Discuss Raw

Wednesday 5 December 2012

Acidifying Foods, Protein, Phosphorus & Bone Health

Are grains acidifying? Should we avoid them if they are?

PRAL (potential renal acid load)is a rating of how potentially acid or alkaline a food is, calculated on the major acid and alkaline substances.[1] 100 grams of brown rice has a PRAL of around 2. 100g of whole wheat bread has a PRAL of 1.1. This means they're slightly acidic. You could argue the acidifying effect could be less as the calculation is partly based on phosphorus content. Grains may have a lot of phosphorus, but a lot of it is in the form of phytate which isn't even absorbed.[2]

If you were to eat cooked brown rice all day, it would give you a PRAL of around 40, but if you ate almost a pound of raw spinach the same day, you would end up at around -6. There are more interesting ways of being net alkaline on a diet including acidifying foods of course.

PRALs of other foods per 100g

Chicken broilers, 17.3
Top sirloin steak, 15
Boiled egg, 8.7
Walnuts, 5.5
Almonds, 3
Kidney beans, -0.8
Orange, -3.6
Potato, -5
Banana, -6
Medjool dates, -13.6

The acidifying substances in the calculation are phosphorus and protein. There is still some debate as to whether high levels of these actually have significant effects on bone health.[3][4][5]

Cooked food toxins and carcinogens

Does cooking create toxins, or carcinogens, like raw food dieters claim?

Some cooking methods create potential carcinogens, but not all do.

Acrylamide is known to cause cancer in animals. Also, certain doses of acrylamide are toxic to the nervous system of both animals and humans. Acrylamide is formed by frying, baking and grilling. Acrylamide has not yet been found in foods cooked below 120 degrees Celsius.[1] If it were found, levels would be very low. High intakes have been linked to certain cancers.[2]

Exposure to high levels of Heterocyclic amines (HCAs)and Polycyclic aromatic hydrocarbons (PAHs)can cause cancer in animals; however, whether such exposure causes cancer in humans is unclear.

Benzanthracene, benzofluoranthene, benzopyrene, dibenzanthracene, and indenopyrene are classified as PAHs. HCAs and PAHs are formed when muscle meat, including beef, pork, fish, and poultry, is cooked using high-temperature methods, such as pan frying or grilling directly over an open flame.[3]

Carcinogenic nitrosamines induce tumours in many species, and the similarity of the metabolism of dimethylnitrosamine by rat and human liver indicates that they are probably carcinogenic to man.[4] Nitrosamines are made from nitrates. Nitrates are found in some vegetables, but aren't converted into Nitrosamines.[5][6]

Small amounts of acrolein may be found in some foods, such as fried foods, cooking oils, and roasted coffee.[7] The Department of Health and Human Services (DHHS) has not classified acrolein as to its carcinogenicity. The International Agency for Research on Cancer (IARC) has determined that acrolein is not classifiable as to carcinogenicity in humans. The EPA has stated that the potential carcinogenicity of acrolein cannot be determined based on an inadequate database.[8]

Advanced Glycation End Product (AGEs)levels aren't significantly different in raw and cooked plant foods. Some cooked items have lower levels than some raw items even.[9]

In summary. High intakes of fried, grilled and baked foods may contribute to cancer. No carcinogens, or toxins, have yet been found in boiled, steamed and microwaved plant foods.

Tuesday 4 December 2012

Is Cacao Toxic?

Theobromine is the toxin in Cacoa.

Cocoa powder is ground cacao beans with the fat extracted. Cocoa powder contains roughly 2000mg of theobromine per 100g.[1] Cocoa butter contains very little, if any, theobromine.[2] I can't see any evidence suggesting cooking has any effect on the theobromine content of cocoa.

Theobromine is a big problem in dogs. It's hard to find much information on the toxic dose of theobromine for humans. However, it is said, by some, to be 3 times that of dogs.[3] The toxic dose for a dog is around 130mg per kilogram of body weight.[4] That makes the toxic dose for humans to be about 27, 300mg (average male)or 390mg per kg of body weight. That means you would have to eat over 1kg of cocoa powder in a day. That's like a whole package of it.[5]

Weight gain on a carbohydrate based diet

There's a claim going around that you can't gain weight (fat)on a high carbohydrate, low fat diet. As far as I can tell, this belief is based on the work of Colin Campbell, Neal Barnard and/or personal experiences.

Whilst observing the diets of Americans and rural Chinese, Colin Campbell noticed Chinese people ate more calories than Americans but were slimmer. He put this partly down to them being more active, but also felt that their low protein diet may have played a part, as rodents, and pigs, fed low protein diet gained less than those fed high protein diets.

I've only seen one study done on humans showing similar effects. They were given high and low protein diets. Overall, people gained less weight on the low protein diet, but for some people the effects of the two diets weren't significantly different. Some even did better on the high protein diet.[1]

Some say thermogenisis mops up any excess carbohydrate calories. A few studies have found that thermogenisis is higher on high protein diets.[2][3] This makes sense as you'll see.

What is thermogenisis or the thermic effect of food?

The thermic effect of food is nothing more than the energy used digesting food. The harder a food is to digest, the higher the thermic effect and the more energy you burn. Out of the three marco nutrients, protein has the highest thermic effect. The thermic effect of protein is 10 – 20% of calories. The thermic effect of carbohydrate is 5 – 10%, and the thermic effect of fat 0 – 5%.[4] This means fat is the easiest macro nutrient to digest. Not carbohydrate as many people believe.

This means a high carbohydrate diet will have a higher thermic effect than a high fat diet with the same protein level. However, a lot of high fat diets are higher in protein than many low fat diets. This might make the difference in thermogenisis less significant.

In a study comparing the thermic effect of different types of carbohydrates, sucrose had the highest thermic effect. 10 healthy males were given 75g, or 300 calories, of each carbohydrate. Over a six hour period, they lost 33 calories, due to thermogenisis, with sucrose.[5] This is nothing to get too excited about.

If you think higher fibre sugar sources will lead to higher levels of thermogenisis, you're wrong. Lower fibre meals induce thermogenisis more than higher fibre meals.[6] There are other nutrients in whole foods that might increase thermogenisis slightly, but lets not over think this. Thermogenisis is merely the energy used to digest food.

What about fat storage?

As with digesting, energy is needed to store energy as fat. Storing fat as fat doesn't require much energy. However, carbohydrate uses 23% of the energy.[7] With this in mind, you should gain less weight over consuming on carbohydrate than fat. Instead of storing 975 out of 1000 excess calories, you would store 770. This is still weight gain.

Assuming you didn't exercise more to burn it off, if you consumed an excess of 500 carbohydrate calories a day for 1 month, you would theoretically gain over 1kg of fat.

500 – 50 (max energy used digesting) = 450 – 104 (energy used converting to fat) = 346 divided by 9 (calories in a gram of fat) = 38.4 (grams of fat) x 28 (4 weeks) = 1076g = 1.08kg

A study done on overfeeding fat and carbohydrate supports this. Fat overfeeding led to 90 – 95% of the excess energy being stored. Carbohydrate overfeeding led to 75 – 85% of the excess energy being stored.[8] Another slightly longer study, found no significant differences between overfeeding on fat and carbohydrate.[9]

Unlimited calories and weight loss

Some people may be aware of Neal Barnard's study where they put people on a low fat vegan diet, and were told they could eat as many calories as they wanted. They lost weight and their diabetes improved. Does this mean you can eat unlimited calories and not gain weight, or lose weight even? No. They were allowed to eat as much as they wanted, but they averaged at about 1400 calories a day, down from an average of 1800 calories a day.[10]