One of our biggest goals here at Superfoodly is to dispel myths and set the records straight on foods based on science. This fruit happens to be one that is definitely misunderstand.

The amount of protein in a banana is extremely high. It must be since bodybuilders and fitness buffs always seem to use them in their post-workout protein shakes. Hey, just Google recipes for shakes and smoothies, then tally up how many do and don’t contain this ingredient.

We did that across a random sampling of sites. About 1/3 of recipes contained bananas in some form or fashion.

arm X-ray

Not much protein, but about 10% of the radiation dosage you get from an arm X-ray

But guess what? The actual amount of protein in bananas is a joke. Likewise for their potassium and other exercise benefits which are widely believed.

Ironically, the most interesting thing about them is something very few people know; how much radiation is in a banana!

On a relative basis, it’s a lot. Eating just 1 banana equals about 1/10th the amount of radiation you would get from an x-ray of the arm. Is that healthy for you?!

We’ll get to that in a second. First, let’s address their alleged fitness benefits.

Protein in banana vs. other fruits

Obviously, no one expects fruits in general to be a good source of protein. But even if you look just within that food category, the content in bananas is not even in the top 100. You can view our list of high protein fruits to see the 40 best sources. There are a number of them which have up to 300% more than what is found in bananas. Goji berries, casaba melons, guavas, starfruit, mulberries, and many others will give you significantly higher amounts and make a much better choice for your post-workout smoothies.

How much protein is there in one banana? About 1 gram, regardless of size. An extra small (under 6″) will yield 0.88g while an extra large (9″ and above) is 1.66g. Here’s the full breakdown, calculated using data from the USDA.

Banana Protein & Amino Acid Content By Serving Size
unit amount per 100 g x-small (<6″ long) 81g small (6″ to 6-7/8″) 101g medium (7″ to 7-7/8″) 118g large (8″ to 8-7/8″) 136g x-large (9″+) 152g NLEA serving 126g
Calories kcal 89 72 90 105 121 135 112
Total Protein g 1.09 0.88 1.10 1.29 1.48 1.66 1.37
Leucine (BCAA) g 0.068 0.055 0.069 0.080 0.092 0.103 0.086
Isoleucine (BCAA) g 0.028 0.023 0.028 0.033 0.038 0.043 0.035
Valine (BCAA) g 0.047 0.038 0.047 0.055 0.064 0.071 0.059
Histidine (E) g 0.077 0.062 0.078 0.091 0.105 0.117 0.097
Methionine (E) g 0.008 0.006 0.008 0.009 0.011 0.012 0.010
Phenylalanine (E) g 0.049 0.040 0.049 0.058 0.067 0.074 0.062
Threonine (E) g 0.028 0.023 0.028 0.033 0.038 0.043 0.035
Tryptophan (E) g 0.009 0.007 0.009 0.011 0.012 0.014 0.011
Lysine (E) g 0.050 0.040 0.051 0.059 0.068 0.076 0.063
Arginine (C) g 0.049 0.040 0.049 0.058 0.067 0.074 0.062
Cystine (C) g 0.009 0.007 0.009 0.011 0.012 0.014 0.011
Glycine (C) g 0.038 0.031 0.038 0.045 0.052 0.058 0.048
Proline (C) g 0.028 0.023 0.028 0.033 0.038 0.043 0.035
Serine (C) g 0.040 0.032 0.040 0.047 0.054 0.061 0.050
Tyrosine (C) g 0.009 0.007 0.009 0.011 0.012 0.014 0.011
Alanine (NE) g 0.040 0.032 0.040 0.047 0.054 0.061 0.050
Aspartic acid (NE) g 0.124 0.100 0.125 0.146 0.169 0.188 0.156
Glutamic acid (NE) g 0.152 0.123 0.154 0.179 0.207 0.231 0.192
BCAA = Branched Chain Amino Acids; increased role in protein synthesis for muscle growth and energy
E = Essential (in addition to the BCAAs)
C = Conditional Amino Acids; normally non essential, except in extreme circumstances of illness and stress
NE = Non Essential Amino Acids; our bodies can produce these even if we do not get them from food
Sources: USDA National Nutrient Database, Release 28 (1) and US National Library of Medicine (2)

Many body builders like to use a scoop or two of protein powder after their workout, which provides 15 to 30 grams or more of protein.

To get just 15 grams, you would need to eat almost 12 medium size bananas, which also clocks in with a count of 1,260 calories!

How much protein do you need per day? About 0.36 grams per pound of body weight, according to the Dietary Reference Intake (DRI) (3).

Obviously no one would attempt this, but if you were relying on this fruit to reach 100% of that amount, this is how many bananas the average sedentary male and female would have to consume per day (4):

56 grams = 43.4 medium bananas per day (4,560 calories and 626 grams of sugar!)

46 grams = 35.7 medium bananas per day (3,750 calories and 515 grams of sugar!)

Of course those amounts are for sedentary people. Assuming you’re at least an average-sized person and you workout several times per week, your dietary requirement will likely be more.

Potassium content, debunked

Ask any random person – or even your doctor – what the health benefits of bananas are are chances are, they will say potassium. If not as the first benefit out of their mouth, almost certainly within the top 2 or 3 they list. Potassium is associated with cardiovascular health and because of that, many people have extrapolated it as meaning potassium = good for fitness.

The problem is that this fruit doesn’t really have that much of it! 4,700 mg/day of potassium is considered Adequate Intake (AI) (4). A medium banana only provides you with 9% of your Daily Value (422 mg).

In fact, they’re such a low source they rank #283 for potassium content in the National Nutrient Database, if you rank the foods according to potassium content per calorie. And if you rank by weight, they’re not even in the top 500!

Even if you look just within the fruit category, on a per calorie basis you will find bananas way down at #77. Many other fruits including cantaloupe, honeydew melons, apricots, papayas, and guava have over 50% more potassium on a per calorie basis.

Plus, guava has about 3x the protein content. Apricots and cantaloupe are 2x higher.

Are bananas radioactive?

nuclear power plantNow let’s address the second surprise. No one thinks of natural foods as being a source of radiation. As it turns out though, all contain it and some a lot more than others.

How much radiation is there in one banana? At least 0.1 micro sieverts (0.1 μSv). In fact – no joke – this amount is scientifically called the Banana Equivalent Dose (BED) and is used for comparing the amounts of radiation exposure from other sources, because it’s a term the general public can wrap their head around (5).

For example, during the infamous Three Mile Island Incident in 1979, a nuclear power plant in Harrisburg, Pennsylvania had a cooling malfunction which resulted in radioactive gas being released into the atmosphere.  In describing the amount of exposure to nearby citizens, those living 10 miles away were told they received an average of 800 BED. In other words, the amount of radiation you get from eating 800 average bananas.

Going back to banana’s potassium content, ironically that hyped benefit is also what’s providing you some potassium-40, which is a radioactive form of it. So you may not be getting much protein and BCAAs from the fruit, but you are eating a fair amount of potassium-40. Not quite as appetizing, is it?

How bad is that?

There’s no such thing as “healthy” radiation. None is good for you. This is because radiation causes cell mutations. The question becomes not how much is a healthy amount, because the answer to that would be zero (which is impossible). Rather, the question is how much radiation and cell mutations can a human endure before one mutates into cancer?

More mutations do not mean you will get cancer. Statically though, the more mutations, the higher the odds.

But don’t be alarmed. You have lots of mutations daily, even right now as you read this. It’s estimated that a human has 10,000 to 1,000,000 molecular lesions per cell, per day. Thankfully, our bodies due an excellent job at repairing the vast majority but some do not get repaired (6).

It’s those un-repaired mutations which accumulate over our lifetime and can cause problems down the road. It’s the reason why cancer isn’t common in younger people but extremely common (even more probable than not) once you reach a certain age in your golden years.

Putting radiation from bananas in perspective

Before you chuck your chocolate-banana protein smoothie in the trash can, you need to realize the number we are talking about here is incredibly small. Here’s how it compares…

common sources and amounts of daily radiation exposure

See those 2 tiny little cubes for this fruit? Now compare that to the flight from NY to LA. If anything, shouldn’t you be more concerned about that? Because that cross-country flight is the same amount you would get from eating 400 bananas. In other words, that 1 flight equals more than if you eat one every single day of the year.

Or hey, your snoring husband or wife may not be the only reason to crash on the couch. Sleeping next to them in bed nightly is about half as much as you get from eating one each day.

Versus other foods

Are bananas the most radioactive fruit? The published literature and studies done have only evaluated the more common foods, so it would be impossible to conclusively say that bananas definitely have more than any other fruit (being that are so many exotic varieties which haven’t been scrutinized). That said, among those commonly tested, it is the worst offender.

But “worst” is a relative term and it’s not much more of an offender than potatoes, carrots, or red meat.

Natural Radiation Levels In Food (pCi per kg)
Food radioactive potassium-40 radium-226
Lima beans 4,640 2 to 5
Brazil nuts 5,600 1,000 to 7,000
Bananas 3,520 1
White potatoes 3,400 1 to 2.5
Carrots 3,400 0.6 to 2
Red meat 3,000 0.5
Beer 390 ND*
Drinking water ND* 0 to 0.17
*ND = not detectable
Source: US Nuclear Regulatory Commission (7)

That’s right, there is literally radiation in everything and there’s no avoiding it entirely. All organic matter – both plants and animals – contain it. All of the earth’s water contains dissolved uranium and thorium, as well as the isotopes which result from it. So after you hit the weights and grab that protein shake, it doesn’t matter whether you’re making it with strawberries, blueberries, or even just plain water and protein powder… all of them will have some amount of radioactive material.

In the case of plants, they get the lion’s share of their radioactive isotopes from sucking it up through the ground via their roots. Which is precisely why root vegetables (i.e. potatoes and carrots) as well trees with deep or elaborate root systems (i.e. banana trees) tend to have higher amounts.

2 Brazil nutsBy far the worst offender – and the one we actually think you should avoid or eat sparingly – are Brazil nuts. It’s potassium-40 level is comparable to that of bananas, but it has an off the chart reading for radium-226 due to the fact that the Brazil nut tree has one of the most extensive and deepest root systems of any plant. Furthermore, it’s easy to get a selenium overdose from Brazil nuts. More than 2 of those nuts per day could do it to you.

You may think meats (or whey protein) is preferred, because those are animal-based and obviously don’t have roots in the ground like a fruit tree, but they are equally as bad. How so? Because even though the cows are not sucking up the earth’s minerals directly, they’re eating plants that do (and a lot of them, if you’ve ever seen a cow poop). That’s why beef ranks about the same as a pure root vegetable.

Verdict: should you eat or avoid?

Your average daily exposure to radiation is about 100 banana equivalent doses (BED). Since 1 banana = 1 BED, even if you ate one every single day, it would only represent about 1% of your total radiation exposure.

protein shake with bananas, oats, peanut butterBut as mentioned above, there’s no such thing as a good radiation amount. Eating one in your acai bowl each week is not going to be a problem. Eating 1 per day won’t hurt you either, but by doing so are there any health benefits that outweigh the 1% increase in radiation exposure?

Given the fact that they’re such a lousy source of protein, have mediocre potassium levels, and very little antioxidant content as demonstrated by their ORAC value, we don’t really see a lot of nutritional reasons to eat them in abundance… unless you really like their taste.

If that’s the case, have at ’em. Even though they don’t give you protein, there’s no denying the fact that they help give your shakes a creamy texture with a lot less calories than actual cream/dairy would.

Even if you do choose to gobble them up daily, the amount of banana radiation you get is perhaps the least of your problems, given that there are countless other more effective ways of reducing daily exposure. Skipping one cross-country flight per year would make up for eating the fruit daily and then some.