Calcium to Phosphorus Ratio, PTH, and Bone Health

Also see:
Calcium Paradox
Low CO2 in Hypothyroidism
Blood Pressure Management with Calcium & Dairy
Hypertension and Calcium Deficiency
Excess Dietary Phosphorus Lowers Vitamin D Levels
Fatty Acid Synthase (FAS), Vitamin D, and Cancer

Quotes by Ray Peat, PhD:
“The ratio of calcium to phosphate is very important; that’s why milk and cheese are so valuable for weight loss, or for preventing weight gain. For people who aren’t very active, low fat milk and cheese are better, because the extra fat calories aren’t needed.”

“The foods highest in phosphate, relative to calcium, are cereals, legumes, meats, and fish. Many prepared foods contain added phosphate. Foods with a higher, safe ratio of calcium to phosphate are leaves, such as kale, turnip greens, and beet greens, and many fruits, milk, and cheese.”

“Recent publication are showing that excess photsphate can increase inflammation, tissue atrophy, calcification of blood vessels, cancer, dementia, and, in general, the processes of aging.”

Br J Nutr. 2006 Sep;96(3):545-52.
High phosphorus intakes acutely and negatively affect Ca and bone metabolism in a dose-dependent manner in healthy young females.
Kemi VE, Kärkkäinen MU, Lamberg-Allardt CJ.
Ca and P are both essential nutrients for bone and are known to affect one of the most important regulators of bone metabolism, parathyroid hormone (PTH). Too ample a P intake, typical of Western diets, could be deleterious to bone through the increased PTH secretion. Few controlled dose-response studies are available on the effects of high P intake in man. We studied the short-term effects of four P doses on Ca and bone metabolism in fourteen healthy women, 20-28 years of age, who were randomized to four controlled study days; thus each study subject served as her own control. P supplement doses of 0 (placebo), 250, 750 or 1500 mg were taken, divided into three doses during the study day. The meals served were exactly the same during each study day and provided 495 mg P and 250 mg Ca. The P doses affected the serum PTH (S-PTH) in a dose-dependent manner (P=0.0005). There was a decrease in serum ionized Ca concentration only in the highest P dose (P=0.004). The marker of bone formation, bone-specific alkaline phosphatase, decreased (P=0.05) and the bone resorption marker, N-terminal telopeptide of collagen type I, increased in response to the P doses (P=0.05). This controlled dose-response study showed that P has a dose-dependent effect on S-PTH and increases PTH secretion significantly when Ca intake is low. Acutely high P intake adversely affects bone metabolism by decreasing bone formation and increasing bone resorption, as indicated by the bone metabolism markers.

Br J Nutr. 2008 Apr;99(4):832-9. Epub 2007 Oct 1.
Increased calcium intake does not completely counteract the effects of increased phosphorus intake on bone: an acute dose-response study in healthy females.
Kemi VE, Kärkkäinen MU, Karp HJ, Laitinen KA, Lamberg-Allardt CJ.
A high dietary P intake is suggested to have negative effects on bone through increased parathyroid hormone secretion, as high serum parathyroid hormone (S-PTH) concentration increases bone resorption. In many countries the P intake is 2- to 3-fold above dietary guidelines, whereas Ca intake is too low. This combination may not be optimal for bone health. In a previous controlled study, we found that dietary P dose-dependently increased S-PTH and bone resorption and decreased bone formation. The aim of the present study was to investigate the dose-response effects of Ca intake on Ca and bone metabolism with a dietary P intake higher than recommended. Each of the twelve healthy female subjects aged 21-40 years attended three 24-h study sessions, which were randomized with regard to a Ca dose of 0 (control day), 600 or 1200 mg, and each subject served as her own control. The meals on each study day provided 1850 mg P and 480 mg Ca. S-PTH concentration decreased (P < 0.001) and serum ionized Ca concentration increased (P < 0.001) with increasing Ca doses. The bone formation marker, serum bone-specific alkaline phosphatase, did not differ significantly (P = 0.4). By contrast, the bone resorption marker, urinary N-terminal telopeptide of collagen type I, decreased significantly with both Ca doses (P = 0.008). When P intake was above current recommendations, increased Ca intake was beneficial for bone, as indicated by decreased S-PTH concentration and bone resorption. However, not even a high Ca intake could affect bone formation when P intake was excessive.

Br J Nutr. 2010 Feb;103(4):561-8. Epub 2009 Sep 28.
Low calcium:phosphorus ratio in habitual diets affects serum parathyroid hormone concentration and calcium metabolism in healthy women with adequate calcium intake.
Kemi VE, Kärkkäinen MU, Rita HJ, Laaksonen MM, Outila TA, Lamberg-Allardt CJ.
Excessive dietary P intake alone can be deleterious to bone through increased parathyroid hormone (PTH) secretion, but adverse effects on bone increase when dietary Ca intake is low. In many countries, P intake is abundant, whereas Ca intake fails to meet recommendations; an optimal dietary Ca:P ratio is therefore difficult to achieve. Our objective was to investigate how habitual dietary Ca:P ratio affects serum PTH (S-PTH) concentration and other Ca metabolism markers in a population with generally adequate Ca intake. In this cross-sectional analysis of 147 healthy women aged 31-43 years, fasting blood samples and three separate 24-h urinary samples were collected. Participants kept a 4-d food record and were divided into quartiles according to their dietary Ca:P ratios. The 1st quartile with Ca:P molar ratio < or = 0.50 differed significantly from the 2nd (Ca:P molar ratio 0.51-0.57), 3rd (Ca:P molar ratio 0.58-0.64) and 4th (Ca:P molar ratio > or = 0.65) quartiles by interfering with Ca metabolism. In the 1st quartile, mean S-PTH concentration (P = 0.021) and mean urinary Ca (U-Ca) excretion were higher (P = 0.051) than in all other quartiles. These findings suggest that in habitual diets low Ca:P ratios may interfere with homoeostasis of Ca metabolism and increase bone resorption, as indicated by higher S-PTH and U-Ca levels. Because low habitual dietary Ca:P ratios are common in Western diets, more attention should be focused on decreasing excessively high dietary P intake and increasing Ca intake to the recommended level.