Putting Celery to the Test

There are some persistent myths about celery, and today, we take them on.

In our first story, NutritionFacts’ Senior Research Scientist, Kristine Dennis asks, “Can celery, a vegetable relatively high in sodium, lower blood pressure?”

Some plants may help us reduce high blood pressure and celery may be one of them. But celery also contains relatively high levels of sodium for a vegetable—about 100 mg of sodium in one cup (~130 g) of chopped celery. Even though it’s relatively high in sodium, it also contains other compounds like NBP, the compound primarily responsible for celery’s taste and aroma, which can relax the smooth muscles that line blood vessels, potentially resulting in lower blood pressure. And there are other compounds in celery that likely have antihypertensive effects, but those are all based on rodent studies—and indeed, celery seed appears to lower blood pressure in hypertensive rats. But what about humans?

You don’t know until you put celery seed to the test, or in this case, celery seed extract, in a randomized, triple-blind, placebo-controlled, cross-over, clinical trial. After four weeks of taking the celery seed extract, systolic blood pressure dropped by at least 10 points, and diastolic blood pressure by about 8 points. But the whole celery seed equivalent would be way more than people could eat.

Is there anything a more modest sprinkle of celery seed a day might help with? Look at this: “Treatment of women’s sexual dysfunction using Apium graveolens L. Fruit (celery seed): A double-blind, randomized, placebo-controlled clinical trial.” And this study used a culinary-friendly dose of celery seed—about 500 mg or about ¼ tsp per capsule, three times per day. At the end of six weeks, there was a significant improvement in the self-reported female sexual functioning among those eating celery seeds, with significant improvements across multiple measures within just three weeks.

What about celery juice? There was a case report of a man who juiced a bunch of celery every day and had a drop in blood pressure and what appeared to be a nonrandomized controlled trial in which an undisclosed amount of celery juice seemed to help. A review concluded that celery can be considered an antihypertensive agent, but the quality of evidence seems slight. What’s the downside though?

Well, celery seed is generally considered safe, and a safety evaluation was performed in the blood pressure trial that indicated so, but maybe not for everybody. Here is a case report of someone who had been taking about two tablespoons of dried celery leaves a day, and it seemed to cause overactive thyroid gland activity; the same happened to this woman who had been taking celery extract powder for weight loss. She did lose 57 pounds (26 kg) in 78 days, but that was likely because the celery extract led to hyperthyroidism. That is not a healthy way to lose weight, risking side effects with names like thyrotoxic paralysis.

Celery is also an allergen for some, often called “pollen-related food allergy.” People who are allergic to some pollens are more likely to have an allergy to celery, such as what happened in this rare case of severe anaphylactic shock after consumption of raw celery. Some only get allergic reactions to celery if they eat it before exercising. Heating celery eradicates symptoms for about 50% of people with a celery allergy, but those who react to raw celery also react when it’s dried.

Even if you don’t have a celery allergy, a warning for those who eat a lot of celery, celery juice, or celeriac (also known as celery root). There are compounds called psoralens in the celery/parsnip/parsley family that can make you sensitive to sunlight. Farmworkers can suffer from a condition known as celery blisters when handling plants without skin protection in the sun. Even grocery store workers who go from the produce aisle to the tanning salon can get into trouble. These compounds can make their way into our skin from the inside out as well, and they are not destroyed by cooking. Too much time in the sun after commencing a “celery soup diet” or spending time on a tanning bed an hour after eating just one large celery root may be enough to result in a serious blistering burn.

Finally today, is it true there are foods like celery that take more calories to digest than they actually provide?

What are some dietary strategies for the prevention and treatment of obesity? Large portion sizes are often targeted, and so, restriction of portion size is an important element of many diet programs, but it’s hard to get people to eat less food. A more effective approach may be to shift the emphasis from the quantity of food eaten to the quality of the food eaten. By choosing foods with lower calorie density, we can eat the same amount of food, or even more food, while losing weight.

Are there foods with negative calories, foods that take more energy to digest than they provide? Does eating celery, for example, result in a negative energy balance? Celery is a readily available whole-food that has the ability to add bulk and flavor to a meal, without adding excess calories. It is also subject to a renowned health myth, that when consuming celery, there is a ‘negative’ intake of calories, and therefore, the energy required for its digestion, assimilation, and nutrient storage is assumed to be greater than the energy it itself contains. So, they put it to the test. A cup of celery—about two stalks—has 16 calories. To digest that much celery takes 14 calories. So no, the consumption of celery does not induce a negative energy balance, but you are only left with two calories. This fact, combined with the high fiber and water content of celery, does make it a good snack for inclusion in a diet for weight loss or management.

Maybe negative calorie foods is not a myth after all, though. Researchers at Penn State offered people a meal of pasta, in which they could eat as much as they wanted. If, in addition to the all-you-can-eat pasta meal, they gave people a small salad, what do you think happened? Did those 50 extra calories of salad just end up on top of the pasta calories? No, they ended up eating less pasta over all, and not just 50 calories less pasta, 65 less calories, and by adding a bigger salad, ended up eating a 100 fewer calories. So effectively, the salad provided “negative calories.” They ate a salad on top of what else they were eating, ate more food, and ended up with less calories in their system, because it bulked up their stomach so much.

Of course, it depends what kind of salad. They’re not talking about typical commercially available salads with like ranch dressing and cheese. You add those kinds of salads and you end up eating less pasta, but there are so many calories in conventional salads, you end up worse off calorie-wise in the end. But healthy salads worked.

They conclude: “eat less” is not always the best advice. For foods very low in energy density, such as water-rich vegetables—like salad—larger portions increase satiety, the feeling of fullness, and reduce meal calorie intake.