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Health Studies Show that Very Low Sodium Intakes Can be Harmful

Updated on July 7, 2016
janderson99 profile image

Dr John uses his Biochemistry & Physiology research background (PhD) to develop authoritative reviews of dieting, weight loss, obesity, food

This is a classic case of what regularly happens in the human health arena. One study highlights a problem, the lemmings all get funded to show that same thing. Someone steps back and says “Hang on a minute”, “Maybe we should check this out, properly”.

Their new study refutes the original conclusion, but the lemmings and various health authorities won’t listen. The weight of evidence wins out. Besides, it’s too expensive to pulp all the brochures.

The health benefits of reducing salt (sodium chloride) consumption in diets have long been accepted. The need to lower salt, especially sodium intake, is widely promoted via various health authority advertisements.

However, several recent major studies have bucked the trend and gone against the dogma. These studies found that people with the lowest sodium intakes actually had the worst cardiovascular outcomes. Strange but true!

It appears that there is a middle ground. People with very high salt consumption also had higher risk of dying sooner, The middle ground ('everything in moderation') appears to be the healthiest. Claims about the need for low calorie diets appear to be ‘making a mountain out of a molehill'.

This article reviews the latest studies to shed light on how salt and sodium intake affects health and how the truth needs to be revealed and confirmed.

Some Foods are Obvious Sources of Excess Salt
Some Foods are Obvious Sources of Excess Salt | Source
Other 'normal' foods are naturally relatively high in salt.
Other 'normal' foods are naturally relatively high in salt. | Source
Salt levels can vary widely even withing the same food type
Salt levels can vary widely even withing the same food type | Source

An Australian study of the salt intake of more than 600 elderly type-2 diabetic patients over a 10 year period found that patients who ate less salt, had higher mortality rates. For every extra 2.3g of sodium (about one teaspoon of salt) in the urine of patients their risk of dying fell by about 30 per cent. Patients who ate more salt tended to be fatter, but fewer of them died from heart disease and stroke over the 10 year period of the study.

This is one of many studies that have shown that restricting salt intake provides no benefits for suffers of diabetes, heart-attack, and people with high blood pressure.

Recent data are very confusing with conflicting outcomes. About seven recent studies have shown a correlation between increased salt intakes and increased death rates. However, more than twice as many studies have found either no link between low salt and mortality rates or the opposite finding - that increased salt was associated with lower death rates.

Outcomes of Recent Research

  • An earlier study, published in 1985 on Japanese immigrants in Hawaii, examined the relationship between sodium intake and subsequent deaths due to heart disease problems. The study failed to show a confirmed relationship between sodium intake and health outcomes. This was one of the studies focused on sodium intake.
  • An Australian study of 4000 patients admitted to a clinic, who had all had the sodium in their urine measured, found that people with the lowest sodium intake had the worst cardiovascular outcomes.
  • A Fiinish study of about 2800 people with type-1 diabetes, found best survival rates for those with moderate salt consumption. The groups with the lowest and highest sodium consumption rates had higher mortality rates.
  • A study of 28,800 Canadians found similar results to that for the Finnish Study – higher mortality rates for the groups with the highest and lowest salt consumption. The impact of extra salt did not occur until it was 3-4 times higher than the recommended intake. The low consumption rates were well within the range currently recommended by health authorities. Both high and low salt consumption groups suffered more cardiovascular events.
  • A study of about 3600 Europeans, who showed no evidence of heart disease, found a mortality risk of about 1% for those with the highest salt consumption, but 4% in those with the lowest salt consumption.
  • A series of seven randomised controlled studies by the non-profit Cochrane Collaboration supported these finding for a group of 6200 subjects. These studies showed no clear evidence that linked salt intake to mortality or heart disease incidence.
  • A major review of 163 studies by the Cochrane Collaboration group found evidence that reduced salt intake appeared to be harmful for patients with heart problems and these with type 1 and 2 of diabetes. After reviewing more than 150 controlled studies and 13 population studies they found no conclusive evidence in favour of sodium reduction decreasing mortality.

So Why the Conflict? Why isn’t the Research More Conclusive?

It appears that this is a classic case of using data to show an association or correlation without demonstrating cause and effect. It is likely that there are many other factors involved that confound the research outcomes, despite the efforts to control them.

Many of the leading researches on salt effects admit there is no direct evidence that reducing salt intake directly saves lives. Various inferences can be made such as reducing salt may help to reduce blood pressure and this in turn may reduce the risk of death from heart related problems, stroke and kidney failure. But once again it is all supposition and not proven conclusively.

There is much stronger evidence that blood-pressure-lowering drugs save lives, because it is easier to do the research and there is more funding available from the drug companies. One reason the same assurance cannot be applied to salt reduction is there's no money in it. Advertisers aren’t going to get lucrative contracts from marketing salt-reduced food. But they will continue to get contracts for advertising processed foods that sell well because they have lots of salt added to make them palatable.

One of the unusual problems with salt research is that many people who are asked to adopt a low-salt diet – hate it, and drop out of the study. One approach is to add potassium to the sodium, as there is research showing that the potassium to sodium ratio is more important than the sodium level itself.

A major research Australian study that has just started, may finally provide some answers. It will be based in northern China and will involve 360 villages. Half the villages will get normal salt and the other half will get a salt mixture containing 10% magnesium chloride and 30% potassium chloride. This mixed ion salt will taste the same, but will have much less sodium. The mortality and health statistics for the 700,000 people in the villages will be monitored over a four year period.

Are the Salt Reduction Targets Realistic and not Risky?

In Australia, the low-salt dietary target is about 4 g of salt a day, which is equivalent to almost one single teaspoon of salt. Most Australians consume about 10 g of salt per day (2 1/2 times as much. But the 4 g target (40% of current levels) is within the range than many studies suggested could increase mortality risks.

It has been claimed that humans evolved to live on a diet of less than 1 g of sodium a day (10% of what we ea now). The average American consumes about 3.4 grams of sodium, or 8.5 grams of salt, a day. So there is clearly a huge mismatch between the amount of salt and sodium we eat now and the recommended amounts.

The two table below summarize the salt and sodium level in a wide variety of foods compared with the recommended daily allowance. This shows that most people exceed the recommended levels by simply eating what is considered a 'normal diet'. This situation mirrors the argument about obesity and calorie intake. A recent major study found that the majority of people are overweight or obese because they 'passively' eat too many calories.

The highly processed foods such as breads and dairy products are manufactured to have very high levels of calories, because that is what people want (supposedly). Most people don't get fat because they eat junk food, but because they eat too much normal food which is calorie dense. The same applies to salt which is added to foods to make them more palatable. People get too much salt by eating 'normal' foods not junk foods.

The conclusion is that we need better and more definitive research on the relationship between salt and sodium and health and what levels are safe. The research needs to establish cause and effect not simple correlations.

Are the Salt Reduction Targets Realistic and not Risky?

In Australia the dietary target is about 4 g of salt a day, which is equivalent to almost one single teaspoon of salt. Most Australians consume about 10 g of salt per day (2 1/2 times as much. But the 4 g target (40% of current levels) is within the range than many studies suggested could increase mortality risks.

It has been claimed that humans evolved to live on a diet of less than 1 g of sodium a day (10% of what we ea now). The average American consumes about 3.4 grams of sodium, or 8.5 grams of salt, a day. So there is clearly a huge mismatch between the amount of salt and sodium we eat now and the recommended amounts.

The two table below summarize the salt and sodium level in a wide variety of foods compared with the recommended daily allowance. This shows that most people exceed the recommended levels by simply eating what is considered a 'normal diet'. This situation mirrors the argument about obesity and calorie intake. A recent major study found that the majority of people are overweight or obese because they 'passively' eat too many calories. The highly processed foods such as breads and dairy products are manufactured to have very high levels of calories, because that is what people want (supposedly). Most people don't get fat because they eat junk food, but because they eat too much normal food which is calorie dense. The same applies to salt which is added to foods to make them more palatable. People get too much salt by eating 'normal' foods not junk foods.

The conclusion is that we need better and more definitive research on the relationship between salt and sodium and health and what levels are safe. The research needs to establish cause and effect not simple correlations.

Salt Content of Popular Foods

Food Type
Product
Child Serving
Salt (g)
Adult Serving (g)
Salt (g)
Percent of Weight that is Salt
Tsp of Salt (adult serving)
Cereals
Coco Pops
30
0.5
120
2
1.7
0.4
 
Nestle Shreddies
30
0.5
120
2
1.7
0.4
 
Muesli
35
0.08
140
0.3
0.2
0.1
 
Cornflakes
40
1
160
4
2.5
0.7
Processed Foods
White bread (4 slices)
100
1.3
400
5.2
1.3
0.9
 
Shepherds pie
200
2
800
8
1
1.4
 
Baked beans
225
2.98
900
11.9
1.3
2.1
 
Chicken curry
200
2.25
800
9
1.1
1.6
 
French fries
100
2
400
8
2
1.4
 
Pizza (1 slice)
225
4.1
900
16.4
1.8
2.9
 
Tomato ketchup
5
0.2
20
0.8
4
0.1
 
Cream of tomato soup
202
2.5
808
10
1.2
1.8
 
Instant sachet soup
25
2.2
100
8.8
8.8
1.5
 
Spaghetti hoops
210
2
840
8
1
1.4
Snacks
Twiglets
30
1.27
120
5.1
4.2
0.9
 
Dry roasted peanuts
30
0.59
120
2.4
2
0.4
 
Crisps
30
0.5
120
2
1.7
0.4
 
Salted peanuts
30
0.3
120
1.2
1
0.2
Biscuits and Cakes
Jaffa cakes (2)
25
0.2
100
0.8
0.8
0.1
 
Chocolate digestive (2)
30
0.33
120
1.3
1.1
0.2
 
Flapjack
100
0.7
400
2.8
0.7
0.5
 
Chocolate cake (slice)
37
0.39
148
1.6
1.1
0.3
 
Milk chocolate
30
0.06
120
0.2
0.2
0.1
 
Plain sponge cake (slice)
37
0.32
148
1.3
0.9
0.2
Cheese and Spreads
Mozzarella
30
0.45
120
1.8
1.5
0.3
 
Cheddar cheese
30
0.5
120
2
1.7
0.4
 
Cottage cheese
30
0.26
120
1
0.9
0.2
 
Slightly salted butter
7
0.13
28
0.5
1.9
0.1
 
Sunflower spread
10
0.17
40
0.7
1.7
0.1
Fish and Meat
Cod fish fingers
90
0.8
360
3.2
0.9
0.6
 
Fresh salmon (cooked)
100
0.13
400
0.5
0.1
0.1
 
Smoked salmon
56
2.5
224
10
4.5
1.8
 
Beefburger
100
2
400
8
2
1.4
 
Chicken nuggets
100
1.27
400
5.1
1.3
0.9
 
Pork sausages (grilled)
126
3.4
504
13.6
2.7
2.4
 
Ham
40
1.2
160
4.8
3
0.8
 
Bacon rasher (uncooked)
40
1.75
160
7
4.4
1.2
 
Chicken breast (uncooked)
100
0.13
400
0.5
0.1
0.1
 
Pork (uncooked)
100
0.15
400
0.6
0.2
0.1
 
Lamb (uncooked)
100
0.07
400
0.3
0.1
0.1
 
Beef (uncooked)
100
0.15
400
0.6
0.2
0.1

Sodium Content of Popular Foods Listed from Highest to Lowest

Food
Serving Size
Sodium (mg) - (1 level teaspoon of salt = 2000mg sodium)
% Daily allowance - Adult (1500 mg)
% Daily allowance - Child (1000 mg)
Gravy Powder
100g
6020
401%
602%
Soup, Dry Mix
100g
4449
297%
445%
Tinned tomato soup
one bowl
1125
75%
113%
Sauce [Recipe Base - wet dry)
100g
1046
70%
105%
Pasta, Dry Mix
100g
831
55%
83%
Salad Dressing
100g
819
55%
82%
Bakery Biscuit, Savoury
100g
805
54%
81%
Biscuit, Savoury, Puffed Corn
100g
800
53%
80%
Bacon
2 rashers
800
53%
80%
Sausage Roll
100g
660
44%
66%
Chicken,Nuggets
100g
625
42%
63%
Potato, Crisp Extruded Snacks
100g
620
41%
62%
Pizza
100g
604
40%
60%
Falafel
100g
581
39%
58%
Foods Popcorn
100g
516
34%
52%
Peanut Butter
100g
510
34%
51%
Spring Roll
100g
501
33%
50%
Mayonnaise
100g
483
32%
48%
Pie, Meat
100g
481
32%
48%
Croissant
100g
475
32%
48%
Margarine Spread
100g
448
30%
45%
Noodles with Vegetables
100g
444
30%
44%
Pastry
100g
432
29%
43%
Fish
100g
418
28%
42%
Doughnuts
100g
408
27%
41%
Bread
2 slices
400
27%
40%
Dumpling, Savoury
100g
376
25%
38%
M uffin, Sweet
100g
366
24%
37%
Cornflakes
one bowl
360
24%
36%
Pancake/Pikelet
100g
359
24%
36%
Pork, W th Sweet Sour Sauce
100g
348
23%
35%
Cake, Shelf Stable
100g
310
21%
31%
Danish Pastry
100g
272
18%
27%
Potato Crisps
1 packet
270
18%
27%
Pastry, Tart
100g
240
16%
24%
Snack Bar
100g
232
15%
23%
Biscuit, Sweet
100g
229
15%
23%
Potato, Chips or Fries
100g
182
12%
18%
Snack Muesli Bar
100g
132
9%
13%
Spread, Sweet
100g
47
3%
5%
Muesli, Toasted
100g
33
2%
3%

© 2012 Dr. John Anderson

Comments

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  • janderson99 profile imageAUTHOR

    Dr. John Anderson 

    5 years ago from Australia on Planet Water

    thanks for your comments

  • carol7777 profile image

    carol stanley 

    5 years ago from Arizona

    I particularly like the charts as so many foods we think do not have sodium do. Also as always there are conflicts in opinions..what is and what is not. Basically eating food that has not been made from anything else works pretty well. And I do used seasoned salt which has less salt. We have no salty snacks in the house but we all eat the wrong things at times...I guess it is just being careful a good percentage of the time. Well written and researched hub. Voting Up and sharing on facebook.

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