Minimizing acid load for health and performance ft. Prof. Ted Weiss
- What acid load is
- How both diet and exercise generate acid load
- How acid depletes nutrients from your body
- Short-term effects of acid load on exercise
- Long-term effects of acid load on kidney health
- What foods to eat to minimize acid load
My guest today is Ted Weiss. Ted is Professor of Nutrition and Dietetics at Saint Louis University, and an expert on health, longevity and fitness. His research spans nutrition and exercise for weight loss, the prevention of diabetes and cardiovascular disease, the slowing of primary aging, and nutrition for optimizing physical performance. One of the key topics in Ted’s research is the concept of acid load, and its effects on health and endurance. Ted is also a keen cyclist and tries to actively apply his research findings to his own body.
Ted, thank you very much for joining us.
Thank you for having me.
One of the topics that’s really close to your heart and your research is this concept of acid load and its effect on health and performance. Can you explain to us what acid load is?
The acid load of the diet – or there’s acid load of exercise as well – is basically the production of acid as a consequence of eating food, or in the case of exercise, the acid produced as a consequence of exercising. And this is the tendency that these actions have to make our body more acidic. When we produce acid, whether it be by diet or exercise or other means, our body needs to regulate that, and it does so through numerous mechanisms involving both breathing and the kidney.
And with respect to diet, acid load of the diet is a consequence largely of the nutrients in the diet, and in particular, there are nutrients that either tend to promote acid production when we eat them, and then there are others that are actually sort of counter, that are opposite that, and they produce base and actually absorb acid or help sequester acid. So the acid load of the diet is of particular interest because in our modern Western diet, we tend to eat a dietary pattern that produces more acid than is thought that we would have historically. And in ancient times, the diet that we evolved to eat maybe is not as acid-promoting as our current diet, so the question becomes – what is the impact of eating a diet that produces an acid load over decades and then a lifespan?
So firstly, what are these sources of acid and alkalinity in the diet? You mentioned that our diets were different before. How have our diets changed in that way?
It’s hard to interpret things when we look at nutrients, but we know that different foods have different proportions of these acid-producing or base-producing compounds, and it’s commonly known that foods that predominate in our modern diet, meats, cheeses, and refined grains, have a lot of the nutrients in their sulfur containing amino acids and phosphorus that are responsible for making our bodies more acidic. These same foods are also very low in minerals that are responsible for producing base. Counter to that, fruits and vegetables, whole fruits and vegetables in particular, are very rich in these mineral ions that contribute to base production or sequester acid and reduce acid levels, and they have very low levels of acid-producing compounds.
Foods that are are acid-promoting tend to be meats, cheeses, and, and grains, refined grains, some of the popular grains in particular, and on the other hand, whole fruits and vegetables are base-promoting or tend to reduce the acid levels in our body. In the diets that we know of from our past, and before the agricultural revolution where large volumes of grains and meats and cheeses were produced, we really had large intakes of fruits and vegetables and low intakes of meats, cheeses, and grains, so we tended to have a lower acid load imposed on us by our diet.
And there’s a tendency for people to think that a food that’s acidic on a plate or in a cup in the kitchen is an acid producing food, and if that held true, then something like lemon juice would create an acid load for the body, but that’s not true at all. As a matter of fact, the impact that a food has on our body’s pH and the acid burden on our body is absolutely unrelated to the pH of that food outside of the body, on the plate or in the cup.
So foods like lemon juice – fruit juices in general are very acidic, but they actually have an alkalizing effect on the body. Coffee and tea are acidic, but they’re relatively neutral, if I recall correctly, on pH. So there’s no relationship between the pH of the food itself and the impact that it has on the pH of the body upon digestion, and the mechanism by which they affect pH is fairly complicated, and it evolves certain things – sulfur metabolism being a by-product, is a sulfuric acid that gets produced. The things like the phosphorus, phosphorus is a cation, and in the intestine it prevents the absorption of bicarbonate, which is an important buffer and a base producer for us. So by blocking absorption of bicarbonate, it effectively shifts us toward more of an acidic state. And cations are also involved in competing with and altering absorption of other nutrients that are themselves more regulating of acid base status than a nutrient of interest itself.
So when you say the acid load is blocking the absorption of bicarbonate, you’re saying that an acidic diet is making it harder for the body to absorb one of the key substances it needs to neutralize that acid load. Is that what you’re saying?
That’s right. And it’s actually what we refer to as a reabsorption because the bicarbonate is secreted into the intestine in the form of bile, and then it’s important that we reabsorb that and it’s normally reabsorbed with sodium, but phosphorus has a tighter binding affinity to the bicarbonate so it can’t be co-absorbed with sodium as it needs to be, so effectively the phosphorus is competitively inhibiting the absorption of the bicarbonate, which is important for controlling acid in our body. So we lose that bicarbonate then.
Very interesting. Are there any other minerals like calcium, sodium, potassium, magnesium, that play a role in neutralizing that acid load?
Potassium and magnesium are actually the key. In the simple equations we use, those are the three cations we quantify that have the biggest impact.
Does it matter what type of protein and what type of carbohydrate we eat? You mentioned about meat and also about refined grains. Does that mean that whole grains have a lower acid load compared to white bread, or fish a low acid low compared to, say, beef?
Not all proteins contain the same amount of sulfur-containing amino acids. It’s very difficult to differentiate between them within databases that we look up nutrients in. For the most part, the predictions we use for the acid load of a diet is based on an assumption that all proteins have a similar proportion of amino acids that are sulfur-containing. In reality we know that that, generally speaking, animal products have more sulfur-containing amino acids in them than plant-based proteins do. We can’t really differentiate between those in the way we analyze these for our studies, but that’s a known limitation to the approach we use and we don’t account for that difference.
With respect to carbohydrates, it’s not necessarily the carbohydrates themselves that impact acid-base regulation. It’s the minerals and the phosphate that are contained in those carbohydrates. It’s really more of the popular carbohydrates that are acid promoting, in particular wheat. We see wheat mostly in our modern diet in refined form, and a whole grain wheat bread, for example, would be no better in terms of acid production than refined grain. However, a lot of the other carbohydrate containing grains such as quinoa don’t have as much of an acid producing effect because they don’t have as much phosphorus.
They don’t have as much of the…they have more of the cations that help regulate acid or reduce acid levels. So a lot of the less conventional grains, I’m drawing a blank in terms of thinking… Maybe teff, quinoa, amaranth, those sort of grains are actually not so much acid producing. Whereas wheat is more of an acid producer.
We know that the body controls its pH very, very tightly, especially in the blood, so why is it a problem to have a high acid load in the diet if the body is able to generally maintain the pH it needs to survive?
It’s an excellent question, and I work with dieticians quite a bit, and the first thing they say to me, when we talk about the effect of an acid load of the diet, is they say, “Well, doesn’t the kidney regulate this?” Absolutely, it does. The evidence is that the vast majority of what would normally disrupt pH is controlled by the kidney and respiration. And there is no question that it’s highly controlled. It’s regulated within a very tight range, the pH of the blood and the cells, but there’s evidence that it’s not perfectly controlled. I think point one is that it’s not perfectly controlled, and if there’s a high acid load on the body, it’s almost perfectly controlled, but not quite. And there are very, very subtle, very much what we call subclinical shifts in pH to a more acidotic state when an acid load is imposed on the body, especially high acid load diet for a sustained periods of time. So there are shifts. We see urine output of acid go way up because the kidney is excreting that acid, but it’s imperfect even in a healthy kidney.
As kidneys get older, even in the absence of overt disease, their capacity to get rid of the acid deteriorates and more and more acid is retained in blood. A second thing is that when we impose an acid load on the body, the body has to use resources in order to control that acid. So the kidney doesn’t just excrete it without cost. We have to mobilize things from muscle and bone in order to buffer it and then have the kidneys excrete it.
For example, bone is a source of carbonate, which is used… It’s actually a very strong buffer, even compared to bicarbonate, but carbonate is a strong buffer that’s mobilized from bone in order to buffer acid. In the process of mobilizing that carbonate, calcium also leaves bone. It’s sort of the innocent bystander in that case, but it’s bound in a structure with carbonate in bone, so when carbonate leaves bone, we also lose calcium. So that’s a resource. We can control it, we can control our pH, but it’s not without a cost, and some of the buffers that are used are coming from bone. There’s also buffers that can be produced from muscle protein as well, that work in the same way. So when we do control a high acid load, that’s a good thing, and it’s very important, but it doesn’t come without a cost. And there’s potential longterm ramifications of mobilizing these buffers from bone and muscle for the purpose of regulating or controlling a diet that’s too much of an acid burden on the body.
You mentioned about calcium and carbonate being taken from the bones to neutralize acidity, and you also hinted at muscles. Are potassium and magnesium being leached to address the acidity, or is it just potassium? Does that mean effectively the muscle tissue is being broken down in some way?
Okay. So we know, for example, that people who are at the older age of the spectrum typically have quite significantly reduced kidney function, and that decline in kidney function from acid load is much more pronounced at that age. It’s much easier to see as a percentage of remaining kidney function. So if someone is younger and they have generally healthy kidney function, the issue for them is that long term they’re going to be accelerating that decline of kidney function, and in the short term essentially their nutritional and physical condition is going to be less optimal than it could be if they had a lower acid load. Would that be a fair statement?
For the kidney to excrete acid does take its toll on the kidney and it does accelerate the decline in kidney function, which in turn leads to a greater acid in the body, which is sort of a snowball effect. The kidney deteriorates quicker in an acid environment, which allows poor regulation of the acid, which further deteriorates kidney. It’s a vicious cycle that accelerates over a lifespan and unfortunately leads to earlier decline in kidney function.
I feel that a number of years ago there was a lot of focus on this idea of the alkaline diet and the idea of “eating alkaline” really took a big hit from a lot of scammy products that were being sold, alkaline water, detoxes and so on. But the way I see it is that this is really about making a long-term investment in our health, especially at a time when many more of us will be living to a hundred and beyond, preserving our kidneys and quality of bone and muscle will only become more important.
I like to think of kidney function as something that’s deteriorating in everybody Once you hit mature adulthood it’s on a downward decline. And just because something doesn’t cause overt kidney dysfunction in a six month study with some some interesting intervention, it doesn’t mean that it’s not accelerating the functional decline of the kidney, because it’s decades and decades that it will be declining on its own, and the question becomes how steeply will it decline. And we do have some control over that, I believe.
Thank you. So now I’d like to talk about acid load and exercise performance. This is something that you’ve researched about, even done studies on. How can acid load affect exercise performance and what kind of exercise might be affected?
Yeah. Acid becomes a very central discussion point in the context of what we call anaerobic exercise performance. And this type of exercise is basically exercise that depends heavily on anaerobic metabolism for the production of ATP, which is of course the currency, the energy currency that muscles can use. They can’t use carbohydrates to trigger muscle contraction. The carbohydrate has to be used to produce ATP, which is used by the muscle for contraction.
When we exercise, we increase our ATP requirements, the muscle demands more ATP because we exercise harder. And at some point the ATP demands exceed our body’s capacity to produce ATP with what we call aerobic oxygen dependent metabolic pathways, so the difference gets made up for by oxygen independent pathways – anaerobic metabolism. So anaerobic metabolism is a wonderful system that allows us to produce ATP at very, very high rates, but for very short periods of time, because it has a very dangerous by-product and that by-product is acid.
And ultimately the acid that’s produced… We’re pigging along, we can produce ATP without oxygen for a limited amount of time, and as a consequence, we produce high amounts of acid, which in turn shut down that metabolic pathway and stop it from continuing. So it’s a very short term energy system, but very high ATP production rates. So it allows us to do things like run a 200 or 400 meter sprint at maximal exertion, or to do a sprint halfway down the field on a soccer field, or to do a track sprint on a bicycle. Any of those sort of things depend heavily on anaerobic metabolism becoming a very important supplement to our aerobic metabolism pathways so that we can produce ATP at high rates. So that acid production, the by-product is ultimately what stops that system from continuing to produce acid.
It’s the acidity that occurs in muscle that ultimately inhibits the enzymes responsible for that metabolism. So if we can somehow prevent the acidity from rising as quickly and allow that anaerobic metabolism to produce ATP, we can continue to work a little bit longer before the acid accumulates to that critical level and causes the system to stop.
So there’s an interest in… Ultimately if a person sprints, the thing that really limits their capacity is that acidity. So if we can buffer acid better, or start in a more alkaline state, for example, by eating a diet that keeps us in a little more alkaline state, we’re starting in a better place so acid can be produced and accumulate longer before it hits that same critical number that ultimately stops the metabolism.
Interesting. So the body in aerobic exercise is converting carbohydrates into ATP for energy, and then when it exceeds the ability to do so, it has to produce ATP, this energy molecule, through an anaerobic process, and this anaerobic process generates acidity. So does that mean aerobic exercise does not generate acidity?
Oh, that’s not necessarily true. As a matter of fact, a big acid producer is the use of ATP. So when the muscles contract, they hydrolyze ATP into ADP and inorganic phosphate, and the phosphate is an acid. It liberates the proton and protons, or free hydrogen ions, are by definition what acid is. So just using ATP produces acid. And it happens to be that when we produce high amounts of it, because we’re using it very rapidly, the production of acid is very high because we’re using ATP very rapidly.
There’s a common notion that lactic acid production as a byproduct of anaerobic metabolism is the cause of acidosis, and while it is a contributor, there’s no question, it’s in combination with ATP hydrolysis that we’re getting all this acid production. So at any time when we use ATP, sitting at rest, we’re producing acid, metabolism in general produces acid, so it is always there. As a matter of fact, anaerobic metabolism is going on 24 hours a day in our bodies at a very low level as well. We always use a mix of aerobic and anaerobic mechanisms. The key is at what point are we producing so much acid that our bodies can’t clear it?
And at that point, the acid accumulates automatically, and thereby causes the metabolic pathway to stop. The enzymes are very sensitive to pH, and when the pH or the acidity goes up, pH goes down, the enzymes stop their action of catalyzing metabolic reactions, and ATP production stops.
Okay. So whether you’re doing aerobic exercise or anaerobic exercise, that’s going to be generating a degree of acidity through the exercise itself, through the production of ATP. But if, for example, you’re training anaerobically at a high intensity, it’s going to produce much more acidity, and maybe if you were doing it for a long duration – even with aerobic exercise – you would again generate a lot of acidity. Would that be correct?
Generally it’s not a problem unless we’re producing a lot of acid at high intensity. The more modest intensity, long duration endurance exercise, acutely, it wouldn’t cause an increase in acidity. Now, I don’t know the literature as well, but long duration exercise, if you go out on a three hour run, for example, even though that itself isn’t going to cause a major acid-base disruption during exercise like a 400 meter sprint would, I think there are other consequences that may be involved in more of the other metabolic pathways that can cause disruption in pH and cause acidity that lasts maybe days afterwards, even.
So the exercise itself, the use of ATP is generating acidity, but there’s also acidity coming from the diet, right? If I’m an athlete and I’m training, doing high intensity exercise, I have to think about two sources of acidity which are competing for the same resources to get neutralized, right?
So what should I do in order to neutralize that effect? Should I have my diet as alkaline as possible to minimize the impact of acid production from training?
The idea is that really the exercise is a very short, transient disruption in acidity that gets resolved fairly quickly, whereas the diet is sort of a long sustained baseline that can be altered over time. But if you keep the dietary impact on pH at a minimum, or keep it toward a more basic state that allows more of those resources to be available for the acute disruptions caused by short term, high intensity anaerobic exercise.
A lot of people may think, “Well, I’m not an anaerobic athlete. Why does that relate to me?” and we oftentimes think of the track athletes and maybe a strongman competition kind of people, but I think almost most sports involve a very substantial anaerobic component. Think of soccer, for example, there’s sprint after sprint after sprint. Bike racing, there’s attacks in bike races repeatedly that are extremely high intensity anaerobic, in the context, on the backdrop of a two or three hour road race, there are plenty of anaerobic bouts. The same thing in running races.
Probably the few places where it doesn’t exist would be in things like maybe ultramarathon running where there’s not generally a sprint finish that determines the victory, but it’s… So anaerobic exercise is really woven into almost any sports and any types of exercise and even a person who’s not a competitive athlete, but is out on a run in the countryside or bike ride for fitness purposes, getting uphill, so it becomes anaerobic, it’s unsustainable. You just hope you get to the top before you run out of energy. And so things that enhance anaerobic exercise performance are very relevant to that broader range of people and exercise tasks.
That’s very helpful, thank you. We’ve looked at the importance of having a low acid load, a diet rich in base (or “akaline”) foods. We’ve also touched on the importance of minerals. What are the other nutritional strategies that you consider to be important, based on your experience and the current state of research?
I think in the broad context, food, in its entirety, is really the big thing it does for exercise is it provides fuel and it regulates our body weight. So if we take in excess food and we have 10 pounds of extra weight, that has a very detrimental effect on food, and this is such a loud and clear, powerful effect that I think is within reach for anybody, and it’s so definite, there’s very little dispute. In most cases that people who have extra weight can benefit from losing some of that. So using food, dietary intervention, is one way to manipulate body weight. And it’s a very reasonable thing.
Now with that said, I think there’s danger in people trying to alter their body weight by reducing energy intake at the wrong times that can have a detrimental effect on performance. So the key is really to adjust, and I call it energy intake, some people call it calorie intake, but is to alter energy intake to match the demands that exercise is going to impose on it in the near future. And in those times when energy demands from exercise are low, then food intake should be low. So I think just conscious regulation of that energy intake to match the subsequent exercise that’s going to happen is really important. It’s a very boring message, but I think it’s one of those things that’s more definitive than almost any other dietary intervention we have, and why wouldn’t a person pay attention to that other than just convenience and social challenges?
Absolutely! That just leaves me to say, thank you Ted for joining us! It’s been a great conversation and really appreciate everything you’ve shared with us. So thank you very much indeed.
I appreciate it, Dan, it’s been a pleasure.
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