Fruitarian foods high in amino acid phenylalanine, per 100 g (~1/5 lb): 

• Spirulina, dried - 2777 mg 
• Soybeans - 2122 mg 
• Pumpkin or squash seeds - 1642 mg 
• Peanuts - 1427 mg 
• Kidney beans - 1370 mg 
• Lentils, sprouted - 442 mg 
• Avocados - 260 mg
• Raisins - 140 mg 
• Grapefruit - 53mg 

A nutritional analysis for the dietary food intake and serum vitamin B12 (cobalamin) level of a group of 6 vegan children aged 7 to 14 who had been living on a vegan diet for 4 to 10 years suggests that consumption of nori may keep vegans from suffering vitamin B12 deficiency.

Rauma et al. also reported that vegans consuming nori and/or chlorella had a serum vitamin B12 concentration twice as high as those not consuming these algae.

Vitamin B(12) concentrations of dried green (Enteromorpha sp.) and purple (Porphyra sp.) lavers nori were determined, in micrograms: 

• green nori: 64 - 69 mcg per 100 g of dry weight,
• purple nori: 32 - 25 mcg per 100 g of dry weight.

Non-coenzyme forms (hydroxo and cyano forms) of vitamin B12 predominate in both. 

Recommended dietary amounts (RDAs) for cobalamin, B12, are 2.4 mcg (micrograms) daily, one can cover it with 4 g of dry green nori. 

The dried lavers contained lesser amounts of dietary iodine (~ 4-6 mg per 100 g of dry weight) relative to other seaweeds, suggesting that excessive intake of the dried lavers is unlikely to result in harmful intake of iodine.

These results indicate that the nori are the best source of vitamin B12 among edible seaweeds, especially for strict vegetarians (vegans).

Substantial amounts of vitamin B12 were found in some edible algae (green and purple lavers, seaweed) and chlorella tablets. A study suggest that algal vitamin B12 is a bioavailable source for mammals.

Pseudovitamin B12 (an inactive corrinoid) predominated in the spirulina tablets, which are not suitable for use as a vitamin B12 source, especially for vegetarians. 

A survey of naturally occurring plant-derived food sources with high Vitamin B12 contents suggested that dried purple laver (nori, Porphyra yezoensis) is the most suitable Vitamin B12 source presently available for vegetarians.

The amount of total vitamin B12 in the dried purple laver was estimated to be 55 -59 mcg / 100 g dry weight. The purple laver contained 5 types of biologically active vitamin B12 compounds (cyano-, hydroxo-, sulfito-, adenosyl- and methylcobalamin), in which the vitamin B12 coenzymes (adenosyl- and methylcobalamin) comprised about 60 % of the total vitamin B12: 

• cyanocobalamin
• hydroxocobalamin 
• sulfitocobalamin 
• adenosylcobalamin 
• methylcobalamin 

Dried purple laver also contains high levels of other nutrients that are lacking in vegetarian diets, such as iron and n-3 polyunsaturated fatty acids. Dried purple laver is a natural plant product and it is suitable for most people in various vegetarian groups.

Vitamin B12 bioavailability significantly decreases with increasing intake of this vitamin per meal. Vitamin B12 is partially degraded and loses its biological activity during cooking and storage of foods.

The intrinsic factor-mediated gastrointestinal absorption system in humans has evolved to selectively absorb active vitamin B12 from naturally occurring vitamin B12 compounds, including its degradation products and inactive corrinoids.  This absorption system is estimated to be saturated at about 1.5 - 2.0 mcg of cobalamin (B12) per meal, 50% of dietary vitamin B12 is absorbed by healthy adults with normal gastro-intestinal function.

Some plant foods, dried green and purple lavers (nori) contain substantial amounts of vitamin B12, although other edible algae contained none or only traces of it. Most of the edible blue-green algae (cyanobacteria) used for human supplements predominantly contain pseudovitamin B12, which is inactive in humans.

The bioavailability of vitamin B12 in healthy humans from fish meat, sheep meat, and chicken meat averaged 42%, 56%-89%, and 61%-66%, respectively, in eggs it seems to be poorly absorbed (< 9%).

Estimated mean requirement and safe level of intake for vitamin A, in Retinol Equivalents (RE) (1 RE = 1 mcg. of retinolor 6 mcg. of beta-carotene):

• Adolescents, 10–18 years: 330–400 (mcg RE/day, mean requirement), 600 (mcg RE/day, recommended safe intake)
• Adult females, 19–65 years: 270 (mcg RE/day, mean requirement), 500 (mcg RE/day, recommended safe intake)
• Adult females, 65+ years: 300 (mcg RE/day, mean requirement), 600 (mcg RE/day, recommended safe intake)
• Males: 300 (mcg RE/day, mean requirement), 600 (mcg RE/day, recommended safe intake)

Food sources, examples (RE per 100 grams).

Fresh fruits and raw and cooked fruit vegetables:

• Mango - 523
• Apricots - 260 (dry - 730)
• Cantaloup 322
• Squash, cooked 714
• Red pepper, raw - 580

Root (tubers) and green vegetables, flowers:

• Carrots, raw - 2574
• Sweet potato, cooked - 2180
• Dandelion, raw - 1400
• Spinach, raw - 674

Seaweed:

• Spirulina - 28333
• Nori - 4895

Prevalence of vitamin B12 deficient Korean centenarians on the traditional semi-vegetarian was not higher compared with those from Western nations with animal-oriented foods. Screening of vitamin B12 contents has revealed that some traditional soybean-fermented foods, such as Doenjang and Chunggukjang, also Gochujang, Ganjang (soy sauce), cabbage Kimchi, and seaweeds (laver, sea lettuce, sea tangle, sea mustard) contain considerable amounts of vitamin B12. Soybeans (steamed) and tofu do not contain B12. 

Laver, dried, seasoned & toasted - 55 -71 mcg in 100 g dry weight

Sea lettuce, raw  -  85 mcg in 100 g dry weight

Fruitarian diet is fruit and seeds based, and may include other foods, and not only plants (e.g. algae, mushrooms) - to answer a few recent questions at once.

Please, do not assume that fruitarianism is eating sweet fruit only. There are many kinds of fruitarians. From those who avoid seeds, if they can, to those who consider honey and eggs to be ethical choices, depending on the circumstances. Usually, fresh fruits are preferable, but the proportion of cooked foods varies. Some fruitarians soak or sprout seeds, some not. Some eat more greens or root/stem vegetables, others prefer botanical fruit, including non-sweet kinds (like tomatoes, cucumbers, squash).

Most fruitarians have ethical or environmental concerns, some may not, health or performance may be their primary motivation. There are frugans, seasonal fruitarians, freegans, raw vegans or vegetarians with high fruit intake, and so on. Everybody is welcome here :)

There is no ideal food or method, there is no competition for higher ethics or better health. The idea is to present this topic to more people for an ongoing public discussion and to share knowledge and experience.