Nutrition Benefits and Considerations for Whole Foods Plant-Based Eating Patterns

Health Promoting Nutrients and Phytochemicals

Whole foods plant-based diets are rich in dietary fiber and a number of phytochemicals (carotenoids, flavonoids, isothiocyanates, lignans, phytosterols, and stilbenoids). Dietary fibers are nondigestible carbohydrates and lignans that are naturally occurring in plant-based foods. The health benefits of dietary fiber include cardiovascular disease risk reduction, diabetes control, and laxation; however, the average intake of dietary fiber among US adults is a mere 16 grams per day, where the recommended intake is 14 grams per 1000 kcal consumed (28 grams for an adult consuming 2000 kcal per day).^1-3

Phytochemicals, or phytonutrients, are naturally occurring compounds found in fruits, vegetables, whole grains, legumes, beans, herbs, spices, nuts, and seeds. These compounds largely contribute to the health benefits that are not accounted for from vitamins and minerals, experienced by those who consume the foods in large amounts. These phytochemicals contribute to the color, taste, and smells of the plant foods. There is growing evidence that these phytochemicals provide health benefits, but there is not adequate research on these compounds to make specific recommendations for intake. The health benefits and food sources for the most commonly consumed and researched phytochemicals can be found in Table 1.

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Table 1.

Phytochemicals Health Benefits and Food Sources.

Phytochemical	Health Benefit	Food Source	Additional Information
Carotenoids 4	Antioxidant activity, reduced fat oxidation, blue-light absorption (vision function), intercellular communication, immune function, reduce lung and prostate cancer risk	Red, yellow, and orange fruits and vegetables (carrots, tomato, bell peppers)	Health benefits noted from dietary intake primarily. Carotenoid absorption is improved when consumed with fat
Flavonoids 5	Cell-signaling modulator; anti-inflammatory, anti-thrombogenic, anti-diabetic, anticancer, and neuroprotection	Anthocyanidins: Red, blue, purple berries, red and purple grapes, red wine Flavan-3-ols: Tea (white, green, oolong), cocoa based products, grapes, berries, apples Flavonols: Onions, scallions, kale, broccoli, apples, berries, teas Flavones: Parsley, thyme, celery, hot peppers Flavanones: Citrus fruits Isoflavones: Soybeans, soy foods, legumes	Consumption with carbohydrate, protein, and fat-rich foods directly influences physiochemical properties. Proteins can reduce polyphenol absorption, milk proteins reduce flavonoid antioxidant capacity 6
Isothiocyanates 7	Antioxidant, anti-inflammatory, anticancer, antibacterial (primarily H pylori)	Cruciferous vegetables—bok choy, broccoli, Brussels sprouts, cabbage, cauliflower, horseradish, kale, kohlrabi, mustard, radish, rutabaga, turnips, watercress	Broccoli extract containing supplements have much lower bioavailability than naturally occurring forms from food 8
Lignans 9	Lignan precursors from plants are metabolized by intestinal bacteria to enterodiol and enterolactone which mimic estrogens	Seeds, whole grains, legumes. Flaxseeds are the richest dietary source	Most health benefits observed with lignan consumption cannot be separated from health benefits of other nutrients in foods (i.e., omega 3 fatty acids in flaxseed and improved blood cholesterol) 10
Phytosterols 11	Lower intestinal absorption of dietary cholesterol to aid in lowering serum cholesterol	Vegetable, nut, olive oils, soybeans, peas, kidney beans	.6 to 1.1 g/day related to 5% reduction in low-density lipoprotein (LDL) cholesterol, average intake of 3.3 g/day yields 12.4% LDL cholesterol reduction 12
Stilbenoids 13	Cardio protection, neuroprotection, anti-diabetic, anti-inflammation, cancer prevention and treatment	Peanuts, grapes, red wine	Resveratrol is the most widely studied of stilbenoids

Nutrients of Concern

The whole foods plant-based dietary pattern is not without limitations. Observational research studies have identified key nutrients that individuals following these dietary patterns have increased risk for inadequate or lower intake; calcium, iron, vitamin D, omega 3 fatty acid—docosahexaenoic acid (DHA), and vitamin B12.

Calcium Adequate calcium intake is essential to maintaining bone mineral density as well as for supporting nerve and muscle function, and blood clotting. Because dairy has been heavily marketed as a source of dietary calcium, vegans are observed to consume substantially less calcium than vegetarians and omnivores.^14,15 Adequate calcium intake can be achieved through the consumption of calcium fortified foods (breakfast cereals and plant-based beverages) and plant-based foods such as soybeans, bok choy, broccoli, collard greens, kale, mustard greens, and tofu. Diets void of animal protein also have lower urinary calcium losses, which can protect against calcium deficiencies. ¹⁶ Table 2 displays the calcium content of selected plant-based foods. It is recommended that adults 19–50 years and men 51–70 years consume 1000 mg of calcium per day; women 51 years and men over 70 should consume 1200 mg per day. ¹⁷

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Table 2.

Calcium Content for Select Plant-Based Foods from United States Department of Agriculture’s Nutrient Lists from Standard Reference Legacy. ¹⁸

Food	Amount	Calcium (mg)
Plant milks, calcium fortified	8 ounces (1 cup)	100–450
Tofu, processed with calcium	4 ounces	200–434
Collard greens, cooked	1 cup	268
Kale, cooked	1 cup	177
Soybeans, cooked	1 cup	175
Mustard greens, cooked	1 cup	165
Bok choy	1 cup	158
Broccoli, cooked	1 cup	62

Because calcium absorption can be inhibited by phytic and oxalic acids, which are present in plant-based foods, calcium absorption from these vegetables can be significantly reduced.^19-21 Oxalate content of green leafy vegetables can be significantly reduced through boiling. ²²

Iron

Iron functions to transfer oxygen via hemoglobin and myoglobin plays a key role in enzyme function, immune function, thyroid hormone synthesis, and metabolism of amino acids. ²³ Dietary iron comes in 2 forms, heme and non-heme iron. The primary differences in these 2 dietary sources of iron are in food sources and absorption, where heme iron comes from animal products and is better absorbed (15–30%) than non-heme iron (5–10%) which comes from plant-based foods. Plant-based dietary sources of iron come from fortified whole grains, legumes, nuts, seeds, dried fruits, iron-fortified cereals, and green leafy vegetables. Because non-heme iron is available from many food sources, iron deficiency risk is not higher among plant-based dieters compared with omnivores.^15,24 The Recommended Daily Allowance (RDA) for iron is 8 mg per day for all ages and postmenopausal women and 18 mg per day for premenopausal women. For individuals following a vegetarian diet, 1.8 times the RDA is recommended for daily intake. ²⁵ Table 3 outlines the total iron available for a number of plant-based foods.

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Table 3.

Iron Content for Select Plant-Based Foods from United States Department of Agriculture’s Nutrient Lists from Standard Reference Legacy. ¹⁸

Food	Amount	Iron (mg)
Lentils, cooked	1 cup	6.6
Tofu	½ cup	6.6
Spinach, cooked	1 cup	6.4
Kidney beans, cooked	1 cup	5.2
Soybeans, cooked	1 cup	4.5
Bagel, enriched	1 medium	4.0
Quinoa, cooked	1 cup	2.8
Peas, cooked	1 cup	2.5

Non-heme iron absorption can be affected by other nutrients. Vitamin C can increase absorption while phytates from foods such as nuts and whole grains can decrease absorption. Absorption of iron is heavily influenced by an individual’s iron status, where when iron stores are low, the body will increase iron absorption. ²⁶

Vitamin D

Vitamin D is essential to calcium absorption, bone mineralization, cell growth, differentiation, inflammation, and immune function. ²³ Dietary intake and cutaneous production of vitamin D from sun exposure support an individual’s dietary needs. Research on vitamin D status of individuals following plant-based (vegetarian and/or vegan) diets varies widely, based on sun exposure, skin pigmentation, sunscreen utilization, and age, but has been noted as problematic. ¹⁵ A more recent study noted that vitamin D intake was adequate among vegetarian and vegan adults, likely due to the fortification of many food products. ¹⁴ The RDA for Vitamin D is 600 IU (15 mcg) for individuals 1 to 70 years of age and increases to 800 IU (20 mcg) for individuals over 70 years per day. ¹⁷ Plant-based food sources of vitamin D can be found in Table 4.

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Table 4.

Vitamin D Content for Select Plant-Based Foods from United States Department of Agriculture’s Nutrient Lists from Standard Reference Legacy. ¹⁸

Food	Amount	Vitamin D (IU)
Mushrooms, chopped	1 cup	400
Fortified cereals	½–1 cup	8 to 100
Fortified plant milks	1 cup	120 IU

Omega 3 Fatty Acids—Docosahexaenoic Acid

Omega 3 fatty acids provide essential fatty acids and intakes are associated with optimal cardiometabolic health, brain development, reduced inflammation, and optimal cognitive health.^27-30 Plant-based foods primarily provide alpha-linolenic acid (ALA), which is converted primarily to eicosapentaenoic acid not DHA. Research suggests that DHA intake is remarkably low for both lacto-ovo vegetarians and vegans, and since conversion is also like from ALA, this can be of concern. ¹⁴ DHA is essential during pregnancy and lactation. Pregnant and lactating women, people with diabetes, older adults, and premature infants have poor ALA conversion and would benefit most from DHA supplements.^31,32 There is no established RDA for DHA or omega 3 fatty acids. Instead, the adequate intake for ALA is 1.6 g per day for males 16 years and up and 1.1 g per day for females 16 years and up. For pregnant women, the adequate intake is 1.4 g per day and for lactating women, it is 1.3 g per day. ² Table 5 lists plant-based sources of ALA and DHA. Algae-based dietary supplements are good source of DHA for individuals following a vegan diet.

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Table 5.

Alpha-Linolenic Acid and Docosahexaenoic Acid Content for Select Plant-Based Foods from United States Department of Agriculture’s Nutrient Lists from Standard Reference Legacy. ¹⁸

Food	Amount	ALA (g)	DHA (g)
Flaxseed oil	1 tablespoon	7.26	0
Chia seeds	1 ounce	5.06	0
Walnuts	1 ounce	2.57	0
Flaxseed whole	1 tablespoon	2.35	0
Canola oil	1 tablespoon	1.28	0

Vitamin B12

Vitamin B12 is essential to formation of red blood cells, DNA synthesis, homocysteine metabolism, and central nervous system function. ²³ Deficiencies in vitamin B12 are common both in individuals following vegan diets as well as individuals with compromised gastric function. For example, elderly and individuals who have undergone bariatric surgery experience impaired absorption of vitamin B12. Vitamin B12 deficiencies can lead to irreversible neurologic damage, but can take years to develop, and thus, sub-clinical deficiencies often go undiagnosed. The RDA for vitamin B12 is 2.4 mcg per day for males and females 14 years and older. For pregnant and lactating women, the RDA is 2.6 and 2.8 mcg, respectively. ³³ The average dietary intake of vitamin B12 of strict vegans falls well below the recommended levels. ¹⁴ Individuals following strict plant-based diets can obtain vitamin B12 from fortified plant-based beverages, fortified breakfast cereals, and fortified vegetarian meat analogs (though not whole food based), but should be strongly encouraged to take a dietary supplement. Fermented soy foods and leafy vegetables may contain B12 but do so in insignificant amounts to meet daily needs, and thus, B12 status should be monitored closely.