Coincidental studies combine to condemn the cardiovascular impacts of sugary, starchy foods, and boost the standing of low-carb “green” diets with regard to heart health
by Craig Weatherby
When researchers talk about “carbohydrates”, they really mean sugars and refined flour products like white bread.
These empty-calorie foods dominate most Americans’ diets… and when consumed in excess, they raise blood sugar levels, promote inflammation, and appear to raise heart and diabetes risks.
Now, new studies from Israel and Canada add more evidence that high-carb diets are heart-unhealthy,.
Their results also reinforce the heart-healthfulness of diets low in carbs but high in fibrous, nutrient-dense plant foods like veggies and beans.
Israeli study links high-carb diets to artery damage
We already have ample evidence that diets high in carbohydrate-laden foods like pastries, white bread, and refined-flour cereals can be detrimental to cardiac health.
In a landmark study, new research from Tel Aviv University now shows exactly how these high-carb foods raise the risk of cardiovascular disease (Shechter M et al. 2009).
The Israeli researchers divided 56 healthy volunteers into four groups and assigned them to eat one of four things:
Corn flakes and sugar are very-high-carb foods with high “glycemic index” numbers, which indicate that they cause sharp spikes in blood sugar levels. Bran flakes are a bit better, but still fairly high in carbs.
- Cornflake mush mixed with milk
- Pure sugar mixture
- Bran flakes
- Placebo (water)
Dr. Shechter applied his method of “brachial reactive testing” to each group. The test uses a cuff on the arm, like those used to measure blood pressure, which can visualize arterial function in real time.
Using a technique pioneered by his laboratory, Dr. Michael Shechter of Tel Aviv University was able to see what happens inside our arteries before, during and after eating high carb foods.
In a first for medical history, his team used novel technology to peer inside the arteries of students after they ate.
The results were dramatic. During consumption of foods high in sugar, there was a temporary and sudden dysfunction in the endothelial walls of the arteries.
Before any of the patients ate, arterial function was essentially the same. After eating, except for the placebo group, all showed impaired arterial function.
Enormous peaks indicating arterial stress were found in the high glycemic index groups: that is, the students who ate cornflakes and sugar. He saw that these high-carb foods distended the students’ brachial arteries for several hours.
Elasticity of arteries can be a measure of heart health. But repeated, sudden expansion of the artery wall can cause a number of negative health effects, including reduced elasticity, which can cause heart disease or sudden death.
Endothelial health can be traced back to almost every disorder and disease in the body. It is “the riskiest of the risk factors,” said Dr. Shechter. “We knew high glycemic foods were bad for the heart. Now we have a mechanism that shows how. “Foods like cornflakes, white bread, french fries, and sweetened soda all put undue stress on our arteries. We've explained for the first time how high glycemic carbs can affect the progression of heart disease.”
“It's very hard to predict heart disease,” added Dr. Shechter. “But doctors know that high glycemic foods rapidly increase blood sugar. Those who binge on these foods have a greater chance of sudden death from heart attack. Our research connects the dots, showing the link between diet and what's happening in real time in the arteries.”
Dr. Shechter says to stick to low-carb, high-fiber, nutrient-dense plant foods like oatmeal, fruits and vegetables, legumes and nuts, which have a low glycemic index.
Exercising every day for at least 30 minutes, he adds, is an extra heart-smart action to take.
Canadian trial finds “green” low-carb diet heart-healthful
The low-carb, high-fat/protein Atkins diet allows ample amounts of fatty meats.
And while studies have shown it can produce modest weight loss
—though no more than calorie-equivalent high-carb diets do
—these studies have not demonstrated reductions in LDL cholesterol or other major heart disease risk factors.
This contrasts with low-carb diets that derive their protein from fish instead of meat, which definitely are associated with reduced heart-risk factors.
Researchers from St. Michael's Hospital and the University of Toronto wanted to test the effects on weight loss and heart disease risk factors of an “vegan” version of the Atkins diet, which would contain no animal proteins.
The researchers labeled this test diet “green”, because vegetables, whole grains, and beans take much less energy and water to produce compared with meats, but can provide adequate protein.
Forty-seven overweight men and women with elevated blood cholesterol and triglyceride levels were given one of two calorie-equivalent test diets for four weeks:
There was similar weight loss and lowered blood pressure in both groups.
- Low-carb, high-protein vegan diet with no animal foods.
- High-carb, low-fat vegetarian diet that included protein from milk products and eggs.
However, the low-carb, higher protein "green" diet group (#1) enjoyed significant reductions in LDL cholesterol and other heart disease risk factors like apolipoproteins, blood triglyceride levels, and blood pressure.
These findings suggest that a much less meaty version of the Atkins diet
—one stressing plant proteins
—is better than a high carbohydrate weight-loss diet at reducing risk factors of heart disease.
“Our study demonstrated that when a low carbohydrate diet was given using plant foods rather than the more usual animal proteins and fats, advantages were seen in cholesterol and blood pressure reduction,” said study leader Dr. David J. A. Jenkins. “Soy proteins and nuts were valuable sources of protein and nuts also provided healthy oils. These foods have individually been associated with cholesterol reduction in other studies.”
Numerous studies show that soy intakes may be associated with a lower incidence of certain chronic diseases, notably heart disease... findings that led the Food & Drug Administration (FDA) to authorize two health claims for soy protein and heart disease risk:
In 2004, the FDA approved a qualified heart-health claim for foods and supplements containing the long-chain omega-3 fats (DHA and EPA) found only in fish and algae:
- “25 grams of soy protein a day, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease.”
- “Diets low in saturated fat and cholesterol that include 25 grams of soy protein a day may reduce the risk of heart disease.”
This health claim is based on the abundant evidence showing that fish is an equally, or heart-healthier protein source than soy protein, and one that also tends to promote weight control and overall good health.
- “Supportive but not conclusive research shows that consumption of EPA and DHA omega-3 fatty acids may reduce the risk of coronary heart disease.”
We should note that it can be hard for people eating vegan diets to raise their blood levels of omega-3 DHA to the levels proven optimal for overall health.
Vegans who want to avoid all animal products can get DHA from supplements containing algae extracts instead of fish oil.
- Food & Drug Administration (FDA). FDA Announces Qualified Health Claims for Omega-3 Fatty Acids. Accessed online at [This URL contains inserted spaces to allow proper page format - remove them to use it: http://www.fda.gov /NewsEvents /Newsroom/ PressAnnouncements / 2004/ucm108351.htm
- Food & Drug Administration (FDA). Federal Register 64 FR 57699 October 26, 1999 - Food Labeling: Health Claims; Soy Protein and Coronary Heart Disease; Final Rule. Accessed online at [This URL contains inserted spaces to allow proper page format - remove them to use it: http://www.fda.gov /Food/LabelingNutrition /LabelClaims/ HealthClaimsMeeting SignificantScientific AgreementSSA/ ucm074740.htm]
- Jenkins DJ et al. The effect of a plant-based low-carbohydrate ("Eco-Atkins") diet on body weight and blood lipid concentrations in hyperlipidemic subjects. Arch Intern Med. 2009 Jun 8;169(11):1046-54.
- Lavi T et al. The acute effect of various glycemic index dietary carbohydrates on endothelial function in nondiabetic overweight and obese subjects. J Am Coll Cardiol. 2009 Jun 16;53(24):2283-7.
- Shechter M et al. Long-term association of brachial artery flow-mediated vasodilation and cardiovascular events in middle-aged subjects with no apparent heart disease. Int J Cardiol. 2009 May 1;134(1):52-8. Epub 2008 May 13.