Thursday, April 25, 2019

Sodium studies blur the picture on what is heart healthy

Probiotics, the beneficial bacteria found in yogurt and other cultured foods, have long been touted for their ability to ease digestive woes. Drug stores and supermarkets feature arrays of different probiotic supplements, often containing Lactobacillus or Bifidobacterium, two of the most commonly used species of bacteria.

Perhaps the strongest evidence for probiotics is in treating diarrhea caused by a viral infection or from taking antibiotics. Both infection and antibiotics disrupt the natural balance of bacteria in your digestive system, which probiotics can help restore. But the opposite problem — constipation — is more common than diarrhea. It affects about 14% of adults and accounts for about 3.2 million medical visits in the United States each year. Americans nearly three-quarters of a billion dollars each year trying to unblock themselves.

Most over-the-counter remedies for constipation, such as laxatives and stool softeners, aren’t all that helpful. Nearly half of users aren’t satisfied with the results of such products, citing ineffectiveness or other issues.

Do probiotics work against constipation? Researchers at King’s College in London scoured the medical literature and found 14 studies that met their criteria for a well-done study. All were clinical trials that randomly assigned people with constipation to take either probiotics or a placebo (or other control treatment).

By pooling the findings of the trials, the researchers found that on average, probiotics slowed “gut transit time” by 12.4 hours, increased the number of weekly bowel movements by 1.3, and helped soften stools, making them easier to pass. Probiotics that contained Bifidobacterium appeared to be the most effective. The study was published in the October American Journal of Clinical Nutrition.

But there’s still not enough evidence to recommend a specific probiotic for constipation, says Dr. Allan Walker, director of the Division of Nutrition at Harvard Medical School and a world-renowned expert in the probiotics field. Each of the small studies in the new report had different designs and widely variable results, making it difficult to glean a specific recommendation.

“I personally think that probiotics may be very helpful in the future as a way of dealing with constipation and other health problems,” he says. He agrees with the study’s conclusion: What’s needed is a large, multicenter trial, with standardized outcomes to determine which probiotic species and strain is most effective, how much to take, and for how long.

Until that happens, experimenting on your own is probably a safe bet. Probiotics don’t seem to have any side effects and are generally considered safe. But keep in mind that dietary supplements like probiotics aren’t tested by the FDA like medications are. You may want to consult with a practitioner, like a registered dietitian, who is familiar with probiotics. And let your doctor know that you are using probiotics for constipation, or doing other things that may affect your health.
Screening is an important part of routine medical care. Screening means checking a seemingly healthy person for signs of hidden disease. It is routinely done for various types of cancer, heart disease, diabetes, and other chronic conditions.

Common cancer screening tests include:

    mammogram for breast cancer
    PSA test for prostate cancer
    colonoscopy for colon cancer
    Pap smear for cervical cancer

Screening makes sense when finding and treating a hidden condition will prevent premature death or burdensome symptoms. But it doesn’t make sense when it can’t do either. That’s why experts recommend stopping screening in older individuals, especially those who aren’t likely to live another five or 10 years.

Yet an article published online in JAMA Internal Medicine shows that many doctors still recommend cancer screening tests for their older patients. Many don’t benefit, and some are even harmed by the practice.

A team from the University of North Carolina, Chapel Hill, looked at cancer screening tests among 27,000 men and women over age 65 who took part in the National Health Interview Survey. They also ranked the participants by risk of dying in the next nine years based on their health.

Among individuals with the highest risk of dying within nine years, many had undergone cancer screening in the two years before the interview. More than half of the men in this group had a PSA test to check for hidden prostate cancer. The screening rates were 41% for colorectal cancer, 37% for breast cancer, and 31% for cervical cancer.
Smarter screening decisionmaking

These findings are troubling. Asking people who can’t benefit from a cancer screening test to have one is a waste of their time and money, not to mention a waste of taxpayer money (since these tests are usually covered by Medicare). Screening tests can also cause physical and mental harm. A colonoscopy can tear the lining of the colon, potentially causing a serious infection.

A high PSA test often sends men to undergo expensive biopsies. These can cause infection and pain. And if prostate cancer is found, many men will opt for treatment with surgery or radiation therapy even though the slow-growing cancer would not have shortened their lives. Mammograms don’t usually cause problems, but many lead to biopsies that show no cancer present.

Medical societies and other expert groups recommend the following:

    Stop routine Pap smears to screen for cervical cancer at age 65 if Pap smears have been negative in the past.
    Stop routine screening mammography for women at average risk of breast cancer after age 75.
    Stop screening colonoscopies for adults at average risk of colorectal cancer at age 75.
    Stop routine screening with PSA for men at average risk of prostate cancer, independent of age.

Unfortunately, many doctors ignore these guidelines. Why? Experts realize that cancer screening recommendations based on age alone are too arbitrary. A frail 75-year-old with heart disease and diabetes is different from a robust 75-year-old who exercises every day. So many experts suggest considering a person’s life expectancy. If it is less than 10 years, cancer screening is unlikely to improve a person’s survival or quality of life, and the risks of screening are greater than the benefits.

But estimating life expectancy is very difficult. So doctors are reluctant to make what amount to a guess for many of their patients.

That’s why a decision about cancer screening should be mutually made by an individual and his or her doctor. Equally important, the person should be well informed about the risks of the test and about what will happen if a test suggests there may be cancer that won’t shorten the his or her life.

At the same time, all of us should be focusing more on preventing cancer in the first place, rather than trying to detect it later. The best ways to do this include:

    staying physically active and spending at least 150 minutes per week on moderate intensity exercise
    maintaining a healthy weight
    not smoking or using other tobacco products
    avoiding alcohol or drinking moderately (no more than one alcoholic beverage a day for women, no more than two a day for men)
    eating a diet rich in fruits, vegetables, and whole grains.
We often look to science to solve life’s difficult questions. But sometimes it hands us more uncertainty. Take three reports in this week’s New England Journal of Medicine. One shows that eating less sodium (a main component of salt) could save more than a million lives a year worldwide. A second came to a nearly opposite conclusion — that current average sodium intake is okay for cardiovascular health while getting too little or too much is a problem. The third study essentially agreed with the second, but found that getting too little potassium may be as bad as getting too much sodium.

The findings are certain to fuel the already heated debate on sodium and the international efforts to get people to take in less of it.
Sodium study results

Too much sodium consumption can increase blood pressure and cause the body to hold onto fluid. High blood pressure (hypertension) is a major risk factor for heart attack, stroke and other cardiovascular problems.  Excess fluid can cause swelling in the legs and even more serious problems (such as congestive heart failure) in people with poor heart function.

In the U.S., guidelines for the average adult recommend getting no more than 2,300 milligrams (mg) of sodium a day. That’s the amount in just one teaspoon of salt. The American Heart Association and other groups recommend a lower target of 1,500 mg a day, especially for certain groups. The average American currently consumes more than 3,400 mg/day.

In one of the New England Journal articles, an international team of researchers led by Dr. Dariush Mozaffarian, a former Harvard Medical School faculty member who was recently appointed Dean of the Friedman School of Nutrition and Public Policy at Tufts university, combined data from more than 100 prior studies regarding sodium intake in 66 countries. They estimated the impact of sodium intake on blood pressure and death due to cardiovascular disease. Here’s what they found:

    Average sodium intake was nearly 4,000 mg a day
    There would be 1.65 million fewer deaths per year worldwide if average sodium intake was closer to 2,000 mg a day.
    40% of deaths linked to excess sodium intake occur in individuals younger than age 70.
    Reducing sodium intake to recommended levels would prevent about 10% of deaths related to cardiovascular disease.

Although these are only estimates, the numbers are impressive. High blood pressure (hypertension) is among the most modifiable risk factors for cardiovascular disease and cardiovascular disease is among the leading causes of premature death worldwide. So, it’s hard to ignore these findings.

Another study in the journal found that the picture might be more complicated. Researchers with the international Prospective Urban Rural Epidemiology study compared sodium excretion in urine (an indirect measure of sodium intake) with rates of death and major cardiovascular disease among more than 100,000 men and women from 17 countries. Higher rates of death and cardiovascular disease were seen among those with high sodium intake, defined as higher than 6,000 mg a day. But the researchers also saw high rates among those with low sodium intake, defined as less than 3,000 mg a day. The sweet spot was between 3,000 and 6,000, or where most Americans are now.

How could lower levels of sodium consumption be riskier than higher amounts? One reason could be that people with high blood pressure, other cardiovascular risk factors, or cardiovascular disease are usually advised to lower their salt intake. Their higher than average rates of cardiovascular disease and related deaths could then be erroneously linked to their lower salt intake.

The third report, also from the Prospective Urban Rural Epidemiology study, compared sodium and potassium intake with blood pressure among more than 100,000 men and women in 18 countries. The higher the sodium intake, the higher the blood pressure. And the lower the potassium intake, the higher the blood pressure.
Too soon to change recommendations

Taken as a group, these three reports raise plenty of questions. Until there are good answers, I think it’s too soon to throw out recommendations to reduce sodium intake, especially in high-risk groups, including:

    anyone over age 50
    African Americans
    individuals with high blood pressure, chronic kidney disease, diabetes, or heart failure

Limiting sodium intake can help people in these groups prevent or control high blood pressure and avoid “fluid overload” in which the body holds on to fluid beyond its capacity to get rid of it.

If you want to take in less sodium, or need to, keep in mind that most sodium in the U.S. diet comes from prepared foods like canned foods, breads and pastries, crackers and chips, deli meats, and restaurant foods. A good way to reduce your consumption of sodium is to prepare your own food or read nutrition labels on prepared foods so you can choose low sodium options.

Another lesson from the three New England Journal articles is worth keeping in mind. The human diet, once rich in potassium, is now low in potassium in developed countries like the United States. Getting more potassium from fruits, vegetables, and other foods is a good way to help keep your heart and arteries healthy. The Harvard Heart Letter has compiled a list of potassium-rich foods and their potassium-to-sodium ratios.
Looking ahead

From my perspective, the scientific evidence demonstrating the hazards of high salt intake is difficult to ignore. I believe that salt consumption will fall over time in the U.S. and in other places where salt intake is high. Long-term clinical trials comparing people placed on diets containing varying amounts of sodium are needed to better understand just how much is too much – and how little is too little. In fact, the ideal amount will likely vary for different groups of people.

Craving salty foods is learned. And it can be “un-learned.” It takes time to get used to foods that are less salty – but for many, I think it’s worth the effort.

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