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Mainstream guidelines recommend two servings of fruit per day.
Mainstream health professionals and current government guidelines recommend a restriction of two servings of fruit per day. There are concerns that the natural sugar in fruit may be detrimental to health. (1, 2)
The concern is primarily that high daily fruit intake may:
- Cause blood glucose spikes due to the effects of sugars on blood glucose levels
- Contribute toxic amounts of fructose (read more..)
Although these concerns may be not substantiated by solid science, these guidelines help in maintaining a balance in one’s diet and prevents us from eating too much of one food group.
Is sugar in fruit bad for you?
There are no studies that show that by eating whole fruit, containing natural sugars (fructose and glucose) have any negative effect on health.
This is most likely due to high amount of fiber, relatively low amount of fructose, the positive physiological effects the high amount of its micro-nutrients have on the body, and the fact that it is difficult to overeat fruit in one sitting.
Note: fruit juices on the other hand, have most of the fiber removed, and are made of around 5 servings of fruit. (read more..)
How much fruit a day is too much?
Fruit consumption has been proven by numerous studies to have positive effects on health. Fruit (and vegetables) contain substances that act as antioxidants, reduce inflammation and improve the health of our blood vessels.
These studies usually use a combination of high vegetable and fruit intake to measure the effects on health. However, there are very few studies on the impact of a high consumption of fruit on its own (discussed below) since it is important to measure the effects on fructose toxicity or blood glucose spikes.
How much fruit should you eat a day without causing a negative impact on your health?
In summary, this is what we know about daily fruit intake from available studies:
- A diet rich in a combination of vegetables and fruit has a positive impact on health;
- There is no evidence that a very high amount of fruit causes ill health effects;
- A limited number of studies, conducted for a period of up to 6 months, have shown that even having 20 fruits per day has no negative impacts on health and some positive outcomes;
- Some studies disprove the major concerns of the impact of very-high fruit intake on the blood glucose and fructose toxicity;
- Having excessive amounts of fruit in the long term (such as in fruitarian diet) at the expense of foods with other essential nutrients leads to nutrient deficiencies.
Summary of studies available on the health effects of various amounts of fruit consumption
- Some observational studies showed that a high fruit intake in non-type-2-diabetics is not associated with elevated blood sugar levels. Quite the opposite, it reduces the blood sugar levels and improves diabetes control. (7)
- One study on type 2 diabetes patients indicated that reducing the daily fruit intake to below 2 doesn’t have an impact on the glycemic control, weight loss or waist circumference.
This study, however, doesn’t indicate the daily limit of fruit for optimal health. The recommendation of this study is that patients with type 2 diabetes should not restrict fruit intake. (7)
- A study from 2012 showed that adding a low-GI fruit to the meal (a low fructose amount of <=10 g/meal) can decrease the blood sugar response after the meal between 15%-30%. (8)
- A 1971 study on a very high fruit diet, supplemented with nuts, measured the effects on various health aspects.
The participants consumed about 20 servings of fruit per day (equivalent to about 200 g of fructose).
No adverse effects (and possible benefits) for the body weight, blood pressure, and insulin and lipid levels were detected in the study conducted over a 12 to 24 week period. (9)
- A more recent study (2001), on a very high fiber, vegetable, fruit and nut diet, was conducted to measure the effects on lipids in blood and the function of colon.
Participants had about 20 servings of fruit per day and no adverse effects on blood pressure, triglycerides and weight were observed. On the contrary, one positive outcome stuck out: a significant drop in LDL cholesterol levels. (10)
- Fructose toxicity may occur at about 50g per day.Note: alcohol/ethanol toxicity has been established at 50 g/day.
Fructose is assumed to be the same, since it has the same metabolic effects as alcohol.50g/day of fructose is approximately the daily average consumption of adults (51g/d), not due to fruit consumption, but thanks to sugar additives, such HFCS, and table sugar.
Half of the population is above the fructose threshold of toxicity which, means they may suffer from the toxicity effects such as increased uric acid production, increased fatty acids in the blood or inflammation). (read more..)
Adolescents consume on average of 75 g/d. (11, 12)The issue is with the doses of fructose, and the author refers to the high amounts of added sugars in products such as sodas rather than whole fruit, although he is not very specific in excluding whole fruit.
- Bruce Bistrian, a professor at Harvard Medical School, says that “fruits are not harmful and are even beneficial in almost any amount”.
He claims that fructose is only detrimental to health, if it is in the form of table sugar or any type of sweeteners. (13)
Note: consumption of very high amounts of dried fruit and its impact on health has not been well investigated, so similar precautions should be made.
Dried fruit is also about 3.5 times more nutrient dense (including fructose concentration) than fresh fruit and may have different impact on health than an equivalent amount of fresh fruit. (read more..)