Report that grapefruit juice may protect against type 2 diabetes ‘misleading’ – NHS
The NHS report into the study concluded: “Grapefruit juice caused improved insulin sensitivity in mice fed high- or low-fat diets. Other than that, grapefruit juice did not have an effect on weight or blood sugars for mice on a low-fat diet.
“These studies showed that grapefruit juice lowered blood sugar as effectively as metformin, a drug widely used for diabetes. However, none of the mice actually had diabetes, so this isn’t a massively useful finding.
“Also, as there are biological differences between humans and mice, we can’t be certain what effect, if any, grapefruit juice would have for people with diabetes. So if you are diabetic and on metformin, you should not stop taking your metformin and switch to grapefruit juice on the basis of this study.
“Grapefruit juice should not be consumed if you are taking certain medications, as it increases their level in the blood. They include statins, amiodarone (for irregular heartbeats), Viagra, sertraline, diazepam and calcium channel blockers.
“If you do have diabetes or have been told that you are at risk of developing it in the future, then you should avoid eating a high-fat diet, even if you are drinking grapefruit juice. Weight gain is a significant risk factor for type 2 diabetes.”
Pam Dyson, Specialist Diabetes Dietitian, Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM) and DRWF leaflet author, said: “Grapefruit is often quoted as a ‘superfood’ and many claims have been made for its properties as an aid to weight-loss. The 1930s were the first time that the grapefruit diet was recommended and the claim was made that grapefruit contained an enzyme that helped to burn off fat. Unfortunately, this was untrue and the main reason that the grapefruit diet worked was because it reduced energy (calorie) intake significantly, sometimes to as low as 800 kcal/day. It is true that grapefruit juice is relatively rich in vitamins and minerals, and has fewer calories than other juices, but its role in weight loss is still open to question.
“Scientists and researchers are always on the look-out for new ways of treating diabetes and obesity, and although it is tempting to think that grapefruit juice would be a useful treatment, there is insufficient evidence to support this at present. The article that created all this fuss was from a study done in non-diabetic mice, so its relevance to humans, and especially people with diabetes, is limited. If we look at the few studies that have been done in human subjects, none of them have involved people with diabetes, and they have produced contradictory results, meaning that we cannot yet draw any conclusions for the role of grapefruit juice.
“On a practical level, the mice in this recently reported study were fed grapefruit juice as their only source of liquids. To apply this on a human scale would mean drinking 1½ - 2 litres of grapefruit juice a day, with no water, tea, coffee or soft drinks! In addition, most people with type 2 diabetes are prescribed statins and blood pressure medication that are affected by grapefruit juice and are routinely advised to avoid it, significantly limiting the potential benefits. In summary, there is insufficient evidence to recommend grapefruit juice as a treatment for either diabetes or obesity at present, and it may well prove dangerous for some people taking certain medications.”
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