Another new diet will likely hit the market soon after a press release this morning. A new study published in PLOS ONE by Lusi et.al concludes that nickel sensitivity may be contributing to obesity and that a low nickel diet may facilitate healthy weight loss. Is there a shred of truth to this daring hypothesis?
Before I provide an analysis of this study I must share that I find the rationale of their proposed theory quite interesting. However, this new kid on the block for weight loss remains theoretical and needs much work before it can become a potential tool for a subset of patients with nickel allergy who struggle with weight loss.
Rationale. A review paper was published in the Indian Journal of Dermatology that observed nickel reactivity is the most common metal associated with dermatitis. But do these conclusions validate the new study published in PLOS ONE?
Let’s dissect this study a bit.
Design. 87 patients were enrolled who were overweight and were tested for nickel reactivity by skin testing. Of the 87 patients enrolled in the study who were overweight or obese (mean body mass index (BMI) was 32 kg/m2; overweight is 26 or greater, obesity is greater than 30) the prevalence of nickel skin reactivity in overweight females was 59.7%, compared with a prevalence rate of 12.5% in the general population. Agreed, those who are overweight or have obesity have a higher chance of nickel sensitivity, but does this cause obesity and does limiting the dietary intake of nickel facilitate healthy weight loss?
Results. The “low nickel diet” was associated with a significant reduction in BMI in 24 out of 43 overweight females with nickel skin reactivity after 24 weeks on a low nickel diet. Relative to baseline, mean BMI decreased 4.2±0.5 (P <0.001) and the mean decline in waist circumference was 11.7±0.6 cm (P< 0.001).
Author’s Conclusions. This pilot observational analysis showed a substantially higher prevalence of nickel allergy among overweight females, especially those with metabolic syndrome and fatty liver disease. A normal caloric low nickel diet was effective in reducing BMI in this population. Further research is strongly needed to confirm these preliminary findings
Analysis. The study was published in PLOS ONE, a bit surprising given that this was a pilot study decorated as a “cross-sectional study” which lacked a control group, randomization or even blinding. Thus a bias is very possible. Let’s examine the “low nickel diet” which was not discussed in detail but was referenced in the text (http://bit.ly/1yr0rIm).
The low nickle diet (LND) acknowledges that many plants and vegetables (particularly in the spring and fall) are high in nickel. To follow the diet, one needs to eliminate these foods and even avoid cooking in nickel-plated steel or with acidic foods in stainless steel. Other sources high in nickel include coffee, green tea, dark chocolate and more. All are to be avoided.
What do these foods have in common? They are superfoods that help burn fat and set a lean metabolism as I describe in my upcoming book The Gut Balance Revolution.
Also the foods to restrict include vegetables, nuts, pulses (i.e. legumes), and even whole grains. Higher intakes of these highly fibrous superfoods rich in anti-inflammatory phytochemicals have been linked to a number of improved health outcomes such as less obesity, hypertension, and diabetes. Ultimately these foods build a biodiverse gut microbiome which promotes a fat-bringing metabolism.
So what’s allowed in the LND? Traditional foods common in Western diets low in nickel such as milk, eggs, all types of meat, fish, refined flour, and limited vegetables and fruit with low nickel content.
Wait a minute. The Western diet was the foundation of the LND and people lost weight?
You may think me mad.
But the LND is a REALLY low-carb diet which is a variation of an Atkins or Dukan. This diet is ketogenic in nature, calorically controlled and destined to help people lose weight in the short term. However, Atkins has an undesirable track record for long-term sustainable weight loss.
It’s also important to note that the LDN is calorie controlled which may have introduced an element of calorie restriction and contributed to the observed weight loss. Data on prior energy intakes in the subjects were not provided.
Interestingly, nickel, as other heavy metals, can trigger an inflammatory response mediated by a compound called interleukin-17. When nickel accumulates in the intestinal lining it triggers gut barrier defects which can drive inflammation throughout the body.
Of particular interest in this study are the obese individuals who had fatty liver disease and insulin resistance. These folks also had the highest prevalence of nickel sensitivity. However, the authors failed to measure systemic inflammation markers before and after the diet as well as nickel levels in whole blood. So we actually don’t know whether nickel had an impact on these paramters or whether it was even reduced.
Finally, nickel bioaccumulation has deleterious effects upon the gut microbiome—a key player in the pathogenesis of obesity.
Bottom Line.A normo-caloric LND is associated with weight loss for those overweight women who are nickel sensitive. The LND should only be used to help with nickle-induced dermatologic manifestations of sensitivity or proven organ contamination i.e. heavy metal toxicity. Otherwise the restriction of foods that are high in nickel such as many vegetables, green tea etc. may inappropriately restrict one from the beneficial disease-fighting properties of bioflavonoids and phytonutrients.
To your good health.