Foods that heal: Can nutraceuticals cure common illnesses?
Garlic, ginseng, glucosamine, oil of oregano: these extracts from common foods, or "nutraceuticals," are touted for their power to relieve or prevent common illnesses. But do they really work? Best Health investigates
Have you read headlines like ‘Ginseng May Help Treat Diabetes‘ and wondered if they were true? Or maybe your best friend swears by oil of oregano during cold and flu season. Health Canada defines nutraceuticals as purified or concentrated extracts from certain foods that are demonstrated to improve health through physiological benefits or to protect against chronic disease. While nutraceuticals, vitamins and minerals all fall under the category of natural health products in Canada, nutraceuticals produce a medicinal effect going beyond basic nutrition, notes Heather Boon, chair of Health Canada’s Expert Advisory Committee for Natural Health Products and an associate professor in the faculty of pharmacy at the University of Toronto.
It’s certainly convenient to pop a pill that has the health benefits of a particular food, without the potential drawbacks’like the antioxidants of red wine minus the alcohol. Still, while many nutraceuticals show promise, they also pose questions. ‘Natural substances can be very complicated,’ says Paul Thomas, a registered dietitian and scientific consultant for the U.S. National Institutes of Health’s Office of Dietary Supplements. ‘Depending on how they are processed, the combination of ingredients in the final product can be very different from brand to brand.’ This means it’s tough for healthcare professionals to recommend how much to take and how often.
Another challenge is that most nutraceutical research is in the preliminary stages. But, perhaps most importantly, ‘natural’ does not always equal harmless. ‘If it has positive biological effects in the body, it also has the potential to have negative effects,’ says Thomas. ‘It’s always a good idea to talk to your doctor about possible side effects and interaction with other medications.’
Clearly, it’s tricky figuring out which nutraceuticals live up to the hype, and which ones are a waste of your time and money. So Best Health took a closer look at some of the most talked-about nutraceuticals. Here’s what the latest research reveals.
Conjugated linoleic acid (CLA)
This is an essential fatty acid found in dairy products, beef, poultry and eggs. It’s usually sold as capsules or tablets.
The claim: It promotes weight loss by decreasing body fat and preventing weight gain.
Does it work? An analysis of 18 studies on CLA and fat mass, published in the American Journal of Clinical Nutrition in 2007, concluded that CLA led to a modest reduction of fat’about 0.2 pounds per week compared to the placebo group. (That’s more than 10 pounds lost in a year, in comparison to the 0.8 pounds typically gained.)
Keep in mind: Study results have been mixed: Some have found increased levels of blood inflammation markers or impaired blood vessel function, while others have not. A 2008 study in the Journal of Lipid Research looked at mice fed CLA and discovered an accumulation of fat in the liver, which is linked to insulin resistance and diabetes. Many experts say longer-term studies are required. CLA may interact with medications for diabetes and hyperlipidemia (high level of fats in the blood).
Bottom line: ‘Compounds like CLA may have a minor effect on weight loss, but no pill is a substitute for exercise and diet,’ says Dr. Mark Tarnopolsky, director of the Neuromuscular and Neurometabolic Unit at McMaster University Medical Centre in Hamilton, who has studied CLA. His research shows CLA seems to be safe, at least over a two- to six-month period, taken at up to three grams per day.
Dehydrated or aged garlic is sold in pills, powder or oil.
The claims: It reduces cholesterol and blood pressure.
Does it work? While previous animal studies suggested that garlic lowers cholesterol, a study published in the Archives of Internal Medicine in 2007 assigned 192 people with moderately high cholesterol levels to consume a garlic supplement, placebo or raw garlic six days a week for six months. The harmful LDL cholesterol levels did not change for any of the participants. More studies are needed.
As for blood pressure, a report in BMC Cardiovascular Disorders in 2008 analyzed 11 garlic studies and found that in people with high blood pressure, garlic supplements reduced systolic pressure (the top number in a reading) by an average of 8.4 mm Hg and diastolic pressure (the bottom number) by 7.3 mm Hg, a result that compares to blood pressure medication. Again, experts believe more studies are needed.
Keep in mind: Garlic can thin the blood, so consult your doctor if you are having surgery or taking blood-thinning medication such as warfarin. Garlic pills may also reduce the effectiveness of birth control pills and medications used to treat HIV.
Bottom line: ‘Garlic pills can lower cholesterol and blood pressure by a modest amount, but weight loss, changes in diet and exercise, and medications like statins [to lower cholesterol] are also needed,’ says Dr. Kenneth Melvin, a Toronto cardiologist. The doses in the blood pressure study ranged from 600 to 900 milligrams per day.
Derived from the dried root of the ginseng plant, the two main types are Asian (Panax ginseng) and North American (Panax quinquifolium). It’s sold in capsules.
The claim: It lowers blood sugar.
Does it work? A 2008 study on Asian ginseng from the University of Toronto found that participants with well-controlled type 2 diabetes who took a ginseng supplement for 12 weeks improved their blood levels of glucose and insulin, compared to diabetics who took a placebo. An earlier study from that research team had shown that North American ginseng helped reduce blood sugar levels of diabetics who were taking medication.
Keep in mind: If you have diabetes or are taking blood thinners, talk to your doctor before taking ginseng. Different varieties have different effects, warns Vladimir Vuksan, who conducted the studies at Toronto’s St. Michael’s Hospital, and holds a dual professorship at the University of Toronto in the departments of medicine
and nutritional sciences. In his research, cultivated North American ginseng (most is grown in Ontario) and some varieties of Korean ginsengs helped lower blood sugar, but Japanese and wild North American ginseng did not, and Siberian and Chinese ginseng actually increased it.
Bottom line: ‘If your diabetes is well-regulated through medication and diet, you can consider adding ginseng because it works with those approaches,’ says Vuksan. ‘We recommend Ontario-grown North American ginseng, one gram taken three times a day before meals.’
This is an amino sugar and a building block of cartilage, which protects our joints. It is derived from chitin
(the outer shells of crabs, lobsters and shrimp), and is sold as capsules or tablets.
The claims: It relieves pain and stiffness from osteoarthritis and slows its progression.
Does it work? Results are mixed. A large clinical trial, published in The New England Journal of Medicine in 2006, had volunteers with osteo-arthritic knee pain take a glucosamine/chondroitin supplement (chondroitin sulfate is also derived from chitin and helps cartilage retain water) for six months. Participants with moderate to severe pain did have better pain relief than those taking a placebo, but those with mild pain didn’t get significant relief. A review of 25 studies from between 1980 and 2004, published by The Cochrane Library, showed that while some studies found that glucosamine improved pain and physical function, others found it was no better than a placebo.
Keep in mind: If you have diabetes or a shellfish allergy, or are on a low-potassium or low-sodium diet, talk to your doctor before taking glucosamine.
Bottom line: ‘I usually tell people to give glucosamine a try for two or three months,’ says Dr. Joanne Homik, director of the division of rheumatology at the University of Alberta. ‘If it helps, stick with it; if it doesn’t help, stop.’ Most studies have looked at 500 milligrams taken three times a day for 30 to 90 days.
Grape seed extract and resveratrol
Grape seed extract contains the antioxidant proanthocyanidin. Resveratrol is an antioxidant derived from grape skins. They are sold in capsules or tablets, and are sometimes packaged together.
The claims: They fight cancer, diabetes and high blood pressure.
Do they work? One of the first human clinical trials to assess grape seed extract dealt with high blood pressure. ‘We found that red wine stimulates the endothelium [the layer of cells that lines blood vessels] and relaxes blood vessels. Then we thought, let’s see what happens when you take out the alcohol,’ says Dr. C. Tissa Kappagoda, director of the preventative cardiology program at the University of California in Davis. ‘We did two studies with grape seed extract. One was on people with metabolic syndrome [a combination of health factors, including high blood pressure, high blood sugar, excess abdominal fat and high cholesterol]; the other was on people with pre-
hypertension. Blood pressure was reduced in both groups.’
Much of the newest research on resveratrol centres on animal studies and laboratory cultures. A study in Cancer Prevention Research in 2008 found that in lab tests, resveratrol inhibited the abnormal cell formation associated with breast cancer, while another 2008 study in Diabetes, Obesity and Metabolism showed that, again in lab tests, resveratrol protected blood vessels from cellular damage caused by complications from diabetes.
Keep in mind: Grape seed extract and resveratrol are generally considered to be safe, but their interactions with medications have not been well studied.
Bottom line: ‘Anyone considering diet and exercise to lower their blood pressure can try grape seed extract to also help control it,’ suggests Kappagoda. People in his study took 150 to 300 milligrams of extract daily for a month. A concentrated form of resveratrol, called Resveravine, is available as 50-milligram capsules.
Oil of oregano
This oil is derived from wild oregano. It’s usually sold as a liquid.
The claims: It helps you fight viruses, bacteria and fungi.
Does it work? Devotees swear by it to ward off colds and flu, but few, if any, published human clinical studies exist. The research is mostly in food science, as oil of oregano deters microbial growth on refrigerated meat. Dr. Harry Preuss, a professor of physiology at Georgetown University in Washington, D.C., found in a lab study that relatively low doses were as effective as standard antibiotics at zapping the growth of harmful staphylococcus bacteria. Other recent lab studies found it inhibited various types of candida yeast (which can cause vaginal yeast infections) and antibiotic-resistant E. coli.
Keep in mind: While no side effects or drug interactions are known, oil of oregano has not been widely studied, so don’t give up on medication. Also, don’t take it if you have an allergy to plants in the mint family, including thyme, sage and basil.
Bottom line: It’s fine to take oil of oregano once or twice a week during the winter to help prevent cold and flu, or when you’re sick, says Iva Lloyd, a naturopathic doctor in Markham, Ont., and the past chair of the Canadian Association of Naturopathic Doctors. ‘I don’t recommend it year-round.’ The dose varies, depending on brand, from two to 15 drops a day, two to three times a day. If concentrated, mix with a glass of water.
This is a dietary fibre from the seed husks of the Plantago ovata plant. It’s sold as capsules or a powder, and is added to some breakfast cereals.
The claim: It promotes heart health by lowering cholesterol and inflammation.
Does it work? Studies’including one in the European Journal of Clinical Nutrition (EJCN) in 2008’show that psyllium helps to lower harmful LDL cholesterol while leaving the good HDL cholesterol unaffected. Findings about its effect on C-reactive protein (CRP), an inflammation marker that signals heart attack risk, are inconsistent: A 2007 study from the Medical University of South Carolina found that a diet high in psyllium fibre from supplements or food significantly reduced CRP, but a 2008 study by the same researcher, which used only supplements, found no change in CRP levels, suggesting that high-fibre foods may be more effective than supplements.
Keep in mind: Talk to your doctor if you have diabetes or digestive tract problems, such as irritable bowel syndrome (IBS)’ psyllium helps some, but not all, people with IBS.
Bottom line: ‘With a whole-grain cereal that contains psyllium, you also get iron, B vitamins, zinc and magnesium,’ says Bonnie Conrad, a registered dietitian in Halifax. Patients in the EJCN study on cholesterol took between three and 20 grams of psyllium per day.
Look for the ‘NPN’
When you are buying a nutraceutical, check for the letters NPN (natural product number) on the label, followed by an eight-digit number (e.g., NPN 12345678). This means the product has been assessed by Health Canada, found to be safe and effective when used according to directions, and authorized for sale in Canada. Check out the Licensed Natural Health Products Database at healthcanada.gc.ca/lnhpd.
This article was originally titled "Turning Foods into Medicines," in the March/April 2010 issue of Best Health. Subscribe today to get the full Best Health experience’and never miss an issue!’and make sure to check out what’s new in the latest issue of Best Health.