|Image 1: Grapefruit does not help with weight loss and, as it turns out, is not even healthy. On the contrary, in conjunction with your favorite statin it is even potentially deadly.|
The myth and the truth about grapefruits
I know that you would never be so stupid to start eating nothing but grapefruit (you would not, right?), but despite the fact that the Grapefruit Diet has rightly gotten a bad rep within the (self-)educated members and followers of the wealth of good and not-so-good blogs and websites dealing with nutrition and weight loss, many people still believe that there must be something about this fruit that will help you lose weight. And in view of the fact that I myself know a couple of these (interestingly all female) unfortunate critters, I believe that it is still worth to take a closer look at the results of a recently published study on the effects of 1.5 fresh Rio-Red grapefruit per day on the outcomes of a 6-week dietary intervention (Dow. 2012). The study involved 74 male and female subjects (age: 41y; BMI: 32kg/m²; Bodyfat: 35.7%) who, despite having problems with their weight, had been weight-stable in the past 6 months (or more). After an initial 3-week "wash out period" in the course of which the subjects had to follow a diet that was restricted in bioactive-rich fruits and vegetables (the intention, here, was to get all to a baseline level as far as the purported "magic fat loss ingredient" in citrus fruits is concerned), the subjects were randomized to one of two groups:
- intervention group (n=42) continued eating the "wash-out diet" and supplemented with their 3x0.5 Rio-Red grapefruit per day 15 minutes prior to their regular three meals
- control group (n=32) continued eating the "wash-out diet"
|Figure 1: Total caloric intake, the number of vegetable servings, the overall macronutrient ratio etc. all were identical between the two groups, except the fruit and (consequently) the vitamin C intake (data based on Dow. 2012)|
|Figure 2: Relative changes in anthropometric data in the course of the 6-week study period; no statistically significant inter-group differences, not even statistical significant pre-post changes (data based on Dow. 2012)|
"But, Dr. Andro, weight loss is not everything" - Correct! And another reason not to eat huge amounts of grapefruits
Another argument of the "grapefruit fanatics" is that, although the weight loss effects of the fruit may be negligible, it still is a healthy superfood that will improve your overall and metabolic health... now, if we take a look at what (unfortunately) is still considered the "gold-standard" as far as the assessment of CVD risk is concerned, i.e. the allmighty lipid profile (imagine a fanfare, here), I guess that only those of you who still believe in the black-and-white version of the lipid hypothesis (HDL = good guy; LDL = bad guy; nothing else counts) will wholeheartedly agree with Dow et al. conclusion that ...
grapefruit consumption does elicit beneficial effects compared with baseline values that areIf you take a look at the actual data in figure 3 you can hardly argue that the 1.5 grapefruits à day gave the "bad guy" (LDL) a slightly more thorough beating than the "wash out diet" with its quasi non-existent polyphenol content, but...
associated with CVD risk reduction.
|Figure 3: Changes in lipid profile (unadjusted and adjusted with ANCOVA for BMI, age, sex, and washout-phase p-values) for the control and grapefruit group (left) and the questionable conclusion the scientists draw based on the observed reduction in LDL and statistically likewise non-significantly greater reductions in blood pressure in the grapefruit group (right) (based on Dow. 2012)|
[...n]onfasting triglycerides maintained an independent graded relationship with CVD in fully adjusted analyses, with elevated 4 h postprandial triglyceride imposing a 4.5-fold increment relative to lower levels [...and that] triglyceride-associated CVD risk occurs even in patients with low low-density lipoprotein cholesterol (Kannel. 2009)Just to make sure nobody is missing the point here, neither the inter-group differences in LDL reduction nor the different outcomes as far as the trigs are concerned, reached statistical significance, but against the background of the results of the meta-analysis of Kannel and Vasan from 2009 and recent findings on the contribution of elevated triglyceride levels to the etiology of cardiovascular and metabolic diseases, I personally feel that beyond not helping with weight / fat loss, eating grapefruit could potentially even contribute to, or aggravate existing metabolic disturbances.
If you are on any medication grapefruit is a no-go, anyway!
|Image 2: If you are healthy eating grapefruits from time to time won't hurt. If you are taking medication, however, it can potentially be fatal - although I's say that the meds, not the fruit are to blame for this|