The Standard New Nordic Diet (NND) and Phosphorus
The New Nordic Diet (NND) was developed to promote a healthy, environmentally sustainable, and culturally relevant diet focusing on local and seasonal Nordic foods. Key elements include copious fruits, vegetables (especially berries, root vegetables, and cabbage), whole grains (rye, barley, oats), fish, and rapeseed oil, with reduced intake of red meat, processed foods, and added sugars.
Despite its plant-centric profile, which typically implies lower phosphorus absorption, a 2016 study comparing the NND with an Average Danish Diet (ADD) yielded surprising results. The study found that the NND group had a comparable, or even higher, mean baseline phosphorus intake than the ADD group. Crucially, there was no significant difference in fractional phosphorus excretion, indicating similar overall absorption rates between the two diets. This demonstrates that simply adopting a plant-rich diet does not automatically equate to lower phosphorus intake or absorption, particularly when whole grains, nuts, and fish are significant components.
The Complexity of Phosphorus Sources and Bioavailability
Understanding the actual impact of dietary phosphorus requires distinguishing between its different forms and sources. Phosphorus is a vital mineral, but its absorbability varies drastically. The standard NND's high phosphorus content and absorption can be attributed to its specific food choices.
Types of Dietary Phosphorus
- Inorganic Phosphates (Food Additives): These are phosphate salts added to processed foods like fast food, baked goods, and soft drinks to enhance texture and preserve flavor. They are almost 100% absorbable by the body, making them a major concern for those needing to limit phosphorus intake. The NND reduces exposure to these by minimizing processed foods.
- Organic Phosphorus (Animal Sources): Found in meat, fish, eggs, and dairy, the organic phosphorus in these foods is moderately bioavailable, with absorption rates typically ranging from 40% to 60%. The NND's encouragement of fish consumption contributes to its phosphorus load through this source.
- Organic Phosphorus (Plant Sources): Present as phytate in whole grains, legumes, nuts, and seeds, plant-based phosphorus has the lowest bioavailability, often less than 40%. The human body lacks the enzyme phytase to break down phytate efficiently, though some processing methods like fermentation (e.g., in rye bread) can release some absorbable phosphorus. The NND's high reliance on whole grains and nuts directly increases the total intake of this type of phosphorus.
The New Nordic Renal Diet (NNRD): A Modified Approach
Recognizing the high phosphorus content of the standard NND, researchers developed a modified version for patients with chronic kidney disease (CKD), known as the New Nordic Renal Diet (NNRD). This version was specifically formulated to meet lower phosphorus, protein, and sodium intake targets, aiming for approximately 850 mg of phosphorus per day.
The NNRD is predominantly plant-based (80%) but strategically modifies the food selection to reduce phosphorus load. It removes some of the most phosphorus-rich NND staples, such as rye bread, certain dairy products, and nuts. Studies on the NNRD have shown promising results, including a significant reduction in urinary phosphorus excretion and improved cardiovascular markers in CKD patients.
Comparison of Phosphorus in NND and NNRD
| Feature | Standard New Nordic Diet (NND) | New Nordic Renal Diet (NNRD) |
|---|---|---|
| Target Population | General healthy population | Patients with chronic kidney disease (CKD) |
| Phosphorus Sources | High intake from whole grains, fish, nuts, and seeds | Select plant foods with lower phosphorus and minimal phosphorus-rich nuts/seeds |
| Phosphorus Additives | Minimized due to emphasis on less processed foods | Actively excluded due to high bioavailability |
| Daily Phosphorus Intake | Can be high, exceeding recommendations (approx. 1976 mg reported in one study) | Markedly reduced to a targeted 850 mg/day |
| Animal Protein | Includes fish (up to 3x/week) and some game | Limited to about 20% of diet; includes fish and poultry |
| Dairy | Low-fat dairy consumed in moderation | Reduced or removed, as it's a phosphorus source |
| Renal Function Impact | Not designed for renal protection; potential concerns with high phosphorus for some | Demonstrates positive effects on phosphorus homeostasis and cardiovascular health in CKD |
Dietary Considerations for Managing Phosphorus Intake
For individuals concerned about phosphorus, whether due to general health or a specific medical condition like CKD, the NND's principles offer some valuable insights, but careful management is key.
Strategies for Controlling Phosphorus
- Prioritize Whole, Unprocessed Foods: The NND's focus on fresh, local, and less processed ingredients is beneficial, as it reduces exposure to high-bioavailability inorganic phosphate additives. Read labels to avoid additives, often listed as E-codes or ingredients like sodium phosphate.
- Modify Protein Sources: While the standard NND includes significant fish and whole grains, those on a phosphorus-restricted diet might need to adjust. The NNRD model of favoring specific plant-based foods (like legumes and root vegetables) over high-phosphorus nuts and certain grains is a good example.
- Leverage Preparation Techniques: Soaking, sprouting, and fermenting whole grains and legumes can help reduce phytate levels, potentially improving mineral absorption and digestibility. These traditional Nordic methods align well with the diet's principles.
- Monitor Intake: For those needing strict phosphorus control (e.g., CKD patients), dietary tracking and guidance from a healthcare professional are essential to monitor total phosphorus intake and ensure nutritional balance.
Conclusion
Research indicates that the standard New Nordic Diet, while healthy, contains higher-than-expected levels of phosphorus, primarily due to its emphasis on whole grains, seeds, and fish. The key takeaway is the difference in phosphorus bioavailability; while plant-based foods are often touted as low-phosphorus, the high intake of less-absorbable plant phosphorus can still result in a significant overall load. In contrast, the New Nordic Renal Diet (NNRD) demonstrates that tailored modifications can effectively reduce phosphorus intake for individuals with compromised kidney function. For anyone managing their phosphorus intake, focusing on whole foods and being mindful of food additives is crucial, with specific dietary adjustments needed for conditions like chronic kidney disease.
For more information on general health benefits of the New Nordic Diet, HEART UK provides a useful overview: https://www.heartuk.org.uk/dietary-patterns/new-nordic-diet.
