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Potassium intake, blood pressure and hypertension

Potassium intake and blood pressure

High dietary potassium (K+) intakes and blood pressure are inversely related: animal studies, observational epidemiological studies, clinical trials, and meta-analyses of these trials support this.
Furthermore, the prevalence of hypertension tends to be lower in populations with high K+ intakes than in those with low intakes.
Finally, an increase in potassium intake (2.5-3.9 g/d) reduces blood pressure in normotensive and hypertensive, and to a greater extent in blacks than in whites.

Dash Diet and potassium intake

Controlled feeding studies (“The Dietary Approaches to Stop Hypertension (DASH) Study” and “OmniHeart Trial”) have highlighted the role of a good potassium intake, along with other minerals and fiber, in blood pressure reduction.
These studies have shown that a dietary pattern rich in fruits, vegetables, and low-fat dairy products, with whole grains, poultry, fish and nuts but poor in fats, red meat, sweets, and sugar-containing beverages reduces blood pressure.
These dietary patterns are rich in foods high in K+, as well as magnesium, calcium and fiber, but poor in total fat, saturated fat and cholesterol.
The best result on lowering blood pressure are with black participants than white participants.

Potassium, sodium and blood pressure

The effects of potassium on blood pressure depend on the concurrent intake of sodium and vice versa:

  • an increased intake of K+ has:

a greater blood pressure-lowering effect when sodium intake is high;

a lesser blood pressure-lowering effect when sodium intake is low;

  • on the other hand, the blood pressure reduction from a lowered sodium intake is greatest when potassium intake is low.

An high K+ intake also increases urinary excretion of sodium, the so-called natriuretic effect.
In the generally healthy population with normal kidney function the recommended potassium intake level is 3.1 g/day. But, in the presence of impaired urinary potassium excretion, a K+ intake less than 3.1 g/day (120 mmol/d) is appropriate, because of adverse cardiac effects (arrhythmias) from hyperkalemia, that is, blood potassium level higher than normal.

Mediterranean Diet and potassium intake

Potassium
Fig. 1 – Fruit, Vegetables, and Blood Pressure

As already pointed out, the best strategy to increase K+ intake is to consume legumes, and fruits and vegetables in season, i.e. foods high in  potassium, that is also accompanied by a variety of other nutrients. No supplements are needed.
Therefore, it is sufficient to follow a  Mediterranean dietary pattern, for:

  • meet the daily requirements of the mineral;
  • consume K+ intake in adequate amounts to ensure its blood pressure-lowering effect.

Potassium content in some foods

High content: >250 mg/100 g of product

  • Dried legumes (chickpeas, beans, lentils, peas and soybeans) and fresh beans;
  • garlic, chard, cauliflower, cabbage, Brussels sprouts, broccoli, artichokes, cardoons, fennel, mushrooms, potatoes, tomatoes, spinach, zucchini;
  • avocados, apricots, bananas, fresh and dried chestnuts, watermelon, kiwi, melon, hazelnuts;
  • sweet dried fruits (apricots, dates, figs, prunes, raisins etc..) and oily dried fruits (peanuts, almonds, walnuts, pine nuts, pistachios, etc.);
  • oat flour, whole wheat flour and spelt;
  • ketchup;
  • roasted coffee;
  • milk powder (also rich sodium);
  • yeast;
  • cocoa powder.

Medium content: 150-250 mg/100 g of product

  • asparagus, beets, carrots, chicory, green beans, fresh broad beans, endive, lettuce, peppers, fresh peas, tomatoes, leeks, radishes, celery, tomato and carrot juice, pumpkin;
  • pineapple, oranges, raspberries, blueberries, loquats, pears, peaches, grapefruit, grapes;
  • meat and fish products, both fresh and preserved (the latter, however, should be avoided because of their high sodium content).

Note: cooking methods tend to reduce the K+ content of the food.
To reduce potassium loss, avoid boiling in plenty of water, for more than an hour, vegetables cut into small pieces (this increases the “exchange area” with water).

References

Appel L.J., Brands M.W., Daniels S.R., Karanja N., Elmer P.J. and Sacks F.M. Dietary Approaches to Prevent and Treat Hypertension: A Scientific Statement From the American Heart Association. Hypertension 2006;47:296-08 [Abstract]

Cappuccio F.P. and MacGregor G.A. Does potassium supplementation lower blood pressure? A metaanalysis of published trials. J Hyperten 1991;9:465-73 [Abstract]

Geleijnse J.M., Witteman J.C., den Breeijen J.H., Hofman A., de Jong P., Pols H.A. and Grobbee D.E. Dietary electrolyte intake and blood pressure in older subjects: the Rotterdam Study. J Hyperten 1996;14:73741 [Abstract]

Mahan LK, Escott-Stump S.: “Krause’s foods, nutrition, and diet therapy” 10th ed. 2000

Matlou S.M., Isles C.G. and Higgs A. Potassium supplementation in Blacks with mild to moderate essential hypertension. J Hyperten 1986;4:61-4  [Abstract]

Nutrient Data Home (USDA)

Pickering T.G. New Guidelines on Diet and Blood Pressure. Hypertension 2006;47:135-6 [Full text]

Rose G. Desirability of changing potassium intake in the community. In: Whelton P.K., Whelton A.K. and Walker W.G. eds. Potassium in cardiovascular and renal disease. Marcel Dekker, New York 1986;411-16

Shils M.E., Olson J.A., Shike M., Ross A.C. “Modern nutrition in health and disease” 9th ed., by Lippincott, Williams & Wilkins, 1999

Tabelle di composizione degli alimenti; aggiornamento 2000. I.N.R.A.N.

Writing Group of the PREMIER Collaborative Research Group. Effects of Comprehensive Lifestyle Modification on Blood Pressure Control: Main Results of the PREMIER Clinical Trial. JAMA 2003;289:2083-2093 [Abstract]

World Health Organization, International Society of Hypertension Writing Group. 2003 World Health Organization (WHO)/International Society of Hypertension (ISH) statement on management of hypertension. Guidelines and recommendations. J Hyperten 2003;21:1983-92. [Abstract]

Metabolic acidosis and “modern diet”

Metabolic acidosis and pH level

Metabolic Acidosis: The pH Scale
Fig. 1 – The pH Scale

Life depends on appropriate pH levels around and in living organisms and cells.
We requires a tightly controlled pH level in our serum of about 7.4 (a slightly alkaline range of 7.35 to 7.45) to avoid metabolic acidosis and survive. As a comparison, in the past 100 years the pH of the ocean has dropped from 8.2 to 8.1 because of increasing carbon dioxide (CO2) deposition with a negative impact on life in the ocean (it may lead to the collapse of the coral reefs).
Even the mineral content of the food we eat (minerals are used as buffers to maintain pH within the aforementioned range) is considerabled influence by the pH of the soil in which plants are grown. The ideal pH of soil for the best overall availability of essential nutrients is between 6 and 7: an acidic soil below pH of 6 may have reduced magnesium and calcium, and soil above pH 7 may result in chemically unavailable zinc, iron, copper and manganese.

Metabolic acidosis and agricultural and industrial revolutions

In the human diet, there has been considerable change from the hunter gather civilization to the present in the pH and net acid load. With the agricultural revolution (last 10,000 years) and even more recently with industrialization (last 200 years) it has been seen:

  • an increase in sodium compared to potassium (the ratio potassium/sodium has reversed from 10 to 1 to a ratio of 1 to 3 in the modern diet) and in chloride compared to bicarbonate in the diet,;
  • a poor intake of magnesium and fiber;
  • a large intake of simple sugars and saturated fat.

This results in a diet that may induce metabolic acidosis which is mismatched to the genetically determined nutritional requirements.
Moreover, with aging, there is a gradual loss of renal acid-base regulatory function and a resultant increase in diet-induced metabolic acidosis.
Finally, a high protein low-carbohydrate diet with its increased acid load results in very little change in blood chemistry, and pH, but results in many changes in urinary chemistry: urinary calcium, undissociated uric acid, and phosphate are increased, while urinary magnesium, urinary citrate and pH are decreased.
All this increases the risk for kidney stones.

pH as a protective barrier

Metabolici Acidosis: pH of Selected Fluids, Organs, and Membranes
Fig. 2 – pH of Selected Fluids, Organs, and Membranes

The human body has an amazing ability to maintain a steady pH in the blood with the main compensatory mechanisms being renal and respiratory.
The pH in the body vary considerably from one area to another. The highest acidity is found in the stomach (pH of 1.35 to 3.5) and it aids in digestion and protects against opportunistic microbial organisms. The skin is quite acidic (pH 4-6.5) and this provides an acid mantle as a protective barrier to the environment against microbial overgrowth (this is also seen in the vagina where a pH of less than 4.7 protects against microbial overgrowth).
The urine have a variable pH from acid to alkaline depending on the need for balancing the internal environment.

References

Fenton T.R., Lyon A.W., Eliasziw M., Tough S.C., Hanley D.A. Meta-analysis of the effect of the acid-ash hypothesis of osteoporosis on calcium balance. J Bone Miner Res 2009;24(11):1835-40 [Abstract]

Fenton T.R., Lyon A.W., Eliasziw M., Tough S.C., Hanley D.A. Phosphate decreases urine calcium and increases calcium balance: a meta-analysis of the osteoporosis acid-ash diet hypothesis. Nutr J 2009;8:article 41 [Abstract]

Fenton T.R., Tough S.C., Lyon A.W., Eliasziw M., Hanley D.A. “Causal assessment of dietary acid load and bone disease: a systematic review and meta-analysis applying Hill’s epidemiologic criteria for causality.” Nutr J 2011;10:article 41 [Abstract]

Schwalfenberg G.K. The alkaline diet: is there evidence that an alkaline pH diet benefits health? J Environ Public Health 2012; Article ID 727630:7 pages doi:10.1155/2012/727630 [Abstract]

Potassium intake and cardiovascular risk factors

Potassium intake and health

In a study published on British Medical Journal a research team has conducted a systematic review of the literature and meta-analyses on potassium intake and health in apparently healthy adults and children without renal impairment that might compromise its handling.
Eleven cohort studies (127038 participants) reporting all cause mortality, stroke, cardiovascular disease, or coronary heart disease in adults and twenty-two randomized controlled trials (1606 participants) reporting blood lipids, blood pressure, renal function, and catecholamine concentrations were included in the study.
In adult with hypertension an increased potassium intake reduced systolic blood pressure by 3.49 mm Hg and diastolic blood pressure by 1.96 mm Hg.
No effect was seen in adult without hypertension (however, the studies were of relatively short duration and did not consider the effect that increased potassium intake may have over time) and in children (there is a lack of data in children: only three controlled studies with 156 partecipants).
There was no adverse effect of increased potassium intake on blood lipids, or catecholamine concentrations in adults whereas an inverse statistically significant association was seen between its intake and the risk of incident stroke (a 24% lower risk).
In healthy adult there was no significant adverse effect on renal function.
This study suggests that, in people without impaired renal function, increased potassium intake (at least 90 mmol/day) is potentially beneficial for the prevention and control of elevated blood pressure and stroke.

How to increase potassium intake

Potassium Intake: Fruits and Vegetables: Rich in Potassium
Fig. 1 – Fruits and Vegetables: Rich in Potassium

It should be noted that an increased potassium intake can be achieved following the largely plant-based Mediterranean Diet, which is characterized by the consumption of large quantities of fresh fruit, vegetable, legumes and unrefined cereals, all rich in potassium (that is also accompanied by a variety of other nutrients).

Aburto N.J., Hanson S., Gutierrez H., Hooper .L, Elliott P., Cappuccio F.P. Effect of increased potassium intake on cardiovascular risk factors and disease: systematic review and meta-analyses. BMJ 2013;346:f1378