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Fruitarianism is a diet that consists entirely or primarily of fruits in the botanical sense, and possibly nuts and seeds, without animal products. Fruitarianism is a subset of dietary veganism.

Is it safe to follow a Fruitarian diet? If not, what are the potential health issues that can occur?

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    can you update the q with a quick description of fruitarianism? I'm sure I'm not the only one who's only encountered it as a joke mention briefly on tv. – yochannah Jan 31 '17 at 22:03
  • @yochannah no worries - I've updated it – lifetimes Jan 31 '17 at 22:05
  • The wikipedia article has a part on nutritional deficiencies, but it seems to be based on only eating fruit (and not seeds, nuts, grains, etc.) which contradicts the article's intro and doesn't seem to be in line with the actual definition of fruititarian? – user116 Feb 1 '17 at 1:28
  • @JoeRocc Only eating fruit is a subset of fruitarianism, kinda like Vegetarians who don't eat eggs for X reason. The "base" is majority-fruit with some nuts/seeds etc I believe. I guess the health warning is towards the subset as they are cutting off their only proper sources of protein – lifetimes Feb 1 '17 at 1:52
  • @lifetimes Do we we need a reason? Eggs are gross. – Tom Kelly Feb 10 '17 at 12:23
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No, it is not safe. And there are no significant benefits to make up for the impact on your health.

First up, fruit is very high in the sugar fructose. The idea that this is "healthy" fructose compared to the corn-syrup derived fructose found in processed foods is a misconception. The only difference is that when you consume fruit, you are also consuming fiber which slows absorption of the sugar, contributes towards you feeling full and toward bowel health. But if you eat mainly fruit, you will still need to consume a very large amount of high-sugar food before feeling satiated.

Risks associated with high fructose consumption include weight gain, tooth decay, type 2 diabetes, liver disease, pancreatic cancer, metabolic disorders (e.g., Gout), and kidney damage. Again: it doesn't matter where the fructose comes from. It's the same molecule found in fruit as is found in cans of soda.

There are further risks which will depend on how much non-fruit food you eat. Your body is programmed to require a certain level of protein and fat. If you don't eat sufficient amounts, your body will attempt to synthesise them from what nutrients you do have. This is metabolically expensive and will require you to eat even more fruit (with an increase in the risks mentioned above) or you will enter adaptive thermogenesis, an exhausting condition where your body starves you of energy to maintain calories.

There are also risks of nutritional deficiencies. High fruit diets provide low levels of vitamin B12, calcium, vitamin D, iodine and omega-3 fatty acids, which can lead to anemia, tiredness, lethargy, immune system dysfunction and osteoporosis.

In return the chief benefit of a high-fruit diet are the consumption of high levels of anti-oxidants. These reduce the risk of cancer and can help with other long-term illnesses. However, given that the diet can, itself, cause long-term illness it would seem sensible to take a more moderate approach.

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    I don't think your claims about pancreatic cancer are very sound, the original study fed pure fructose or glucose to cancer cells. This is far from the tumour environment and does not compare to high fructose corn syrup, let alone fresh fruits in a balanced diet. The authors were only concerned about fructose for patients with cancers during treatment, not that fructose causes cancer. Media claiming so is scaremongering. – Tom Kelly Feb 9 '17 at 6:00
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    However, diets high in fructose/sugar have been linked to risk of diabetes, obesity and more recently Gout along other autoimmune and metabolic disorders. – Tom Kelly Feb 9 '17 at 6:05
  • @TomKelly As a compromise, I have edited to include your suggestion of metabolic disorders, which is certainly correct and a useful addition. – Matt Thrower Feb 9 '17 at 9:58
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    Thanks, that's research from my university, they do good work. However my comment stands. Your answer is very comprehensive and otherwise good but (as a cancer researcher) I can not endorse it with false claims of cancer risk, the source article you've cited itself calls in to question of it's relevance to dietary intake. Fructose feeds existing cancers. It is well known that cancers are hypoxic and can grow without oxygen or glucose with altered metabolism. This occurs during disease progression and has nothing to do with the risk of getting cancer in the first place. – Tom Kelly Feb 9 '17 at 10:08
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Fruits are missing niacin, thiamine, and b12. There are also caloric challenges with sticking to a pure fruit diet. Grains and nuts provide necessary protein that the human body requires as well.

An alternative to a complete commitment to full-time fruit diet is to on occasion implement this diet. Some religions call for partial fasts in which adherents may choose to temporarily follow a diet such as a fruit-based one.

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    some fructarians eat nuts and seeds, although I generally agree that this diet poses nutritional challenges – WetlabStudent Feb 1 '17 at 7:22
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    Some sources to backup the claims would be great. – kenorb Feb 1 '17 at 12:52
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The nutrients deficient in a Fruitarian diet will be very similar to Veganism (e.g., B12), These can generally be managed with supplements and a balanced diet.

However, grains, fruits, and nuts are very high in calories. Fruits are a particularly high source of fructose. As with any diet high fructose sugars, it would not be considered healthy unless the fruits are eaten in moderation.

I'd recommend careful portion sizes and consulting a medical professional if following this diet long-term.

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    Some sources to backup the claims would be great. – kenorb Feb 1 '17 at 12:52
  • Which claims specifically? I've personally experienced B12 deficiency and it's a widely acknowledge concern for vegans. As for the fructose content of fruit, is that not "common knowledge"? This is my expert opinion as a long term vegetarian and health researcher by profession. If you want exact studies, your google is as good as mine. – Tom Kelly Feb 1 '17 at 12:59
  • Here's the B12 issue discussed in a web post: webmd.com/food-recipes/news/20030618/… I've linked the primary study in the answer. This study is from 2003 but the consensus in the vegetarian communities I've dealt with has not changed nor has the advice of my doctor. I suppose you have a point but in this specific case, I'll be (pleasantly) surprised if a study can change my health situation and debunk a study that's held up for over a decade. – Tom Kelly Feb 1 '17 at 13:31
  • Recently there was a study saying that milk increases risk of bone fracture and is shortening a lifespan despite what we heard for decades. So common knowledge can change in a short amount of time. – kenorb Feb 1 '17 at 13:36
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    Thanks for the info. I was not aware how strict this diet it is. In that case I would not recommend practicing this long-term, it is not medically safe to do so. If you are practicing this diet, you should be monitoring your nutrient levels as you are at severe risk of deficiency and may be medically recommended to cease such as strict diet. I would also recommend against raising children on such a diet due to the health risks. – Tom Kelly Feb 2 '17 at 21:15

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