Table of Contents
- Blood Pressure
- Sodium in Food Table
Science and Medical:
- Standard Atmosphere; Atmospheric Pressure;
- Pressure Measurement (Manometers); mmHg – Millimeters of Mercury;
- Blood pressure;
- Stethoscope; Sphygmomanometer – device to measure blood pressure;
- Blood Pressure Measurement; Ambulatory blood pressure monitoring;
- Hypertension; Labile Hypertension; Hypertension and the brain.
Salt and sodium:
- Salt; Sodium Chloride – chemistry of salt, more history and other uses;
- Health effects of salt; Sodium in biology.
USA – re Salt
- US Food and Drug Administation (FDA) Guidance on salt.
- US Department of Agriculture (USDA) 2020-2025 Dietary Guidelines.
USA – Re Nutrients, Food Components
The US Department of Agriculture Agricultural Research Service’s FoodData Central (“USDA FDC”) can search 5 data sets called
- Foundation Foods,
- Standard Reference Legacy Foods,
- Human Research Center Food and Nutrient database for Dietary Studies (“FNDDS Survey Foods”),
- Branded Foods,
- Experimental Foods.
It may be necessary to repeat searches in each set. The American government collect or tests samples for the FNDDS Survey Foods data, but not the others. The government requires tests from accredited services at a manufacturer or distributor’s expense in most instances.
Other countries, including Canada, have data sets on products offered for sale in those countries. The data comes from manufacturers or hired services. Government or independent testing is limited.
Canada Department of Heath (Health Canada):
- Canada Food Guide,
- Dietary Guidelines,
- Guidance on sodium,
- Sodium detector, and
- information on sodium content of common processed foods.
The American Heart Association (AHA),
- Get the Scoop on Sodium and Salt – web page;
- Understanding Blood Pressure Readings – web page;
- published medical scientific journal Hypertension.
- diet guides and cookbooks. The AHA sells a Low-Salt Cookbook, first published in 1990. The 2011 4th edition is the most modern, and is currently for sale on the internet at the AHA website;
Pressure, Measurement, Devices
Medical science, in the 19th and 20th centuries, credited the idea that blood circulated through the body by vessels from and to the heart to William Harvey, in 1628. This theory was accepted as a better idea than the idea of “humours” postulated by classical and medieval Greek, Roman, Arabic, and middle Eastern writers. The noises of the heartbeat, the flow of blood through blood vessels, and the detectable pulse in blood vessels have been known for a very long time.
In 20th century medical practice:
Blood pressure is one of the vital signs … that healthcare professionals use in evaluating a patient’s health.Wikipedia, Blood Pressure, September, 2023
The health care professions describe the ausculatory and oscillomatric methods as “non-invasive”. Blood vessels are not pierced or penetrated. Ausculatory blood pressure measurement started in the 19th century. The stethoscope and the sphygnomanometer were invented and came into use. The method involved:
- listening to the the artery – ususally the brachial artery, a major artery in the upper arm – with a stethoscope applied to the inside of the limb above the elbow, to detect when blood is flowing,
- restricting the flow until the sound was not detected, then releasing it, and
- using a sphygnomanometer to measure the pressure in the artery.
Systolic pressure is the maximum pressure during one heartbeat. Diastolic pressure is the minimum pressure between two heartbeats. The units of measurement are millimeters of mercury (abbreviated mmHg), derived from the original mercury column sphygnomanometer. In the 20th century medical offices, clinics and hospitals were equipped with Aneroid sphygnomanometers, which were supposed to be calibrated to the ambient air pressure for proper use.
Since the early 20th century, the flow in the artery flow has been been restricted with an inflatable cuff device – at one time a manually inflated pneumatic device. It was wide enough to apply pressure without bruising or injury to the limb, and applied above the elbow. The pressure in the cuff was a measure of the blood pressure.
With an electronic sensor, the pump could detect oscillations in the cuff. The oscillations could used to measure blood pressure with the oscillometric method.
The idea of using compressed air in durable hose to trigger a switch had been used commercially to design devices that could monitor traffic in the 20th century. Automobile service stations used devices made up of a hose, a pressure switch and a bell to alert staff that vehicle had entered the lot and was in a position to purchase gasoline. Such devices are still on the market in the early 21st century to monitor entry to some properties.
A sensor could detect the pressure applied by the cuff when the oscillations of the artery in the limb to which the cuff was applied had stopped. Oscillometric devices are sensitive, to the point that the standards of normal and healthy pressure and unhealthy hypertension are being redefined according to statistical analysis of sample groups of readings among patients with different characteristics.
Automated oscillometric blood pressure cuffs and meters were available to health care providers in 1976. These devices do not detect the sounds in the artery or correlate sounds to pressure. These devices inflate the cuff, detect when blood flow through the limb has paused, take readings, release the cuff, record and display blood pressure and pulse. They appears to work like a health care worker using a stethocope and an aneroid sphygnomanometer:
- shut down at a pressure slightly higher than the pressure when the ocillations stopped,
- release pressure gradually,
- record the systolic and diastolic pressure, and
- release pressure.
The cuffs on automated oscillomatric monitors are held in a fixed position against the body by the fabric shell of the cuff, which is closed with a fastener. The adhesive hook and loop fastener system, known as Velcro is used in devices built in and after the late 20th century.
The airtight inflatable cuff is the inner layer of a cuff assembly. Its outer layer has a fastener sewed the outside
The oscillometric inflatable cuff is used to measure blood pressure in automated devices used in
- medical care facilities and diagnostic settings, and
- for home use for patients to monitor and report blood pressure.
In the first groups, the cuffs are put on patients and the devices are used by persons who observe and record the readings. In the case of home use, a patient must install the cuff, take the reading and record the result.
Many home devices use a flexible internal plastic shell between the inner cuff and the outlayer. The shelll curves around the part of the body where the cuff is applied. This makes the cuff easier to fit on an arm, and easier to fasten.
Automated monitor methods are less expensive and time consuming for health care providers. Automated devices are built to standards. A device is regarded as accurate if the design and the manufacturing process meet standards. In theory, automated device are self-calibrating, and deliver acceptably accurate readings every time they are used, if:
- the device is working as the manufacturer says,
- the cuff is applied properly,
- the patient
- is properly seated,
- has been inactive, and is warm and comfortable, and
- is not stressed by anything.
Automated meters are also used in ambulatory measurement.
The Canadian advocacy entity Hypertension Canada allows manufacturers to use its Gold and Silver marks on product packages based on its review of how the manufacturers have met certain standards1“Those with a Gold rating meet the highest and most current international standards, and those with the Silver ratings meet the highest international standards available prior to their most recent updates. (Both Gold and Silver levels are accepted as accurate)”. The rating is necessary to make the devices marketable. The rating process is not transparent. It does not appear that Hypertension Canada tests devices to verify accuracy. It appears that it has a standard of requiring a manufacturer to say that its process meet standards.
The basic home device would has:
- a cuff connected by a hose to a
- device containing g the pump, the sensor and an LCD display.
An automated home device, sold in 2020-23 might have Bluetooth to upload data to another device, or other data collection and transmission functions.
The manufacturers of home devices provide detailed instructions to users on attaching the cuff, posture during readings, and the operation of devices. A manual will suggest the cuff be applied to upper part of the left arm at a distance above the elbow, usually with the inflation tube aligned to the inside of the limb. It may suggest a different place and alignment on the right arm.
The display area has an area that flashes the systolic pressure as the cuff inflates, and as the cuff deflates. This area gives the systolic reading when the device stops. A separate heartbeat symbol flashes when oscillations are detected as the cuff is inflated, and as the cuff is deflated and the reading is taken.
Some devices will display icons for “movement error” and irregular heartbeat”. Irregular heart beat icon can be triggered by movment errors, which may occur when the cuff is not attached properly, as well as when the user moves the limb with the cuff, or coughs or sneezes.
A manual will have “tips” about taking readings including taking readings in a quiet place, at the same time, keeping warm, avoiding stresss and not taking readins fir at least 30 minutes after bathing, consuming alcohol or caffeine, smoking ot excercising. Similiar advice can also be found in resources like the Canadian advocacy entity Hypertension Canada’s pamphlet for professionals.
The normal blood pressure of a healthy adult is 120 mmHg systolic and 80 mmHg diastolic. This is written as 120/80, spoken as 120 over 80:
“… the average blood pressure, age standardized, since 1975 to the present, at approx. 127/79 in men and 122/77 in women, although these average data mask significantly diverging regional trends.”
… in many older people, systolic blood pressure often exceeds the normal adult range”.
Blood pressure fluctuates from minute to minute and normally shows a circadian rhythm over a 24-hour period, with highest readings in the early morning and evenings and lowest readings at night. Loss of the normal fall in blood pressure at night is associated with a greater future risk of cardiovascular disease and there is evidence that night-time blood pressure is a stronger predictor of cardiovascular events than day-time blood pressure. Blood pressure varies over longer time periods (months to years) and this variability predicts adverse outcomes. Blood pressure also changes in response to temperature, noise, emotional stress, consumption of food or liquid, dietary factors, physical activity, changes in posture (such as standing-up), drugs, and disease. The variability in blood pressure and the better predictive value of ambulatory blood pressure measurements has led some authorities, such as the National Institute for Health and Care Excellence (NICE) in the UK, to advocate for the use of ambulatory blood pressure as the preferred method for diagnosis of hypertensionWikipedia, September 2022, Blood Pressure
Readings play a major role in the diagnosis and treatment of hypertension. The AHA’s online pamphlet Understanding Blood Pressure Readings classifies of 5 bands of BP readings.
Blood pressure is assumed to stable for periods of time depending on what the patient is doing, and the patient’s emotional state. Some people may have labile hypertension. Labile means changeable and connotes unstable.
Measurement is complicated by environmental and psychological factors. Health care professionals recognize white coat hypertension which is studied in reference to the effect of being monitored in a clinical setting and labile hypertension. Health care professionals generally trust the devices to provide an accurate measurement of blood pressure at a point in time.
Hypertension can be described(by the AHA stage 2, above) as a medical condition in which the blood pressure in the arteries is persistently elevated – systolic blood pressure is elevated (>140 mmHg) with a normal diastolic blood pressure. Isolated systolic hypertension may present a health concern. This is called elevated by the AHA or prehypertension in some material. Where elevated readings (>140/>90) appear twice, a medical doctor can diagnose hypertension. Doctors often prescribe medications to reduce blood pressure to levels under 140/90. Medical care is often dedicated to managing medications and adverse side-effects. The medications have adverse side-effects. ACE inhibitors (e.g.), can cause persistent dry coughing, among other things. Calcium channel blockers (e.g. Amlodypine) often cause peripheral edema.
Hypertension … is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high blood pressure, however, is a major risk factor for stroke, coronary artery disease, heart failure, atrial fibrillation, peripheral arterial disease, vision loss, chronic kidney disease, and dementia. Hypertension is a major cause of premature death worldwide.
High blood pressure is classified as primary (essential) hypertension or secondary hypertension. About 90–95% of cases are primary, defined as high blood pressure due to nonspecific lifestyle and genetic factors. Lifestyle factors that increase the risk include excess salt in the diet, excess body weight, smoking, and alcohol use. The remaining 5–10% of cases are categorized as secondary high blood pressure, defined as high blood pressure due to an identifiable cause, such as chronic kidney disease, narrowing of the kidney arteries, an endocrine disorder, or the use of birth control pills.
Blood pressure is classified by two measurements, the systolic and diastolic pressures, which are the maximum and minimum pressures, respectively. For most adults, normal blood pressure at rest is within the range of 100–130 millimeters mercury (mmHg) systolic and 60–80 mmHg diastolic. For most adults, high blood pressure is present if the resting blood pressure is persistently at or above 130/80 or 140/90 mmHg. … Ambulatory blood pressure monitoring over a 24-hour period appears more accurate than office-based blood pressure measurement.Wikipedia, September 2022, Hypertension
Treatment of Hypertension
Drugs vs Lifestyle
Physicians in most places diagnose hypertension on the basis of blood pressure readings, and treat it by prescribing anti-hypertensive medication and testing patients periodically. A few countries cover the cost of prescribed medications under health insurance or drug cost insurance.
Lifestyle changes and medications can lower blood pressure and decrease the risk of health complications. Lifestyle changes include weight loss, physical exercise, decreased salt intake, reducing alcohol intake, and a healthy diet. If lifestyle changes are not sufficient, then blood pressure medications are used. Up to three medications taken concurrently can control blood pressure in 90% of people. The treatment of moderately high arterial blood pressure (defined as >160/100 mmHg) with medications is associated with an improved life expectancy. The effect of treatment of blood pressure between 130/80 mmHg and 160/100 mmHg is less clear …
The first line of treatment for hypertension is lifestyle changes, including dietary changes, physical exercise, and weight loss. Though these have all been recommended in scientific advisories, a Cochrane systematic review found no evidence for effects of weight loss diets on death, long-term complications or adverse events in persons with hypertension.The review did find a decrease in body weight and blood pressure.Their potential effectiveness is similar to and at times exceeds a single medication. If hypertension is high enough to justify immediate use of medications, lifestyle changes are still recommended in conjunction with medication.
Dietary changes shown to reduce blood pressure include diets with low sodium, the DASH diet (Dietary Approaches to Stop Hypertension), and plant-based diets. … There is evidence from randomized, double-blind, placebo-controlled clinical trials that Hibiscus tea consumption significantly reduces systolic blood pressure (-4.71 mmHg, 95% CI [-7.87, -1.55]) and diastolic blood pressure (-4.08 mmHg, 95% CI [-6.48, -1.67]). Beetroot juice consumption also significantly lowers the blood pressure of people with high blood pressure
Increasing dietary potassium has a potential benefit for lowering the risk of hypertension. The 2015 Dietary Guidelines Advisory Committee (DGAC) stated that potassium is one of the shortfall nutrients which is under-consumed in the United States. However, people who take certain antihypertensive medications (such as ACE-inhibitors or ARBs) should not take potassium supplements or potassium-enriched salts due to the risk of high levels of potassium.Wikipedia, September 2022, Hypertension
Some governments and advocacy groups (e.g. the AHA) have promoted the Dietary Approaches to Stop Hypertension (“DASH”), eating plan.
In the short run, drinking alcohol increases blood pressure for a short period after consumption. One drink will raise blood pressure for about two hours. Long term regular drinking contributes to hypertension, The causation is still under discussion. A 2014 paper says:
… the mechanism through which alcohol raises blood pressure remains elusive. Several possible mechanisms have been proposed such as an imbalance of the central nervous system, impairment of the baroreceptors, enhanced sympathetic activity, stimulation of the renin-angiotensin-aldosterone system, increased cortisol levels, increased vascular reactivity due to increase in intracellular calcium levels, stimulation of the endothelium to release vasoconstrictors and loss of relaxation due to inflammation and oxidative injury of the endothelium leading to inhibition of endothelium-dependent nitric oxide production. Loss of relaxation due to inflammation and oxidative injury of the endothelium by angiotensin II leading to inhibition of endothelium-dependent nitric oxide production is the major contributors of the alcohol-induced hypertension. For the prevention of alcohol-induced hypertension is to reduce the amount of alcohol intake. Physical conditioning/exercise training is one of the most important strategies to prevent/treat chronic alcohol-induced hypertension on physiological basis. The efficacious pharmacologic treatment includes the angiotensin-converting enzyme (ACE) inhibitors or angiotensin II type 1 receptor blockers (ARBs) which have antioxidant activity and calcium channel blockers.Abstract, Husain, Ansari, Ferder; Alcohol-induced hypertension: Mechanism and prevention 6 World J. Cardiol. 245 (2014)
Abstention by long term regular drinkers can reduce blood pressure readings during the period of absention. Studies:
- Alcohol consumption and hypertension, (1987)
- Alcohol consumption and hypertension, (1993)
- Lifestyle modifications to prevent and control hypertension. 3. Recommendations on alcohol consumption. Canadian Hypertension Society, Canadian Coalition for High Blood Pressure Prevention and Control, Laboratory Centre for Disease Control at Health Canada, Heart and Stroke Foundation of Canada (1999)
- The effect of a reduction in alcohol consumption on blood pressure: a systematic review and meta-analysis (2017)
The American Heart Association says that limiting alcohol consumption to less than two drinks a day is advised.
Caffeine has many side effects.
It can elevate blood pressure temporarily, which will affect blood pressure readings.
It is not discussed as a significant lifestyle or dietary factor causing hypertension.
Salt is found as a crystaline solid, or in solution in water. Salt can be mined from mineral deposits, or extracted from seawater by evaporation. Salt was used to preserve, store and prepare food for centuries, . It was not believed to be harmful until medical research was conducted in the 20th century.
Most salt for cooking is processed to standard sized crystals sold as table salt. It is the standard presentation of the salt sold in grocery stores for household use in cooking and baking. The crystals are small enough to fit the holes in a salt shaker, and dissolve in water including in the amounts used to mix bread dough in industrial bakeries. Table salt is treated with anti-caking agents. Depending on manufacturer and brand, it may be treated with or without iodine and other chemicals.
Kosher salt is a table salt with slightly larger crystals, and normally not treated with chemicals other than anti-caking ingredients. Sea salt may have crystals of varying sizes, some of which may not dissolve and distribute uniformly during cooking and baking.
Humans became habituated to salt. During the industrialization of food processing, the food industry used salt to mask the changes to the taste of food that was processed in canneries, and began to use salt as flavour enhancer to increase the sales of processed foods.
Salt is chemically described as sodium chloride. One molecule of salt has one atom of sodium (Na) and one atom of chlorine (Cl). Salt crystals dissolve in water. Salt molecules consumed by living organisms becomes use in extracellular fluid and interstitial fluid.
Sodium is an element, an alkaline earth metal in Group 1, in the periodic table. In living organisms, salt is separated into sodium cations (positively charged ions) and chlorine anions. Before industrial food processing manufactured other products made with sodium, humans consumed animals and plants, or salt, to acquire sodium. Most plants consume little salt, but animals, including humans, require sodium. Sodium is a vital nutrient:
Sodium in Biology, September 2022
Sodium is the primary cation in extracellular fluids in animals and humans. Sodium ions pass into cellular fluid by the enzyme in the cell walls known as the sodium-potassium pump.
Humans have taste receptors that detect sodium ions. These receptors also detect the ions of other alkali metals as salty. Humans taste salt. The sense is not calibrated. Humans can detect that a mouthful of food contains salt but cannot tell how much sodium they consume.
The adequate intake for sodium is 1,200 to 1,500 milligrams per day. On average, people in the United States consume 3,400 milligrams per day, an amount that promotes hypertension. Salt contains about 39.3% sodium by mass; the safe upper limit for sodium is under 1 teaspoon per day. 1 tsp of table salt weighs 5.7 grams, and contains 2,240 mg. of sodium.
The food industry resists reducing the use of sodium in the preparation of packaged foods and restaurant meals. It markets some salty items as traditional foods. Its lobbyists and lawyers disputes the harms of salt. The food industry argues that
- consumers make informed decisions (the argument tobacco companies and drug companies used to defend their profit from the sale of addictive harmful products), and
- manufacturers have the right to use salt and marketing to sell products.
Manufacturers are required to disclose facts to the USDA in the USA, and to disclose facts to persons purchasing packaged foods with a label on the package headed “Nutrition Facts”.
Sodium is listed in the Food/Nutrition facts labels in milligrams; (.001 or 1/1000 of a gram). Sodium is also stated as a % of the national recommended daily allowance (usually the USDA RDA) in a stated amount called a serving, as defined by the manufacturer. It is usually given as a volume and often also as a weight measured in grams.
There are regulations in the USA requiring chain restaurants to disclose sodium content on menus and in some instances tag the content with health risk logo that may alert consumers. These regulations are resisted by restaurants and manufacturers, by lobbying, occasional litigation, obscurity, equivocation and evasion. The Canadian CBC Network covered sodium in restaurant food in Canada in its television/streaming program Marketplace‘s episode Putting takeout to the test: the shocking amount of sodium in some restaurant meals (Season 50, Episode aired January 6, 2023) – Text for internet article, with link to YouTube video.
I have put sodium content of several food items in a table at the end of this post that I can alter without changing the rest of this post.
Salt Free Foods
Salt is essential to the preparation of some foods.
Some mineral compounds interact with the salt sensors in the human mouth. Potassium Choride is one such compound. The food manufacturer French’s began to manufacture and distribute a product called NoSalt, now packaged as the Original Sodium Free Salt Subsitute salt. In 2017 the French’s brands were acquired by McCormick & Company. NoSalt is sold by some retail grocery chains and by some specialized internet vendors. There are other salt substitute products.
Salt Free Prepared Foods
Some manufacturers have produced salt free foods and brought them to market. Some have been abandoned for unknown reasons. Some salt free processed food products are on the market.
In British Columbia, Canada, the Thrifty’s grocery stores (now part of the retail group that manages the Sobeys stores) sold a store brand of no sodium whole wheat bread. It wasn’t good but it appeared to sell. The store stopped offering it during the pandemic, in about 2020.
Becel (an Upfield brand) packaged a low sodium margerine spread for retail distribution and sale in Canada for several years. It disappeared from retail grocery stores on Vancouver Island in British Columbia, Canada and everywhere Upfield did busness, as far as I can tell, in 2019. Becel’s other margerine spreads generally have about 70 mg. of sodium per 2 tsp. of margerine spread. Becel/Upfield does not post Nutrition Facts on the Web (it complies with the law and has Nutition Facts labels on its product tubs and wrappers. Becel/Upfield promotes Becel margerine spreads as healthy plant based oil products. Becel still manufactures a salt free margerine, sold in blocks. It is not spreadable.
Some zero salt products available before 2020 fell victim to supply chain problems or disappeared for retail stores during the pandemic
The journal Hypertension published Salt Sensitivity of Blood Pressure; A Scientific Statement From the American Heart Association in Volume 68, No. 3 in September 2016 which argued for the existence of a physiological trait by which the blood pressure of some members of the population exhibits changes parallel to changes in salt intake. Physicians in most places do not diagnose salt sensitivity.
Salt used in baking yeasted or yeast-leaving bread to flavour bread and to affect the formation of gluten. It is a normal ingredient in recipes and formulas for yeasted bread, as I discuss in my post Sodium in Bread.
Baking soda, also known as sodium bicarbonate is used in baking as a chemical leaving agent. It is also used as an ingredient in manufacturing baking powder. It is not uncommon for baking recipes to use both baking powder and baking soda. Baking soda has some other uses in cooking, and several other uses.
There is a sodium free baking soda substitute called Ener-G Baking Soda Substitute, manufactured by Ener-G Foods Inc., and available for sale online.
Baking powder is a chemical leavening agent used in baking, made with baking soda. There is a sodium free baking powder substitute called Featherweight, manufactured by Hain Pure Foods, and available for sale online.
Sodium in Food Table
This table is mainly a survey of Food Facts data on several product labesl.
This table does not include food products used in baking, including salt. That information is in a table embedded in the post for baking ingredients
The column headings list the items, in groups. The column headings identify the item and
- the Food/Nutrition Facts Unit (“serving”) size (“LabelUnit”), normally set by the manufacturer;
- the weight or mass (metric, in grams) of the Unit or the volume (metric in milliters), as stated by the mfr., in the Food Facts label;
- for some items, a realistic amount (“RA”) used in a recipe by volume and by weight (metric, in grams);
- the sodium (“Na”) in the RA, by weight, in milligrams. If no RA is given, the Na is per Unit;
- the potassium (“K”) in the RA, by weight, in milligrams. If no RA is given, the K is per Unit.
[table id=96 /]