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Low salt diet

Figure out the difference between "salt" and "sodium" and how much salt is recommended on a low sodium diet. Rishi is a pediatric infectious disease physician and works at Khan Academy. Created by Rishi Desai.

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Video transcript

So, two words often get thrown around and confused for one another. And I thought we would take a few minutes to clarify the differences between salts and sodium. And we know they're related, but I wanted to get exactly what the differences are, and how to make sense of all the different numbers I hear around how much I'm supposed to get every day. So, I always think for salts, of my salt shaker at home. It sits right next to my pepper shaker, and whenever I have dinner I often reach for it. And sometimes I think, am I eating too much of it or am I putting on more than I should? And so I was thinking about this in terms of a spoon. So if you have a spoon, let's say a teaspoon of salt. And let's say I took this teaspoon of salt-- here it is-- and I weighed it on a scale. I would find that one teaspoon of salt weighs about 6 grams. Let me write that here. So it's about six grams. And six grams is the same as 6,000 milligrams. So that's the weight of one teaspoon of salt. Now, the question comes up, how much of that is from sodium? So, to answer that, we know that sodium chloride, NaCl is salt. That is what salt is made of. And if I imagine there's nothing in my salt shaker except for sodium chloride, no ants have gotten in there, no other stuff besides the sodium chloride, then I can assume that all 6,000 milligrams of salt is going to be either from the sodium or from the chloride. OK. Now the Na, just be totally clear, is the sodium part and the Cl is the chloride part, that's what that means. And they actually, all atoms have a certain atomic mass unit. So you can actually weigh the atoms, and line them up by size, and which is the largest in weight, and which is the smallest in weight. And sodium weighs out at about 23 units, and chloride is about 35 units. So this is chloride right here, and this is sodium right here. And so if I was to sum it up, I would get 23 plus 35 is 58 units. And units, just to say it again or to write it out rather, is atomic mass units. So now that I have the total atomic mass units, I can try to figure out what proportion is from the sodium, and what proportion is from the chloride. So for the first part, the sodium, I can simply take the 23 units over the 58 unit total. The units cancel out. And that works out to about 40%. So that means that about 40% of the weight of salt is actually coming from the sodium part, and the chloride part is the rest of it. So I've got 35 units over 58 units, and that is about 60%. And again, the units cancel out 60%. So I know that in salt, 40% of the weight is coming from the sodium, 60% from the chloride. Got it. Now, I have to go back to my teaspoon. In my teaspoon I had 6 grams, or 6,000 milligrams. So in that teaspoon, I can just multiply by these numbers to figure out how much of the weight comes from the sodium and how much comes from the chloride. So the sodium gives me 40% of 6,000, which, when you multiply those two numbers you get 2,400 milligrams of sodium. And 60% times 6,000 is 3,600 milligrams of chloride. So now I know in each teaspoon I have 2,400 milligrams of sodium. And now I've actually looked and I've seen that there are recommendations on how much sodium you should get in your diet, if you're not having any medical problems in general. So I'll call that a normal daily salts amount, or normal amount. And this is regular, this would be a regular amount of salts, and then there's a low salt amount. So this would be a low salt amount. So if you're on a low-salt diet, we'll figure out how much salt you're supposed to take in, or how much sodium you're supposed to take in, and the same for regular. How much you should be taking if you're on a regular diet. And I'm going to do it both from a salt perspective and also from a sodium perspective. So let's do the sodium prospective first. So normal amount you should get-- actually, let me write "per day." And let's do of sodium and over here we'll do salt. So regular amount of sodium you should get per day is about 2,300 milligrams. And on a low-salt diet you should get about 1,500 milligrams. Now we know that 1 teaspoon has 2,400 milligrams and 2,400 and 2,300, I think, are pretty close. So in my conversion I'm going to assume that that means I can have about one teaspoon per day of salt. And on a low-salt diet, you're recommended to have no more than about 1,500 milligrams of sodium. And if one teaspoon equals 2,400 milligrams of sodium, then 1,500 is about 2/3 of it, so that's about 2/3 of a teaspoon of salt. So when I look at a teaspoon of salt now, I just remember that if this is my teaspoon, that if I'm on a regular diet I can basically take one of them each day, not each meal but each day. And if I'm on a low-salt diet I can only fill it up about 2/3 of the way, and I'd have to stop there because that's the limit of sodium that I'm recommended.