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.
Diet high in potassium, blood pressure, and ictus
Controlled feeding studies, such as “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. And such dietary patterns are characterized by foods high in potassium, 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.
In another study, a systematic review of the literature and meta-analyses has been conducted on potassium intake in apparently healthy adults and children without renal impairment. The study showed that, 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 and in children. In addition, there was no 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. Hence, this study suggests that, in people without impaired renal function, increased potassium intake is potentially beneficial for the prevention and control of elevated blood pressure and stroke.
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 K+ intake
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;
- roasted coffee;
- milk powder (also rich sodium);
- 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).
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