The Sardine Diet

Dear Alla,

You are absolutely right that olive oil is largely omega-9 oil. But omega-9 is not an essential oil (or fatty acid). In addition to the omega-9, most of the rest of it is omega-6 rather than omega-3.

Best regards,

David

Dear Earlene,

I did ask her whether a new edition or reprint of "The Sardine Diet" would be coming out. But she didn't think so.

Best regards,

David

Dear Ballot,

If the sardines you ate on your hike were too strong for you, then you may want to try milder ones, like the King Oscar brand.

Good question about weight loss on "The Sardine Diet." That is a part of Keri's subtitle. Sardines are one part of the diet, a high-protein part. But her diet is also high in fiber and low in carbs. All together, that does make it a weight loss diet.

Best regards,

David

Hi Neal,

I can address both of your concerns:

BPA in sardine can linings

There is no BPA in the lining of our sardine, tuna, mackerel, or salmon cans.

The evidence on BPA is mixed. The widely reported April, 2008 draft report issued by the U.S. National Toxicology Program found that some questions remain concerning its estrogenic (hormone-like) potential and its safety for developing fetuses and infants.

This report, whose findings are more negative than the FDA evaulation and other scientific reviews of BPA safety, has created a public reaction disporportionate to the implications of entire body of evidence on BPA.

Once past infancy, it appears that humans have little to fear from canned foods lined with resin that includes tiny amounts of BPA.

Nonetheless, we felt it was prudent to get the BPA out of our can linings.

25-hydroxycholesterol in canned tuna and other fish

The heat of cooking would likely increase oxidation of the lipids in canned fish to some extent. Unfortunately, I could not find the reference for professor Loren Cordain's statement about canned tuna on page 122 of The Paleo Diet in his 20-page bibliography.

However, he is referring to standard canned tuna, which is cooked twice and packed in refined olive oil, while ours is cooked once and packed in antioxidant-rich EVOO.

The critical questions (which he doesn't address) are the precise increases in oxysterols in canned tuna caused by various cooking temperatures and durations, and the possibly dramatic differences in oxysterol levels among tuna packed in water and in various oils.

It makes sense to presume that the cardiovascular benefits of omega-3s would more than counterbalance any increases in oxysterols.

Perhaps more importantly, EVOO, which is used for our oil-packed canned Tuna, Mackerel, and Sardines, is the richest food source of tyrosol phenols, including hydroxytyrosol, which ranks among the most potent antioxidants known, and would likely block creation of oxysterols to a very substantial extent.

Similarly, our canned Salmon is rich in astaxanthin, another potent antioxidant.

The changes in blood lipids seen after eating olive-oil packed tuna are positive, according to the following Spanish study using standard (i.e., probably twice-cooked) canned tuna:

[Changes in lipid profile after regular intake of canned fish. The influence of addition of isoflavones, omega-3 fatty acids and fitosterols]

Otero-Raviña F, Grigorian-Shamagian L, Blanco Rodríguez R, Gómez Vázquez JL, Fernández Villaverde JM, González-Juanatey JR; Grupo Barbanza. Med Clin (Barc). 2007 Jun 16;129(3):81-5. Spanish.

Servicio Galego de Saúde, Santiago de Compostela, A Coruña, España.

BACKGROUND AND OBJECTIVE: Changes in dietary habits are associated with an improvement of lipid profile. We decided to assess changes in lipid profile reached with a dietary enrichment with canned tuna in olive oil and compared them with those reached with canned tuna with additional supplementation. SUBJECTS AND METHOD: In a prospective, randomized, single blind study, 400 participants were assigned to a daily intake of canned tuna in olive oil alone (control group) or enriched with: isoflavones, omega-3 fatty acids of phytosterols, during three months. Plasmatic lipid levels were measured before and after intervention. Changes of lipid levels between basal and final visits and differences between the 4 types of supplementations were evaluated. RESULTS: The mean age of the study population was 53 years, 45% of them being males. In all 4 groups a significant reduction of total cholesterol, low-density lipoprotein (LDL)-cholesterol levels and total cholesterol/high-density lipoprotein (HDL)-cholesterol ratio was observed after 3 months of follow-up; there were no significant changes of triglycerides nor HDL-cholesterol levels. The comparison between different types of supplementation revealed that only phytosterols addition reached a greater reduction of total cholesterol and LDL-cholesterol levels than canned tuna in olive oil alone (p < 0.05), and the differences between the remaining 2 supplementations and the control group were not significant. CONCLUSIONS: Regular intake of enrichment with canned tuna supplementation is associated with improvement of lipid profile. The addition of isoflavones, omega-3 fatty acids or phytosterols supplementations increases fish consume effect, although only the enrichment with phytosterols reaches significantly better results.

Finally, a search on Medline turns up very little on the topic of processing temps and creation of 25-hydroxycholesterol, except discussion of analytic methods and this study on pork:

Fatty acid modifications and cholesterol oxidation in pork loin during frying at different temperatures.

Echarte M, Ansorena D, Astiasaran I. J Food Prot. 2001 Jul;64(7):1062-6.

The effect of frying with sunflower oil for 4 min at different temperatures (160, 170, and 180 degrees C) on fatty acids and cholesterol of pork loin meat was studied. Total fat content increased from 5.6% in fresh loin to 7.3, 7.8, and 12.1% at 160, 170, and 180 degrees C, respectively. Interactions with culinary fat gave rise to a significant increase in unsaturated acids/saturated acids and polyunsaturated acids/saturated acids ratios, which could be considered an advantage from a nutritional point of view. Less than 1 ppm (microg/g of sample) of cholesterol oxidation products was detected in fresh loin, whereas fried loin pork contained between 8.58 and 10.89 ppm. 7-Ketocholesterol (5.99 to 8.47 ppm in fried samples) and 7beta-hydroxycholesterol (1.43 to 2.55 ppm in fried samples) were the main cholesterol oxidation products. Cholestanetriol was not detected in any sample, and small quantities of 25-hydroxycholesterol and 5,6alpha-epoxycholesterol were found in the fried sample.

Neal,

I should add the following information about extra virgin olive oil (EVOO), as it suggests that EVOO would prevent oxidation of cholesterol in during the cooking of fish in cans containing EVOO.

The first study coted below (Amati L et al. 2008) finds that very substantial amounts of phenols and antioxidant capacity remain intact in the EVOO in tuna or sardine cans heated to 284 F / 140 C for 30 minutes, and that significant amounts remain even when it is heated to 356 F/180 C for 30 minutes. (Fish is typically cooked in the can at temperatures well below 356 degrees F.)

Re: the 2^nd study below, I do not know the concentration of polyphenols in our tuna and sardines packed in EVOO, but it is likely quite high.

Re: the 3^rd study below, the EVOO in which our canned fish is packed is from Picual olives, so it resists lossof polyphenols more than the more common Arbequina

variety.

New investigation of the isothermal oxidation of extra virgin olive oil: determination of free radicals, total polyphenols, total antioxidant capacity, and kinetic data. Amati L, Campanella L, Dragone R, Nuccilli A, Tomassetti M, Vecchio S. J Agric Food Chem. 2008 Sep 24;56(18):8287-95. Epub 2008 Aug 22.

Dipartimento di Chimica, Università La Sapienza, Piazzale Aldo Moro 5, 00185 Roma, Italy.

As a follow-up of the research programs carried out by our group concerning the artificial isothermal rancidification process in extra virgin olive oil (EVOO), in the present work the trends of both the total antioxidant capacity and the total polyphenols concentration as well as the main kinetic parameters of the process during the thermal oxidation of EVOO were studied and compared. In addition, the possibility of evaluating the increase in radicals concentration during the thermal oxidation process using a superoxide dismutase biosensor was also studied. The present investigation concerning this important food product is highly topical as it refers to the state of alteration of the EVOO used for cooking or frying, as a function of the temperature reached.

Comparison of natural polyphenol antioxidants from extra virgin olive oil with synthetic antioxidants in tuna lipids during thermal oxidation.

Medina I, Satué-Gracia MT, German JB, Frankel EN. J Agric Food Chem. 1999 Dec;47(12):4873-9.

Instituto de Investigaciones Marinas del CSIC, Eduardo Cabello 6, E-36208 Vigo, Spain. medina@iim.csic.es

Polyphenols extracted from extra virgin olive oil (EVOO) were tested for their ability to inhibit lipid oxidation of canned tuna. Hydroperoxide formation during oxidation was monitored by measurement of peroxide value and decomposition of hydroperoxides by static headspace gas chromatographic analysis of volatiles. In tuna oxidized at 40 and 100 degrees C, 400 ppm of the EVOO polyphenols was an effective antioxidant as compared with 100 ppm of a 1:1 mixture of the synthetic antioxidants butylated hydroxytoluene and butylated hydroxyanisole. However, at concentrations <100 ppm, the EVOO phenolic compounds promoted hydroperoxide formation and decomposition. The EVOO polyphenols were effective antioxidants when added to heated tuna muscle in the presence of either brine or refined olive oil. The oxidation rate in tuna muscle packed in brine was higher than that of tuna packed in refined olive oil. The EVOO polyphenols had higher antioxidant activity in the brine samples than in the refined olive oil. The higher antioxidant activity of EVOO polyphenols in tuna packed in brine may be explained by their greater affinity toward the more polar interface between water and the fish oil system.

Influence of thermal treatments simulating cooking processes on the polyphenol content in virgin olive oil.

Brenes M, García A, Dobarganes MC, Velasco J, Romero C. J Agric Food Chem. 2002 Oct 9;50(21):5962-7.

Instituto de la Grasa (CSIC), Avenida Padre García Tejero 4, 41012 Sevilla, Spain. brenes@cica.es

Virgin olive oils were subjected to simulated common domestic processing, including frying, microwave heating, and boiling with water in a pressure cooker. The impact of these processes on polyphenol content and physicochemical characteristics of oils was assessed. Thermal oxidation of oils at 180 degrees C caused a significant decrease in hydroxytyrosol- and tyrosol-like substances. In contrast, oils heated for 25 h still retained a high proportion of the lignans 1-acetoxypinoresinol and pinoresinol. Thermal oxidation also resulted in a rapid degradation of alpha-tocopherol and the glyceridic fraction of oils. Microwave heating of oils for 10 min caused only minor losses in polyphenols, and the oil degradation was lower than that in thermoxidation assays. Again, lignans were the least affected polyphenols and did not change during microwave heating. Boiling a mixture of virgin olive oil and water in a pressure cooker for 30 min provoked the hydrolysis of the secoiridoid aglycons and the diffusion of the free phenolics hydroxytyrosol and tyrosol from the oil to the water phase. Losses of polyphenols were detected only at pH lower than 6. Moreover, alpha-tocopherol and the glyceridic fraction of oils were not modified during this process. It is worth noting that all the heating methods assayed resulted in more severe polyphenols losses and oil degradation for Arbequina than for Picual oil, which could be related to the lower content in polyunsaturated fatty acids of the latter olive cultivar. These findings may be relevant to the choice of cooking method and olive oil cultivar to increase the intake of olive polyphenols.

Wow thanks for your reply. It was more than thorough. All the articles on polyphenol count and oxidized cholesterol were conivincing. However, I won't go that far on BPA. Dr. Joseph Prendergast has posted some interesting articles on BPA recently most concerning their role in metabolic disorders namely Type 2 diabetes. It appears that BPA has a strong influence on adiponectin's metabolic regulation and who knows how many other hormones and processes BPA is influencing that are as of yet unstudied. I wouldn't pay much credence to the majority of the studies on BPA as they have been industry sponsored and poorly designed or monitored.

Were BPA the only environmental assailant out there I wouldnt be concerned. But we are being assaulted by so many xenobiotic elements these days that may act synergystically to disrupt our metabolic and reproductive health. I doubt our liver and detoxification systems can adequaltely address all these issues at the same time.

Dominic,

Great question! Anchovies are among the highest foods in omega-3 oil, according to my analysis of the USDA data. They have 2.1 grams of n-3 (omega-3) fatty acids per 100 grams.

They are strong! That makes anchovies an acquired taste. But I certainly have acquired it and added a can of anchovies to my shitake pasta stirfry for lunch just yesterday.

David