Medical professionals and dietitians may now recommend the consumption of limited amounts of fresh fruits with diabetes, but fruit juices are largely still off the table. In some cases, it’s simply a matter of the juices providing too much simple sugars and a concern the diabetic patient may exceed the limited amounts allowed with their condition, which would definitely cause spikes in blood sugar levels. But with grapefruit juice there are other more valid concerns as to why it’s not good for diabetes.
Grapefruit juice as well as the whole fruit contain bergamottin, dihydroxybergamottin and naringenin. These three naturally occurring compounds alter enzymatic processes and affect the metabolism of diabetes medication. Even as little as a small glass of grapefruit juice can raise concentrations of certain diabetes medication in blood plasma or, on the contrary, impair absorption in the intestinal tract. In both situations, there may be side effects for the diabetic patient. The higher the intake of juice for a diabetic person on medication, the more likely the side effects.
The fruit juice is unsafe only if the diabetic person is on medication because the compounds in the juice interact with it, but not with the condition itself. Grapefruit juice interactions are not limited to just blood sugar lowering medication, but also include high blood pressure and cholesterol medication for treating heart disease associated with diabetes as well as other forms of treatment for conditions that are not necessarily associated with diabetes, such as autoimmune conditions, allergies, asthma or anxiety.
What does grapefruit juice do to the body of a diabetic?
Special compounds in the juice (bergamottin, dihydroxybergamottin and naringenin) alter the normal activity of liver and gut enzymes responsible for the metabolism of various medicines for diabetes and related conditions. These compounds can impair the activity of an enzyme called Cytochrome P450 3A4 and prevent it from metabolizing diabetes medication which then causes an increase in blood plasma concentrations and associated side effects with potentially serious outcomes. The same compounds can also prevent the absorption of certain medication at the intestinal level and reduce their effects, with consequences for diabetics requiring treatment.
Diabetics who are not on any medication have no contraindications and may consume grapefruit juice safely in small amounts, as part of an overall clean, varied and balanced diet, as long as they don’t exceed their daily recommended intakes of carbohydrates and sugar. Also see Can You Eat Grapefruit With Diabetes?
Grapefruit juice nutrition relevant to diabetes
1) Moderate sugar content: 9.2 to 10.4 g of sugar per 100 g of raw, unsweetened juice.
2) Low glycemic index (under 55) which means it doesn’t contribute to blood sugar spikes if intake is limited to small amounts.
3) Grapefruit juice calories: 39 to 45 kcal per 100 (low energetic value).
4) Low fat content: 0.1 g of fat per 100 g.
5) Good vitamin C content: 38 mg per 100 g.
6) Good potassium content: 162 mg per 100 g.
What are the benefits of drinking grapefruit juice for diabetics not on medication?
1) No blood sugar spikes. Grapefruit juice glycemic index (GI) is low (under 55, but slightly variable depending on the fruit variety and its natural level of sweetness). A low glycemic index means that the sugars in the juice will be absorbed less quickly and thus contribute to more steady blood sugar levels.
At the same time, if you have too much juice at once, the sugar will ultimately accumulate and raise blood sugar levels too fast too much, despite the low glycemic index. Keep in mind that grapefruit juice is still a fruit juice and its GI is in the higher percentile of the low glycemic foods list (over 45). For this reason, medical professionals and dietitians recommend limiting intake to small amounts, ideally no more than one serving a day and not every day.
2) Improved insulin resistance. A randomized controlled trial study on 91 obese participants showed that eating fresh grapefruit or drinking grapefruit juice helps improve insulin resistance (The effects of grapefruit on weight and insulin resistance: relationship to the metabolic syndrome. By Fujioka K, Greenway F, Sheard J, Ying Y. Published in J Med Food. 2006 Spring;9(1):49-54). The findings of the study suggest the fruit and its juice may hold similar benefits for diabetics who are not on medication.
3) Grapefruit juice weight loss benefits. The juice is low in calories and has almost no fat and a low glycemic index, so its nutrition is already supportive of a healthy weight. In addition to this, studies show an improvement in metabolic syndrome parameters, notably weight reduction. Introducing whole grapefruit or the unsweetened juice may help diabetics struggling to reach a healthy weight begin their weight loss journey for better health.
4) Benefits for wound healing. The good amounts of vitamin C in the freshly-made fruit juice activate the production of the structural protein collagen and enhance the immune system components and response, contributing to a faster healing time of wounds, a major advantage for a diabetic. However, 100 ml of grapefruit juice provides only 38 mg of vitamin C and studies show you need 8 to 50 times more vitamin C (500 mg to 3 g a day) a day to accelerate collagen production and produce visible wound healing benefits (Vitamin C and human wound healing. By Ringsdorf WM Jr, Cheraskin E. 1982). Since juice intake is limited with diabetes, supplementation may be considered to help you reach wound healing goals.
5) Good for high blood pressure. Hypertension is a common complication of diabetes but, fortunately, one that is perfectly reversible through diet in numerous cases. Anyone with high blood pressure benefits immensely from lowering their sodium intake while increasing their intake of magnesium and potassium. Grapefruit juice is a good source of potassium, providing 162 mg of potassium per 100 ml of juice (out of the current RDI -recommended daily intake- of 4700 mg, or 4.7 g).
In simple terms, potassium, which is an electrolyte, counteracts the negative effects of too much sodium and decreases tension in blood vessel walls, contributing to better blood pressure numbers by lowering high blood pressure. As an electrolyte, it further regulates muscle contractions, helping prevent irregular contractions in the heart muscle. Best results are achieved by ensuring you have a sufficient intake of other electrolytes as well, especially magnesium. Thanks to its minor benefits for weight loss and ability to improve blood lipid profile, grapefruit juice offers further benefits for cardiovascular health.
So does grapefruit juice help diabetes?
Yes, it does help prevent and manage diabetes type 2 in diabetics not on any medication because it promotes weight loss, does not raise blood sugar levels when consumed in the limited amounts allowed by a diabetic diet, supports wound healing and skin regeneration as well as contributes to lower blood pressure levels and better blood cholesterol profile, reducing the risks of cardiovascular disease.
At the same time, not everyone will respond the same way to the juice. The effects of grapefruit juice on diabetes and general health are variable and will differ from person to person.
But is it safe for all diabetics to drink grapefruit juice?
No, not for all of them. Grapefruit juice is perfectly safe for diabetics who are not on any medication. Although they still need to limit their intake to small amounts so they don’t exceed their daily recommended intakes of carbohydrates and sugar and prevent blood sugar spikes. But it’s not safe for diabetics on medication due to compounds in the juice affecting the way said medication is absorbed and eliminated. If you are a diabetic currently receiving treatment for your condition or diabetes associated conditions (hypertension, high blood cholesterol), refrain from consuming the juice and whole fruit until you’ve talked to your doctor about the possible interactions, contraindications and side effects.