Friday, August 17, 2007

Exercise cannot reduce a sodium-retaining hormone in African Americans known to potentially cause hypertension

Anna Nguyen:

Exercise cannot reduce a sodium-retaining hormone in African Americans known to potentially cause hypertension, found Michael D. Brown, Ph.D., the senior author of a study in the September issue of Experimental Physiology. Brown is an associate professor of kinesiology at Temple University’s College of Health Professions.

The hormone, aldosterone, influences the kidney’s regulation of blood pressure, but too much of it can contribute to the development of hypertension because it causes the kidney to retain salt. Aldosterone, released by the adrenal glands on top of the kidneys, plays a role in the complex system used by the body to regulate blood pressure.

“Although the results are discouraging for African Americans and hypertension, it’ll point us in other directions that may have more potential and could be the key to reducing hypertension,” said Brown, who has a background in exercise physiology.

Many African Americans develop the salt-sensitive form of hypertension. Approximately 40 percent of African Americans have hypertension — the highest rate of any racial or ethnic group in the United States — but there is little data about what makes them more susceptible to this condition, Brown said.

This study is based on the premise that the prevalence of blood pressure sensitivity to salt is extremely high is African Americans. Alterations in aldosterone regulation may play a role because aldosterone causes the kidney to retain salt. Brown said he wanted to find out if exercise could lower the levels.

In the study, he found that the level of aldosterone was related to how the two racial groups distributed body fat. Caucasians generally stored fat in the abdomen area, whereas African Americans had fat distributed throughout the body in a layer under the skin. The six-month study involving 35 Caucasians and African Americans with hypertension found that aerobic exercise training program reduced aldosterone levels in Caucasians by 32 percent, but levels for African Americans were reduced by only 8 percent. Total body fat was reduced only in Caucasians, which might be a clue to the drop in aldosterone.

“The kidneys help to regulate blood pressure by changing the levels of salt and water in our body. Sometimes the kidneys reset at a higher blood pressure level if it has retained too much salt,” Brown said.

While the study showed exercise did not lower aldosterone in African Americans, exercise still has many other benefits for this population, Brown said.

“Exercise has the capacity to affect so many things. It’s a way for the body to correct itself,” he added.

Brown will continue his research in this area with a $3.5 million National Institutes of Health grant awarded earlier this year. In September, Brown will recruit African Americans with hypertension for a study on how exercise can improve the blood vessel condition. The study will also take an in-depth look at how genes can contribute to hypertension.

“Solving the cause of hypertension is similar to solving a big puzzle. Each piece of the puzzle represents a contributing factor to hypertension. Each of these pieces, or possible causes of hypertension, needs to be studied in a systematic way,” Brown said.

Doctors seem to be slowly accepting the fact that racial differences are biological.


At 8:15 PM, Anonymous Dragon Horse said...

It was interesting though that a few weeks back it was discovered that there was a common gene in white Americans that lead to hypertension but it was not common in African Americans, so as to not be the source of the African American hypertension rate.

The article below is interesting because one can argue that Carribean blacks live in a tropical climate such as West Africa (or closeer to than the U.S.) however black American hypertension is lower than many white populations in Europe.

"Higher rates of hypertension among African Americans compared with whites has produced speculation that black populations are more susceptible to hypertension and led to a genetic hypothesis to explain these differences, the researchers write. However, this research has been limited mainly to the US. International studies comparing populations could shed light on the issue, but comparisons have been hampered by a lack of standardized methods between surveys. Within the past decade this has changed, with more comparable methods being developed, they write.

This report used 11 such surveys to glean information on about 85 000 participants in three black populations in the US, Jamaica, and Nigeria and eight white populations in the US, Canada, and Europe. Cooper et al report that US black populations did have a higher prevalence of hypertension than both African and Caribbean blacks and higher than white North Americans, but the prevalence was actually lower than most of the predominantly white European populations.

There was significant variation in hypertension prevalence within both black and white populations, ranging from 27% to 55% for whites and 14% to 44% for blacks. "

Point at hand: how can you determine this to be due to the genetics of race when African Americans are about 20% White, Western European and have lower rates of high blood pressure than many European groups. At the other racial end of the spectrum West Africans and some Carribbeans (Carribbeans being directly related to the ancestors of African Americans as they came from the same pool of West African slaves) have much lower rates of hypertension than black Americans.

There is more going on than genes.

At 3:08 PM, Blogger Adam Lawson said...

black American hypertension is lower than many white populations in Europe

What research are you referring to?

At 4:17 PM, Anonymous Dragon Horse said...

Total (%)
Men (%)
Women (%)

African-origin populations



-US black

European-origin populations

-US white








"Higher rates of hypertension in African Americans unlikely to be related to genes"

Susan Jeffrey 2005

At 2:17 PM, Anonymous Mark said...

Higher rates of hypertension in African Americans unlikely to be related to genes

Then what are the high rates related to?

At 8:40 PM, Anonymous Dragon Horse said...

have you ever seen what Soul Food looks like?

Have you ever seen a black woman jogging, ever? How many black women have you seen swimming?

Most don't want to mess up their hair which cost so much money to braid or straighten.

It is really not hard to figure out the environmental factors if you think about it.

About 20% of blacks live in poverty...and we know ghettos are stressful places...not shocking if a black man who lives in the ghetto his entire life or a woman develops high blood pressure...gun shots all hours of the night tends to do that to people.

Genes are fine to look at and they can be quite instructive but if you let your personal bias allow you to disregard or not investigate some obvious things then there is a problem.

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