Wednesday, April 10, 2013
A new boogeyman for the gullible to fret about
Doctors long have assumed that saturated fat and cholesterol in red meat are what raise the risk of heart disease. But a study in the journal Nature Medicine fingers another culprit: carnitine, a compound abundant in red meat that also is sold as a dietary supplement and added to energy drinks.
Carnitine typically helps the body transport fatty acids into cells to be used as energy. But researchers at the Cleveland Clinic found that in both humans and mice, certain bacteria in the digestive tract convert carnitine to another metabolite, called TMAO, that promotes atherosclerosis, or a thickening of the arteries.
The researchers, led by Stanley Hazen, chief of cellular and molecular medicine at the Cleveland Clinic’s Lerner Research Institute, examined records of 2,595 patients undergoing cardiac evaluations. They found that the more TMAO in their blood, the more likely they were to develop cardiovascular disease, heart attack, stroke and death.
Many studies over the years have linked consumption of red and processed meat to cardiovascular disease and some cancers. The Harvard School of Public Health reported last year that among 83,000 nurses and 37,000 male health professionals followed since the 1980s, those who consumed the highest levels of red meat had the highest risk of death during study, and that one additional serving a day of red meat raised the risk of death by 13%.
Some researchers long have thought that the added risk of death was higher than the saturated fat and cholesterol in red meat could explain.
Dr. Hazen speculated that carnitine could be compounding the danger. “Cholesterol is still needed to clog the arteries, but TMAO changes how cholesterol is metabolized—like the dimmer on a light switch,” he said. “It may explain why two people can have the same LDL level [a measurement of one type of cholesterol], but one develops cardiovascular disease and the other doesn’t.”
One surprising finding, Dr. Hazen said, was how long-term dietary patterns affected the amount of TMAO-producing bacteria in the gut and thus magnified the risk. In the study, when a longtime omnivore consumed an eight-ounce steak and a carnitine supplement, both his bacteria and TMAO levels rose considerably. But when a vegan voluntarily ate the same combination, he showed no increase in TMAO or bacterial change.
“Vegans basically lose their ability to digest” carnitine, said Dr. Hazen.
The study, sponsored by the National Institutes of Health, didn’t assess how little red meat people could consume and still have elevated TMAO. Nor did it look at how long someone had to abstain from red meat to end the process. “We know it will be longer than one week, but shorter than one year,” Dr. Hazen said.
He and his colleagues have been exploring how altering gut bacteria might influence the risk of heart disease. “In the future, maybe there will be a heart-healthy yogurt, or a drug to block the formation of TMAO,” he said.
Trade groups for meat producers have questioned the link between red meat and cardiovascular disease on the grounds that studies that ask people to recall what they ate over long periods are imprecise.
As a dietary supplement, carnitine is designated as “generally regarded as safe” by the Food and Drug Administration, but few studies have looked at its long-term safety. A 2006 risk assessment found no adverse effects when subjects consumed 2,000 milligrams a day for six months.
Ads for supplements promote carnitine as helping boost energy levels, particularly in endurance sports, and assisting in recovery after intense exercise; some also claim that it helps reduce belly fat, shed pounds and improve brain function.
Duffy MacKay, vice president for scientific and regulatory affairs at the Council for Responsible Nutrition, a trade group for the supplement and energy drink industry, called the Nature study “a new, emerging hypothesis,” but said the researchers were drawing large conclusions from small studies of mice, bacteria and human biomarkers.
“The concept that one component of your diet, or one molecular, is responsible for your health woes is questionable,” Mr. MacKay added.
Dr. Hazen noted that some energy drinks have more carnitine in a single can than a porterhouse steak. “I worry about what happens in 10, 20 or 30 years of consumption,” he said.
He said humans generally have plenty of carnitine in their diet, which also is found in small amounts in nuts, beans, vegetables and fruit, and don’t need to take it in supplement form.
A glass of wine a day will NOT affect a woman's chance of beating breast cancer
The journal article is: "Alcohol Consumption Before and After Breast Cancer Diagnosis: Associations With Survival From Breast Cancer, Cardiovascular Disease, and Other Causes". The data is retrospective self-report -- a very weak reed to lean on
Women with breast cancer can have a glass of wine a day without fear of damaging their chances of beating the disease, claim researchers. In fact, they may improve their overall chance of survival because modest consumption of alcohol cuts the risk of dying from heart disease.
A new U.S. study could help women tackle the dilemma of whether they can safely drink after a diagnosis of breast cancer.
Previous research has blamed alcohol for at least 13,000 out of almost 300,000 cases of cancer diagnosed each year in the UK, including breast, mouth, oesophagus and bowel.
It is estimated that five per cent of breast cancers in women are caused by drinking.
Studies show a couple of drinks a day raise the chances of developing breast cancer by a fifth, say experts.
It is unclear how drinking promotes breast cancer but it may work by raising levels of the sex hormone oestrogen in the body.
However, a new study has found modest drinking before and after diagnosis does not affect your chances of dying of breast cancer.
Women drinking moderate levels of alcohol - around three to six drinks a week - in the years before their cancer diagnosis were 15 per cent less likely to die from cardiovascular disease than non-drinkers.
Moderate wine consumption was linked with a reduction in risk of dying from heart disease - a major cause of death among breast cancer survivors.
Drinking beer or spirits did not have the same benefit, and heavier levels of alcohol consumption harmed survival chances.
The study in the Journal of Clinical Oncology was led by Polly Newcomb, head of the Cancer Prevention Program at Fred Hutchinson Cancer Research Centre, Seattle.
Dr Newcomb said: 'Our findings should be reassuring to women who have breast cancer because their past experience consuming alcohol will not impact their survival after diagnosis.
'This study also provides additional support for the beneficial effect of moderate alcohol consumption with respect to cardiovascular disease.'
The study was based on data from almost 23,000 women who participated in the Collaborative Breast Cancer Study, sponsored by the National Cancer Institute.
About 5,000 participants were sent a follow-up questionnaire between 1998 and 2001 about their alcohol consumption habits after diagnosis.
Among study participants with a history of breast cancer, the authors found the amount and type of alcohol a woman reported consuming in the years before her diagnosis was not linked with her risk of dying from breast cancer
But three to six drinks a week in the years before a cancer diagnosis was linked with a 15 per cent lower risk of dying from heart disease than non-drinkers.
Similarly, the amount and type of alcohol consumed after diagnosis did not affect breast cancer survival, but the risk of dying from heart disease was up to 50 per cent lower in moderate drinkers.
Dr Newcomb said because some types of breast cancer are fuelled by oestrogen - which is promoted by alcohol - they may be more likely to occur in drinkers.
But they may be more controllable by drugs that switch off oestrogen supplies, making sufferers less likely to be affected by modest drinking.
In addition, small amounts of alcohol have a well-known effect on reducing heart problems.
She said: 'It could be that the kind of breast cancer that is more likely to be diagnosed among women who drink may be more responsive to hormone-reduction therapies.'
NHS guidelines advise that men should drink no more than three to four units a day while women should not go over two to three units a day.
The World Cancer Research Fund recommends restricting alcoholic drinks, if consumed at all, to two a day for men and one a day for women, to limit cancer risk.
Posted by jonjayray at 12:15 AM