs should be checked for cancer of these organs. By removing these organs, the doctors hoped to prevent cancer from developing in their patients. Thirty-nine of the 43 patients agreed to undergo the preventive surgery. Of these patients, 46% of them already had cancerous growths in the removed tissues. In addition, 19 of the remaining 21 patients had abnormal growths in the urinary system. The investigators also analyzed DNA samples taken from the kidneys and ureters of each patient. The DNA samples for every patient showed changes typically found after exposure to aristolochic acid. The researchers compared these results to analysis of DNA samples taken from eight patients with end-stage kidney failure unrelated to Chinese herbs. None of these control samples showed DNA changes formed by aristolochic acid.The doctors calculated the cumulative dose of the implicated herb and other treatments for each patient. They found that the risk of cancer was related to the cumulative dose of A. fangchi. Because many of the patients had also taken appetite suppressants as well as a diuretic, the doctors noted that these drugs might enhance the toxicity of aristolochic acid.This case study provides strong evidence suggesting a relationship between the Chinese herb A. fangchi and urothelial carcinoma. While a manufacturing mistake led to the introduction of this herb into an herbal preparation for weight loss, this study highlights the risks involved in taking herbal remedies. There is little control over the quality of herbal medicines. This means that the label on an herbal medicine may not accurately represent what is actually in the container, as was the case with S. tetrandra. Several countries have banned the use of herbs that contain aristolochic acid, yet Aristolochia is readily available in the United States in capsule form.In the United States, the FDA does not have the authority to assess the safety and efficacy of a dietary supplement before it reaches the shelves of stores. The agency is allowed to restrict a supplement only after it proves the substance is harmful as commonly consumed, but there is no adequate system for reporting serious side effects associated with these products. Furthermore, the FDA does not have any way of knowing which herbal remedies contain harmful substances such as aristolochic acid. The case of the Chinese herbal diet pill and its association with urothelial cancer is just one of a number of cases that demonstrate the need for greater oversight of dietary supplements and caution in the use of supplements on the part of consumers.