Grape fruit and Metformin - apparantly a big 'no no'

[bilwardo]

I'd like to hear another viewpoint regards the dangers of people with type 2 diabetes taking Metformin and having grape fruit, which according to a South African doctor is dangerous as it causes an increase in lactic acid.
Is this a fact, as I do enjoy grape fruit with breakfast, both for the taste and it helps to control blood sugar level, and I believe helps to keep the 'kg's' in check.

 

[phoenix]

I don't take metformin but this is what google revealed.
Owira PM,Ojewole JA (*)reported the findings of a short term trial with Non diabetic rats.
Rats given high doses of metformin had higher blood latic acid levels than those not treated with metformin. When treated with metformin and grapefruit juice the levels of blood lactic acid were significantly higher than metformin alone and there was a higher concentration of metformin in the liver. They also found that the GFJ lowered fasting glucose levels.
The researchers suggested that

'Although GFJ may be beneficial to diabetic patients, it may exacerbate lactic acidosis in diabetic patients taking metformin concurrently'

In contrast to this a large Cochrane review looked at lactic acidosis and metformin in human trials.
They pooled the data from 347 comparative trials and cohort studies. This revealed no cases of fatal or nonfatal lactic acidosis in 70,490 patient-years of metformin use or in 55,451 patients-years in the non-metformin group.Statiscally they found the

' upper limit for the true incidence of lactic acidosis per 100,000 patient-years was 4.3 cases in the metformin group and 5.4 cases in the non-metformin group. There was no difference in lactate levels, either as mean treatment levels or as a net change from baseline, for metformin compared to non-metformin therapies'

ie there is (statistically) a a slightly higher chance of developing lactic acidosis when not on metformin than when on it !
A recent medscape article also points out that although the use of metformin has increased, the rate of lactic acidosis has not increased.
It also quotes another study that found that

per 100,000 patients, the crude incidence of lactic acidosis in patients treated with metformin was 3.3, and that all the patients that developed it had another underlying condition that predsiposed them to it.

(such conditions 'include congestive heart failure, liver disease, shock, alcohol use, hypoxic states, renal failure, sepsis, and advanced age'
see http://www.medscape.com/viewarticle/714920

If it were me, and I'm not a doc ,I wouldn't worry unless I had other medical problems(which would probably mean you weren't or shouldn''t be taking metformin anyway)
Grapefruit juice does strengthen the effects in many drugs, amongst them statins and people taking Statins are normally told to avoid drinking it.

*Grapefruit juice improves glycemic control but exacerbates metformin-induced lactic acidosis in non-diabetic rats. Methods and findings in experimental and clinical pharmacology, November 2009, vol./is. 31/9(563-70), 0379-0355

 

[Bigglesworth]

There seems to be greater concerns about the dangers of consuming grapefruit when taking statins.

 

[Sid Bonkers]

My usual breakfast is half a grapefruit, occasionally scrambled egg and bacon or cereal but 90% of the time 1/2 a grapefruit.

Not sure whether to worry or not, what time of the day were the rats fed grapefruit juice if it lowered their fasting bg levels?

Is drinking or ingesting, in the case of lab rats, grapefruit juice much different to eating actual grapefruit flesh?

:? :cry: :?:

 

[witan]

Owira PM,Ojewole JA (*)reported the findings of a short term trial with Non diabetic rats.
Rats given high doses of metformin had higher blood latic acid levels than those not treated with metformin. When treated with metformin and grapefruit juice the levels of blood lactic acid were significantly higher than metformin alone and there was a higher concentration of metformin in the liver. They also found that the GFJ lowered fasting glucose levels.

Rats are far from an ideal human model, just somewhere to start testing on living creatures. I don't have the detail but in the quotes there are so many vagueries, like 'the rats were given high doses of metformin', they had 'higher blood lactic acid levels', this is really quite meaningless. Humans are much bigger than rats and our metabolism very different, so I won't worry about these tests at all.

The Human trials are much more relevant, so I would carry on drinking grapefruit juice - if I wasn't on statins.

Sid has a good point too - does a glass at breakfast really have an effect on fasting levels or should it be drunk for supper?

 

[phoenix]

'the rats were given high doses of metformin', they had 'higher blood lactic acid levels', this is really quite meaningless.

To be fair to the researchers they do give precise dose and reaction. That was my simplification/summary/interpretation

Three groups (A, B, C) of 20 male Wistar rats each, were treated with stepwise, escalated oral doses of 0, 7.0, 2.0, 3.0 (group A), and 3.0 ml/kg body weight (groups B and C) of GFJ. Group C rats additionally received 250 mg/kg body weight of metformin

.

Blood lactic acid levels were similar in GFJ-treated test (2.81 ± 7.4 mmol/L) and control (2.54 ± 0.7 mmol/L) rats, respectively, but were significantly increased (P = 0.0079) in rats that were treated with either metformin alone (5.38 ± 2.53 mmol/L) or in combination with GFJ (8.31 ± 3.48 mmol/L).

 

[bilwardo]

Hello everyone, I would like to say a big thank you to you all for your replies. There is so much info, and it has put my mind at ease - and I can continue to enjoy the grapefruit segments at breakfast every 2nd or 3rd day. I appreciate your help, thanks again. Bye for now, bilwardo