Sodium and Hypertension

What is sodium?

Sodium is a major mineral that is mostly found in the fluid surrounding our body cells and small amount found in bones. Excess sodium will be excreted in the urine. The chemical formula for sodium is natrium (Na).

What does sodium do in our body?

Sodium is very important to our body. Among the functions of sodium are:

•  Maintain electrolyte balance
•  Maintain normal blood pressure
•  Maintain normal blood volume
•  Maintain pH balance
• For proper muscle and nervous system function (brain and in controlling heartbeat)
• Enable cells to draw in nutrients from the blood circulation.

Where can I find sodium in food?

The most common form that we can get sodium in our diet is from table salt or also known as sodium chloride. Natural sources that contain high sodium are protein foods such as meat, poultry, eggs, fish and seafood, and milk. For examples:

• 1 medium size (LxWxT, 12.5x11.3x3.2 cm) chicken thigh contains 71 mg of sodium.
• 1 pieces (LxWxT, 15x9x2 cm) of lean beef contains 180 mg of sodium.
• 1 whole (D, 3 cm) hen eggs contains 56 mg of sodium.
• 1 whole blue crab / Sea crab contains 413 mg of sodium.
• 1 slice (LxWxT, 8x2x15 cm) of Spanish mackerel contains 155 mg of sodium. 
• 1 cup (250 ml) of fresh cow's milk contains 31 mg of sodium.

Other sources of sodium are: processed / canned food (sausages, ham etc), pickled food, condiments and sauces. 

Do you know?!

When people see the word “sodium”, the first thing that they will think of is “salt”. So, people tend to only relate sodium to salty food. However, DO YOU KNOW that sodium can actually be found in those “not-so-salty” foods such as:

1.  Soft drinks
2.  Vegetables and fruit
3.  Cakes, jams, ice cream, and candies
4.  Milk
5.  Mineral water, energy drinks

Sodium is not only used to provide salty taste to the food but also possess other function when sodium exists as compounds. And the below are some examples of more common types of sodium (other types of sodium that are not listed here are usually used as preservatives, stabilizer, provide sour taste and other similar functions):

Table 1: Some common types of sodium and their respective uses in food production.

Types of sodium	Uses in food production
Sodium bicarbonate (baking soda)	As leavening agent (to rise the dough) Stabilizer Give effervescence (like in carbonated beverages) Reduce acidity Examples: cake, bread, ice cream, yoghurt, pudding, cereals, pasta, cookies, processed meat, vinegars, soy sauce, sports drink, and energy drink.
Monosodium glutamate (MSG)	As flavour enhancer Examples: packaged / ready-to-eat foods, sauces and seasonings, fast foods, and snacks.
Sodium caseinate	As thickener Examples: cheese and protein supplement for body building
Sodium saccharin	As artificial sweeteners Examples: bakeries (cakes, cookies, and pies), soft drinks, and ice creams.
Sodium hydroxide	Used in food processing: chemical peeling of fruits and vegetables, cocoa processing, poultry scalding, soft drink processing, thickening of ice cream, and Chinese yellow noodles production
Sodium nitrate / nitrite	As preservatives Curing of meat and poultry Drinking water

What are the foods that are high in sodium content?

According to the Nutrient Composition of Malaysian Foods, some of the foods of high sodium content are:

Food groups	Food items	Portion size in household measure / as purchased	Weight of food items (g)	Sodium content (mg)
Cereals and cereal products	Noodle, dry, instant	1 rectangular piece (LxWxT, 10x8x2cm)	85	103
	Noodle snack, chicken flavoured	1 medium packet	30	184
Legumes & legume products	Soy sauce “thick”	1 tablespoon	20	564
	Soy sauce “thin”	1 tablespoon	17	1255
Vegetables and vegetables products	Cabbage, Chinese, salted	1 cup (chopped)	148	2763
	Chilli sauce, bottle	1 tablespoon	20	224
	Tomato ketchup	1 tablespoon	18	171
	Tomato soup, canned	1 tin (2 ½ cup)	305	1800
Fruits and fruit products	Fruit, mixed, spicy pickled	-	-	1480
	(other pickled fruits)	(> 1 tablespoon)	-	(>480)
Meats and meat products	Chicken curry, canned	1 tin	324	1173
	Beef burger patty	1 round piece (DxT, 10x1cm)	74	309
Eggs	Duck egg, salted, whole	1 whole (LxD, 7.5x4cm)	97	249
Fish, shellfish and products	Anchovy, dries, without heads and entrails	½ cup	28	101
	Fish ball	2 whole, large (D, 3cm)	57	378
	Fish sauce (budu)	1 tablespoon	16	1032
	Sardine, canned	1 small tin (DxT, 5x9cm)	155	476
	Shrimp paste (belacan)	1 piece (LxWxT, 3.5x3.2x3cm)	44	629
Milk and milk products	Cheese, processed, cheddar	1 square piece (LxWxD, 8.4x8.4x0.3cm)	18	261

Source: Tee ES, Ismail, MN, Mohd Nasir A & Khatijah I (1997). Nutrient Composition of Malaysian Foods (4^th Edition). Institute for Medical Research, Kuala Lumpur.

What happen when I take excessive sodium in my diet?

High sodium diet will cause increase in blood pressure (hypertension) and it is the leading cause of chronic diseases such as cardiovascular disease, stroke, and kidney failure. Reduction in sodium intake is proven scientifically to be able to lower the blood pressure.

When there is too much sodium in the blood, the sodium will tend to attract water and hence, retaining water in the body. This causes the blood volume to increase, making the heart need to work harder to pump that much volume of blood. At the same time, the kidneys also need to work harder to filter the sodium in blood. The increased workload and stress in both organs will cause them to eventually lead to failure in functioning.

How much is too much?

According to FDA, an adult, regardless of gender, should not consume more than 2400mg of sodium (6g of salt) per day. As for Malaysian, the Malaysian Dietary Guideline (MDG) 2010 recommends intake for a normal adult of not more than 2000mg of sodium, equivalent to 1 teaspoon of table salt (5g). 

*The amount of 1 teaspoon of salt for Americans and Malaysians are different due to different size of teaspoon used in the two countries.

Extra info: sodium chloride (salt) is made up of 40% sodium and 60% chloride. Hence, 1g of salt = 0.4g of sodium (400mg).

So… what should I do to reduce my sodium intake?

According to MDG 2010, the two most important and basic recommendations are:

Objective 1: To limit the intake of salt to 1 teaspoon (2000mg of sodium) daily

Principles:

• Use lesser salt and other flavour enhancers such as MSG and sauces that also contain high sodium when cooking at home.
• Use natural herbs and other types of food ingredients to enhance the flavour like garlic, onion, spices, white pepper, lemon, vinegar, and lemon grass.
• Learn to enjoy the natural flavour of foods without adding salt.
• Learn to consume low saltiness food. (This habit can be inculcated in everyone and it is true!)
• Prefer home cooking over eating outside.
• Request for less salt / sauce or no MSG when eating out.
• Limit the consumption of fast food to once or twice per month.
• Parents should educate their children about healthy diet, and inculcating low saltiness food to the children since childhood.

Objective 2: To reduce consumption of highly salted foods and condiments

Principles:

• Limit the intake of high sodium foods such as salted fish, salted eggs, salted vegetables, snacks, and processed meats (such as ham, sausage, nuggets, and burger patty).
• Choose more foods of low sodium content within the same food group. For example, choose to take fresh vegetables instead of pickled vegetables for lower sodium consumption.
• Choose fresh foods (fruits, vegetables, meat, seafood etc.) over processed or canned foods.
• Soak preserved foods such as dried anchovies and shrimps in water prior to cooking to reduce the sodium content. (In fact, dried anchovies will be crunchier when they are soaked before being deep fried! Do try this at home!)
• Read the food label (and not just the price tags…). Read the ingredients list to detect hidden sodium (such as sodium bicarbonate that is used as leavening agent in cake, sodium phosphate that is used as preservatives in canned foods).
• Compare the nutrition facts panels of different brands of the same type of food products and choose the one with lower sodium content. Choose brands with claims such as “low salt” or other similar meaning statements on the food packages if available.