Gut-friendly foods may harm heart health, experts have warned, urging consumers to look beyond their probiotic reputation to the potentially high levels of salt and sugar many contain.
The hidden salt factor in fermented favourites
The British Heart Foundation (BHF) is highlighting that many popular fermented foods, such as kimchi and sauerkraut, are frequently prepared with significant amounts of salt. Regular or large consumption of these can contribute to elevated blood pressure, a primary risk factor for heart attacks and strokes.
The mechanism is direct: excessive salt intake causes the body to retain more water, increasing blood volume and pressure on vessel walls. This concern is acute in the UK, where the average salt intake is 8.5g per day, exceeding the recommended limit of 6g, with most coming from packaged and everyday foods.
A single 150g serving of kimchi can contain 747 milligrams of sodium—a substantial portion of the daily maximum of 2,300 mg recommended by US federal guidelines, and far above the American Heart Association’s ideal limit of 1,500 mg. The BHF notes that high salt intake can also reduce the effectiveness of blood pressure medications. A study in the journal *Hypertension* further suggests a diet rich in fruits and vegetables may not fully offset the harm of high salt consumption.
The sugar conundrum in drinks and yoghurts
Elsewhere, the charity warns that the sugar content in other gut-health staples poses a separate risk. While kombucha can be a better alternative to fizzy drinks, many commercial brands contain added sugars.
Similarly, flavoured yoghurts and blended smoothies can cause blood sugar levels to rise quickly because blending fruit releases “free sugars”—the same category as added sugars. The UK government is tightening nutritional standards to focus on these “free sugars,” which are a major contributor to the obesity epidemic. The UK has one of the highest sugar consumption rates in Europe.
Eating too much sugar leads to weight gain, which heightens the risk of heart attack or stroke, the BHF states. Sugars are often “hidden” in processed foods under various names, making it difficult for consumers to track their intake.
Navigating the benefits and drawbacks
Nutritional research reveals a complex picture for specific foods. For kimchi, recent studies point to potential benefits: a lactic acid bacterium from kimchi may help remove nanoplastics from the body, and South Korean data links higher intake to lower systemic inflammation. Some research even indicates kimchi consumption may lead to blood pressure improvements, suggesting beneficial bacteria could offset sodium’s effect, while other studies note it can help decrease unhealthy LDL cholesterol.
For kombucha, evidence from animal and lab studies suggests it may support cardiovascular health by reducing inflammation and modulating gut microbiota, but robust human clinical trials are lacking. The key pitfall remains its sugar content.
Fruit smoothies present a specific nutrient absorption issue. A study in the Royal Society of Chemistry’s journal *Food and Function* found adding bananas to smoothies reduces the body’s absorption of heart-healthy flavanols by up to 84%, due to an enzyme in the fruit.
Practical advice for consumers
In response, the BHF has issued guidance for those seeking gut-friendly options without compromising their heart. The charity advises opting for smaller portion sizes—limiting smoothies to a 150ml serving, for instance—and actively seeking lower-salt or “no added sugar” alternatives.
Tracy Parker, nutrition lead at the BHF, said: “We encourage everyone to choose foods that can keep their gut microbiome healthy… A lot of these products can contain high levels of salt or sugar though, so it is important to be aware of the potential drawbacks.”
She urges consumers to scrutinise product labels for added salt and sugars, noting that food labels often use a traffic light system. There is a growing call for mandatory front-of-pack warning labels, with studies suggesting they effectively deter choices of high-salt items. This is particularly pertinent as public concern about salt in food has been declining in the UK, possibly due to a greater public health focus on sugar.
The overarching message is one of informed moderation. “By ensuring you check package labels… and eat each in moderation, you can make sure the risks do not outweigh the benefits for your heart health,” Ms Parker concluded.