Potential Dangers of Dietary Supplements to Health
Dietary supplements are billed as immune triggers, weight-loss wonders, “brain power”, muscle-expanding elixirs, and much more. They can be bought from the shelves of health food stores, drug stores, and supermarkets. They are a category of nutritional additives that once included just vitamins and minerals, but now also encompass herbs, amino acids, fish oils, hormones, and many other substances.
Not only is the array of supplements dazzling, but also their popularity is soaring. According to market research firm, Euromonitor International, sales of vitamins and minerals in America alone have reached $4.1 billion annually. The more exotic substances, including herbs such as ginkgo and echinacea and hormones such as melatonin, have drawn an even more impressive crowd. The reason for this is partly as a result of rising medical costs which encourages both prevention and self-care.
Even science has lent credence to a handful of the claims made for dietary supplements. Some studies have suggested, for example, that vitamins may help prevent serious illnesses such as heart disease and cancer. All this has fed a media frenzy regarding the latest research into natural remedies.
At the same time, supplements of all kinds have moved from niche retailers such as health food stores into drugstores and supermarkets, making them more widely available and also more appealing to the mainstream public. And the claims have gone far beyond what science has shown, appealing to everybody from athletes to people with chronic diseases.
There are presumptive claims that Garlic could lower cholesterol levels and blood pressure, boost a weakened immune system, unstuffy sinuses, and ward off some cancers. That the mineral chromium picolinate allegedly promotes weight loss, prevents or reverses diabetes, reduces cholesterol, and builds muscle. Some claims even suggest that amino acid mixtures have the potential to produce muscle-bound individuals without sweat, while Dong quai, a root from China, will supposedly relieve menstrual cramping and other ailments in women.
While a few of the claims have scientific backing, most do not. And many supplements have unmentioned, but documented, dangers. Even ordinary vitamins such as vitamin A and niacin (a B vitamin) can produce morbid ailments from birth defects to liver damage at excessive doses. And the recent spate of illnesses and deaths from the stimulant ephedrine, sold in seemingly drug potions under such brand names as Herbal Ecstasy and Ultimate Xphoria, underscores the potential risks from taking herbs that have not been studied for possible side effects.
There are no safeguards or guarantees. Government regulatory agencies do not sanction these pills nor do they evaluate most of what is written on or inside their bottles. Unlike most over-the-counter drugs, dietary supplements are only very loosely regulated by government legislation. In fact, supplement manufacturers have more leeway than food producers and can legally print all manner of unsupported claims on their labels.
Many nutrition scientists are skeptical of these claims, even those supported by sound scientific reasoning and a smattering of studies. The reason isn’t far-fetched. Only rarely does a consistent body of research, including large studies in humans, buttress a health claim for a vitamin, mineral, or herb. For instance, chemical analysis shows that Dong quai contains compounds known to expand blood vessels (which may help relieve cramps), but no study of its effect on humans supports this claim. The evidence for the benefits of chromium picolinate and garlic is conflicting, and the claims made for amino acids are little more than wishful thinking, according to medical experts.
Some people seem to be helped by supplements that prove ineffective in scientific studies. That is often because of something called the “placebo effect,” in which a substance works only because a person believes it works. The placebo effect is quite real, and because of it, all reliable studies include a control group, a group of people who get dummy pills or sugar syrups instead of the real thing. By comparing the control group to subjects who get the substance under study, scientists can see whether the supplement has a genuine biological effect or is no better than a placebo.
There is no doubt that vitamins and minerals are critical to good health. Vitamins are carbon-containing substances derived from living things. They are used by the body in tiny amounts to build, maintain, and repair tissues. For example, the various compounds dubbed vitamin A are used in eye tissues for vision, and in cell nuclei to aid gene expression, among other functions. Vitamin D is needed for bones to develop properly, and the B vitamin, folic acid, aids in the digestion of amino acids and plays a role in the metabolism of deoxyribonucleic acids (DNA) and ribonucleic acids (RNA). DNA is genetic material that codes instructions for the production of proteins-the basic building blocks of life; RNA is a molecule that helps carry out those instructions.
Unlike vitamins, minerals are inorganic (not bound to carbon). They come from soil and water, but make their way into the plants and animals people eat. Essential minerals include calcium, phosphorous, magnesium, iron, zinc, iodine, and selenium. These minerals have myriad biological roles. Some work in enzymes (protein moieties that make possible many critical biological processes). Others enable blood to carry oxygen to the body’s tissues; strengthen bones and teeth; help cells grow and repair themselves; or keep the heart beating properly.
Unlike macronutrients-the fats, proteins, and carbohydrates people burn for energy-vitamins and minerals are used by the body in much smaller quantities. How much of these micronutrients are needed to meet an individual’s requirement depends on the nutrient and on the person. However, in most developed countries, general guidelines on recommended dietary allowances (RDAs) are set which are revised about once every five years.
These are educated guesses about nutrient requirements based on evidence derived from studies in large human populations, test-tube experiments, and everything in between. In setting RDAs, scientists account for the body’s inability to completely digest or absorb certain vitamins and minerals in foods or pills, and include a margin of safety.
RDAs are, in most cases, designed to prevent nutrient deficiency diseases such as scurvy, caused by a lack of vitamin C, and goitre, resulting from too little iodine. The consequences of such diseases can be serious. In scurvy, the gums become spongy, the teeth loosen, and tiny blood vessels called capillaries bleed into the skin and mucous membranes. Goitre, an enlargement of the thyroid gland at the base of the neck, can lead to a type of mental retardation known as cretinism.
In Nigeria and most parts of sub-Saharan and Central Africa, severe micronutrient deficiencies are commonplace because most people’s diets are not good enough to prevent them. Indeed, many experts believe it is a lack of certain vitamins and minerals in the foods Africans in these parts of the continent eat that raises their risk of chronic ailments. In a few cases, the RDA reflects this notion. For instance, the RDA for calcium is set at a level to ward off a disease of weakened bones called osteoporosis that usually shows up in old age. But the RDA for many nutrients may be too low to stave off certain illnesses. Some studies even suggest that truly protective doses far exceed what a person could eat in a day and thus, supplements are necessary.
An argument for supplements could certainly be made for folic acid, a B vitamin that recent evidence has shown can prevent certain deadly or paralyzing birth defects and may also ward off heart disease. The RDA for folic acid, also called folate, is 200 micrograms (A microgram is one-thousandth of a milligram) for adult men and 180 micrograms for adult women. However, many experts now recommend that all women of child-bearing age consume at least 400 micrograms of folate a day to prevent birth defects.
What is the basis for this recommendation? Controlled studies (studies that include control groups) have shown that women who took folic acid supplements when they conceived were far less likely to give birth to infants with neural tube defects such as anencephaly, in which the brain does not develop fully, or spina bifida, when the spinal cord does not completely close. Folic acid, it appears, is critical for the closure of the neural tube, the tissue that encloses a developing embryo’s brain and spinal cord.
Folate is also used by the body to break down an amino acid called homocysteine, and that role is critical to its presumed ability to prevent heart disease. In large amounts, homocysteine is thought to scar arteries and cause them to clog, leading to heart attacks. Recent studies have shown that people with high homocysteine levels are at increased risk for heart disease. Other recent work has indicated that people with low blood levels of folic acid are likewise at increased risk. Folate supplements can lower homocysteine levels. However, no one has yet shown that taking folic acid supplements prevents heart attacks and prolongs lives.
Thus medical experts still recommend getting folic acid from foods such as leafy green vegetables, beans, and orange juice instead of supplements, since these foods have other beneficial nutrients as well. But since most Nigerians do not consume even the RDA for folic acid, women of childbearing age are advised to take supplements, especially since the folic acid in supplements is better absorbed than that in foods.
Scientists have also been turning up evidence suggesting that large doses of vitamins E and C and beta-carotene, a substance the body converts into vitamin A, may prevent chronic illnesses such as heart disease and cancer. These nutrients are thought to get rid of unstable chemicals in the body known as free radicals that can damage tissues and contribute to disease.
Free radicals are formed all the time-whenever the body uses oxygen or is exposed to a toxin such as cigarette smoke-and can harm cells in a number of ways. They can chemically alter fats in low-density lipoproteins (LDL) (components in the blood that carry cholesterol), making them more likely to clog arteries. Free radicals can also damage DNA, possibly raising the risk of cancer.
Vitamins C and E and beta-carotene are thought to work as anti-oxidants(molecules that block the formation of free radicals and thus lower the risk of heart disease and cancer). But what is the evidence for this theory? Numerous studies have shown that people who eat lots of fruits and vegetables-the major sources of many anti-oxidant nutrients-have a lower risk of heart disease than those who do not. Similarly, a lot of research indicates that people whose diets are produce-poor have a higher risk of several kinds of cancer.
While those studies strongly support the advice of most herbal medicine practitioners to eat at least five servings of fruits and vegetables a day, they do not prove that isolated anti-oxidants in the form of supplements provide disease protection. Although test tube and animal studies do suggest benefits from anti-oxidant supplements, the evidence in people has been mixed.
Earlier research showing associations between intake of beta-carotene and reduced cancer incidence have not held up in the latest intervention trials. One of these trials, the Beta Carotene and Retinol Efficacy Trial (CARET), had to be discontinued because preliminary results indicated that a combination of beta-carotene and vitamin A was not preventing lung cancer in high-risk men and women and may actually have been harming study participants. Published in the New England Journal of Medicine, the study found 28 per cent more lung cancers and 17 per cent more deaths in participants taking 30 mg of beta-carotene and 25,000 IU of vitamin A.
This result was similar to that found in two other trials. Researchers conducting the Physicians’ Health Study reported in the same issue of the New England Journal that they found no benefit or harm from beta-carotene on cancer or heart disease. Not all of the intervention trials have reported negative results, however. A recent study published in the Journal of the National Cancer Institute suggested that a combination supplement of beta-carotene, vitamin E and selenium reduced the stomach cancer mortality rate by 21 per cent on average among subjects in Linxian, China.
Many scientists and physicians are excited about the recent results from studies of vitamin E and heart disease and are taking E supplements themselves. However, given the contradictory nature of much of this data, especially the beta-carotene and cancer work, other experts are cautious in recommending anti-oxidant supplements for the prevention of chronic diseases. A better option, they say, is to get as many of these nutrients as possible from foods.
What might be better about fruits and vegetables? The micronutrients identified so far may not actually be the protective ones or foods may contain other chemicals that magnify a nutrient’s protective effect. In some cases, evidence indicates that the form of a nutrient in foods is better absorbed than the form that comes in pills or powders. Calcium in milk and other dairy products, for example, is known to be better absorbed by the body than in pill form.
Potential Dangers
Taking high doses of certain supplements can be dangerous. Although they are not called drugs, vitamins and minerals at high doses act like drugs and can have similar side effects to drugs. For example, it is known that doses of vitamin A above 25,000 IU can cause, among other things, severe liver damage, bone diseases, and, when taken by pregnant women, birth defects. Recent evidence has shown that doses even as low as 10,000 IU can cause some types of birth defects.
Other vitamins can also be toxic. Taking more than 100 mg per day of vitamin B6-about 50 times higher than the RDA-can harm the nervous system, causing problems with balance and altered sensations. Nevertheless, this vitamin often is sold in capsules containing 100 mg to 500 mg. And niacin, which comes in supplements of 250 mg, 400 mg, and 500 mg, can trigger vomiting, diarrhea, and even liver damage, among other maladies, in doses of 500 mg from slow-release formulations and 750 mg from immediate-release pills.
Toxicity also has been associated with high doses of iron, selenium, and even vitamin C. Folic acid doses above 1 mg can mask symptoms of vitamin B12 deficiency, a rare condition that is most often seen among the elderly and some strict vegetarians. If it goes undetected, vitamin B12 deficiency can lead to irreversible nerve damage. There may be unidentified dangers as well. While doses of vitamin E up to 800 IU appear to be safe for most healthy people, it will take long-term studies of the use of vitamin E, involving thousands of people, to know whether high doses are safe for everyone.
Herbal Remedies
Unlike vitamins, which consumers use primarily for prevention, herbs are typically used as treatments for everything from colds to cancer. Unrefined herbs-the leaves, bark, flowers, berries, or roots of plants-are now becoming part of mainstream medicine in most countries.
In China, herbal remedies-such as Yin Chiao, an herbal formulation used to treat colds, and stephania, a root used for weight loss-dominate medical practice. European doctors also readily incorporate herbs into their practices. In Germany, a concentrated extract made from the leaves of the ginkgo tree is used as a treatment for headaches and tinnitus (a ringing in the ears), among other maladies. In the South Sea Islands, tea-tree oil, pressed from the leaves of a tropical tree, has been used for centuries as a skin antiseptic.
In the United States, herbal remedies have caught on among the general public, if not physicians. Experts say that herbal remedies are the fastest growing segment of the supplement market. Their appeal lies largely in the word “natural.” But natural is not a synonym for safe. It does not mean the stuff works either.
Some herbs probably are effective. After all, about 25 per cent of prescription drugs found in the U.S. alone are derived from plants. For example, digitalis, the heart-muscle strengthener, is an herb derived from a plant called foxglove, and taxol, a cancer treatment, comes from the Pacific yew tree. To date, the FDA has judged at least 16 herbs as safe and effective, allowing them to be sold over the counter as drugs. These include elm bark, sold as Throat Coat Tea, and the laxatives senna, marketed under the brand name Senokot, and psyllium seeds, sold under the label Metamucil.
That still leaves hundreds of herbs sold in the United States whose effectiveness is unproven. For instance, there is little documentation for the purported ability of a Chinese root called ginseng to build up the body’s resistance to stress and disease and to enhance sexual potency. Similarly, garlic’s power to strengthen the immune system, prevent cancer, or unstuff sinuses remains highly controversial.
Still, that does not mean that these herbs and others do not do something to the body. In fact, ingredients in some products sold as herbs are similar to over-the-counter drugs. White willow bark, for instance, is a lot like aspirin. Both belong to a class of compounds called salicylates and so have similar effects on the body. And the Chinese herb Ma Huang, derived from an evergreen plant of the genus Ephedra, contains ephedrine, a stimulant used in many over-the-counter and prescription drugs.
Because herbs are not required to undergo safety tests, it is difficult to be sure any are completely safe. The safest herbs are those for which no one has reported toxic effects. Examples of such herbs include ginger, milk thistle, and garlic. The absence of negative reports about a substance is not, however, proof of safety, since people do not always associate their symptoms with herbs they are taking. Thus, many adverse effects probably go unnoticed and unreported.
Meanwhile, many herbs known to be toxic remain on the market. Perhaps the best known example is Ma Huang. As mentioned earlier, it contains ephedrine, a stimulant that can harm the nervous system and heart, and is a component in dietary supplements that manufacturers claim can promote weight loss and boost energy. In some cases, it is supposed to produce a natural “high” like that from illegal drugs such as “ecstasy.” Its harmful effects range from dizziness, headaches, and stomach aches to heart attacks, strokes, seizures, and death. So far, more than 600 reports of injuries and 17 deaths linked to ephedrine products have been recorded in the U.S. alone. The majority of injuries were reported by women taking weight-loss formulations containing the substance.
Herbs can also pose risks because they are unregulated and thus bear no warning labels mentioning side effects or safe dosages. For instance, consumers are not told on a package of white willow bark that this herb, like aspirin, can upset the stomach, cause bleeding during pregnancy, increase the risk of a stroke, or spawn Reye’s syndrome, a serious illness appearing in some feverish children given aspirin.
In addition, herbal products are not subject to careful quality control; thus, undesirable substances can sneak in without anyone knowing. Ayurvedic herbs, made in India and used in traditional Hindu medicine, are boiled in clay or metal pots, which can leave behind traces of toxic substances such as lead, mercury, or arsenic. And sometimes products contain misidentified plant parts. In the early 1990s, 70 women at a clinic in Belgium took an herb for weight loss that clinic administrators thought was stephania. Instead, it was a toxic plant, called aristolochia that poisoned their kidneys.
Amino Acids
Amino acid supplements are, like herbs, largely unstudied and unregulated; thus, as a group, their safety and efficacy cannot be assured. Still, Americans are consuming them for undocumented promises, ranging from building muscles to calming jittery nerves. Last year, amino acid supplement sales rang up about $400 million in the United States, according to estimates by Euromonitor International.
Should anyone be taking amino acid supplements? Most experts believe there is certainly no health reason to do so. The body does need amino acids, which it uses to build proteins and to make other vital molecules, including those that send messages in the brain. However, most humans are highly unlikely to face a shortage. Of the 20 amino acids that make up animal and plant proteins, the body can manufacture all but 9. And all of those 9-histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine-are typically plentiful in the diet in the form of proteins.
So, it is quite clear that most people are not popping amino acid supplements because they are worried about meeting their protein requirement. They are after druglike effects. Some are amateur bodybuilders looking for legal, muscle-building alternatives to steroids (illegal drugs derived from the male hormone testosterone that are believed to increase muscle size and power). Others are less concerned about brawn than brain: They take high-potency supplements of single amino acids to give them more energy, calm them down, or even make them smarter.
Many of the claims have logic behind them. Amino acids make up proteins and proteins pack muscle, so it is theoretically possible that some amino acid mixtures could help increase muscle mass. However, they certainly will not have that effect in the absence of weight training or other muscle-building exercises. And even when combined with exercise, the evidence that amino acid supplements are beneficial is tenuous at best, top scientists say. A more likely effect of taking such supplements, they add, is nitrogen-rich urine, since amino acids contain nitrogen.
Taking large doses of single amino acids could, in some cases, affect the brain, experts say. Overloading the body with a single amino acid can cause more of that amino acid to enter the brain, where it may be used to make neurotransmitters, chemicals that carry messages between brain cells and influence mood. For instance, the amino acid tryptophan is used to produce the neurotransmitter serotonin, which can have a sleep-inducing effect. And a few studies suggest that tryptophan can have a sedative effect on humans; it may also suppress appetite. But consumers no longer can find this supplement on store shelves because it has been banned for its potential toxicity.
Although some amino acids may turn out to be useful drugs, the evidence supporting their purported effects is still slim. And some of those claims are downright fanciful. For instance, experts discount the possibility that any amino acid supplement could influence such a broad-based brain function as intelligence. Even for amino acids such as tryptophan that may indeed alter mood, no one knows what the effective-and safe-doses are.
Indeed, the biggest question about amino acid supplements is safety. In humans, short-term studies have shown that high doses of some amino acids are safe-up to a point. To date, however, scientists have not established safe intake levels for any amino acid.
Animal studies have suggested that amino acids may be harmful. In large doses, single amino acids can depress the growth of lab animals, change their brain chemistry, and cause damage to organs such as the pancreas and kidneys. The reason, experts say, is that a particular balance of various amino acids is crucial for the health of many body organs; thus, taking a lot of one amino acid can upset this balance and damage organs from the liver to the brain.
At least two amino acids in dietary supplements have been associated with serious injuries in healthy people. The use of phenylalanine has been linked to various ailments including scleroderma, a disease in which fibrous connective tissue accumulates in the skin and often internal organs.
Under current law, such potentially hazardous products can easily wind up on the market. Dietary supplements have never had to stand up to the scrutiny that drugs do, meaning they do not have to be approved-or even evaluated-by the government before they are sold. Traditionally, they were considered to be only vital nutrients such as vitamins and minerals. Today, the definition of dietary supplement has been expanded to include a greater range of substances and chemicals such as herbs, amino acids, fish oils, enzymes, and mixtures of these within this loosely regulated realm giving supplement manufacturers even wider latitude in the claims they can make.
In this circumstances , the regulatory agencies still retain some control over what a supplement can say on its label, especially in the area of health claims, which specify a relationship between a substance and a disease. To make a health claim for a supplement, a manufacturer must get approval from the agencies which will grant it only when there is “significant scientific agreement” that the claim is true.
For the many untested pills, capsules, powders, and liquids that remain on the shelves, it pays to be cautious. Here are a few tips for dealing with the supplement conundrum.
�ºBefore taking a supplement, find out what evidence supports its advertised benefits-and dangers. It is a good idea to glean information from a variety of sources, not just one book or magazine article.
�ºLearn what scientists know about safe dosages and do not exceed them. In particular, do not use a large variety of herbs on a regular basis. There are no data on the safety of any botanical when combined with another herb or drug.
Ã?ºIt can make any number of claims that are not backed by good science or, in some cases, any science at all. Do pay attention to the print that reads: “This statement has not been evaluated by the Food and Drug Administration.”
�ºInform your doctor about supplement use, including vitamins. Pregnant women and people with genetic defects that impair their ability to metabolise a nutrient should not use any supplements without approval or recommendation from their physicians.
�ºWhen possible, it is generally better to get nutrients from food than from supplements. Consumers should learn what foods supply those they need most and include them in their diet.
Biography
Tunde Odumosu is a Lagos-based journalist, motivational speaker, trainer and entrepreneur with more than 8 years experience in science, business and investigative journalism. A winner of many national awards, including the Nigerian Media Merit Awards, his articles have featured in some of the most widely read magazines and national dailies such as The Guardian, Exploits magazine, The Financial Standard and The Capitol. A seasoned writer, he is currently on the staff of the Nigerian Tribune. For comments or questions, please feel free to email him at tupaski@yahoo.com
