Advertised as a natural sweetener with a low glycemic index, agave nectar has become popular with dieters and diabetics alike. Although agave doesn't immediately increase blood sugar levels, it can still contribute to insulin resistance and increase the risk for diabetes, obesity, premature aging, heart disease and liver problems. Understanding the way it works in the body reveals why everyone should avoid agave and other products full of fructose.
Fructose
Traditional agave sweetener is boiled sap from the succulent desert plant native to Mexico and the southwest United States. But the modern agave nectar found in stores today is an entirely different food. This syrup is made by refining the starchy root bulb through chemical processes using genetically modified enzymes to concentrate fructose. Like high fructose corn syrup, agave contains more fructose than glucose so it scores low on the glycemic index, where foods are ranked according to their effects on glucose levels in the blood.
Fructose occurs naturally in fruits and some root vegetables, but it is present in only small amounts and exists as part of a complex. Bound to fiber, fatty acids, vitamins and minerals, natural fructose in whole foods is digested and absorbed slowly. In contrast, fructose found in simple carbohydrates like agave nectar, agave syrup, high-fructose corn syrup and sugar (which is 50 percent glucose and 50 percent fructose) is free, unbound, quickly digested, and absorbed into the bloodstream in large quantities.
Carbohydrate Metabolism
After carbohydrates are consumed and digested, rising levels of glucose in the blood trigger the pancreas to secrete insulin. This hormone allows glucose to enter cells where it is burned for immediate energy. Insulin also prompts the body to store excess glucose for future energy use, as glycogen in the liver and muscles and as fat in adipose tissue. When insulin levels are high, the body will always accumulate fat.
High levels of insulin send a message to the brain that immediate energy needs have been met and the brain responds with feelings of satiety. Insulin also triggers fat cells to secrete leptin, another hormone that reduces hunger and food intake. But fructose enters cells through transporter proteins that are absent from brain cells and insulin-producing cells in the pancreas, so fructose can never trigger the secretion of insulin or leptin, nor their signals to stop eating.
Large amounts of fructose in the blood inhibit the conversion of glucose to glycogen. As a result, glucose levels remain high and the pancreas secretes even more insulin in an attempt to clear it from the blood. If levels of insulin are chronically high, over time cells will compensate by becoming resistant. When cells aren't sensitive to insulin, they can't take up glucose as effectively, and without enough glucose, cells starve. Starving cells stimulate appetite and the body is motivated by hunger to continue eating. This cycle is a key contributor to weight gain and obesity.
Insulin resistance and elevated glucose levels worsen symptoms of diabetes, and in healthy people, they can cause diabetes. In the short term, high levels of blood sugar can lead to fatigue, dehydration, susceptibility to infections and blurry vision. In the long term, they can cause cardiovascular disease, neurological complications, kidney failure and blindness. Execssive insulin and glucose levels can also stimulate the growth of cancer cells.
Advanced Aging
Other effects of high levels of fructose and glucose in the blood are increased production of reactive oxygen species, like free radicals, and advanced glycation end-products (AGEs). Free radicals are a normal part of metabolism, usually neutralized by antioxidants before they do serious damage to cells. However, too many can overwhelm the body's capacity to control them and increased cellular damage is one cause of aging. Unnaturally high amounts of AGEs can also cause premature aging because they easily bind together in a process called cross-linking and become resistant to natural disposal mechanisms. When AGEs accumulate in tissues, they cause rigidity and interfere with normal function.
Collagen, a fundamental component of connective tissue, is particularly susceptible to cross-linking. Collagen cross-linking in skin causes it to lose elasticity and take on a prematurely old appearance. Collagen cross-linking in bones, cartilage and tendons can cause joints to stiffen. In the cornea, lens and retina of the eye, it can cause browning, opacity and cataract formation. In kidneys: renal failure. In blood vessels: increased pressure and hypertension. In nerve endings: peripheral neuropathy. AGEs have also been found in the brain plaques and tangles associated with Alzheimer’s disease.
Cardiovascular Disease
Because fructose cannot be used as immediate energy like glucose, it is converted into triglycerides in the liver and stored as fat. Triglycerides are attached to lipoprotein molecules that shuttle them through circulation and deposit them in fat cells. Classified as low-density lipoproteins (LDL) and very low density lipoproteins (VLDL), they contain a high percentage of fat and a small percentage (or low density) of protein. After the triglycerides are delivered to fat cells, the proteins become small and dense LDL particles.
Small, dense lipoproteins remain in the blood longer and are more likely to oxidize than the large, fluffy LDL particles produced when triglyceride production is low. Oxidized LDL particles and free radical damage initiate blood vessel injury associated with atherosclerosis and coronary artery disease. Like grains of sand, small, dense lipoproteins get stuck in atherosclerotic plaques and clog blood vessels. Additionally, high levels of insulin stimulate the proliferation of smooth muscle cells that line blood vessels, occluding them even further.
When blood can no longer flow because vessels are too narrow, or because an atherosclerotic plaque ruptures and a piece that breaks off blocks blood flow in a smaller vessel, tissues die. If blood can't circulate through small vessels of the lower leg, it can become gangrenous. If blood flow in the brain is interrupted, a stroke occurs. If arteries around the heart are affected, a heart attack happens. Any organ can be affected.
Liver Disease
Fructose has also been linked to liver problems. A 2008 study found that people who consume it regularly have a two- to three-fold higher risk of developing non-alcoholic fatty liver disease (NAFLD) compared to adults of similar age, gender and body mass index. A 2010 study from Duke University Medical Center found that fructose consumption in people with NAFLD can cause hardening and scarring of the liver which may lead to cirrhosis, liver failure, liver cancer and the need for a liver transplant.
The Bottom Line
Agave nectar is an unhealthy sweetener and it isn't alone. High fructose corn syrup and sugar are also harmful, and artificial sweeteners are poor alternatives. If you're hungry for something sweet, have a piece of fruit. Packed with nutrients and fiber, it's the best sweet treat yet.
References
Abdelmalek MF et al. Increased fructose consumption is associated with fibrosis severity in patients with nonalcoholic fatty liver disease. Hepatology. 2010 Jan 28. DOI 10.1002/hep.23535.
Basciano H et al. Fructose, insulin resistance, and metabolic dyslipidemia. Nutrition and Metabolism. 2005 Feb 21;2(1):5.
Elliott SS et al. Fructose, weight gain, and the insulin resistance syndrome. American Journal of Clinical Nutrition. 2002 Nov;76(5):911-22.
Ouyang X et al. Fructose consumption as a risk factor for non-alcoholic fatty liver disease. Hepatology. 2008 Jun;48(6):993-9.
Back to School Guide
The Back to School Guide from the Environmental Working Group details the best choices for nontoxic and green school supplies.
From recycled notebooks and natural-fiber backpacks to water-based art supplies and lunchboxes free of lead, PVC and PBA, learn which products are best for your kids and best for the environment.
Before you start shopping, download the PDF to print out and take along.
Or shop online using EWG's link to Amazon and Amazon will donate a portion of the proceeds to the Environmental Working Group. Get good stuff and support the people who help you make good choices at the same time.
From recycled notebooks and natural-fiber backpacks to water-based art supplies and lunchboxes free of lead, PVC and PBA, learn which products are best for your kids and best for the environment.
Before you start shopping, download the PDF to print out and take along.
Or shop online using EWG's link to Amazon and Amazon will donate a portion of the proceeds to the Environmental Working Group. Get good stuff and support the people who help you make good choices at the same time.
Whole Living Magazine
Read about why she chose naturopathic medicine on page 119.
Prostate Cancer Screening: Risks, Benefits and Alternatives
Screening tests for prostate cancer are regularly recommended as tools of prevention. Testing doesn't reduce the risk of developing cancer, it only increases the chance of finding it, but early detection may improve survival and the American Urological Association recommends that men start screening at age 40. However, the procedures carry risks and recent clinical trials have questioned their benefit. Understanding the research, risks, benefits and alternatives helps men make decisions best for them.
Studies
Screening tests for prostate cancer commonly include a blood test for prostate-specific antigen (PSA), a compound secreted by prostate tumors (both benign and malignant), and a physical exam, where doctors palpate the gland to detect abnormalities in size or shape, often referred to as a digital rectal exam or DRE. Two large, landmark trials published last year in the New England Journal of Medicine evaluated outcomes associated with these procedures.
The European Randomized Study of Screening for Prostate Cancer included 182,000 men from seven European countries between the ages of 50 and 74. Participants were randomly assigned to two groups. One group received PSA tests once every four years, while the other group was not screened for prostate cancer. At the end of the study, researchers found that the men who were tested experienced 20 percent fewer deaths from prostate cancer than those who were not tested. However, they also found that 1,410 men would have to be screened and 48 would have to undergo cancer treatment in order to prevent one man from dying of prostate cancer.
The other research study followed almost 76,700 men in the United States and randomly assigned them to two groups. One group received "usual care," which sometimes included screening. The other group received regular screening: a PSA test every year for six years and a DRE every year for four years. After seven to ten years of follow-up, researchers analyzed the rates of death from prostate cancer and concluded that there was no significant difference between the two groups.
Risks
When screening tests are positive, biopsies are performed so that cells can be evaluated by a pathologist and a diagnosis can be made. When cancer is found, it is often treated with surgery and radiation.
For some men, these tests and treatments save lives. But they do not guarantee that cancer will be cured or that men will live longer. Aggressive prostate tumors can be incurable regardless of how early they are detected.
And not all prostate cancers need treatment. In most men, tumors of the prostate are slow-growing and unlikely to spread to other parts of the body or cause death. Many older men diagnosed with prostate cancer will not live long enough to benefit from treatment because they will die of other causes. Autopsy studies show that more men die with prostate cancer than from prostate cancer.
Additionally, tests and treatments carry risks, side effects and complications. Biopsies can be associated with pain, bleeding and urinary tract infections, and men may have difficulty passing urine after the procedure. Cancer treatment can cause impotence, urinary incontinence and bowel problems.
Side effects of screening tests are not only physical. Studies have shown that false positives (test results that indicate prostate cancer is present when it isn't) cause psychological harm that may persist for up to one year. And false positives are a common occurrence, accounting for approximately 75 percent of all PSA results. According to the Mayo Clinic, only one out of four men with a positive PSA test actually has cancer. False negatives (test results that indicate cancer is not present when really it is) can also occur if malignant tumors grow quickly without producing much PSA.
Benefits
Certain men may benefit from prostate cancer screening. African-American men, who are more likely to be diagnosed with prostate cancer at a younger age, and whose PSA levels at the time of diagnosis are likely to be higher, may benefit. Any man with a father or brother diagnosed with prostate cancer before the age of 65 has an above-average risk of developing the disease himself and may also benefit. And for men who have already been treated for prostate cancer, monitoring PSA levels can help predict possible recurrence. Men who meet these criteria should consider screening tests and ask their doctors for individualized recommendations.
Alternatives
For the majority of men, prostate cancer screening provides no benefit and subjects them to uncomfortable and unnecessary tests and treatments. Instead, most men should focus on optimal health and cancer prevention. Here are the best strategies:
• Eat a healthy diet full of whole foods, including seven or more servings of pesticide-free vegetables and fruits each day. Choices especially good for reducing the risk of prostate cancer include lycopene-rich tomatoes; foods high in folate like spinach, lentils and beans; and cruciferous vegetables like kale, cabbage and broccoli because they contain diindolylmethane, a nutrient that increases the excretion of hormones.
• Eat foods rich in omega-3 fatty acids, especially wild fish living low on the food chain like Alaskan Salmon, Pacific Halibut, sardines, herring and anchovies.
• Include phytoestrogens in your diet. These plant-based compounds can reduce the risk of hormone-related cancers including prostate cancer. The best sources are ground flax seeds and traditional soy foods like tofu, tempeh and miso. Ground flax seeds are an especially good choice because they contain omega-3 fats and lignans, compounds that positively affect the metabolism of hormones in the liver.
• Drink several cups of green tea each day and alcohol only in moderation, favoring antioxidant-rich red wine.
• Avoid refined carbohydrates and unhealthy fats. These include processed foods, sugar, flour, refined vegetable oils, oxidized and trans fats, and meat, eggs and dairy products from animals exposed to hormones or pesticides.
• Avoid foods and beverages that have been stored in plastic containers and cans unless they are labeled BPA-free and phthalate-free.
• Exercise regularly and maintain a healthy weight. Studies have found that men who are overweight and obese have a higher risk for developing prostate cancer and having more aggressive tumors. Waist-to-hip ratio is also important because excessive abdominal fat may better correlate to cancer risk than adipose evenly distributed.
• Get plenty of sleep. A large study of Japanese men found that those who slept an average of nine hours or more each night had less than half the risk of prostate cancer compared to those who slept less.
• Ask your doctor to test your vitamin D. Low levels have been linked to several kinds of cancer, including prostate cancer.
References
Andriole GL et al. Mortality results from a randomized prostate-cancer screening trial. New England Journal of Medicine. 2009 Mar 26;360(13):1310-9.
Carroll P et al. Prostate-Specific Antigen Best Practice Statement: 2009 Update. American Urological Association.
Kakizaki M et al. Sleep duration and the risk of prostate cancer: the Ohsaki Cohort Study. British Journal of Cancer. 2008 July 8; 99(1): 176–178.
Lin K et al. Benefits and harms of prostate-specific antigen screening for prostate cancer: an evidence update for the U.S. Preventive Services Task Force. Annals of Internal Medicine. 2008 Aug 5;149(3):192-9.
Schröder FH et al. Screening and prostate-cancer mortality in a randomized European study. New England Journal of Medicine. 2009 Mar 26;360(13):1320-8.
Shao YH et al. Contemporary risk profile of prostate cancer in the United States. Journal of the National Cancer Institute. 2009 Sep 16;101(18):1280-3.
United States Preventive Services Task Force. Screening for Prostate Cancer. August 2008.
Studies
Screening tests for prostate cancer commonly include a blood test for prostate-specific antigen (PSA), a compound secreted by prostate tumors (both benign and malignant), and a physical exam, where doctors palpate the gland to detect abnormalities in size or shape, often referred to as a digital rectal exam or DRE. Two large, landmark trials published last year in the New England Journal of Medicine evaluated outcomes associated with these procedures.
The European Randomized Study of Screening for Prostate Cancer included 182,000 men from seven European countries between the ages of 50 and 74. Participants were randomly assigned to two groups. One group received PSA tests once every four years, while the other group was not screened for prostate cancer. At the end of the study, researchers found that the men who were tested experienced 20 percent fewer deaths from prostate cancer than those who were not tested. However, they also found that 1,410 men would have to be screened and 48 would have to undergo cancer treatment in order to prevent one man from dying of prostate cancer.
The other research study followed almost 76,700 men in the United States and randomly assigned them to two groups. One group received "usual care," which sometimes included screening. The other group received regular screening: a PSA test every year for six years and a DRE every year for four years. After seven to ten years of follow-up, researchers analyzed the rates of death from prostate cancer and concluded that there was no significant difference between the two groups.
Risks
When screening tests are positive, biopsies are performed so that cells can be evaluated by a pathologist and a diagnosis can be made. When cancer is found, it is often treated with surgery and radiation.
For some men, these tests and treatments save lives. But they do not guarantee that cancer will be cured or that men will live longer. Aggressive prostate tumors can be incurable regardless of how early they are detected.
And not all prostate cancers need treatment. In most men, tumors of the prostate are slow-growing and unlikely to spread to other parts of the body or cause death. Many older men diagnosed with prostate cancer will not live long enough to benefit from treatment because they will die of other causes. Autopsy studies show that more men die with prostate cancer than from prostate cancer.
Additionally, tests and treatments carry risks, side effects and complications. Biopsies can be associated with pain, bleeding and urinary tract infections, and men may have difficulty passing urine after the procedure. Cancer treatment can cause impotence, urinary incontinence and bowel problems.
Side effects of screening tests are not only physical. Studies have shown that false positives (test results that indicate prostate cancer is present when it isn't) cause psychological harm that may persist for up to one year. And false positives are a common occurrence, accounting for approximately 75 percent of all PSA results. According to the Mayo Clinic, only one out of four men with a positive PSA test actually has cancer. False negatives (test results that indicate cancer is not present when really it is) can also occur if malignant tumors grow quickly without producing much PSA.
Benefits
Certain men may benefit from prostate cancer screening. African-American men, who are more likely to be diagnosed with prostate cancer at a younger age, and whose PSA levels at the time of diagnosis are likely to be higher, may benefit. Any man with a father or brother diagnosed with prostate cancer before the age of 65 has an above-average risk of developing the disease himself and may also benefit. And for men who have already been treated for prostate cancer, monitoring PSA levels can help predict possible recurrence. Men who meet these criteria should consider screening tests and ask their doctors for individualized recommendations.
Alternatives
For the majority of men, prostate cancer screening provides no benefit and subjects them to uncomfortable and unnecessary tests and treatments. Instead, most men should focus on optimal health and cancer prevention. Here are the best strategies:
• Eat a healthy diet full of whole foods, including seven or more servings of pesticide-free vegetables and fruits each day. Choices especially good for reducing the risk of prostate cancer include lycopene-rich tomatoes; foods high in folate like spinach, lentils and beans; and cruciferous vegetables like kale, cabbage and broccoli because they contain diindolylmethane, a nutrient that increases the excretion of hormones.
• Eat foods rich in omega-3 fatty acids, especially wild fish living low on the food chain like Alaskan Salmon, Pacific Halibut, sardines, herring and anchovies.
• Include phytoestrogens in your diet. These plant-based compounds can reduce the risk of hormone-related cancers including prostate cancer. The best sources are ground flax seeds and traditional soy foods like tofu, tempeh and miso. Ground flax seeds are an especially good choice because they contain omega-3 fats and lignans, compounds that positively affect the metabolism of hormones in the liver.
• Drink several cups of green tea each day and alcohol only in moderation, favoring antioxidant-rich red wine.
• Avoid refined carbohydrates and unhealthy fats. These include processed foods, sugar, flour, refined vegetable oils, oxidized and trans fats, and meat, eggs and dairy products from animals exposed to hormones or pesticides.
• Avoid foods and beverages that have been stored in plastic containers and cans unless they are labeled BPA-free and phthalate-free.
• Exercise regularly and maintain a healthy weight. Studies have found that men who are overweight and obese have a higher risk for developing prostate cancer and having more aggressive tumors. Waist-to-hip ratio is also important because excessive abdominal fat may better correlate to cancer risk than adipose evenly distributed.
• Get plenty of sleep. A large study of Japanese men found that those who slept an average of nine hours or more each night had less than half the risk of prostate cancer compared to those who slept less.
• Ask your doctor to test your vitamin D. Low levels have been linked to several kinds of cancer, including prostate cancer.
References
Andriole GL et al. Mortality results from a randomized prostate-cancer screening trial. New England Journal of Medicine. 2009 Mar 26;360(13):1310-9.
Carroll P et al. Prostate-Specific Antigen Best Practice Statement: 2009 Update. American Urological Association.
Kakizaki M et al. Sleep duration and the risk of prostate cancer: the Ohsaki Cohort Study. British Journal of Cancer. 2008 July 8; 99(1): 176–178.
Lin K et al. Benefits and harms of prostate-specific antigen screening for prostate cancer: an evidence update for the U.S. Preventive Services Task Force. Annals of Internal Medicine. 2008 Aug 5;149(3):192-9.
Schröder FH et al. Screening and prostate-cancer mortality in a randomized European study. New England Journal of Medicine. 2009 Mar 26;360(13):1320-8.
Shao YH et al. Contemporary risk profile of prostate cancer in the United States. Journal of the National Cancer Institute. 2009 Sep 16;101(18):1280-3.
United States Preventive Services Task Force. Screening for Prostate Cancer. August 2008.
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