- Written by Eduardo Pinheiro
- Category: Nutrition
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Most kidney stones are made of calcium oxalate and these are the ones I had. So I'll be focusing on preventing this type of kidney stones. Here's what I've found out.
Increase fluid intake - water and lemonade
The most fundamental nutrition change one can make is to drink more water. I've seen anywhere from 1.5 to 3 liters a day being recommended. The rule of thumb is to keep increasing water intake until one's urine is clear. If one can't do that with 3 liters a day, something must be wrong.
Another good liquid to ingest is lemon juice or lemonade (lemon juice plus water). The reason is that citric acid reacts with calcium and can dissolve stones that are forming in the kidneys. It's unclear whether it can reduce big stones or simply prevent smaller ones. And the amount of citric acid needed for this hasn't been established, so drinking lemon juice is beneficial, but should not be exaggerated.
Liquids to avoid (or reduce) are: black tea, colas, grapefruit juice and cranberry juice due to high oxalate contents (see below).
Maintain or increase calcium
Increasing natural calcium intake might be beneficial to stone formers, says current research. Even though calcium is a major part of the calcium oxalate stone, the stone is only formed with the calcium that is not expelled by the intestinal tract. That is, if not enough calcium is eaten with oxalate, the oxalate will bind with calcium in the kidneys instead of binding earlier in the intestines.
That means that when eating a salad (typically rich in oxalate), add some cheese or yogurt to it.
It's not clear that calcium supplementation is necessary. Some studies suggest it might be beneficial. If chosen to do so, don't do it at bedtime and prefer to take it with a meal during day time, according to this research, if taking calcium carbonate. The best form of calcium supplements for stone formers is probably calcium citrate due to its link with citric acid. It can be taken at any time.
Sodium competes with calcium for reabsorption in the kidneys and hence sodium and calcium contents in urine tend to increase and decrease together. Hence, a reduced sodium intake can prevent calcium from being expelled and hence reduce stone formation. This finding is supported by early research as well as more recent studies.
Control oxalate intake, meat
Oxalate is present in a lot of vegetables and nuts. A rigorous control of oxalate is difficult and possibly unnecessary as it would eliminate a lot of healthy foods. So, controlling the ingestion of foods deemed very rich in oxalate is important. Various lists abound online. The common items are spinach, rhubarb, nuts and some berries.
Avoiding meat can be helpful too since meat digestion produces uric acid, which lowers urine ph, which in turn is associated with higher risk of stone formation (see below).
Control urine ph
A goal for kidney stone formers should be to keep their urine ph neutral (close to 7). Mainly because that's what a neutral ph is and that's the level the kidneys are trying keep the blood at. If the blood is too acidic, the urine will be acidic. If it's too alkaline, the urine will be alkaline. To keep the kidneys from stressing too much, strive for a balanced diet that can keep the urine close to neutral (ph 7).
Foods that lower the ph (make it more acidic): meat products, cranberry juice.
Foods that raise the ph (make it more alkaline): citrus fruits and juices, vegetables, and dairy products. (source)
High protein intake (often associated with low-carbohydrate diets, such as Atkins) can lower the ph in urine and thus increase propensity of forming stones.
Potassium citrate is a type of salt that can raise urine ph and therefore might be beneficial against kidney stones. Research so far has only been conducted in children, with good results (extra citation). For supplementation, observe the RDA of 2g per day. The highest supplement amount allowed by the FDA is 100 mg though, which may not be enough for serious cases.
Testing the ph of urine is simple, safe and cheap. One can buy test strips and track urine ph over time, noting how changes in diet affect overall urine ph.
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- Written by Eduardo Pinheiro
- Category: Nutrition
- Hits: 4164
I wanted to start this section with my view on vitamins and minerals and my plans to live to 120 years of age. But instead I was drawn to another topic: kidney stones. It turns out that I had my first one a few weeks back, just to discover that the one that passed -- a 2mm calcium oxalate one -- has company: two more remain, one in the right kidney and one in the left, 2.5 and 6 mm (now I forget which one is where, but it doesn't matter).
So, what would a scientist with interest in nutrition would do? Read about how kidney stones are formed, what to eat and what not to eat and how to avoid them.
I'm still collecting my findings and my thoughts on this, but the most important things to know at this point are:
- Hydration is the most important mechanism to avoid stones. Water and lemonade are the best. Avoid cranberry juice and black tea.
- Do not avoid calcium, but don't supplement either. Calcium oxalate stones are a combination of calcium and oxalate (a component found in plants). Reducing calcium intake is bad for one's health in general and it is not likely to reduce stone formation (the body has a lot of calcium stored in bones and teeth). So, do not avoid calcium. In fact, I'm currently reading about adding more calcium to my diet. More on this later. However, taking calcium supplements may be unnecessary or even bad. The jury is still out on this one, which seems contradictory, but I believe it has to do with the various types of calcium supplements (carbonate, citrate, malate, phosphate, etc). More on this later too.
- Avoid high-oxalate intake. If avoiding calcium is not the solution, then avoiding extra oxalate is the only other possibility. Turns out that current research supports this. The bad news is that oxalate is present in a heck of a lot of yummy vegetables, nuts and fruits. Since these are essential to good health, one should not avoid all vegetables, nuts and fruits, but instead limit consumption of those with very high oxalate amounts. From an initial cursory look it seems that spinach, rhubarb and almonds are the top offenders, followed by chocolate, aspargus and black tea. Everywhere I look shows a slightly different list, but some items appear on all lists, such as chocolate, all nuts and spinach. More investigation is needed.
That's it for my initial investigation.
About 80% of stone avoidance can be gotten with proper water intake -- 2 liters a day or more.
I've actually setup my cell phone to page me every hour of every day, to remind me to take a sip of water. It's harder than it seems, but the theory is that once one gets adjusted to higher water intake, the body will respond better and the urges to use the restroom will slowly decrease and craving water early (before one is even mild dehydrated) will become second nature.
I hope the literature is right. So far, it's annoying to drink so much water. But I'm starting to get used to the idea.
I'll soon write more about my other findings about kidney stones and how to avoid them.
For now, salute! Time for another glass of H2O.
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