6 kinds of food that the kidneys are afraid of. Many people eat them almost every day, but they don’t know

The kidney is a very important "filter" in our body and one of the important organs for excreting waste from the body. If there is a problem with it, our body will also show a series of symptoms, and in severe cases it can be life-threatening.

If you want to protect your kidneys, you should try to stay away from foods that are not friendly to the kidneys, and also change some bad habits that damage the kidneys.

These 6 foods are not good for your kidneys

1. High-salt foods

The salt we consume in our diet is mainly metabolized by the kidneys. If we eat strong flavors and eat too much salt, it will inevitably increase the metabolic burden on the kidneys.

A high-salt diet can damage the kidneys in many ways. On the one hand, TGF-β1 is a key factor that promotes renal fibrosis. Excessive salt intake will increase its production, accelerating renal sclerosis and fibrosis by enhancing its signal transduction function. On the other hand, a high-salt diet can cause oxidative stress in the kidneys, which can lead to renal failure and renal structural remodeling, damaging the kidneys. In addition, high salt intake increases urine protein. Long-term high-salt diet destroys the selective permeability of the glomerular basement membrane and promotes the progression of kidney disease. Salt restriction can significantly reduce urine protein.

On the other hand, a long-term high-salt diet increases the risk of high blood pressure, which can also affect the normal function of the kidneys.

What should we do: According to the recommendations of the Dietary Guidelines for Chinese Residents (2022), the daily salt intake per person should be controlled within 5 grams, which is about no more than 1 beer bottle cap (with rubber pad). At the same time, we should also eat less foods containing hidden salt, such as sauces, fermented bean curd, pickles, sausages, ham, instant noodles, spicy strips, etc., and use condiments such as onions, ginger, garlic, and vinegar when cooking.

2. High-sugar foods

A high-sugar diet not only increases the risk of obesity and high blood pressure, but also increases the risk of type 2 diabetes, which in turn endangers kidney health.

What should we do: The Dietary Guidelines for Chinese Residents (2022) recommends that we limit our daily sugar intake to less than 50 grams, preferably no more than 25 grams. At the same time, we should also reduce the intake of sweetened drinks and carbonated drinks, and drink less or no fruit juice.

Figure: 1 A mineral water bottle cap contains about 5 grams of sugar (photographed by the author)

Picture: 1 tablespoon is about 10 grams of sugar (photo taken by the author)

3. High Oxalate Foods

Calcium oxalate stones are a common type of kidney stones and urinary stones. Oxalic acid combines with calcium to form calcium oxalate crystals. Under normal circumstances, urine contains some substances that can inhibit the formation and growth of crystals. For example, mucin and citric acid can inhibit the formation of calcium oxalate crystals.

But when the oxalic acid content in the urine is too high, the urine may be in a supersaturated state, causing calcium oxalate crystals to precipitate and combine together, eventually forming stones.

What we should do: For foods with too high oxalic acid content, they must be blanched before eating to remove most of the oxalic acid, such as spinach, amaranth, water spinach, wild rice stem, winter bamboo shoots, etc.

4. Starfruit

Although carambolas are delicious, they are not only high in oxalic acid, but also contain a neurotoxin that needs to be excreted from the body through the kidneys. Healthy people with normal kidney function can excrete this neurotoxin through urine, so there is no need to worry about eating one or two carambolas.

However, people with poor kidney function should eat less or no carambola, otherwise they may experience nausea, vomiting, abdominal pain, diarrhea, back pain and acute kidney injury. Literature data mentioned that the mortality rate of carambola poisoning in patients with abnormal kidney function can be as high as 20% to 40%.

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5. Wine

Alcohol may damage the kidneys through a variety of mechanisms, such as inducing the production of reactive oxygen species, leading to oxidative stress, causing excessive free radicals, which in turn damage tissues and increase inflammation. In addition, the effects of excessive alcohol intake on the liver, heart, intestines, and skeletal muscles will also synergistically increase its pathological damage to the kidneys.

There are also documents mentioning that long-term drinking will not only aggravate the formation of calcium oxalate crystals in the body, but also affect purine metabolism and increase the incidence of kidney stones.

What we should do: Drink less or no alcohol. Children, adolescents, pregnant women, and nursing mothers should not drink alcohol. Adults should control their daily alcohol intake to no more than 15 grams, which is equivalent to the amount of alcohol consumed in the figure below.

Figure: "Dietary Guidelines for Chinese Residents (2022)"

6. Traditional soup, hot pot soup

Some people always think that old soup is very nourishing and hot pot soup is nutritious. In fact, neither of them is recommended. Both have been stewed for a long time. The soup contains high purine, which will increase the excretion of uric acid. Drinking it often can easily form uric acid stones.

In addition, people with impaired renal function should avoid high-protein diets, especially high animal protein, otherwise it may increase the burden on the kidneys.

5 bad habits that may harm your kidneys

1. Don’t like to drink water

Drinking enough water helps the kidneys excrete waste from the body. If you drink too little water, your urine will become concentrated, increasing the risk of urinary stones. Drinking enough water can reduce the risk of initial and recurrent urinary stones.

It is recommended that women and men drink at least 1500ml and 1700ml of water respectively every day, drinking in small sips and multiple times.

2. Taking medicine randomly

Many drugs need to be metabolized by the kidneys after taking them. Taking drugs indiscriminately or taking excessive amounts of drugs will increase the burden on the kidneys and may even cause kidney damage.

3. Holding urine

Holding urine is very common in life. If you hold urine frequently, it can easily lead to upward reflux of urine, increase the risk of urinary tract infection and kidney infection, and also damage kidney function.

4. Staying up late

Physiological evidence shows that sleep can regulate kidney function, and long-term sleep deprivation can damage kidney function. A study that followed up for 11 years and included more than 4,000 nurses showed that compared with people who slept an average of 7 to 8 hours a night, people who slept less than 5 to 6 hours a night had a significantly faster rate of kidney function decline.

5. Smoking

Not only does smoking accelerate the progression of kidney disease in patients with chronic diseases such as diabetes and hypertension, but it can also lead to kidney damage and disease in healthy people with no history of chronic kidney disease, manifested as reduced glomerular filtration rate and/or proteinuria.

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To ensure quality of life, it is essential to protect kidney health.

In addition to paying attention to the kidney-unfriendly foods and bad habits that are not conducive to kidney health mentioned in the article, we must also pay attention to the intake of fresh fruits and vegetables in our diet. The rich dietary fiber, mineral potassium, antioxidants, etc. in fruits and vegetables can help us better protect kidney health.

References

[1] Ye Xingxing, Zhang Hongmei. Effects of dietary salt intake on chronic kidney disease and research progress on salt restriction[J]. Chinese Journal of Integrated Traditional and Western Medicine Nephrology, 2015, 16(6): 557-559

[2] Chinese Nutrition Society. Dietary Guidelines for Chinese Residents[M]. People's Medical Publishing House. 2022

[3] Niu Qingyu, Zhao Huiping. Research progress on carambola poisoning in patients with chronic kidney disease[J]. Chinese Journal of Blood Purification, 2018, 17(6): 407-411

[4] Zhang Lihan (review), Fu Ping (review). Pathogenesis of alcoholic renal injury[J]. Journal of Nephrology and Dialysis Kidney Transplantation, 2020, 29(4): 358-362

[5] Li Ruibao, Li Bijun, Lin Weiming, Nong Yi. Analysis of the composition characteristics and risk factors of kidney stones in Zhanjiang area[J]. Chinese Folk Therapy, 2022, 30(21): 85-87

[6]McMullan, Ciaran J et al. “Association of short sleep duration and rapid decline in renal function.” Kidney international vol. 89,6 (2016): 1324-30. doi:10.1016/j.kint.2015.12.048

[7] Zhang Chun (review), An Lianqing (review), Liu Zhenjiang (review), Chen Junhua (review), Cai Guangyan (review). Research progress on smoking and related chronic kidney disease in soldiers[J]. Armed Police Medicine, 2023, 34(8): 715-718

[8] Xie Wengui, Xi Qilin. Research progress on tea in preventing kidney stone formation[J]. Journal of Clinical Urology, 2021, 36(01): 76-82. DOI: 10.13201/j.issn.1001-1420.2021.01.017.

Review丨Zhang Yu, researcher/PhD, Chinese Center for Disease Control and Prevention, national health science expert