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In the news: Pre-BBQ Beer Marinade; Metformin Ups Risk of Vitamin B12 Deficiency

Beer for Safer Summertime Grilling

Pulling out the backyard BBQ in summer is an American pastime. But the National Cancer Institute (NCI) has long informed us that meats cooked at high temperatures, especially above 300ºF (as in grilling or pan frying), that are cooked for a long time, or that are exposed to smoke or charring via grilling, tend to form unsafe compounds.

These compounds, called polycyclic aromatic hydrocarbons (PAHs) and heterocyclic amines (HCAs), have been shown to cause cancer in animal models. And population studies link greater intake of well done, fried, or barbecued meats with a higher risk of colorectal, pancreatic and prostate cancers.

The NCI has some tips for reducing the formation of these compounds: avoid direct exposure of meat to an open flame or a hot metal surface, avoid prolonged cooking times, use a microwave oven to cook meat prior to exposure to high temperatures, continuously turn meat over while cooking, and remove any charred portions before eating.

Now, a university research team in Spain offers another suggestion: marinate meat in dark ale before grilling. The researchers marinated samples of pork for 4 hours in Pilsner beer, non-alcoholic Pilsner beer or “Black” beer (dark ale) prior to grilling the meat on a charcoal grill to well done. The dark ale was the most effective, decreasing the level of PAHs by more than half compared to the level in grilled, non-marinated pork (1).

They later conducted the same experiment, this time looking at the effect of the beer marinades on HCA formation (2) in charcoal-grilled pork. All the beer marinades reduced total HCA levels. But, again, the dark ale was most efficient with a level of 90% inhibition. So for safer grilling, look to the NCI tips and have dark ale on hand for pre-grill marinades.

Higher Risk of B12 Deficiency with Metformin

Metformin is usually the first drug prescribed for those with type 2 diabetes to improve blood sugar control. The use of metformin has long been associated with low blood levels of vitamin B12, and this interaction has been evaluated again in the longest and largest study to date (3).

The study was a secondary analysis of the Diabetes Prevention Program/Diabetes Prevention Program Outcomes Study (DPP/DPPOS). Over 2100 participants from DPP/DPPOS received either metformin or placebo for 3.2 years. The metformin group then continued taking the medication for an additional 9 years.

The longer a participant took metformin, the greater their risk of developing B12 deficiency, with the risk rising 13% yearly. Low and borderline-low levels of B12 combined were more common in metformin users than placebo: about 19% vs. 9.5% after 5 years. More neuropathy – damage of peripheral nerves that can result from B12 deficiency or diabetes – was also seen with long-term metformin use.

How metformin and vitamin B12 interact is not fully understood. But according to some studies, 10-30% of people taking this drug show evidence of decreased B12 absorption. Since people over the age of 50 are generally less efficient at absorbing B12 anyway, this drug-nutrient interaction could exacerbate levels that are already low or marginal.

If you are taking this medication for type 2 diabetes, be sure your physician is monitoring your serum B12 levels. B12 injections and/or supplemental B12 may be used to prevent marginal levels or to treat overt deficiencies of this important vitamin.

References

1. Viegas O, et al. Effect of beer marinades on formation of polycyclic aromatic hydrocarbons in charcoal-grilled pork. J Agric Food Chem. 62:2638-43, 2014.
2. Viegas O, et al. Influence of beer marinades on the reduction of carcinogenic heterocyclic aromatic amines in charcoal-grilled pork meat. Food Addit Contam Part A Chem Anal Control Expo Risk Assess. 32:315-23, 2015.
3. Aroda VR, et al. Long-term metformin use and vitamin B12 deficiency in the Diabetes Prevention Program Outcomes Study. J Clin Endocrinol Metab. Epub Feb. 22, 2016.