The Skinny On Grapefruit

The humble grapefruit holds promise for fighting some of the fastest-growing diseases plaguing Canadians and burdening our health-care system. The secret is in the pith—the bitter white material between fruit and peel—something most people discard.

Scientists at the Robarts Research Institute at the University of Western Ontario in London have found a grapefruit flavonoid that prevents weight gain and development of metabolic syndrome, the combination of extra weight, increased cholesterol and triglycerides as well as insulin resistance and blood glucose levels that can lead to heart disease and type 2 diabetes.

Researchers fed four groups of mice identical high-fat Western diets for four weeks. One group was also fed the flavonoid naringenin; that group stayed slim while the other mice gained weight.

New research has shown naringenin also causes chubby mice to lose weight and that the flavonoid prevents atherosclerosis, the buildup of plaque in blood vessels that leads to heart disease, said lead researcher Murray Huff. Naringenin turns up the genes that cause the liver to burn up fatty acids and turns down the genes responsible for storing fat in the liver as well as those that synthesize fat from carbohydrates.

As promising as this is, for the moment there are bitter pills for consumers. First, mice are not men; research on humans is needed and it will take several years before the team can move on to human trials. Just because a substance is safe at concentrations ingested as food “doesn’t necessarily translate into it being equally safe if it’s taken at higher concentrations in a purified form,” Huff said. If proved safe, then work will begin on developing a pharmaceutical using naringenin for treatment and prevention of metabolic syndrome. It will take years before a naringenin-based drug is on the market.

As well, we can’t just add grapefruit to our diets and expect similar results—the mice were given a more concentrated dose than is found in a serving of fruit. “That’s not to say that over a lifetime…low concentrations of something like naringenin or a similar molecule ingested with food might keep your metabolic profile in tune. We don’t know that,” said Huff, but “it’s unlikely.”  And he warns that other substances in grapefruit can interact with prescription medications, particularly those for lowering cholesterol and treating type 2 diabetes. (People on such prescriptions should talk to their doctors about drug interaction before eating grapefruit.)

Consumption of flavonoids, health-promoting substances found in fruits, nuts and vegetables, is already associated with reduced risk of cancer and heart disease. Adding metabolic syndrome to that list is good news on the personal and public health fronts. The Public Health Agency of Canada projects health-care costs for diabetes will top $8 billion annually by 2016. Diabetes has been called a modern epidemic; more than two million Canadians have diabetes and 60,000 new cases are diagnosed annually.

Bugs And The Battle Of The Bulge

New research shows there’s a direct connection between the bugs in your belly and the size of your waistband—a finding that promises new therapies for weight loss based on the discovery that gut microbes of thin animals (including humans) are different from those in fat animals. Does this mean we could lose weight by changing gut microbes?

Researchers at Imperial College of London in England have discovered at least one way microbes contribute to weight gain. When mice genetically predisposed to developing insulin resistance were fed a high-fat diet, their gut microbes transformed choline into something else. Choline is essential for metabolizing fat and transporting it out of the liver, and its lack leads to insulin resistance—a condition in which insulin can’t usher energy-producing glucose into cells, even though the cells are calling for it. The pancreas responds by pumping out even more insulin, which still can’t get into cells; thus glucose accumulates in the bloodstream, setting the stage for type 2 diabetes.

As well, gut microbes of fat mice have more genes for digesting fibre, so wring more calories from food, researchers at the Washington University in St. Louis, Mo., discovered. They also discovered that mice with no gut microbiota of their own stay thin when fed the same high-fat diet that bulks up normal mice, and that lean mice can be fattened up by injecting them with microbe colonies from obese mice.

At the Nestlé Research Centre in Lausanne, Switzerland, researchers gave obese diabetic animals antibiotics to change the colonies of gut microbes, resulting in lowered insulin resistance, less fat storage in the liver and improved glycemic control.

Other researchers have found obese people are also more abundantly blessed with microbiota that efficiently digest fibre. It was an evolutionary advantage to hunter-gatherers with unpredictable access to food, but less helpful to their well-fed descendants with access to 24-hour doughnut shops.

Washington University researchers have discovered that diet can change populations of gut bacteria. Obese volunteers recruited for a year-long low-fat, low-carbohydrate diet shed 25 pounds (about 12 kilograms)—and the colonies of bacteria in their guts changed to resemble those of thin people.

Meanwhile, researchers at the Stanford University School of Medicine in California discovered a probiotic supplement increased weight loss in obese patients having operations to reduce the size of their stomachs. Hoping to prevent post-surgical overgrowth of harmful gut bacteria, doctors gave a daily dose of 2.4 billion lactobacilli to some patients and saw an unexpected benefit: those patients lost 70 per cent of their excess body weight, compared to a 63 per cent loss for other patients.

Researchers at the University of Turku in Finland have found probiotics can also prevent weight gain. They found women were less likely to put on belly fat after giving birth if they took probiotics in their first trimester. Only 25 per cent of women given probiotics and diet advice during pregnancy had a body mass index of 30 or more post-pregnancy, compared to 43 per cent who’d had dietary counselling alone.

Other Turku research has found counts of bifidobacteria are higher in breast-fed babies, and twice as high in infants who become thin children.

Such promising research may very well lead to a microbial “thin pill” in future, but development of consumer products usually lags years behind research. Meanwhile, you can get or keep trim by watching calorie intake and exercising regularly. And it wouldn’t hurt to encourage a healthy population of beneficial gut microbes.

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