Robert F. Kennedy Jr.'s Affinity For Fermented Foods Isn't A Safe Diet For Everyone

Fermented foods like kombucha and sourdough bread are having a moment. They enjoy a constant presence in the news, among the budding health trends to watch in 2025. Even the United States Secretary of Health and Human Services, Robert F. Kennedy, Jr., has climbed onto the pro-fermentation bandwagon.

Kennedy has gone on record as saying he fills his plate with fermented dishes, as well as meats and meat byproducts. And it's hard to argue that — at least for him — his food choices have produced results. (Videos from 2024 show he has a surprisingly cut physique for a man in his 70s, which some attribute to a "dirty carnivore" style diet.)

But before you reach for another bowl of sauerkraut, you may want to hear about the hidden issues of eating fermented foods. Although it's generally a safe strategy to include fermented foods in your diet (here are 14 fermented foods to try), it isn't the safest eating plan for everyone.

First, let's look at why Kennedy and others are gushing over fermentation in the first place. According to a 2022 article in Nutrients, fermentation changes the nutritional characteristics of foods in a way that supports the gum biome, notably through the introduction and growth of lactic acid bacteria (LAB).

As LAB enters the body, it may boost immunity and promote nutrient bioavailability. Fermentation tends to be a "good" way to preserve perishable foods,  unlike preservatives and additives (such as butylated hydroxytoluene, butylated hydroxyanisole, and some artificial dyes). But if you're sensitive to histamine or you have certain gastrointestinal problems, you might want to steer clear of fermented foods.

Histamine naturally occurs in your body and even helps you get to sleep. However, histamine can go full-tilt when it senses that you've encountered something you're allergic to, which can lead to you dealing with a ton of allergy symptoms. You might get a runny nose, itchy eyes, or even have trouble swallowing. In that case, you might require the help of an antihistamine to feel like a normal human again.

Plenty of fermented foods contain histamine, too, which can disrupt your system by encouraging a flood of allergic reactions. As a 2007 article in the American Journal of Clinical Nutrition notes, one way to resolve histamine-based allergic responses is to consume a histamine-free or low-histamine diet. This would mean cutting out most fermented foods to reduce your chances of a serious allergic attack (per Johns Hopkins Medicine).

Even if you're fine with the histamine in fermented foods, you may not love the way your intestines feel after eating natto or yogurt if you have inflammatory bowel syndrome (IBS). In some people with IBS, the fermentation process irritates their guts, leading to discomfort. Those that experience this type of reaction to fermented products may adopt a low-FODMAP diet that doesn't include any (or as many) fermented food options.

As a side note, you also may want to skip a few fermented foods if you're hypertensive. Fermented foods can be high in sodium (e.g., a cup of traditional kimchi has 747 milligrams of sodium; the same amount of sauerkraut has 939 milligrams). Excessive sodium intake has been linked with increased blood pressure. Therefore, paying attention to the nutritional label of any fermented foods you try can ensure you stay within the healthy daily sodium limits for your age if you're controlling your blood pressure through your diet.