A Paleolithic diet puts strong emphasis on consuming plant matter (which is typically done in a carbohydrate conscious way). Obviously, vegetables, fruits, nuts and seeds are an essential source of vitamins and minerals. But there is another, equally important reason to consume these foods: acid-base balance. What does this mean? Well, I’m sure you’re thinking about what acids you know (vinegar, lemon juice, battery acid) and what bases you know (baking soda, soap, bleach). Yes, we are talking about the same thing, but not how acidic or alkaline foods are when you eat them. Rather, the important part here is whether the digested compounds from those foods are acidic or alkaline (which means the same as basic) when they are filtered by your kidneys.
The kidneys are a pretty wonderful pair of organs. Of course, they are responsible for filtering our blood, adjusting the level of essential chemicals in the body, and eliminating unnecessary elements and wastes. But, they are also responsible for regulating the salinity of the blood, for producing hormones that regulate blood pressure, for producing hormones that stimulate red blood cell production, and for regulating the body’s pH by adjusting the body’s acid-base balance.
All food, once digested, contains compounds that must be filtered by the kidneys. These compounds can be acidic (meaning they have hydrogen ions to donate) or alkaline/basic (meaning they are short hydrogen ions and would like to gobble some up from somewhere) or neutral (just the right number of hydrogen ions). If the blood is too acidic, meaning that there is an excess of hydrogen ions, the kidney moves these ions to the urine. If your diet is deficient in alkaline foods, your kidneys use calcium from your bones to process the extra hydrogen ions. The body runs most effectively in a slightly alkaline state. The normal pH of blood is 7.4 (slightly basic) and this is necessary for the health of every cell in your body.
So what foods are acidic and what foods are basic? Well first, many of the foods we already avoid on a Paleolithic diet are acidic. Grains, legumes, dairy products, modern vegetable oils and salt are all moderately to highly acidic at the level of the kidneys. If these foods form any part of your diet, it is important to balance these acidic foods with lots of alkaline foods. Alkaline foods are basically all fruits and vegetables. Eggs are very slightly alkaline (you could just consider them neutral). Some nuts and seeds are alkaline while others (especially those higher in omega-6 fats) are acidic. Many people believe that in order to balance the acidic load of meat, poultry, fish and shellfish in a Paleo diet, that we need to consume large amounts of alkaline vegetables. However, recent research shows that high-protein, low-carbohydrate diets do not cause bone demineralization. This may be because meat, poultry, shellfish and fish actually contribute enough dietary calcium, magnesium and phosphorous as well as essential amino acids to your diet to protect your bones. What does this mean for acid-base balance? Actually, it’s still important. No one has yet looked at the effect of a pure protein and fat diet on bone health. Also, meat quality likely plays a key role here since high omega-6 content seems to contribute to the acid load on your kidneys. Consuming vegetables is still an important way to protect your bones and your kidneys, while also providing many key vitamins and minerals unavailable in meat. And it is still true that the more alkalizing foods you consume, the better. If you are being careful not to consume too much fruit due to the fructose content, then you need to make sure you are eating lots of vegetables. I eat vegetables at every meal. It may seem strange at first (especially eating vegetables at breakfast), but shifting toward a high vegetable intake will make an enormous difference to your long-term health.