Not only good for lowering blood pressure …
Potassium Bicarbonate Is Good for Bones
New study shows benefits for neutralizing the body’s acid load
In a recent study, veteran potassium researchers note that the acid load resultant from modern diets may have adverse effects on bone and muscle metabolism (Dawson-Hughes et al, 2015).1 High acid load is quite common in the American diet, which typically consists of higher ratios of cereal grain and protein to vegetables and fruits. Treatment with alkaline salts of potassium can neutralize the acid load, but the optimal amount of alkali hasn’t been established. The objective of the study was to determine the effectiveness of two doses of potassium bicarbonate (KHCO3) compared with placebo on biochemical markers of bone turnover, and calcium and nitrogen excretion. The potassium bicarbonate capsules used in this study, along with the placebo, were obtained from Life Enhancement Products, Inc. Independent testing found that the contents of each capsule of KHCO3 contained 101% of the stated content.
Median Doses: 6 and 9 Capsules/Day
In this double-blind randomized placebo-controlled study, 244 men and women, age 50 years and older, were randomized to placebo or 1 mmol/kg or 1.5 mmol/kg of KHCO3 daily for 3 months. 233 subjects completed the study. The median administered doses in the low and high dose groups were 81 mmol and 122 mmol/day, which correlates to 3.16 and 4.76 g of KHCO3/day. That’s about 6 and 9 capsules per day, respectively.
Nitrogen and Calcium Excretion
To measure nitrogen (N) excretion, the primary outcomes were changes in 24-hr urinary N-telopeptide (NTX) and N; changes in these measures were compared among the placebo and test groups. In bone physiology, NTX is a telopeptide that can be used as a biomarker to measure the rate of bone turnover. A telopeptide is an amino acid sequence that has a function in building or conforming a protein. Exploratory outcomes included 24-hr urinary calcium excretion, serum amino-terminal propeptide of type I procollagen (P1NP), and muscle strength and function assessments.
Bone-Turnover and Bone Loss Declines
When compared with placebo, urinary NTX declined significantly in the low dose group, when adjusted for baseline NTX, sex, and change in urine creatinine. Serum creatinine is an important indicator of kidney health. Also, serum P1NP declined significantly in the low dose group (adjusted for baseline P1NP and sex). The decline of P1NP exerts a counteracting effect to bone loss.
The potassium bicarbonate capsules
used in this study were obtained from
Life Enhancement Products, Inc.
Significant Urinary Calcium Decline
Urinary calcium declined significantly in both KHCO3 groups versus placebo (adjusted for baseline urinary calcium, sex, and changes in urine creatinine and calcium intake). There was no significant effect of either dose of KHCO3 on urinary N excretion or on the physical strength and function measures. KHCO3 has favorable effects on bone turnover and calcium excretion, and the lower dose appears to be the more effective dose. The decline of urinary calcium excretion represents a counteracting effect to bone loss.
Correcting Mild Metabolic Acidosis is Beneficial to Bone
The recent Dawson-Hughes et al, 2015 study indicates that correcting mild metabolic acidosis is beneficial for bone health. Metabolic acidosis is a condition in which there is too much acid in the body fluids. When compared with placebo, urine calcium excretion was reduced by 169% (lower dose of KHCO3) and by 213% (higher dose of KHCO3). These findings are consistent with a recent report of decline in calcium excretion with increasing alkali dosage.2 This study showed that the use of another alkaline salt (potassium citrate) resulted in sustained improvements in calcium balance.
Also, in a randomized, double-blind, placebo-controlled study, 52 men and women (mean age 65.2 ± 6.2 years) were randomly assigned to potassium citrate 60 mmol/day, 90 mmol/day, or placebo daily. The researchers took measurements of bone turnover markers, net acid excretion, and calcium metabolism, including intestinal fractional calcium absorption and calcium balance. They found that the reduction in calcium excretion likely resulted from reduced calcium losses from bone.
Dawson-Hughes et al indicate that
correcting mild metabolic acidosis is
beneficial for bone health.
Other studies have found that alkali supplementation can reduce calcium excretion. However, this has not been an entirely consistent finding.
Supplementation with KHCO3 is Good for Bones
In the Dawson-Hughes et al study, KHCO3 significantly reduced circulating levels of biochemical markers of bone turnover. Surprisingly, the high level of reduction of both markers was observed with a lower dose of KHCO3. This indicates that 1 mmol/kg per day of alkali is both sufficient to optimize short-term indicators of bone health. Treatment with the lower dose of KHCO3 reduced the bone resorption marker urinary NTX, by 18.7%, and the formation marker serum P1NP by 10.7%. Bone resorption is the process by which specialized cells known as osteoclasts break down bone and release the minerals, resulting in a transfer of calcium from bone fluid to the blood.
The observed decline in serum P1NP likely reflects the coupling of bone formation to bone resorption. Nonetheless, it is not clear why the higher dose did not significantly reduce NTX and P1NP, although the direction of change in both markers was as predicted.
NTX Result Is Consistent with Other Reports
The NTX result is consistent with the work of other researchers. One team found maximal reduction in the bone resorption marker, serum beta C-terminal telopeptide (CTX), at the lower of two doses given, 60 mmol/day dose of alkali.2 By contrast, in that study neither the 60 nor the 90 mmol dose significantly altered the bone formation marker, bone specific alkaline phosphatase.
One other study examined multiple doses in which potassium citrate was used at levels of 18 and 50 mmol/day (MacDonald et al).3 The researchers did not find any effect of either dose on serum CTX or P1NP.
Finally, another study reported that supplementation with 60 mmol/day of potassium citrate significantly increased serum P1NP levels by 13.8% and decreased urinary NTX by about 5% over a two-year study period.4 To the best of the researchers’ knowledge, this is the only other report of an increase in a bone formation marker with alkali supplementation.1
Reduction in calcium excretion
likely resulted from reduced
calcium losses from bone.
They did not identify any impact of supplementation with either dose of KHCO3 on N excretion in the group as a whole, or in men or women separately. This is in agreement with an earlier Dawson-Hughes et al (2010) finding that supplementation with 67.5 mmol/day of KHCO3 did not alter N excretion in men, but is at odds with their previous observation that supplementation lowered N excretion by 7 to 8% in women.5
Controlled High Protein Diets Don’t Work
In an intervention study in women on controlled high protein diets, treatment with alkali decreased nitrogen excretion,6 and in a small study in 24 women, alkali reduced N excretion by 12%.7
These mixed findings raise questions about the impact of acid-base balance on N excretion and muscle mass that can only be answered in subsequent studies. Supplementation had no significant effect on handgrip strength, as seen previously5 or on the physical function measures, stair climbing and the Short Physical Performance Battery (SPPB), perhaps because of ceiling effects (the level at which an independent variable no longer has an effect on a dependent variable). The mean baseline SPPB score, for instance, was >11 on a 12 point scale. The researchers had previously observed improved double leg press power and endurance in women treated with 67.5 mmol/day of KHCO3.5
Optimal Range of Net Acid Excretion
One of the goals of the current study was to identify the optimal range of net acid excretion (NAE) for bone and describe the diet composition of subjects in that range. The researchers examined the association of NAE with bone-related measures after 84 days of treatment to try to identify a potential NAE target for optimal bone health.
A reasonable estimate of the NAE range for maximal suppression of bone resorption, as indicated by the lowest urinary NTX, is -5.0 to 5.0 mmol/day. Reductions in bone turnover are of clinical significance because of their associations with reduced bone loss and fracture rates. The other two measures, urinary calcium and serum PINP, had minimal values at NAE levels slightly below this range, and the significance of this for bone health is uncertain.
Reductions in bone turnover are of
clinical significance because of their
associations with reduced bone loss
and fracture rates.
In the Dawson-Hughes et al, 2015 study, at baseline, 36% of the subjects were in the desirable -5.0 to 5.0 mmol/day range of NAE and 64% were above the range. Examination of the subjects’ diets at entry revealed that intakes of protein and dairy foods were not linked to baseline NAE. Protein is acid-producing, but, in this study did not vary across categories of NAE, perhaps because of the balance of animal and plant protein sources consumed by the participants.
Dairy foods, with the exception of hard cheeses, are generally metabolized to neutral compounds and were not associated with the NAE level. Indeed, subjects in the desired NAE range had higher fruit and vegetable intake and lower grain intake than those above the range. They consumed an average of 8.1 servings per day of fruits and vegetables and 5.5 servings of grains giving them a high daily mean fruit + vegetable/grain servings ratio of 1.47 (8.1÷5.5). The diet composition of these subjects was within the 2010 Dietary Guidelines, which are for a 2,000 calorie diet, 2.5 cups of vegetables, 2 cups of fruits, and 6 oz of grains.
Subjects with daily ratios of
fruit + vegetable/grain servings < 1.2
are expected to benefit from KHCO3
or potassium citrate supplementation.
KHCO3 Along with an Acid Reducing Diet
The diet of the subjects in the current study translates to about 9 servings of fruits and vegetables and 6 servings/day of grains (ratio 1.5). These subjects’ diets were similar to the DASH diet,* which contained 9.6 servings of fruits and vegetables and 7.5 servings of grains per day. Consumption of the DASH diet did not only lower blood pressure, it lowered bone resorption markers to a similar degree as the lower dose of KHCO3.
* The DASH diet plan was developed to lower blood pressure without medication in research sponsored by the US National Institutes of Health.
Specifically, serum C-terminal telopeptide (CTX) levels were decreased by 16 to 18% on that diet, and serum osteocalcin levels, an indicator of bone formation, decreased by 8 to 11%. In bone physiology, CTX is a telopeptide that can be used as a biomarker in the serum to measure the rate of bone turnover. The low acid load of the DASH diet likely contributed to the reduction in bone turnover in that study. From the current study, Dawson-Hughes et al would expect that subjects with daily ratios of fruit + vegetable/grain servings < 1.2 would be most likely to benefit from KHCO3 or potassium citrate supplementation. These subjects would also be expected to benefit from changing their diets to increase that ratio.
Will it Work Over Time?
Will maintaining a near neutral NAE over the long term reduce bone loss and lower risk of fracture in older adults? It is reasonable to expect that success, based on the prior work of Jehle et al,4 who found that older men and women treated with 60 mmol/day of potassium citrate for 2 years had reduced rates of bone loss from the spine and femoral neck. In that study, the mean NAE level in the supplemented group was in the target range identified in this study.
Consumption of the DASH diet did
not only lower blood pressure, it
lowered bone resorption markers as
the lower dose of KHCO3.
No Safety Concerns with Lower Doses of KHCO3
However, MacDonald et al3 did not find an effect of supplementation with potassium citrate on rates of bone loss (or bone resorption. Moreover, the achieved NAE level in that study is unknown.3 There were no safety concerns with the lower dose of KHCO3. However, the higher dose did cause a few more episodes of hyperkalemia (a condition caused by abnormally high levels of potassium in the blood). The safety of long-term ingestion of alkaline salts of potassium has not been rigorously evaluated as intervention trials have been of no more than 2 years duration.
In conclusion, supplementation with the lower dose of KHCO3, 1 mmol/kg/day or a median dose of 81 mmol/day (3.16 g/day, or 6 capsules), significantly improved intermediary indicators of bone health (lowered calcium excretion, NTX excretion, and serum P1NP levels) but had no significant effect on N excretion or measures of muscle strength or function in healthy older men and women. This dose was safe and well tolerated.
Six capsules significantly improved
indicators of bone health.
No Greater Decline from Higher Dose
The higher KHCO3 dose of 1.5 mmol/kg/day produced no greater decline in urinary NTX but did cause a few episodes of hyperkalemia. The lowest levels of urinary NTX during treatment were seen at a NAE range of -5.0 to 5.0 mmol per day, suggesting that this may be a reasonable target range for bone health.
The Use of KHCO3 for Osteoporosis?
The subset of 16 individuals in this range at entry into the study, comprising 36% of the researchers’ population study, had diets resembling the DASH diet with respect to fruit and vegetable grain intake. Their diets were also compatible with the 2010 Dietary Guidelines. Further work is needed to determine whether achieving and sustaining the nearly neutral NAE range of -5.0 to 5.0 mmol/day would reduce risk of osteoporosis.