A Link Between Skin Cancer and High Phosphate Intake

Nutrition article posted on May 08, 2010 by Joséphine Beck, Digestive Care Advisor

Researchers at Emory University School of Medicine have found that a high dietary intake of phosphate promotes tumor formation in an animal model of skin cancer. The results, published in the journal Cancer Prevention Research, suggest that a high intake of phosphates may promote tumor development and contribute to tumor growth in skin cancer, while restricting phosphate intake may help prevent cancer.

Source: High dietary phosphate intake may promote skin cancer formation (EurekAlert.org)

What is Phosphate?
What are the Foods High in Phosphate?
Do Many Foods Naturally Contain Phosphate?
What is the Reference Daily Intake (RDI) for Phosphorus?
Are There any Other Dangers of High Intake of Phosphate?
More Information about Phosphate

What is Phosphate?

Phosphates are natural compounds – salts containing phosphorus and other minerals. They are nutrients and are essential to human, animal and plant life because they have critical functions in key biochemical processes such as metabolism.
It is the second most abundant mineral in the body after calcium. It can also bind with calcium to form calciumphosphate which is important for bones.
Plants also need phosphorus, and phosphorus-containing compounds are vital to photosynthesis.

See: Phosphate (Wikipedia.com)

What are the Foods High in Phosphate?

Phosphate is found in many food and is also added to a variety of processed foods such as meats, baked goods and soft drinks to improve texture and durability.

Here is a list of foods usually high in phosphate:

Soft drinks, soda drinks, especially cola or coke and fizzy lemonade
Cordials/fruit syrup beverages
Chocolate, lollies, sweets, candy, and anything else with a high citric acid and sugar content
Ice-cream
Skim milk powder (often added to processed foods)
Biscuits, cookies, cakes from the supermarket
Tomato ketchup
Mayonnaise
Fish fingers
Processed cheese, especially soft cheese spread
Frozen pizzas
Hot dogs
Processed meats
Baking powder and self-raising flour often contains phosphate aerator
Foods that list as an ingredient mineral salts, emulsifiers and lecithin.

Source: Foods/Additives High in Phosphate (Phosadd Australia)

Do Many Foods Naturally Contain Phosphate?

Some natural foods also contain relatively high levels of phosphate, such as:

Egg yolks
Milk
Nuts
Wheat germ
Soybeans and their by-products
Peas
Beans
Lentils
Corn
Mushrooms
Oats
Cocoa beans (chocolate)
Sweet breads - liver, brains, kidneys

However, Senior author George Beck, PhD, assistant professor of medicine (endocrinology) and member of the Winship Cancer Institute, Emory University, cautions that many foods naturally contain phosphate, but not all of it is absorbed equally, so the amount of phosphate consumed does not always reflect phosphate levels in the blood. In addition, phosphate requirements by the body may vary according to age, sex and daily activity, he says.

What is the Reference Daily Intake (RDI) for Phosphorus?

Life Stage        Age                            Males/Females (mg/day)
Infants            0-6 months                 100 (AI)
Infants              7-12 months              275 (AI)
Children            1-3 years                   460
Children             4-8 years                   500
Children    9-13 years                 1,250
Adolescents       14-18 years               1,250
Adults               19 years and older      700
Pregnancy       18 years and younger 1,250
Pregnancy    19 years and older      700
Breast-feeding 18 years and younger 1,250
Breast-feeding 19 years and older      700

Source: Dietary Reference Intake: Elements (USDA.org)

Phosphorus is an essential mineral in all living things, and is critical to each cell's ability to store and convert energy. Like most nutrients, some phosphorus is continually lost during normal biological processes and must be replenished. Calcium and phosphates are essential to maintaining healthy bones and teeth and proper blood chemistry. However, most people eat more than what their body needs. This is why it is important to limit dietary phosphate intake.

Public health researchers say that phosphate dietary intake has increased over the last 30 years and also may be underestimated because of the increasing contribution of food additives.
Dietary phosphorus derived from food additives is not calculated in most food databases, so the total amount of phosphorus consumed by the average person is not entirely clear. But here is a number of phosphorus rich foods along with their phosphorus content in milligrams (mg):

Food                                            Serving                    Phosphorus (mg)
Milk, skim                    8 ounces                    247
Yogurt, plain nonfat                      8 ounces                  385
Cheese, mozzarella; part skim     1 ounce                    131
Egg                                               1 large, cooked          104
Beef                                              3 ounces, cooked*     173
Chicken                                         3 ounces, cooked*    155
Turkey                                           3 ounces, cooked*    173
Fish, halibut                                  3 ounces, cooked*     242
Fish, salmon                                 3 ounces, cooked* 252
Bread, whole wheat                     1 slice                         57
Bread, enriched white                  1 slice                         25
Carbonated cola drink                  12 ounces                  40
Almonds#                                     1 ounce (23 nuts)      134
Peanuts#                                     1 ounce                      107
Lentils#                                        1/2 cup, cooked         178

*A 3-ounce serving is about the size of a deck of cards.
# Phosphorus from nuts, seeds, and grains is about 50% less bioavailable than phosphorus from other sources.

Source: Food Sources (Linus Pauling Institute)

Are There any Other Dangers of High Intake of Phosphate?

Because the kidneys help control the amount of phosphate in the blood, high level of phosphate in the blood is usually caused by a kidney problem. Therefore, a low phosphate diet is often recommended for kidney patients. However, there are other risks of a high phosphate diet for people who don't necessarily suffer from kidney disease. The new study reveals that a high dietary phosphate intake may promote skin cancer formation. Here are some other risks of high levels of phosphate for your health:

Bone and tooth Decay

Long-term ingestion of extremely high levels of the element phosphorus (more than five times the Required Daily Amount) can lead to bone and tooth decay.

According to Jane Higdon, Ph.D., from the Linus Pauling Institute of Oregon State University, High phosphate levels in the blood reduce the formation of the active form of vitamin D (calcitriol) in the kidneys, reduce blood calcium, and lead to increased PTH, protein hormone release by the parathyroid glands. PTH is the most important regulator of the body's calcium and phosphorus levels. If sustained, elevated PTH levels could have an adverse effect on bone mineral content, but this effect has only been observed in humans on diets that were high in phosphorus and low in calcium.

Source: Is high phosphorus intake detrimental to bone health? (Linus Pauling Institute)

Skin Aging

Scientists from Harvard University and Nagasaki University Graduate School of Biomedical Sciences in Japan reported that high levels of phosphate may accelerate the signs of aging. Their findings, obtained using genetically engineered mice, have been published in the FASEB Journal. The industry was quick to respond to the statements. Richard Laming, media director at the British Soft Drinks Association (BSDA) said:"One should not read too much into the findings of this study. It is a study of mice with a specific genetic deformity, and does not in fact mention soft drinks at all."

Source: Phosphate-ageing study dismissed by industry (Foodnavigator-usa.com)

This study has been conducted so far on rats, but it still reveals that drinking fizzy beverages on a regular basis can actually accentuate the aging process by making the skin and muscles wither, and this happens because phosphate is included among the ingredients.