Tuesday, September 14, 2010

Garlic and Grape Seed extracts - good for you but need high volumes

As I have written before, it is one thing to say a food or product is good for you. It's another thing to eat the level required. Today we look at garlic oil and grape seed extract.

Garlic oil protected rat brains from nitrates that are found in preserved meats. Sounds good to me. However the level of garlic was 5 ml / kg of body weight. So for a 100kg human that would be 500ml of garlic oil/extract. Now suddenly the study doesn't look very promising - are you going to drink two full glasses of garlic oil extract a day??? I think not. However on the flip side the nitrate levels feed to the rats were 80 mg / kg of body weight. So again the same average 100 kg person would need to eat 8 000 mg or 8 grams of nitrate. Now what level does this mean. Taking the maximum nitrate level allowed in the US is 1 pound per 100 pounds of dry cured meat. Converting this into grams and applying the maths, this results in having to eat 750 grams of meat to obtain the 8 grams of nitrate. Clearly this is a very high level.

However assuming the dose effects were linear...... if had 75 grams of bacon or other nitrated meat, which is not unreasonable as 100 grams is standard meat portion in a meal. This is a reduction of a factor of 10. Therefore 50 mls of the garlic oil extract would be taken. Even 50 mls is a huge amount of oil, that is almost 6 tablespoons of oil. Gross!!!!

OK so we can safely say that people are not going to eat enough garlic or garlic extracts to obtain the benefits.

So how about the Grape Seed Extract (GSE). From this study they concluded:
intake of GSE may be a feasible therapeutic strategy for prevention of a high-fructose diet-induced insulin resistance and oxidative stress
This is good news, but what level was the GSE? It was 1 % of the diet. Apparently we eat about 2 kg of food a day. Thus 1% would be 20 grams, which would be quite a large supplement tablet!! Tablets typical range from 100 mg to 300 mg. So to obtain 20 grams of GSE you would need to take between 200 to 70 tablets.   

References: Wannaporn Suwannapheta, Aramsri Meepromb, Sirintorn Yibchok-Anuna and Sirichai Adisakwattana. Preventive effect of grape seed extract against high-fructose diet-induced insulin resistance and oxidative stress in rats. Food and Chemical Toxicology Volume 48, Issue 7, July 2010, Pages 1853-1857

Hanaa A. Hassana, Hani S. Hafezb, and Fawzia E. Zegheba. Garlic oil as a modulating agent for oxidative stress and neurotoxicity induced by sodium nitrite in male albino rats. Food and Chemical ToxicologyVolume 48, Issue 7, July 2010, Pages 1980-1985

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