Like a jewel-encrusted Fabergé egg or a vintage 1953 Studebaker, your body’s system for managing blood sugar is a beautiful anachronism. Built to withstand the frequent famines, scarce feasts, and heavy physical demands of Stone Age life, it’s out of place in a 21st-century landscape of Cinnabons, stuffed-crust pizza, and pay-per-view. Your body lives by prehistoric rules designed to keep mind and body running oh-so-frugally on a sometimes meager supply of glucose. It extracts every molecule of sugar from the foods you eat, then conserves precious glucose—hoarding the energy in muscle and liver cells for the times you need it most.
Yet Twinkies have replaced wild raspberries; grain-fed beef and supersize fries have replaced freshly dug roots and lean wild game rich in good fat. Calorie consumption has soared, and daily exercise means walking from the front door to the car—not a 15-mile trek to the next watering hole.
The world has changed; our bodies have not. And a growing stack of research links that fundamental mismatch to an amazing variety of modern-day, blood sugar–related health problems including heart attack, stroke, high blood pressure, diabetes, cancer, infertility, and even Alzheimer’s disease, as well as birth defects, sexual dysfunction, blindness, kidney failure, and amputation. Even more alarming: The workings of this ancient sugar control system can put you at high risk for serious conditions even if your blood sugar levels look normal. Of course, risk rises higher if sugar levels soar into the prediabetic range, and higher still if you develop full-blown type 2 diabetes.
The problem isn’t just sugar. Insulin—the hormone that tells cells to absorb blood sugar—plays a major role, too. In tiny amounts, this powerful protein is healthy and essential. But if inactivity, belly fat, and a high-fat, high-sugar diet have made your cells insulin resistant—a condition affecting as many as one in two American adults—your body pumps out two to three times more insulin than normal in order to force sugar into cells. The ploy works. Your cells receive the sugar they need (and your blood sugar levels will look normal on a fasting blood sugar test). But the excess insulin can raise your blood pressure, clog your arteries, overtax your pancreas (raising diabetes risk), promote the growth of cancer cells, stop ovulation, and dim memory.
Once this hidden high blood sugar begins to do its damage, you develop a condition called metabolic syndrome, in which biochemical changes triggered by insulin resistance begin to alter systems throughout your body. Metabolic syndrome can simmer undetected for decades. (Turn to Chapter 20 for a list of the warning signals.) Blood sugar levels will rise into prediabetic and then diabetic zones if your pancreas can no longer produce enough insulin to overcome insulin resistance.
Diabetes adds new health risks, including vision problems, kidney failure, and bodywide nerve damage. A sobering new finding: These complications may begin to develop when your blood sugar is still in the prediabetic range (100 to 125 milligrams of glucose per deciliter of blood, or mg/dl, on a fasting blood sugar test). “The complications of diabetes may begin years before diagnosis and much earlier than we thought,” said Richard Kahn, PhD, chief scientific and medical officer for the American Diabetes Association. “That is really the big news, because we have not known when the changes start to occur.”
Here’s more of the latest research on the profound links between blood sugar control and your health.
In a new Swedish study that tracked 1,826 people for 20 years, researchers found that those with metabolic syndrome had a 69 percent higher risk for heart attack than those without it. Others estimate that metabolic syndrome could sometimes triple heart risk. Diabetes magnifies the problem, as high glucose levels further assault arteries. People with diabetes are four times more likely to have a heart attack or stroke and are more likely to die than people who don’t have diabetes, say Harvard Medical School researchers. Atherosclerosis accounts for virtually 80 percent of all deaths among diabetes patients.
High insulin levels turn your blood into a superhighway for bad fats—raising triglycerides; lowering good HDL cholesterol, the kind that mops up artery-choking LDL cholesterol; and making nasty LDL extra small and better able to invade artery walls. They raise levels of fibrinogen, which makes blood clot, and up your risk for high blood pressure by altering the way your kidneys process sodium. People with metabolic syndrome also have signs of more chronic, low-level inflammation—as if their immune systems are constantly on alert. This churns out compounds such as C-reactive protein that help pack extra fatty gunk into artery walls and raise the risk for heart-stopping blood clots.
One in three people with metabolic syndrome will go on to develop type 2 diabetes. The turning point may be encoded in your DNA.
Researchers from Iceland’s Decode Genetics, a gene research company, recently announced the discovery of a “diabetes gene” carried by an astonishing 45 percent of humans around the world. The gene alone can’t doom you to a diabetic future; experts say lifestyle pulls the trigger. A genetic “weakness” can prompt overtaxed insulin-producing cells in your pancreas to burn out, allowing blood sugar to rise. (Want to know if you’re headed for type 2 diabetes? Ask your doctor for a fasting blood sugar check, as recommended in Chapter 1.)
The life cycle can profoundly affect blood sugar. Here’s what happens.
This life stage results in insulin resistance that has nothing to do with weight or fat, says Michael Goran, PhD, professor of preventive medicine at the Keck School of Medicine at the University of Southern California in Los Angeles. The cause? Probably a combination of the body’s need for extra energy to fuel rapid growth, along with the sudden flood of sex hormones.
“Kids who go through puberty get very insulin resistant—regardless of how fat, thin, big, or small,” Dr. Goran explains. If they’re lean, their bodies can handle it with no long-term effects. But if they’re overweight, the stress of puberty on the pancreas may push the entire system over the edge, resulting in longer-lasting insulin insensitivity or full-blown diabetes.
Nearly all pregnant women develop some insulin resistance—that is, their cells don’t readily obey insulin’s signal to absorb blood sugar, says Thomas A. Buchanan, MD, professor of medicine, obstetrics and gynecology, and physiology and biophysics at the Keck School of Medicine. “As you become more and more resistant to insulin, your glucose and other nutrients stay in circulation a bit longer after you eat than if your insulin reactivity were normal,” Dr. Buchanan explains. “That may be a way to get some of the maternal nutrients to the fetus.” In other words: more for baby.
Gabriele E. Sonnenberg, MD, professor of medicine at the Medical College of Wisconsin in Milwaukee, says many of her patients with type 1 diabetes (when the immune system destroys insulin-producing cells, so you must receive daily insulin injections) find it harder to control their blood sugar right before their periods. Some report problems at midcycle (during ovulation), while others say the changes come during menstruation itself. In fact, several of her patients change their insulin dose to coincide with their changing needs during the menstrual cycle.
Studies confirm this mysterious correlation. In one survey of 406 women with type 1, 67 percent said they had changes in blood glucose control just before their periods, and 70 percent reported changes during menstruation. Other studies find that even women without diabetes have higher blood sugar after meals during the 2 weeks between ovulation and menstruation.
Insulin may not dock as effectively with receptors on cell surfaces in the second half of the menstrual cycle. Or, estrogen may interact with insulin to raise or lower blood sugar.
Those cyclical/hormonal changes of menstruation should stop with menopause. But a new factor arises: weight gain, which can increase insulin resistance and ultimately raise sugar levels.
With age, the body’s ability to produce insulin and absorb blood sugar declines. Blame it on wear-and-tear, genetics, and a tendency to eat more and sit more. Also, part of the reason may lie within tiny structures inside cells called mitochondria—the little power plants that turn glucose into energy. Mitochondria work less efficiently as we grow older, burning less blood sugar. The result: Risk for diabetes rises over age 40 and rises even faster after age 60.
The Rx: exercise. Muscle is one of the major users of glucose, Dr. Sonnenberg notes. If you maintain it—with resistance training and aerobic activity—you can improve your blood sugar status at any age.
The link between insulin and cancer keeps getting stronger. High insulin levels tripled risk for breast cancer in a surprising University of Toronto study of 198 women. And among women with breast cancer, those with the highest levels were three times more likely to see cancer recur.
Researchers are also finding links between high insulin and prostate and colon cancer. National Cancer Institute scientists recently documented a doubled risk for pancreatic cancer among smokers with type 2 diabetes who had the highest levels of insulin and the most insulin resistance.
Insulin acts as a growth factor, making cancer cells grow quickly and divide wildly, says breast cancer researcher Pamela Goodwin, MD, of Toronto’s Mount Sinai Hospital. Some cancer cells have more insulin receptors than normal cells do, allowing the hormone to dock easily.
Women with a common infertility problem called polycystic ovary syndrome (PCOS) have insulin resistance and higher-than-normal insulin levels. While high insulin isn’t the only cause of PCOS, it’s a major factor—and helps explain why half of all women with PCOS develop diabetes by age 40 and 40 percent have signs of seriously clogged arteries by age 45.
In PCOS, high insulin may disrupt ovulation and prompt miscarriages by signaling a woman’s ovaries to produce extra male hormones, says infertility specialist Sandra Carson, MD, a reproductive endocrinologist at Baylor College of Medicine in Houston. Signs of PCOS include menstrual periods that are more than 6 weeks apart, stubborn weight gain, acne, and abnormal facial or body hair.
Meanwhile, having diabetes before pregnancy can raise your baby’s risk of birth defects—especially of the heart and spinal cord—two to five times higher than normal. Developing diabetes during pregnancy, a condition called gestational diabetes, raises your odds of delivering a high-birth-weight baby and developing preeclampsia, a dangerous pregnancy-related elevation in blood pressure.
Both overweight and diabetes increase the odds for dementia. Now researchers think insulin resistance in brain cells is one reason why.
In lab studies at the Joslin Diabetes Center in Boston, researchers found that the brain cells of insulin-resistant mice produced a protein also found in the brain lesions of people with Alzheimer’s disease. As you’ll read in Chapter 6, diabetes and insulin resistance may also shortchange a brain region responsible for memory—in some cases shrinking it significantly, new research shows.
If you have diabetes or even prediabetes, high blood sugar levels can damage and destroy tiny capillaries in the eyes. The capillaries swell and weaken, clog, and burst—a condition called diabetic retinopathy that blurs vision and often leads to blindness. Diabetes is the leading cause of blindness in adults age 20 on up.
Also, chronically high blood sugar levels activate a substance called protein kinase C, which causes abnormal production of new blood vessels in the eye. The problem is, you don’t need these new vessels—and they’re more prone to leaking and bursting.
About 70 percent of lower-leg amputations performed in 2003 were on people with diabetes, says the federal Agency for Healthcare Research and Quality. The cause: high blood glucose that damages nerves and reduces circulation, making even the smallest cut or blister potentially a wound that won’t heal.
Nerve damage can also cause impotence, arousal and orgasm difficulty for women, out-of-rhythm heartbeats, slowed digestion, and urinary problems.
High blood sugar presents a triple threat to good oral health. First, it compromises your ability to fight infection, so even a small cold sore or tiny pocket of bacteria below the gum line could lead to serious trouble. Second, it raises the level of glucose in saliva, says Sol Silverman Jr., DDS, professor of oral medicine at the University of California, San Francisco, School of Dentistry and a spokesman for the American Dental Association. This “sweeter” saliva supports the growth of fungal (thrush) and bacterial infections. Third, high blood sugar can dry up saliva, leaving you with less of this vital infection-fighting moisture when you need it most.
The damage? In a new Italian study of 212 patients at the Dental Institute of the University of Sassari, researchers found three times more gum-disease bacteria in the mouths of people with diabetes than in those without diabetes. People with diabetes also had more dental plaque, more bleeding gums, and deeper openings at the gumline around each tooth, a sign of gum disease.
At least 41,000 Americans with diabetes live with kidney failure and need regular dialysis to filter waste products from their blood. Some even receive transplanted kidneys. Even more shocking: New research from the International Diabetes Institute in Caulfield, Australia, finds that 10 percent of people with prediabetes have higher-than-normal levels of a protein called albumin in their urine, a telltale sign of early kidney disease.
In a healthy kidney, millions of tiny blood vessels called glomeruli act as strainers, trapping waste that’s eventually flushed from your body in urine. But high blood sugar can damage the glomeruli. They leak, then fail. Eventually, the damage can lead to kidney failure.
Laugh if you will, but a recent study conducted in Japan found that a chuckle a day just might keep high blood sugar at bay.
Researchers at the University of Tsukuba tested the guffaw/glucose connection by measuring the blood sugar levels of 19 men and women with high blood sugar. On one day, the participants listened to a 40-minute lecture, which the researchers described as “monotonous” and “without humorous content.” On the second day, they were included in an audience of 1,000 people who laughed loud and long during a performance of manzai, the Japanese version of stand-up comedy.
Before both performances, volunteers ate a 500-calorie meal. Afterward, their blood sugar was tested. Sugar levels were significantly lower after the comedy.
Laughing makes us move, and as a result, muscle cells may absorb more blood sugar, speculates researcher Keiko Hayashi, PhD. It’s also possible that mirth affects hormones that help regulate blood sugar.