According to a new study by UC Davis researchers published as an article this week in the Clinical Journal of the American Society of Nephrology, the human brain naturally regulates its own sodium intake for the entire body. It’s a controversial article based on a research study that has prompted nutritionists to ask more questions than the study answers.
The new study gives UC Davis researchers the opportunity to challenge FDA guidelines asking consumers to reduce sodium levels when eating, especially when choosing processed or restaurant food.
According to the study, "Dietary Sodium and Cardiovascular Health in Hypertensive Patients, the Case Against Universal Sodium Restriction," the Journal of the American Society of Nephrology reports in the newly published abstract of the study that, "Only a single study has been reported in hypertensive patients that links baseline sodium, measured by 24-hour urinary excretion, and subsequent cardiovascular outcomes."
In that study, controlling for other risk factors, there was a "significant, independent, inverse association of urinary sodium excretion and coronary morbidity and mortality. Indeed, an increase of 66 mmol/24 h was associated with a 36% reduction in events."
The study’s abstract reports, "Taken together, these data provide no support for the notion that either normotensive or hypertensive individuals should routinely decrease (or increase) dietary sodium intake." So what should you do, decrease or increase your salt intake or just follow your doctor’s orders without asking?
That’s the decision nutritionists are trying to make based on the evidence. And nutritionists also are asking is the plausible evidence valid for people in various health situations? What if your kidneys are not doing well on the salt diet you have? That’s a medical question answerable only by your personal physician and medical team.
The study doesn’t even mention what happens when restaurants or food packagers process foods not only with a lot of added salt, but also flavor extenders such as monosodium glutamate (MSG) to amplify flavor. When adding salt to food or even MSG and salt, is the motive possibly to get customers addicted to the enhanced taste so they’d buy more of the same food and make more money for the food industry or restaurant?
Or is the real reason for adding so much salt or other types of sodium or even calcium chloride, known to raise blood pressure in some people who are sensitive to it, to processed food simply to preserve the food or its color? What the study actually was focusing on is whether the body adjusts to sodium levels naturally, regardless of what you put in your body. And the brain is what does the adjusting.
Just as government intervention had proposed an ideal level of salt intake for restaurants and food processing companies to think about and voluntary reduce salt in their products, this new study comes out in the face of nutrition policy advocates that want to inform people to reduce sodium intake because excess sodium, most nutritionists say, is not healthy.
Physicians know there are salt sensitive people as well as salt resistant people. It’s genetic. Either you have a common gene variant that controls how your kidneys process and eliminate excess salt in a certain way, or you have a salt resistant gene that lets your kidneys process and get rid of salt in another way. Scientists know that around 60 percent of hypertensive people where the cause usually is said to be unknown may be sensitive to salt and react to excess salt by releasing renin and a form of angiotensin, whereby the blood pressure could be raised too high.
It’s supposed to be genetic the way you handle salt. But the new study now is controversial because it is saying sodium (salt) intake is regulated by the brain. Now you have to separate the human reaction to salt (sodium) as in bicarbonate of soda from sodium chloride (table salt).
You have to ask whether it’s the choloride raising the blood pressure in salt-sensitive people rather than the sodium. In some cases, a small amount of sodium from baking soda (sodium bicarbonate) doesn’t raise the blood pressure. So is it the choloride in sodium, just as calcium chloride raises blood pressure when it’s put in some canned vegetables to preserve color? These are some questions nutritionists are asking.
What annoys nutritionists is that for years emphasis has been put on restaurants and food packagers and processors to lower the salt they put in food such as bread, frozen meals, canned soups, cheese, and other processed food items including restaurant food. The new study is saying that because sodium intake is regulated by your brain, your own body won’t let you eat outside of that boundary. Your brain controls how much salt your body needs.
Nutritionists disagree and argue that if you put food in front of a person, the individual won’t be able to tell how much salt his or her brain is going to limit the person from eating at that meal or during the day. Researchers also say that although the food supply contains too much salt, that doesn’t necessarily mean that people are eating that much salt. On the other hand, the UC Davis researchers explain that your brain won’t let you go very far outside the boundary of how much salt your brain tells your body that you really need.
The argument nutritionists have against the new evidence is that they might doubt your body actually would gravitate toward low sodium foods once you had enough salt? What do you think? In the study, researchers collected data from 20,000 adults in 32 countries.
What researchers looked at was the evidence that the adult range of sodium intake was a narrow 2,700 to 4,900 mg of sodium (table salt or sea salt) each day. The cultures varied widely. This amount of sodium is far beyond what doctors, nutritionists, and HMOs hand out to patients to keep their salt levels below 1,500 mg a day if they have essential high blood pressure, and around 2,000 mg a day if they are not salt sensitive and don’t have high blood pressure.
What the new research concludes is that people all over the world keep a normal range of salt intake for their own body, a pretty strict lower and upper limit on salt intake as determined by the human brain controlling what the rest of the body will eat.
The latest UC Davis study published evidence that your body, specifically your brain naturally adjusts the salt levels that you need without you adjusting your salt levels from the outside. Nutritionists want the FDA dietary guidelines to stay as they are. But the study’s researchers think the FDA dietary guidelines regarding salt intake is too strict. The current FDA guidelines recommend no more than 2,300 mg of sodium be eaten each day, which is 14.8 percent lower than the latest research study’s lower limit of 2,700 mg of salt daily.
The amount of salt the FDA recommends as the upper limit, is that for large males or small women, both, or averaged out? That’s one question consumers would like to know. As for the study, even thought he evidence is clear, what should the priorities be for the average consumer–on salt intake or on childhood obesity? That’s the big nutrition question of the year. The studies are scientifically plausible. But as a consumer, who are you going to follow, your doctor that tells you to eat less salt to avoid the risk of heart disease and strokes or because your blood pressure is too high? Or the plausible evidence of the study?
Where you could turn to in order to read information on the topic is the Center for Science in the Public Interest, a Washington, DC nutritional advocacy group. Should you lower your salt intake or not? You’ll find information online telling you to do one or the other. High salt intake mostly comes from processed foods. In prehistoric times, humans didn’t use salt at all. They received salt from eating foods that already contain salt such as various animal proteins and plants such as celery, carrots, and parsley.
If you look at various tribes in Australia, for example and other areas of the world, many don’t add salt to their natural foods and live on less than 1,000 mg of sodium daily. You can search the names of these areas online or look at the programs in various European countries such as Finland that has mixed magnesium in salt shakers on some restaurant tables in the past to get people to balance their sodium intake with magnesium and other multiple minerals in small, balanced amounts.
The decision you’ll have to make as a consumer is whether the amount of salt you eat is posing a risk of heart disease, heart attack, or stroke or not, or whether your multiple minerals are balanced and in small enough amounts not to do any harm. So the ball is back in the nutritionist’s court for now, but of course, the studies do go on, and the research, remember, is plausible. For further information, see the Sacramento Bee article, October 17, 2009, "Don’t sweat your salt intake, UC Davis study says," by Anna Tong.
So whose side are you going to take– the UC Davis researchers, Center for Science in the Public Interest, or the UC Davis nutritionists? How much salt do you eat daily? And is your health fine or challenged based on your sodium intake?
Michael H. Alderman
Dietary Sodium and Cardiovascular Health in Hypertensive Patients: The Case against Universal Sodium Restriction
Journal of the American Society of Nephrology, Jan 2004; 15: S47 – S50. Published: Saturday, Oct. 17, 2009.
Eric N. Taylor, Teresa T. Fung, and Gary C. Cu August 13, 2009.
Journal of the American Society of Nephrology 20: 2253-2259.
Photo credits: Flickr.com – science.