The acid/alkaline balance is said to be important in preventing disease. IN 1931, Otto Warburg won the nobel prize by showing that cancer cannot develop in bodies with slightly alkaline pH-levels (7.35 - 7.45).
The paleo diet consists of quite some acidifying foods (most importantly animal protein), even more so than the standard grain-based diet, it seems. A healthy diet should consist of about 60% alkaline-forming foods and 40% acid-forming foods (80/20 in a healing diet). My impression is that it's more or less the other way round in a paleo diet (40% alkaline-forming, 60% acid-forming)
The evidence I'm aware of seems to show that acid forming diets may cause calcium to be leached from the bone to balance pH levels. So an important comment is that most people wont experience metabolic acidosis eating an "acid forming diet", they'll just lose some skeletal calcium to maintain their alkaline pH. So bone health is probably the most important health marker to look at when discussing acid forming diets, in my opinion. Which brings me to some studies...
In this study, increasing protein from low to moderate levels improved bone health.
In another study, in which protein intake was increased significantly, the authors stated "We conclude that increasing protein intake from 0.78 to 1.55 g/kg·d with meat supplements in combination with reducing carbohydrate intake did not alter urine calcium excretion". This and other studies discuss the importance of protein on bone health and mechanisms by which protein does not cause net calcium loss from the bone.
In this study the authors stated "Under practical dietary conditions, increased dietary protein from animal sources was not detrimental to calcium balance or short-term indicators of bone health".
In this study in which protein intake was increased from 1 to 2.1 g/kg, the authors wrote "These data directly demonstrate that, at least in the short term, high-protein diets are not detrimental to bone".
This study, in which women increased protein intake from 61 to 118 grams a day, provides more evidence that "a high-protein diet has no adverse effects on bone health".
So ultimately I think animal protein may be acidifying, which leads to calcium loss, but it may also increase calcium absorption, negating the possible negative effects. And perhaps for a few reason, protein is a beneficial nutrient for bone health. I think eating a fair amount of fruits and vegetables is good, but as long as you're eating some and your "acid" comes from meat, pH balance isn't something I'd worry to much about.
*Much of this answer is copied from an answer I gave a few weeks ago, but the question was very similar.
I notice overall that I feel better when eating a lot of raw veggies. Not sure if this has more to do with the alkaline issue or the live enzymes.
The human body's most effective acid buffering system is the respiratory system. We have a bicarbonate buffer system every time we breathe. Most people just sort of breathe in and out very shallowly all day. Slow, deep breaths, in my opinion, are one of the best ways to balance acidity. (I've always wondered if this also has something to do with why deep breathing is considered to be therapeutic. Probably also because it just calms you down overall when you're forced to slow down and just breathe.)
Anyway, I've wondered about this a lot too, but overall, I think you're okay on the acid/base issue as long as you have no pre-existing kidney conditions. People who don't know any better like to claim that "too much protein is bad for your kidneys" or will give you some kind of disease, but research has shown that higher protein (within reason) is fine. It doesn't leach calcium out of your bones, as some also claim. Problems with "too much" protein usually arise in people whose organ function is already compromised by something else. (Because they can't filter/buffer properly, like a healthy person would.)
I can dig up some studies if you really want 'em, but it'll take a day or so.
If you're concerned about the acid/alkaline thing, some people do a kind of "alkalinity drink" every morning -- a glass of water with apple cider vinegar and freshly squeezed lemon juice. (WHAT?! Vinegar are lemon juice? I thought you said this was alkaline! It is. There are some foods that are acidic to the taste, but which become alkaline upon digestion.
And yes, grains and dairy are the other most acidifying foods besides meat, so depending on what else you're eating (lots of veg and fruit, for example), your overall load is probably alkaline.
Ben, check out Robb Wolf's discussion of Acid/Base Balance starting on page 12. http://robbwolf.com/wp//wp-content/uploads/2011/09/Episode99.pdf
First, he takes exception to the idea that cancer growth requires acidic ph levels. He suggests that the acidic levels are a cause and not effect of the cancer.
Second, he also discusses the acid buffering system of the respiratory system, mentioned by Amy B above.
For what it's worth, neither he nor Mat Lalonde worry about acid/alkaline balance.
This was considered to be a big deal early on in the Paleo diet. Loren Cordain may still be recommending the alkaline side of things. I don't know whether or not he has changed his mind on this issue, but for most of us the body's buffering system seems to be doing fine.
I think too that you have to think about the quality of the animal protein you are eating. I don't know if there's science behind it, so this is just assumption, but when you're eating ultra-processed, medicated, feed-lot 'lean' meat then I don't think you're ever going to be in balance internally. When you're choosing good quality, pastured, grass-fed, organic and/or local meat, or organ meats, and ensuring you eat all the nutrient dense fat, you're going to have less of a problem with the acidity. Maybe that's wrong but it seems there could be something there. Constructive criticism very welcome.
Even if we take for granted the importance of having a proper alkaline/acid balance, should meats be considered de facto acidic foods regardless of factors such as how the animal was raised, its omega-6 fatty acid content, general quality etc? Is there a relationship between o-6 content and overall acidity?
I'd imagine grass-fed beef for example has a more alkalising effect on the body than grain-fed.
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