TO SALT OR NOT TO SALT?

2010
04.21

Monday, January 11, 2009, NYC’s Health Commissioner Thomas Farley announced salt reduction targets for restaurants and food manufacturers. Farley said that this was done to prevent premature deaths from heart attacks and strokes. Michael Alderman, Professor at NYC’s Albert Einstein College of Medicine stated that “the available data provide no support for any universal recommendation of a particular level of dietary sodium.” Now NYC’s Mayor Bloomberg wants to ban restaurants from preparing food with salt.

THE FACTS: Sodium intake does not vary much around the world. When we examined the data from over 19,000 people from 33 countries including the United States, we found that sodium intake ranged from 2,700 – 4,900 mg daily. This may be because sodium appetite (or behaviors that drive us to consume salt) causes us to naturally regulate our salt intake within a narrow range. It fact, if sodium intake is too low, blood pressure can actually increase. If sodium intake is too high, blood pressure can also increase. In carefully controlled experiments, Norman Hollenberg, Harvard Medical School, found that when people were given high levels of sodium, 8050 mg per day, there was no effect on blood pressure. An increase to 18,400 mg did increase blood pressure. The lower level is much higher than what the average American consumes.

There are over 50 studies that show when sodium is low, insulin sensitivity decreases. In one study, lowering sodium from ~ 3,500 mg/day to ~ 900 mg/day decreased insulin sensitivity in people who have Type 2 Diabetes. This makes it harder to control blood glucose.

For people at high risk for heart disease, there is some justification to restrict sodium intake. Salt can increase blood pressure in some people who are older, black, salt sensitive and those who have kidney damage.  But, based on a study done in Italy, even for high risk patients, the data are not clear. My practical advice is if you have high blood pressure, you should work with your doctor to see what approach works best including taking certain drugs.

WHO MAY NEED EXTRA SALT?: People who work and exercise in hot and humid environments like during the summer in Davis; athletes who run marathons; football players; tennis players. They can collapse from heat stroke and even die.

MY BOTTOM LINE: NYC’s campaign to “Hold the Salt” is misguided and not based in science. It cannot change our physiology. It violates the principle to “Do no harm.”

Some References

Alderman MH. 2006. Evidence relating dietary sodium to cardiovascular disease. J Am College Nutr. 25:256S-261S.

Franco V, Oparil S. 2006. Salt sensitivity, a determinant of blood pressure, cardiovascular disease and survival. J Am College Nutr. 25:247S-255S.

Hollenberg N. 2006. The influence of dietary sodium on blood pressure. J Am College Nutr. 25:240S-246S.

Logan AG. 2006. Dietary sodium intake and its relation to human health: A summary of the evidence. J Am College Nutr. 25:165-169.

McCarron, DA, Geering JC, Kazaks AG, Stern. JS. 2009. Can Dietary Sodium Intake be Modified by Public Policy? Clinical J Am Soc Nephrology. 4:1878-1882.

Petrie JR, Morris AD, Minamisawa K, Hilditch TE, Elliott HL, Small M, McConnell J. 1998. Dietary sodium restriction impairs insulin sensitivity in noninsulin-dependent Diabetes Mellitus. J Clin Endocrinol Metab. 83:1552-7.

Smith WCS et al. 1988. Urinary electrolyte excretion, alcohol consumption, and blood pressure in the Scottish heart health study. British Med J. 297:329-330.

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