Fruit has long been a recommended source of calories, fiber and a host of nutrients. However, is there such a thing as eating too much fruit?
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A major meta-analysis examined about 350 studies performed in various parts of the world, to try and pinpoint various effects of consuming both fruits and vegetables. They looked at health outcomes which included cardiovascular events, cancers and early death. All the studies were prospective cohort studies, and therefore the results proved association between the preceding events and the outcomes but could not prove causation.
The conclusion was that the group of people who habitually ate 800g or more of fruit and vegetables a day – which atv10 portions, is considerably higher compared to the 5 currently recommended – lowered their risk of adverse health conditions. Cancer risk was reduced around the 600g mark, in fact. This study also tried to identify the benefits of different fruit and vegetables in various health conditions. However, this study is unlikely to translate into a current recommendation for the simple fact that most people today do not eat even the 5 portions that have been promoted by public health agencies.
This is a classic case of expediency overcoming scientific accuracy in determining what advice is given to the general population, on the plea of not wanting to put pressure on them by unrealistic goals. However, the truth is that in one study, the easily achievable intervention of physically providing food to a target group of very young adults, without any other reminders or nagging, immediately lifted the number of portions in this group by 1.2 servings a day, as well as producing significant improvements in many aspects of their mental health. This was in contrast to the lack of benefit seen in a control group who received vouchers to purchase roughly the same amount of fruits and vegetables of their own choice and to prepare them for consumption as they wished, with twice-daily reminders, even though these latter messages were not perceived as irritating but rather helpful. The bottom line may be that making fresh fruit available and free wherever people gather to eat may be the best way to increase consumption rather than endless education campaigns.
Increased fruit and vegetable consumption was analyzed by 200g increments, in respect to:
- Ischemic heart disease: each 200g increase in consumption reduced the risk by 8%, especially with sources of vitamin C, and with apples or pears, fruit juices, green leafy vegetables, carrots and sweet potato
- Stroke: risk reduced by 16% per 200g increase in consumption, particularly apples or pears, citrus, green leafy vegetables and vegetable pickles
- Cardiovascular disease in general: 8% reduction per 200g increase, especially with apples or pears, citrus, carrots, green leafy vegetables and other vegetables outside the cruciferous (Brassica) family
- Cancers: 3% reduction per 200g increase, with cruciferous vegetables in particular, and with increases up to 600g per day
- Mortality from all causes together: 10% reduction per 200g increase, especially with apples or pears, citrus fruit, berries, vegetables of all kinds and potatoes
In other words, 5.6 million early deaths occurred in the year examined (2013) because these individuals ate less than 500g of fruits and vegetables a day. On the other hand, eating 800g of these daily could prevent the deaths of 7.8 million people a year.
Of course, it goes without saying that simply eating more fruits and vegetables is not a magic wand to make disease vanish. But it certainly is one of the best ways to make your food work for you and not against you, and if you also remain physically active and don’t consume harmful things, such as smoke, alcohol and other toxins, you are likely to live longer and more healthy than those who do.
Eating fresh fruit is even helpful in preventing diabetes mellitus as well as reducing the risk of some small-vascular complications of diabetes such as renal disease or diabetic retinopathy by an astonishing 28%. Apart from a 12% lesser risk of new-onset type 2 diabetes in people who regularly ate fruit, diabetics who did so had a 14% lower risk of death or secondary cardiovascular disease compared to those who ate fruit less than once a week. Apples and pears are preferred because of their low glycemic index (GI) and prolonged slow release of sugar into the blood. Bananas, grapes and tropical fruits have a higher GI in comparison.
The global pattern is dismal, with less than 20% of people eating fruit as a regular part of their diet, and over 6% admitting to eating it rarely or never.
Health Benefits
Fruit does a lot of things for the body:
- It reduces weight and prevents weight gain
- It reduces the risk of diseases brought on by obesity, such as diabetes mellitus and heart disease, and protective effects increase as consumption of fruit increases
- Lower blood pressure
- Lower blood glucose levels
- Prevents dyslipidemia
- It reduces the rate of death due to all causes
How Does Fruit Reduce Body Weight?
Many mechanisms have been suggested for the anti-obesity effect of increasing fruit consumption:
- Reduced caloric intake because of the low fat content and the high water and fiber content of most fruits
- Producing a feeling of fullness, which reduces overall food intake and meal frequency, by the gelling of dietary fiber within the gut, and the prolonged digestion process of fruit means that satiety receptors are occupied for a longer duration
- Providing micronutrients and vitamins, which are negatively associated with weight gain by reducing gene expression in relation to fat cell production and maturation
- Phytochemicals such as resveratrol, proanthocyanidins, catechins, caffeic acid and the like which are potent anti-oxidants and suppress fat cell formation and fat storage
- Undigested fruit fiber provides a vital substrate for gut microbiota to feed upon, to produce changes in the relative proportions of various bacterial groups, increasing the number of Bacteroides and Actinobacteria (abundant in lean people) but reducing Firmicutes and Proteobacteria which are found in obese individuals
Acting via these numerous pathways, fruit succeeds in both reducing total energy intake and in maintaining satiety, which in turn leads to a net lowering of fat stores (especially central) by their utilization within the body for daily energy and metabolic needs, and so reduces the body mass. In addition, its nutrient composition favors adipocyte non-differentiation and so reduces obesity.
Apples and pears are consistently associated with risk reductions in many types of disease. It is noteworthy that these contain 6% of fructose and less than half that amount of sucrose. The fructose is mostly fermented within the colon because it is not well absorbed. The resulting increase in short-chain fatty acid (SCFA) production is of great value in many metabolic and physiological processes.
The few trials which support a pro-obesity effect of fruit have often failed to distinguish natural and processed forms of fruit, and are often confined to a specific age-group or category, in contrast to the numerous population-based trials which confirm its anti-obesity activity. A single trial suggested that an overly high consumption of high GI fruits during the second trimester led to increased rates of gestational diabetes, but the authors recommend further study to confirm and examine the findings. Another trial showed an increase in body mass with increased fruit intake at dinner time. It is yet to be confirmed that fresh fruit, rather than preserved or juiced fruit, carries such a risk.
In short, the net conclusion is that increasing fruit intake is rarely a health risk, and carries a host of benefits – which only increase with more fruit in its natural form, whatever the glycemic load of the individual fruit.
Further Reading
Study sheds light on genetic influences on fatty acid use in minority populations