Low carb diets linked to hardening of the arteries and impaired vessel growth

Low carb diets could clog your arteries. One Harvard study linked low carbohydrate diets to hardening of the arteries and impaired blood vessel growth, whereas athletes who run long distances wolf down high carbohydrate meals for energy. How does it all work out as a health trend? First you can take a look at the August 24, 2009 published study from Beth Israel Deaconess Medical Center and Harvard university.

Harvard's 2009 study suggested that the very low carb but popular diet regimen may have adverse effect on body's restorative capacity. Even as low-carbohydrate/high-protein diets have proven successful at helping individuals rapidly lose weight, little is known about the diets' long-term effects on vascular health.

Back in 2009, a study led by a scientific team at Beth Israel Deaconess Medical Center (BIDMC) provides some of the first data on this subject, demonstrating that mice placed on a 12-week low carbohydrate/high-protein diet showed a significant increase in atherosclerosis, a buildup of plaque in the heart's arteries and a leading cause of heart attack and stroke. The findings also showed that the diet led to an impaired ability to form new blood vessels in tissues deprived of blood flow, as might occur during a heart attack.

Described in the August 24, 2009 online Version of the Proceedings of the National Academy of Sciences (PNAS), the study also found that standard markers of cardiovascular risk, including cholesterol, were not changed in the animals fed the low-carb diet, despite the clear evidence of increased vascular disease. "It's very difficult to know in clinical studies how diets affect vascular health," says senior author Anthony Rosenzweig, MD, Director of Cardiovascular Research in BIDMC's CardioVascular Institute and Professor of Medicine at Harvard Medical School, according to the August 24, 2009 news release, Low-carb diets linked to atherosclerosis and impaired blood vessel growth.

"We, therefore, tend to rely on easily measured serum markers [such as cholesterol], which have been surprisingly reassuring in individuals on low-carbohydrate/high-protein diets, who do typically lose weight. But our research suggests that, at least in animals, these diets could be having adverse cardiovascular effects that are not reflected in simple serum markers."

Plaque build up

Rosenzweig and his coauthors found that the increase in plaque build-up in the blood vessels and the impaired ability to form new vessels were associated with a reduction in vascular progenitor cells, which some hypothesize could play a protective role in maintaining vascular health. "A causal role for these cells has not yet been proven, but this new data is consistent with the idea that injurious stimuli may be counterbalanced by the body's restorative capacity," he explains in the 2009 news release. "This may be the mechanism behind the adverse vascular effects we found in mice that were fed the low-carb diets."

The study's first author Shi Yin Foo, MD, PhD, a clinical cardiologist in the Rosenzweig laboratory at BIDMC, first embarked on this investigation after seeing heart-attack patients who were on these diets – and after observing Rosenzweig himself following a low-carbohydrate regimen. "Over lunch, I'd ask Tony how he could eat that food and would tell him about the last low-carb patient I'd admitted to the hospital," says Foo. "Tony would counter by noting that there were no controls for my observations."

"Finally," adds Rosenzweig, "I asked Shi Yin to do the mouse experiment – so that we could know what happens in the blood vessels and so that I could eat in peace."

The investigators proceeded to study a mouse model of atherosclerosis mimicking a typical low-carb diet

These "ApoE" mice were fed one of three diets: a standard diet of mouse "chow" (65 percent carbohydrate; 15 percent fat; 20 percent protein); a "Western diet" in keeping with the average human diet (43 percent carbohydrate; 42 percent fat; 15 percent protein; and 0.15 percent cholesterol); or a low-carb/high-protein diet (12 percent carbohydrate; 43 percent fat; 45 percent protein; and 0.15 percent cholesterol).

"We had a diet specially made that would mimic a typical low-carb diet," explains Foo. "In order to keep the calorie count the same in all three diets, we had to substitute a nutrient to replace the carbohydrates. We decided to substitute protein because that is what people typically do when they are on these diets."

Mice fed the low-carb diet developed clogged arteries

The scientists then observed the mice after six weeks, and again at 12 weeks. Consistent with experience in humans, the mice fed the low-carb diet gained 28 percent less weight than the mice fed the Western diet. However, further probing revealed that the animals' blood vessels exhibited a significantly greater degree of atherosclerosis, as measured by plaque accumulation: 15.3 percent compared with 8.8 percent among the Western diet group. (As expected, the mice on the chow diet showed minimal evidence of atherosclerosis compared with either of the other two groups.)

"Our next question was, 'Why do the low-carb mice have such an increase in atherosclerosis?'" says Foo. Searching for an explanation, she and her coauthors proceeded to measure the usual markers thought to contribute to vascular disease, including the animals' cholesterol and triglyceride levels, oxidative stress, insulin and glucose, as well as levels of some inflammatory cytokines.

Why do the low-carb diet mice have such an increase in atherosclerosis?

"In each case, there was either no difference in measurements compared with the mice on the Western Diet [which contains the same amount of fat and cholesterol] or the numbers slightly favored the low-carb cohort," she adds. "None of these results explained why the animals' blood had more atherosclerotic blockages and looked so bad."

Since there was no difference in the noxious or inflammatory stimuli that the animals' blood vessels were exposed to, Foo wondered whether the restorative capacity of the animals might be contributing to the difference. The investigators, therefore, looked at the animals' endothelial or vascular progenitor cell (EPC) counts. Derived from bone marrow, the EPC cells may play a role in vessel regrowth and repair following injury.

Low-carb diet sickened the mice by clogging their arteries

"Examinations of the animals' bone marrow and peripheral blood showed that the measures of EPC cells dropped fully 40 percent among the mice on the low-carb diet – after only two weeks," says Rosenzweig in the news release. "Although the precise nature and role of these cells is still being worked out – and caution is always warranted in extrapolating from effects in mice to a clinical situation – these results succeeded in getting me off the low-carb diet."

Watch out for the possible disconnect between weight loss or serum markers and actual vascular health

Even more important, he notes, the findings point out that there can be a disconnect between weight loss or serum markers and vascular health, and that vascular health can be affected by macronutrients other than fat and cholesterol – in this case, protein and carbohydrates.

"Understanding the mechanisms responsible for these effects, as well as the potential restorative capacity that may counteract vascular disease, could ultimately help guide doctors in advising their patients," adds Rosenzweig. "This issue is particularly important given the growing epidemic of obesity and its adverse consequences. For now, it appears that a moderate and balanced diet, coupled with regular exercise, is probably best for most people."

A moderate, balanced diet with exercise may help, but why are so many different diets recommended for athletic runners?

Why are there so many different recommended menus for runners? There's an article in the Sacramento Bee, June 24, 2010 by Sam McManis, "Ultra-runners eat for the long haul - Running/Walking - sacbee.com," where several ultra-runners are interviewed to find out what foods they eat for endurance. Basically, their diets are high vegetarian carbohydrates. Is eating for endurance healthy for most people or just for runners?

You may also want to listen to a Health Radio sports fitness and medicine radio show online. It also broadcasts radio talk shows on a variety of other health and nutrition topics, including audio podcasts on Eastern medicine. When endurance is the goal, some of the runners interviewed viewed running as more of an eating and drinking liquids contest, blaming loss of a running contest based on what they ate or drank rather than whether or not they had the genes for long-haul running. Some people have the genes, such as numerous native Kenyans. Others have to train more intensively, forcing themselves to eat and drink all day to run long distances.

Marathon runners view their performance based on eating choices. Ultra runners are in constant motion for sometimes 16 to 30 hours. Their high-carb loading diets are used in order to keep glycogen pumping and tapping hard-to-access fat stores means constant care and feeding. When it comes to drinking water, if you drink too much, it's life-threatening. The brain swells because the kidneys can't get rid of the water fast enough. You also lose electrolytes that can result in the electrical system of your heart going out of whack. The fatal result of drinking too much water is called hypoatremia.

Drink too little water, and it's also a case of life-threatening dehydration. Runners have a wide variety of eating strategies. The rule is to eat as little as you actually need. If your stomach doesn't feel good, you can't run. The focus is on eating only as much as your body needs to do the running.

Eating Strategies

Since each runner's body is different because of the genetic signature and expression, the first question a runner asks is how much should the individual eat? Runners may eat a mixture of solid foods and/or concentrated energy gels. They have to tailor their foods to their body. Some runners need to eat a lot early. Others have to wait until later. Some runners have a genetic signature that works well with only carbs, whereas other body types need to splurge on protein and fat. And some need to combine all these foods in balanced amounts.

Is there a definitive answer? Only that runners must eat something throughout the day, even if the thought of food makes them feel full. The basic answer is runners eat whatever it takes. If the stomach starts to ache or feel queasy, the runner is out of the race.

What runners consume in food and water

If you check out the Sacramento Bee article, "Ultra-runners eat for the long haul - Running/Walking - sacbee.com," the runners are named in that interview and what they consumed is noted. For example, one runner ate electrolyte replacements such as the contents of a 100-calorie gel packet (glucose and maltodextrin – pure sugar) every half-hour along with her electrolyte replacement drink during her 18 hours, 24 minutes and 17 seconds on the course.

Another runner in that interview consumed a buffet of dried fruit during races in her 19 hours, 53 minutes and 14 seconds. The dried fruit worked well for her running endurance and speed, and she has signed an endorsement deal with Sunsweet, the company that makes dried fruit products such as raisins and prunes.

According to the Sacramento Bee article, back in 2009 a runner that began a race with jelly beans, dried plums and gels, switched to a turkey sandwich with avocado and cream cheese by Mile 29, then continued with the dried fruit before adding baked beans and another turkey sandwich around Mile 55, followed by hot potato soup and protein drinks like SlimFast. For beverages, she alternated straight water and electrolyte replacement beverages.

Both women runners in the Sacramento Bee interview noted that they could not eat the same foods as what the other runner ate. That's why food is tailored to the response of the digestive system of each individual runner. Add whatever you would eat to the stress of endurance competition, and the result helps you decide what you can 'stomach' as you run for miles.

Some runners have stomachs that can't tolerate a lot of gels

Other runners go a hundred miles only on gels and water. The runners who eat only gels can run beside another person eating a sandwich. Numerous runners can't eat anything other than gels while they run. Some people are slowed down if they eat a sandwich. You get other runners eating ice cream and drinking milk. It works for certain individuals.

Some runners are small eaters. Other runners eat a lot of calories for an ultra run. One runner mentioned in the Sacramento Bee article eats turkey and avocado wrapped in a tortilla followed by chicken and cheese, then a grilled cheese sandwich, then macaroni and cheese, chicken soup, cookies, and tortilla chips. Basically that runner is getting a mixture of salty and sweet tastes. But don't try this yourself. You might not be able to walk, let alone run.

Your body will tell you how small the portions have to be or whether you need 8,000 calories a day as an ultra runner. Find out what foods you crave and why. You could be in the middle of a race and suddenly crave fat.

What ultra-runners eat

Ask professionals who coach ultra-runners what the food is like and what stress to expect. Many runners can't eat solid food because it weighs them down. Or they feel sick to their stomach after eating solid food and then running. That's why any runner (or walker) who feels nauseated after eating solid food usually uses gels instead of solid food.

The gel-eating runner interviewed in the Sacramento Bee article, can't run after eating solid food and instead sucks down 30 gel packets that contain 100 calories each. So basically as far as calories, the individual is getting 3,000 calories--but during more than 16 hours of running. That runner also drinks about 48 ounces of sports drink every two hours.

If you were drinking a lot of water, when you'd drink more than 20 ounces in an hour, your brain might begin to swell or you'd lose electrolytes too fast, and it could be fatal. The runner is able to consume 48 ounces of sports drink every two hours while running.

Don't try to gulp down dry nut butter sandwiches. You might be better off with watermelon or an orange. That's what some runners do late in the race. Other runners don't like gels. What can you do in a race when everything starts to taste awful?

Then, the craving starts at some point in a race. You might crave bean burritos. But if you take a bite, your stomach might feel pretty bad. Some runners have iron stomachs, and others just can't eat. If you ask nutritionists who also run, many of them use gel packets. According to the Sacramento Bee article, "A fully carb-loaded runner begins a race with 135 grams of glycogen in the liver. They lose about a gram a minute, meaning muscle depletion happens after 2 hours and 20 minutes if no carbs are ingested. Endurance athletes therefore need 60 grams of carbs per hour, about 240 calories."

One way to find out about what runners eat or drink, is to look up the audio recordings of the American College of Sports Medicine. According to the Sacramento Bee article, the American College of Sports Medicine's studies noted how many calories in food or fluids were consumed per hour of running race finishers. One study in June 2010, from the American College of Sports Medicine, noted at the annual meeting that ultra-runners who finished the race consumed 304.7 calories in food and 24.5 ounces of fluids per hour, and lost an average of 4 pounds during the race.

What the sports scientists were looking for emphasized the difference between finishers and nonfinishers

That difference focused on the number of calories they were able to consume (304 vs. 200 per hour), according to the study. How many calories you can handle is based on your body's response. Some runners can't consume more than 200 calories an hour. What happens when you try to run on energy drinks and gels? You would slow down if that's not for you. You could switch to soup broth and soda pop. Some runners feel sick if all they eat are gels because gels don't have fiber. All you are getting basically are the sugars, the glucose or maltodextrine. But that type of sugar is what muscles crave.

Only when you're running for miles, your stomach may no longer be able to handle sugar. Some runners have to train themselves to eat solid foods. The theory is if you can train your body to run for more than 100 miles, you can train your stomach to eat solid foods and run. But is this healthy for your heart, considering the stress? Then again, what do you need to be genetically designed to be a runner, a slow heartbeat and low blood pressure? Or can you train your body and switch the tags on your genes to change your inherited destiny as far as endurance?

When a runner finishes a race, the individual needs protein and carbohydrates, but most aren't able to eat. They don't have any appetite after a race. A lot of runners take a nap after a race and then get up and eat. The answer as to what ultra runners eat is to eat what your stomach will tolerate and what makes your body feels best to do what you're training for--running. And after a race, you do need a nap before the next meal.

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