Tuesday, March 13, 2012

Sodium Study's Surprising Suggestions


Salt is the stuff of life and has been an essential and prized nutrient since the dawn of civilization. Salt used to be hard to obtain and civilizations often thrived or perished based on their access to it, as Mark Kurlinsky describes in his book titled simply “Salt” (well worth a read if you have the opportunity).

New research suggests that salt is indeed critical to our health and that eating too little can be just as unhealthy as eating too much. Table salt is actually made from two elements, sodium and chloride. In this post we are going to specifically examine the sodium portion of salt because that is what the researchers looked at in their study.

So let’s look at sodium, how it creeps into our diet, and how we can decide whether we are getting enough or too much.

WHERE DOES SODIUM COME FROM IN OUR DIETS?

Salt, or sodium chloride, is used to enhance the flavor of food and as a food preservative. For thousands of years we have used it make foods taste better, to aid during the cooking process, and to prevent food from spoilage. Recently, many variations of sodium have been added to processed foods to not only improve taste, but to also increase the shelf life of many foods. Unfortunately, there are now so many sources of salt in our diet that getting too much of it can be shockingly easy.

The most common form of sodium in our diet is probably sodium chloride (table salt). We know when we add table salt to our food, but there are many other sources of sodium in our diets that aren’t quite so obvious. Foods like milk, beets, and celery have a significant amount of natural sodium, and then there are the processed foods.

Sodium is added to virtually all processed food products. Processed meats, such as bacon, sausage, and ham often contain added sodium. Furthermore, sodium often gets added to enhance flavor as occurs in canned soups and canned vegetables. Condiments and seasonings such as Worcestershire sauce, soy sauce, onion salt, garlic salt, and bouillon cubes also contain a lot of sodium.

Then there are the chemical constituents that are added to many processed foods for flavoring or as a preservative. Examples of these types of  added sodium are listed on food packaging as monosodium (and disodium) glutamate, sodium nitrite, baking soda (sodium bicarbonate), and sodium benzoate. Sodium benzoate is a very commonly used preservative in many foods and is almost always found in sodas. As you may know, fast food products in general have extremely high levels of sodium.

Any one of these sources by themselves might not be considered too much, but if you add them together (as we do in our diet), they can quickly add up to a very significant and harmful sodium load that we may not even realize.

NEW RESEARCH; TOO MUCH OR TOO LITTLE SODIUM IS UNHEALTHY

Doctors have long told patients that eating too much sodium is dangerous, especially for patients at risk of heart disease. Sodium has a nasty tendency to raise blood pressure, which can be bad for an already stressed heart. In fact, sodium is one of the leading causes of high blood pressure. There is a well understood and studied link between high sodium diets and increased risk of heart disease.


Too much sodium in your diet can cause an increase in blood pressure.

But it turns out that eliminating too much sodium from your diet appears to be dangerous as well. As a recent study shows that if your diet is too low in sodium, your risk of death can increase significantly. The study results are published in the November 23, 2011 issue of the Journal of the American Medical Association. Researchers took a look at a number of studies done on sodium levels and the effects on health.

In people who consumed below the daily recommended intake levels of sodium (about 3800mg per day), the risks to health were significant. In the group of people below this level, the risk for “all cause mortality” (i.e. dying from any health issue) increased by up to 20%. So you can’t just blindly eliminate every trace of sodium from your diet, as that appears to be just as harmful as having too much.

THE SWEET SPOT

As with many other things in health, too much or too little of virtually everything can be bad. So, in this case, it’s all about finding the “sweet spot” of sodium levels. The optimum level will vary between people, because some people can be more sensitive to sodium than others, but in general, about 3800 mg (about a teaspoon) per day seems to optimal. Consulting with your doctor to determine a level that is safest for you is important, but the standard recommendation of telling patients with hypertension to eliminate as much salt as possible from their diet does not appear to be a healthy choice.

WHY DO WE NEED SODIUM AND WHAT DOES IT DO?

Sodium is very closely tied to water in your body. It is responsible for regulating blood volume, blood pressure, osmotic equilibrium, and pH levels. About 90% of the sodium in your body is found in the fluid that makes up your blood stream. This “extracellular fluid” (i.e. fluid outside the cells) is pretty salty stuff.

Your body generally tries to keep the level of sodium and water in your blood stream balanced. If you add more sodium (through diet), then you tend to “retain water” to balance it out. If you’ve ever eaten a particularly salty meal and felt “bloated” after, then you’re familiar with the concept. The problem is, having more fluid in your blood stream tends to increase blood pressure, because there’s more volume to pump around and your heart has to work harder. On top of this, your kidneys also have to work harder to get rid of the extra sodium.

Too much sodium also has an effect on two key chemicals that relate to blood pressure, vasopressin and nitric oxide. Vasopressin is a chemical which causes arteries to constrict (i.e. get smaller), also increasing blood pressure. Nitric oxide does exactly the opposite, causing arteries to expand (vasodilate), lowering blood pressure. High levels of sodium causes vasopressin to increase (causing arteries to constrict) and nitric oxide levels to decrease (making them less able to expand again); both of these effects cause blood pressure to rise. These decreased levels of nitric oxide also lead to atherosclerosis (damaged arteries) which ultimately increases blood pressure even further.

So it makes sense that reducing sodium intake can be good for patients with hypertension, but overdoing it can be counter productive. If you take in too little sodium, the amount of extracellular fluid in your blood stream decreases. This lowers your blood pressure and makes blood “thicker” (i.e. more blood cells, less fluid between them) which can cause its own problems. It may be that the increase in mortality from eating too little salt has something to do with this mechanism.

CONCLUSION

The message is the same, no matter if you have high blood pressure or not. Eating too much salt is bad for you. However, this study seems to suggest that eating too little can also be bad for your health. While the reasons why are not entirely clear, the results show that getting too little sodium can increase “all cause mortality” (chance of death by any means) by up to 20%.

A good general rule of thumb is that you should aim to get at least 3800mg (about a teaspoon) of salt per day as a part of your diet. Your body needs a certain amount to operate normally and, for most people at least, this amount appears to be reasonable.

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source - http://www.medscape.com/viewarticle/754077?src=mp&spon=34


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Researched and written by Dr. Rebecca Malamed, M.D. with assistance from Mr. Malcolm Potter.

1 comment:

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