Fructose in different apple varieties

Peer-reviewed | Manuscript received: March 23, 2017 | Revision accepted: November 28, 2017

Implications for apple consumption in persons affected by fructose intolerance

Introduction

Fructose intake has increased significantly in recent years [1] and this trend is partly responsible for the increasing prevalence of fructose malabsorption (FM) [2]. Fructose is also the substrate involved in diseases of fructose metabolism, such as hereditary fructose intolerance (HFI).

Therefore, fructose content in food is an important issue for patients who have diseases in which fructose is a key factor. Fructose malabsorption is often erroneously referred to in the media as fructose intolerance, which means that it can be easily confused with the metabolic disease hereditary fructose intolerance [2]. The different forms of fructose intolerance should be clearly distinguished from one another [3]. • Table 1 provides a comparison of HFI and FM with regard to their pathomechanisms, symptoms, diagnosis, and treatment. In both of these diseases, treatment is based on nutritional therapy with fructose restriction playing a key role, but the focus of the treatment is completely different for each.

Abstract

Fructose malabsorption (FM) and hereditary fructose intolerance (HFI) are pathological diseases that should be clearly distinguished from one another, but for both of which fructose is a relevant substrate. The treatment for both diseases consists of fructose restriction, but with a completely different focus for each. In the case of HFI, consumption of fructose must be avoided completely, but in the case of FM, a desensitization strategy can be adopted. This strategy exploits the mechanism of glucose-induced fructose transport. Thus, for FM (unlike for HFI) it is not necessary to abstain from consuming foods containing fructose completely.

Apples have a high fructose content, and also have an unfavorable fructose/glucose ratio of > 1, which means that at first glance, they appear unsuitable for patients with FM.

Our investigations have shown that depending on the variety, the fructose content of apples can vary considerably. Although in every variety of apple, the fructose content is higher than the glucose content, it is still not necessary to abstain from the consumption of apples completely in the case of FM. In addition to selecting an apple variety with the lowest possible fructose content, other recommendations that can help to improve fructose absorption can also be taken into account. The extent to which glucose promotes the absorption of fructose or improves the symptoms of FM by doing so requires further investigation.

Keywords: Food intolerances, fructose malabsorption, hereditary fructose intolerance, fructose/glucose ratio, fructose content, apples, fruit

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