Fruits are one of the key components in any balanced diet as they are rich in fiber, vitamins, minerals, and antioxidants. Fruits bring multiple health benefits including protection against some forms of cancer, reducing blood pressure and cholesterol, maintaining healthy body weight, etc. However, fructose sugar derived from fruits, honey is found to bring harmful outcomes if consumed in excess or in concentrated form according to a considerable body of evidence. Also, excess high-sugar fruits combined with other carbohydrate food sources may have potential adverse effects on people living with diabetes. That said, it’s important to remember that fructose is derived from whole fruits and fructose in other forms is not the same. Then too, the type and amount of fruits eaten daily need planning as part of a balanced diet.
This column discusses –
*Effect of excess fructose on body
*How much fruit is too much?
*Fruits as part of low-carb diets
Too much fructose can harm your vital organs, cause negative health outcomes
Excess fructose is converted to fat by the liver in a process called lipogenesis. During this process, the fat molecules get accumulated in the liver and lead to Non-Alcoholic Fatty Liver Disease (NAFLD). NAFLD is the most common liver disease affecting 25 per cent of the global population and 9-32 per cent of Indians.
High consumption of fructose was found to be one of the major contributing factors to NAFLD. Dietary history of 49 patients with confirmed NAFLD reported the affected group was consuming two to three times more dietary fructose than usual. Other than lipogenesis, excess fructose consumption is also linked to liver inflammation, oxidative stress injury to the liver cells.
The effect of fructose on brain health is less explored to date. However, most recent evidence suggests even short-term fructose consumption can affect brain health negatively by aggravating neuroinflammation, brain mitochondrial dysfunction and oxidative stress.
A 2021 review mentioned long-term consumption of fructose could be a threat to brain function and may lead to the development of multiple neurological disorders.
A University of California study by their life scientists found that fructose can damage hundreds of brain genes and can lead to a range of diseases from diabetes to cardiovascular disease, and from Alzheimer’s disease to attention deficit hyperactivity disorder.
Heart health, obesity and diabetes
High fructose consumption also leads to insulin resistance, obesity, and diabetes. Regular function of leptin, the hormone that regulates body weight is affected by excess fructose consumption resulting in fat accumulation, insulin resistance and glucose intolerance.
A 2016 animal study reported that a two-month fructose supplementation caused triglycerides accumulation in the liver and impaired insulin function. Similarly, a 7-day high fructose diet led to the accumulation of Very Low-Density Lipoprotein (VLDL) triglycerides and increased the risk of cardiovascular diseases as reported by a 2009 study.
Other than causing obesity and diabetes, fructose raises the level of uric acid in blood that leads to gout, increases blood pressure and triglycerides too.
Excess fructose may cause diarrhea and Irritable Bowel Syndrome (IBS). IBS is a digestive disorder with abdominal pain, bloating, indigestion, constipation and/or diarrhea. In many people, improper digestion and absorption of fructose lead to diarrhea, flatulence, and belching. Around 68 patients with known symptoms of IBS improved significantly after consuming a low-fructose diet, reported a 2013 intervention study.
Risks of eating a fruit-based diet
The fruitarian or fruit diet is a highly restrictive diet that recommends excluding all animal products, including dairy. People eating a fruit diet primarily consume raw fruits. This diet recommends avoiding other food groups such as whole grains, legumes, etc with some allowance for vegetables, nuts, and seeds. A fruit diet thus lacks several vital nutrients – protein, B vitamins, omega 3, calcium, iron that cause nutritional deficiencies in the long term. This diet is also very heavy on fructose sugar that makes it a harmful choice for people living with diabetes, insulin resistance, or polycystic ovarian syndrome.
How much is too much?
The high water and fiber content of whole fruits make them incredibly filling. Due to this, it’s impossible for most people to eat too many fruits. Existing prevalence data shows a small percentage of people meet their recommended fruit intake on a regular basis. Fewer than one in 10 Americans eat the minimum daily recommended fruit per day. In India, the average intake of fruit and vegetable per day is just 3.5 servings, much lower than the general recommendation per day–five servings or 400 g per day.
Few studies evaluated health outcomes of consuming as much as 20 servings of fruits per day and found no adverse side effects. However, the scientific credibility of these studies is low as the sample sizes were very small involving only 10 and 17 participants respectively.
Eating fruits more than general recommendation didn’t produce any additional benefits as found by a large analysis of 16 scientific studies.
Fruits as a part of low-carbohydrate diets in managing diabetes
Growing prevalence of obesity and type 2 diabetes is making different low-carbohydrate diets popular among the global population. Latest evidence suggests replacing the traditional high-carb diet with a healthy fats diet could improve insulin sensitivity in most.
A low-carb diet recommends 100-150 g of carbohydrate per day. Ultra-low-carb diets or ketogenic diet recommend fewer than 50 g carbs per day. The scope of eating fruits is limited in keto-style meals as fruits contain around 15-30 g of carbs per piece.
Fruits are recommended as a part of a balanced diet in people living with diabetes and the amount is highly individualised as there is no general ‘diabetic diet’. However, the choice of fruits is crucial for diabetes management due to the high fructose content in fruits. This choice is based on the glycemic index (GI) value of each fruit. GI value is defined as how much a particular food can raise the blood sugar level after they are consumed. Fruits with GI a value of 70 and higher are considered very high in sugar and need to be avoided while planning a diabetes meal plan. Moderate GI fruits have a GI value between 56 and 69. Low GI fruits are those having a GI value of 55 and lower.
A list of fruits according to their GI value to help plan a diabetes meal –
High and moderate GI fruits – watermelon, dates, pineapple, over-ripe banana, grapes, pomegranate, papaya, muskmelon
Low GI fruits – cherries, apple, grapefruit, avocado, orange, plum, strawberries, blueberries, pears, guava.
It’s undeniable that fruits have numerous health benefits. At the same time, fructose, the fruit sugar is found to be affecting vital organs. This begs the question if excess fructose in fruit form may have a similar outcome! The research is still inconclusive. Having said that, make whole, fresh, raw fruits as part of your balanced diet in moderation. But don’t overdo fruit especially in commercial liquid form.
Next column – Mindful eating to achieve sustainable weight loss