Here’s another of Dr. Greger’s videos. This one talks about metabolic acidosis. It dispels the notion that eating an acid-forming diet (lots of meat and dairy) draws calcium from bones and sets one up for osteoporosis. Well, it dispels that direct link (somewhat, you have to eat enough calcium to break even), but it doesn’t get rid of the idea entirely. One way animal protein can be bad for bones: acidosis can lead to muscle wasting; and you need strong muscles to maintain strong bone.

Some studies from his video:

• This earlier study found that there is a “progressively worsening low-level metabolic acidosis” as we age, and that “such age-related increasing metabolic acidosis may reflect in part the normal decline of renal function with increasing age.”
  Age And Systemic Acid-Base Equilibrium: Analysis Of Published Data, Journal of Gerontology: Biological Sciences, 1996
• This study began, “metabolic acidosis promotes muscle wasting.” And concluded, “Higher intake of foods rich in potassium, such as fruit and vegetables, may favor the preservation of muscle mass in older men and women.”
  Alkaline Diets Favor Lean Tissue Mass In Older Adults, American Journal of Clinical Nutrition, March 2008
• This study says that diet-induced metabolic acidosis (eating lots of meat and dairy) increases slowly over time and that the kidneys compensate, in part, by nitrogen wasting. Insulin resistance also plays a role in muscle loss:
  Diet-Induced Metabolic Acidosis, Clinical Nutrition, August 2011
• This was a review. It presented a body of evidence that reinforces a link between metabolic acidosis and poor health, including loss of muscle mass and bone deterioration. “Muscle wasting however seems to be reduced with an alkaline diet and back pain may benefit from this as well.” The Alkaline Diet: Is There Evidence That An Alkaline pH Diet Benefits Health?, Journal of Environmental and Public Health, 2012

That last paper concluded:

Increased fruits and vegetables in an alkaline diet would improve the potassium/sodium ratio and may benefit bone health, reduce muscle wasting, as well as mitigate other chronic diseases such as hypertension and strokes.

Blue Is Best

According to Greger, and these studies, it’s not good to see your pee becoming more acidic as you age. You can test it if you like with either inexpensive pH strips, or with purple cabbage water. Purple cabbage in the presence of acid turns red; it turns blue in the presence of alkaline (or less acid). I think this would also work with beets and maybe blueberries and purple sweet potatoes, i.e. red is acid, blue is alkaline.